CONSULTATION ON THE IMPLEMENTATION OF ENGINEERING RECOMMENDATION ER G77
VOLUME I: SUMMARY REPORT
ETSU S/P2/00356/REP/1
DTI/Pub URN 02/809
Contractor Halcrow Group Ltd Subcontractors SunDog Energy Ltd EA Technology Ltd I-Power Ltd
Prepared by J Thornycroft M Cotterell A Collinson
The work described in this report was carried out under contract as part of the DTI Sustainable Energy Programmes. The views and judgements expressed in this report are those of the contractor and do not necessarily reflect those of the DTI.
First published 2002 © Crown copyright 2002 EXECUTIVE SUMMARY
This report presents the results of continued consultation within the Electricity Industry and PV Industry leading to the publication of Engineering Recommendation ER G77/1: ‘Connection of Single-phase Inverter Connected Photovoltaic (PV) Generating Equipment of up to 5kVA in Parallel with a Distribution Network Operators (DNOs) Distribution System ’.
It also incorporates a specific piece of technical work carried out under a Subproject ETSU/S/P2/00400. The final subgroup report on that work is reproduced in Volume II.
OBJECTIVES
This project continues the objectives of a previous ETSU project ETSU/S/P2/00215 that set-up the ‘ER G77 Working Group’ as part of the initiative to:
• Continue consultation with the DNOs principally through the ER G77 Group • Continue consultation in the PV Industry through PV-UK membership • Monitor and include experience from the implementation of ER G77 • Act as a forum for discussion of issues arising and recommended improvements to ER G77 • Provide a source of expertise and consultation on PV electrical matters for projects such as the DTI supported Domestic Field Trial • Provide a link to BSI Standards Work in the field • Define and provide a link to Subprojects investigating specific technical questions related to ER G77
The aim has been to help develop the final version of ER G77/1 that is acceptable to the PV industry and electricity supply industry.
BACKGROUND
Engineering Recommendation ER G77 was published in 2000 by the Electricity Association to facilitate the connection of photovoltaic (PV) generators to public distribution networks. It was developed by the ‘ER G77 Working Group’ that was set up under a previous ETSU contract.
An initial ‘bedding-in ’ period was allowed to enable experience from the increasing number of installations to be included, and also allow time for more in depth examination of some issues. An example of this was the ‘Disconnection Relay’ issue that is discussed in Chapter 3 of this report.
i ER G77 is now due to be reissued as ER G77/1 in early 2002 to include this feedback.
SUMMARY OF THE WORK
A series of meetings and consultations were held with the electricity and PV industries, mainly focused on the ER G77 Working Group and the photovoltaic trade association PV-UK. These meetings recorded comments from all parties on a common comments sheet format and discussed editorial changes to address them.
A major item for discussion was produced by a subgroup to the ER G77 Working Group tasked with investigating the ‘Disconnect Relay’ issue and reporting back to the main group. This work is summarised in Chapter 3 and the subgroup report is included in full in Volume II to this report.
Links and collaboration were established with other projects such as the DTI Domestic PV Field Trial, as well as Standards work and related projects such as the PV Installation Guidelines.
To address some areas where additional expertise was required, consultations and meetings were held with independent authorities such as the Health & Safety Executive which helped to gain endorsement for the recommendations in the ER G77/1 document.
CONCLUSIONS AND RECOMMENDATIONS
A series of changes to ER G77 were agreed as noted on the comments sheets and suitable wording was drafted to incorporate them into ER G77/1.
The main changes were: • To require self-certification by the manufacturer that the inverter, including the control circuits, meets specific test levels in the IEC60255 standard (these are required in the absence of a product specification, which would otherwise allow this aspect to be covered by the normal CE mark). • To require the unit to have a self-monitoring function that ensures that no unsafe output is produced in the event of a fault within the unit. • To require an additional switch-disconnector to be mounted locally to the inverter in the event that this is remote from the Consumer Unit lockable device. • To allow semiconductor switching subject to the above being met.
A revised version of ER G77/1 is included as Appendix A.
ii CONTENTS
Executive Summary i
1 Introduction 1 1.1 Preface 1 1.2 Content 1 1.3 Background 1 1.4 Aims & Objectives 2
2 ER G77 3 2.1 Introduction to Development 3 2.2 Industry Consultation 3 2.3 Meetings 3 2.4 Technical Topics 4
3 Disconnect Relay 5 3.1 Aim 5 3.2 Methodology/ Subgroup 5 3.3 List of Concerns 6 3.4 Isolation vs Disconnection 6 3.5 Summary of Semiconductors in Inverters 8 3.6 Tests 9 3.7 AC Module Connection 10
4 Conclusions & Recommendations 13 4.1 Conclusions 13 4.2 Recommendations 14
Acknowledgements 15
Further Reading 17
Appendices 19 Appendix A: ER G77/1 Final Draft 19 Appendix B: ER G77 Comments Sheet 45 Appendix C: Results of Disconnect Tests 53
iii iv 1 INTRODUCTION
1.1 Preface
This report has been prepared as a part of the Department of Trade and Industry’s New and Renewable Energy Programme, under Agreement No. ETSU/S/P2/00356/00/00 with ETSU for the DTI. It constitutes the final report for the project “Consultation on the Implementation of Engineering Recommendation ER G77”.
It also includes a summary of a related Subproject ETSU/S/P2/00400 “Research into Aspects of PV Inverters and Engineering Recommendation ER G77” which is fully described in Volume II to this report.
The project was managed by Halcrow Group Ltd with subcontractors SunDog Energy Ltd, EA Technology Ltd and I-Power Ltd. The work was carried out between May 2000 and January 2002.
1.2 Content
This report presents the results of continued consultation within the Electricity Industry and PV Industry leading to the publication of Engineering Recommendation ER G77/1: ‘Connection of Single-phase Inverter Connected Photovoltaic (PV) Generating Equipment of up to 5kVA in Parallel with a Distribution Network Operators (DNOs) Distribution System ’.
Chapter 2 presents the developments to ER G77 that have occurred during the period of the project. A copy of the final draft of ER G77/1 is included as Appendix A along with a table of the editorial changes in Appendix B.
Chapter 3 presents a summary of work from a related Subproject that was defined from and fed back into this project (ETSU/S/P2/00400). It concerns an investigation into the testing of the output stages of inverters or ‘Disconnect Relays’, and especially addresses the use of semiconductor or ‘solid-state’ devices. These are common in AC Modules and lower power inverters.
Conclusions from the work are listed in Chapter 4, along with recommendations for future activities in the area.
1.3 Background
ER G77 was developed between 1995 and its official publication by the Electricity Association in mid-2000. Co-ordination was provided by an ETSU project which established a group of electricity companies under the ‘umbrella ’ of the Electricity Association, and also channelled the feedback from the PV industry trade association via two official PV-UK representatives. As much of the work was ground breaking, with existing guidance being only for much larger generators, some parallel research projects were sponsored by
1 ETSU. This included the development by a joint University project of the ‘Type Tests’ which are a key part of the recommendation.
Much of the interest from the Electricity Companies was not just in the applications to PV which were seen to have a relatively slow introduction, but also the implications for other emerging ‘micro-generator’ technologies such as micro-turbines which can be inverter connected. These are now being developed under a separate Engineering Recommendation which is strongly based on the work carried out for ER G77.
The decision to publish in mid-2000 was made in the knowledge that because there were relatively few installations and thus limited experience in the UK at the time, it was best to publish the recommendation to make it available to all. It would then provide increased help to connection managers in interpreting G59/1, which was the existing recommendation, and would also provide feedback on its effectiveness and practicality. This project covers the 18 months from mid-2000 to the end of 2001 to include this feedback.
1.4 Aims & Objectives
This project was part of an on-going programme of work to assist the electricity supply and PV industries in the development of Engineering Recommendation ER G77/1 as a workable standard for safe and benign PV generation systems that can be installed at a cost that is as low as reasonably practical.
The work continued essential consultation and supporting activities for approximately 18 months, until ER G77/1 was ready for formal adoption and the current issues had been adequately researched. The main objectives were to:
• Continue consultation with the DNOs Consultative Group • Continue consultation in PV industry through PV-UK membership • Monitor implementation of ER G77 • Act as forum for discussion of issues arising and recommend improvements to ER G77 • Provide a source of expertise and consultation on PV electrical matters for new DTI supported BIPV and domestic field trials projects and others.
It also incorporated the aims of a subgroup that provided specific technical input to the process to:
• Develop an appropriate strategy within ER G77 for the safe assessment and accreditation of PV inverter topologies incorporating solid-state switched protection systems • Develop appropriate strategies within ER G77 for the safe cost-effective installation of PV systems utilising AC Modules (ACMs).
2 2 ER G77
2.1 Introduction to Development
As outlined in the introduction, ER G77 has been developed by the ER G77 Working Group over the period from 1995 to its publication in mid-2000. During this time, new work has been input from other ETSU sponsored research and also the international collaboration provided by the International Energy Agency (IEA) Task 5.
This project covers the development of ER G77 into ER G77/1 in the 18 months from its publication in mid-2000 to the end of 2001.
2.2 Industry Consultation
Promotion of the ER G77 and the ongoing consultation and liaison has been via the activities below: • promotion in the electricity industry via the ER G77 Working Group representatives • in the PV industry via PV-UK and the PV industry representatives • with international research via IEA Task V • standards work via BSI/ IEC representatives • via the PV-UK website • dissemination under IEA Task I • liaison with BRE and their project to develop installation guidelines • liaison especially concerned with the detailed monitoring in the Domestic Field Trial • close working with the 'Disconnection Relay' project.
2.3 Meetings
Results from the consultation and liaison were brought to the ER G77 Working Group meetings. Five full meetings of the ER G77 Working Group were held during the period as listed below. These were well attended with between 15 and 20 attendees. The list of the main contributors is included in the Acknowledgements section of this report, although many others have given crucial input over the period from 1995.
Typical agendas for the meetings included a review and discussion based on the Comments Sheet, feedback from current installations, exchange of information with other related projects such as the IEA Task V international activities and a link to the work of the subgroup on ‘Disconnection Relays’ .
To help the PV-UK representatives stimulate feedback from the PV Industry, presentations and discussions were held at PV-UK meetings as well as publishing material and a feedback form on the PV-UK website.
3 Meeting Schedule May 2000 - Dec 2001 Glasgow May 2000 ER G77 Working Group Chester October 2000 ER G77 Working Group London November 2000 PV-UK Millbank January 2001 ER G77 Working Group Millbank April 2001 ER G77 Working Group Millbank May 2001 Editing Group Meeting Birmingham May 2001 1st Disconnect Subgroup Chester July 2001 2nd Disconnect Subgroup London October 2001 ER G77 Working Group Milton Keynes October 2001 PV-UK Millbank November 2001 HSE & Disconnect Subgroup
2.4 Technical Topics
The technical topics covered were:
• to develop appropriate strategies to address the ‘wider protection system ’ issue of testing the control circuits of inverters rather than just the power disconnection components themselves • to investigate if these strategies could be extended to address the issue of PV systems incorporating solid-state switched protection systems such as AC Modules (ACMs) which were not currently allowed under ER G77 • to clarify if three phase systems should be included • to consider if the scope should be extended to other inverter connected generators not using PV as the power source • to decide how the issue of multiple-inverters interacting and possibly overriding the effectiveness of the anti-islanding protection should be addressed in tests and procedures • to add the Type Test Certificate as an Appendix to ER G77, and extend its scope to incorporate other ER G77 requirements such as the CE Mark and whether the settings are adjustable etc, in a format familiar to connection engineers • to add an Application Form as an Appendix • to add a Commissioning form as an Appendix • to introduce a flowchart to the application and commissioning process as an Appendix • to replace the ‘typical ’ diagram of figure 1 with a block schematic to avoid misinterpretation of the information.
These topics are dealt with in more detail in the Comments Sheet included in Appendix B. Where appropriate they have been incorporated into the final draft of ER G77/1 which is included as Appendix A.
4 3 DISCONNECT RELAY
3.1 Aim
The work on the topic of ‘Disconnection Relays’ was defined by the main ER G77 Working Group as an area which required further work, and which was outside of the current scope of the ER G77 group.
To this end, it defined a work programme to be carried out under the control of a Subgroup of ER G77, which would then report back to the main group so that a decision could be made based on the new information. Project ETSU/S/P2/00400 was issued to cover the development work required.
Two aims were given to the subgroup:
• To investigate and define new tests to add to those already existing in ER G77, to include the ‘wider protection system’ issue of testing of the control circuits.
• To investigate and address the issue of solid-state switched protection systems and assess if they could be included in the above.
The full report from the Subgroup can be found in Volume II to this report.
3.2 Methodology/ Subgroup
The subgroup was set up from members of the electricity companies with special expertise in the area and participants in the ETSU funded work including Halcrow Group Ltd, SunDog Energy Ltd, and EA Technology.
The methodology was to: • assess existing guidance for conventional ‘mechanical relay’ protection devices as currently used in the electricity industry, and other related guidance such as that for Uninterruptible Power Supplies (UPS), and international recommendations. • consult with industry experts to agree an approach to the problem • based on this, draw up a set of additional tests, if necessary augmented by additional standards to apply to the equipment • try out the tests in practice on a representative ‘conventional ’ and solid- state protected inverter • present the results to the independent authority experts, and the main ER G77 Working Group • modify the test procedure if necessary • suggest editorial changes to the ER G77 document to incorporate the findings.
5 Members of the subgroup who progressed the work are listed in the Acknowledgements section at the end of this report.
3.3 List of Concerns
DNOs and the Electricity Industry listed several concerns regarding the current type tests for ER G77 and the use of semiconductors within power systems. The major areas of concern identified by the disconnection relay sub-group included:
Isolation • Is the semiconductor or mechanical relay providing an 'isolation' or ‘disconnection’ function?
Control Circuits • Are there issues in integrating the control and switching as part of the inverter compared to having it 'stand-alone' as in a G59/1 relay? • Are control circuits included in any Type Test as well as the output circuits? • Which parts of the control remain active during loss of mains? • Is the quality of the software in the controller sufficient?
Semiconductors • What are the failure modes of semiconductors? • To what faults can this lead in inverter equipment? • What are the effects of these faults in terms of voltage & current on the network? • Are there any differences in failure mode between mechanical & semiconductor switched types? • Is 'leakage' of semiconductor devices when in the 'off state' a problem compared with equivalent relay equipment? • Are the EMC immunity levels as great for semiconductors as relay based equipment?
General As the PV only 'switches off' when there is no sun does this give the possibility of sustained faults not present in normal generators?
3.4 Isolation vs Disconnection
One of the main issues that affected how the automatic protection should be considered was the topic of whether it was providing an ‘isolation’ or ‘disconnection’ function.
6 This centred on discussions of how DNOs maintain their networks. The conclusion was that although live working shall not be assumed by DNOs as it is necessary to justify each and every live working task prior to the work taking place (see Electricity at Work Act, Regulation 14), the DNOs do carry out these risk assessments, and almost all maintenance on the Low Voltage Network is now carried out using live line working practices.
This has an impact on whether the inverter, as a generation source, should be made safe by a physical opening of contacts (isolation), or need only have its output ‘switched-off (‘disconnection’ or Functional Switching as in BS7671). This is important as in the case of ‘disconnection’, semiconductor devices are allowed. This discussion makes reference to guidance in the Electricity at Work Regulations and IEE Wiring Regulations BS7671, as discussed in more detail in the Subgroup report to be found in Volume II.
Following discussions with the Health & Safety Executive (HSE) the following was agreed:
PV
DC Rated Switch Disconnector Inverter (Double Pole)
(Mounted near to inverter) DC Side
AC Side (Mounted near to inverter)
AC Switch Disconnector (Double Pole)
AC Switch Disconnector (Double Pole) Lockable
Consumer Unit (Mounted near to consumer unit)
PV Single Line Diagram
'Isolation' for maintenance at various parts of the system can be achieved as below: • Maintenance of the inverter will require two fully rated double pole switch-disconnectors as shown in the diagram above, one on the DC side and the other on the AC side of the inverter. Although the device on the DC side shall be rated for full-load switching, the AC switch should be operated first followed by the DC switch.
7 • Maintenance on the conventional house system from the Consumer Unit, will require use of the double pole (lockable) switch-disconnector already provided for under ER G77 at the Consumer Unit. The requirement for it being lockable is where the isolating device is remote from the equipment to be isolated. • Maintenance of the cable between the inverter and the Consumer Unit will require operation of both actions above. • Maintenance at the Meter position (upstream of the Consumer unit) will require isolation by use of the lockable double pole switch disconnector located at the Consumer Unit position. This will be indicated by the label at the meter position. 'Disconnection' for maintenance of the DNOs network can be achieved as follows: • Maintenance by DNO staff on their own Low Voltage Network is now almost all carried out using live line working practices. In this case, a means of electrical isolation is not required to permit work to take place on the network, only a means of disconnection. This limits the purpose of the inverter protection to a disconnection or 'functional switching' function as in BS 7671, which allows the use of semiconductor devices. • To protect against the failure of the semiconductor device (or indeed relay), an appropriate self-monitoring function is required to safely shut down the inverter in the event of an internal fault condition. This is required to prevent harmful voltage at the output of the device. For accessible output connections located in a dry open environment this should not exceed 'extra low voltage' at 50Vac, 120Vdc. However, if the environment is conducting or confined then these voltage levels will need to be reduced to those set out in IEC Technical Report 1201. In the case of PV installations, where the IEC standards are at an early stage of development, it was agreed that manufacturers should be required to self-certify their equipment to this effect. In time, it is expected that the CE Mark underpinned by a product standard will be sufficient to ensure that this requirement is met.
3.5 Summary of Semiconductors in Inverters
Semiconductor switches are often favoured over electromechanical relays for small inverters such as AC Modules for the following reasons:
• Compact size • Lower cost • Better environmental specification • Higher reliability • Longer life • Increased ease of verifying state of "contacts" • Lower drive requirements • Higher speed
8 They differ from relay contacts mainly in the lack of a visible air gap and the presence of leakage current. However, in practice leakage currents through modern semiconductor devices are usually less than the leakage currents through snubber or spark extinguishing circuits such as those found in parallel with both relay contacts and semiconductor switches.
Also, in failure mode, over-currents and fast switching currents can cause damage to both types of switch. Relay contacts can weld and semiconductors can overheat and fail short or open circuit.
In designing tests to account for both types of unit, use was made of existing standards for UPS or Uninterruptible Power Supply units which have some similarities in operation as they are connected in parallel (but then designed to ‘island’ in the event of a mains failure). In addition the existing requirements for ‘relay based ’ G59/1 protection were used especially for the EMC requirements (see below).
3.6 Tests
The tests recommended by the subgroup are fully described in Appendix C. They include:
• Leakage current/terminal voltage test • Susceptibility to radiated EMC (industrial level) tests • Susceptibility to conducted EMC • Impulse tests • Surge immunity tests • Burst immunity tests
When submitted to the main ER G77 Group it was decided that the leakage tests need not be repeated for every inverter, as the trial test results had backed up the theoretical results that leakage for solid state inverters was no worse than from mechanical relay units.
The remainder of the tests were included in Appendix 1 to ER G77/1 as below:
‘On the basis of ensuring the inverter will continue to operate safely when subject to overvoltages, the following test levels are of particular interest to DNOs. In the absence of self-certification they shall be performed as additional tests.
Test Standard Test level Radiated electromagnetic IEC 60255-22-8 10 V/m, 1 kHz, 80 to 1000 MHz sweep and 80, 160, field disturbance test (RFI) 450, 900 MHz spot frequencies. Test Disconnect Function at Each Spot Frequency Radiated electromagnetic IEC 60255-22-8 10 V/m, spotfeguency field from digital radio 900 & 1890MHz telephones immunity test Test Disconnect Function at Each Spot Frequency Conducted electromagnetic IEC 60255-22-6 10 Vrms, 80% mod, 1 kHz. 0.15 to 80 MHz sweep field disturbance tests and 27 and 68 MHz spot frequencies. Applied to all ports.
9 Test Standard Test level Test Disconnect Function at Each Spot Frequency at Each Port Impulse tests (high voltage, IEC 60255-5 5kV, 0.5J L to N low energy) 5kV, 0.5 L+N to E Electrical fast IEC 60255-22-4 Level IV, 4 kV. Applied to all ports. transient/burst immunity Surge immunity test IEC 60255-22-5 Level 3, 2 kV common, 1 kV differential. Applied to all ports. The pass criteria is that the 'Protection system is still operational OR fails safe. ’
It is expected that in future once the product specification for the inverter is completed under the IEC standards process, this table will not be necessary as levels will automatically be accounted for by the manufacturers CE Mark.
3.7 AC Module Connection
With the change to ER G77/1 to accept semiconductor based automatic protection systems, the technical constraint that had been imposed on introduction of this equipment was now lifted. The next part of the study under ETSU/S/P2/00400 was to investigate if the connection to the electricity system could be simplified, again to be more in line with the costs of the devices. This was not an issue for ER G77 as it concerned the connection within the house, but was part of the interpretation of the IEE Wiring Regulations BS7671.
The main issue investigated was whether and under what conditions, they could be safely connected into a standard ringmain rather than requiring installation of a special dedicated circuit back to the consumer unit. As this could be from the attic of the house a cost of perhaps £150 to £200 for an electrician might be incurred compared with the cost of the AC module of perhaps £500. The alternative of connecting via a lockable isolator to a hardwired ‘spur box ’ installed in place of a conventional 13A socked outlet, might cost of the order of £25 to a competent home installer.
Text suggested for connection guidelines was:
‘The following provisions apply only to 'Ringmain' final circuits designed in accordance with the IEE Wiring Regs BS7671.
PV systems may be connected to 'Ringmain' final circuits to which power-consuming appliances are connected (not 'dedicated'), provided that the total current of the PV systems connected to the ringmain does not exceed ?.??A. This is equivalent to ???Wp at 230V. (The contribution to the current per PV system should be taken from the data on the inverter's rating plate).
Physical connection shall be via a dedicated fused spur and a lockable double pole switch disconnector mounted adjacent to the spur. Standard signage must also be installed.
10 Note: As a special case, very small powers of PV such as 'AC Modules’ may be connected to a standard ringmain, rather than using a dedicatedf&eder.
This is allowed, as it has been calculated that using the 'headroom' built into a Ring main final circuit, a certain level of PV current can be drawn before the thermal rating of the cable is compromised.
This current is derived from PV power used locally by an adjacent load. This can lead to additional current flowing locally in a length of the ringmain cable that is not 'seen' by the ringmain protection MCB/fuse in the Consumer Unit.
The question of what value of current may be allowed was not able to be resolved straight away as the tables in the IEE Regs seemed to be contradictory.
BS7671, 433-02-04 states that the current-carrying capacity (Iz) of the ringmain cable is to be not less than 0.67 times the rated current or the current setting (In) of the protective device. For a 32A MCB/fuse this would be 0.67x32=21.44A allowed in the cable.
However, BS7671, Table 4D2A states that for 2.5mm 2 cable, a ringmain installed to Method 3 can carry up to 23A, and one installed to Method 4 18.5A. This seems to rule out Method 4 for installation of the ringmain (and would allow no 'headroom' for the connection of PV). However the IEE On Site Guide shows that 2.5mm 2 and Method 4 are allowed.
Also the calculation to derive the 0.67 factor to allow for imbalance in the ring circuit was uncertain, although it appears to be from 2/3rds expressed to two places of decimals.
However, as the subject had not been resolved this was modified to:
‘An AC module is an integrated solar panel and inverter package with an AC output. The type of inverter in an AC module is small (100Wp to 300Wp) and is usually physically attached to the PV module.
The absence of DC wiring potentially opens the installation to the non-specialist DIY owner/ installer.
AC connection shall be to a dedicated feeder as detailed above {in the guide}, although alternative connection arrangements are being investigated. ’
Further work involving the IEE Wiring Regulations is required to take this further.
11 12 4 CONCLUSIONS & RECOMMENDATIONS
4.1 Conclusions
The conclusion of the disconnect work was that ER G77/1 has been reworded to: • require self-certification by the manufacturer that the inverter, including the control circuits, meets specific levels for IEC60255 as listed (these are required in the absence of a product specification, which would otherwise allow this aspect to be covered by the normal CE mark). • require the unit to have a self-monitoring function that ensures that no unsafe output is produced in the event of a fault within the unit.
• require an additional switch-disconnector to be mounted locally to the inverter in the event that this is remote from the lockable device placed adjacent to the Consumer Unit.
• allow semiconductor switching subject to the above three requirements being met.
Other editorial changes included in ER G77/1 during the period were to:
• clarify that three phase systems can be included with a single phase inverter on each phase, provided the total power does not exceed 5kW and that the phases are balanced as far as practicable
• include a statement that the DNO should assess the likelihood of interaction of the automatic protection based on a statement from the supplier on which active anti-islanding method is used. Also include that the Type Tests are already designed to test against this effect as far as possible
• add the Type Test Certificate as an Appendix, and extend its scope to incorporate other ER G77 requirements such as the CE Mark and whether the settings are adjustable etc, in a format familiar to connection engineers
• add an Application Form as an Appendix
• add a Commissioning form as an Appendix
• introduce a flowchart to the application and commissioning process as an Appendix
• replace the ‘typical ’ diagram of figure 1 with a block schematic, to avoid misinterpretation of the information
13 4.2 Recommendations
The following recommendations are drawn from the work:
• Work from ER G77/1 is used to feed into the new Micro-generation Engineering Recommendation being developed:
• Electricity Company representatives who contributed to the development of ER G77/1 would have a valuable contribution to make to the new recommendation
• Eventually ER G77/1 might be absorbed into the new Recommendation, keeping the PV specific recommendations in an Annex specific to PV
• The UK maintains and increases its involvement in the IEC Standards development. This is especially important in the definition of an international Type Test, where the UK Type Test definition can be input
• Set up a formal register of Type Approved inverters on behalf of the electricity and PV industries, and allocate responsibility for keeping it updated and ensuring that the technical requirements are met (at present there is an ‘informal’ register on the PV-UK website)
• Continue collaboration between the PV Industry and Electricity Industry to maintain the open discussion that has been established
• Progress investigation of use of ringmain circuits for connection of a limited proportion of AC Modules, by clarification of calculations behind IEE Regulations.
14 ACKNOWLEDGEMENTS
The project was led by Halcrow Group Ltd with sub-contractors:
• SunDog Energy Ltd (Martin Cotterell) • EA Technology Ltd (Alan Collinson) • I-Power Ltd (Tony Lakin)
The main contributors at the ER G77 Meetings were as below, although many others provided crucial input to the process over a number of years:
Rod Hacker Halcrow Group (chair) John Sinclair Electricity Association
Russell Batchelor SEEBOARD Terry Davies Scottish-Southern (Southern) Ray Dodds GPU Power Stuart Falconer Scottish-Southern (Scottish) Steve Hayes GPU Power Geoffrey Hensman Yorkshire Electricity John Holmes 24Seven (London) Andrew Hood Western Power David Hoyle Norweb Ian Hunter Scottish Power Ruth Isaac Yorkshire Electricity Howard Postlethwaite Manweb Colin Ray NEDL Trevor Richards East Midlands Electricity Ivor Rogers Western Power Glenn Spirrett PowerGen Alex Spivey 24Seven (TXU) Peter Thomas Manweb
Jim Thornycroft Halcrow Group Martin Cotterell SunDog Energy Ltd (PV-UK representative) Tony Lakin I-Power Ltd (PV-UK representative) Alan Collinson EA Technology John Crabtree EA Technology (‘Disconnection’ tests) Harry Edwards ETSU (DTI) Ray Arnold Siemens (Type Testing) Paul Cowley IT Power (IEA Task 1)
15 A major input to the Disconnection Relay work was made by members of the electricity industry who sat on the Disconnection Relay Subgroup:
• Ray Dodds & Steve Hayes (GPU) • Howard Postlethwaite (Manweb) • Geoffrey Hensman (Yorkshire) • John Holmes (24Seven, London)
In addition Andy Hills of Futronics acted as a special advisor on the technical aspects of inverter design.
Independent authority inputs that were crucial to the process were provided by John McLean of the Health & Safety Executive, and John Steed of the DTI Engineering Inspectorate.
In addition to this, the wider participation of representatives from the electricity companies the Electricity Association and the PV industry in the various discussions and meetings is gratefully acknowledged.
16 FURTHER READING
The following reports have been written in the ‘ETSU’ series, which together give the history of research into the area in the UK:
ETSU S/P2/00356/00/REP - VOL II, ‘Consultation on the Implementation of Engineering Recommendation ER G77’, 2002 (Full report of Subgroup dealing with disconnect issues. Work carried out under ETSU contract S/P2/00400/00)
ETSU S/P2/00332/00/REP ‘Industry Consultation on Grid Connection of Small PV Systems’, 2000
ETSU S/P2/00233/2, ‘Co-ordinated Experimental Research into PV Power Interaction with the Supply Network - Phase 2, 2000
ETSU S/P2/00233, ‘Co-ordinated Experimental Research into PV Power Interaction with the Supply Network - Phase 1, 1999
ETSU S/P2/00215/00/REP ‘Low-voltage Grid-connection of Photovoltaic Power Systems’, 1999
ETSU S/1394-P1, ‘Grid Connection of Photovoltaic Systems’, 1993
17 18 APPENDIX A ER G77/1 ER G77/1 FINAL DRAFT
The version of G77/1 that follows is a DRAFT and is still subject to change prior to publication
19 ENGINEERING RECOMMENDATION G77/1
PURPOSE
This document provides recommendations for the connection of a single inverter-connected photovoltaic (PV) generation unit in parallel with a Distribution Network Operators (DNOs) distribution system. Where the generation unit is either single or multi-phase, with a rating up to 5 kVA
This document also contains guidance on the approval and type testing of inverters. The aim of this document is to encourage the use of “approved ” inverter equipment and recognised connection procedures in order to lessen the need for DNO personnel to perform or witness local tests.
This document does not cover practical or safety issues related to the customer’s installation.
G77/1 ver 4 Page 1 of 25 Jan 02 ENGINEERING RECOMMENDATION G77/1
CONTENTS
1. SCOPE...... 3 2. REFERENCES...... 4 3. DEFINITIONS...... 6 4. PROTECTION...... 7 4.1 Automatic Protection...... 7 4.2 Automatic Disconnection...... 7 5. POWER QUALITY...... 8 5.1 Harmonics...... 8 5.2 Power Factor...... 8 5.3 Voltage Flicker...... 8 5.4 Electromagnetic Compatibility (EMC)...... 9 5.5 DC Injection...... 9 6. OPERATION & SAFETY...... 9 6.1 Connection Arrangements...... 9 6.2 Labelling ...... 10 6.3 Maintenance & Routine Testing...... 10 6.4 Earthing ...... 10 7. COMMISSIONING / ACCEPTANCE TESTING...... 11 7.1 Connection Requirements...... 11 7.2 Interaction between PV Inverter Generators...... 11
FIGURE 1 - Typical PV Inverter-Connected generator installation, single line diagram...... 11
APPENDIX 1 APPROVAL & TYPE TESTING...... 13 APPENDIX 2 TYPE TEST CERTIFICATE...... 18 APPENDIX 3 GUIDE TO CONNECTION...... 21 APPENDIX 4 APPLICATION FOR CONNECTION...... 21 APPENDIX 5 INSTALLATION COMMISSIONING...... 23
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1. SCOPE
This Engineering Recommendation is only concerned with the technical requirements at the interface between the DNO’s distribution system and the inverter-connected PV generator.
The PV inverter should be an ‘Approved Inverter for PV Generators’ as defined in the Approval and Type Testing Appendix.
This Engineering Recommendation has been written from a functional perspective. It is not intended to be technology specific; i.e. it does not require specific technologies to be used for connection to the DNO’s distribution system or for the energy generation schemes themselves. This approach allows for ongoing development to continually improve the cost and technical performance of the equipment connected to the DNO’s distribution system.
This Engineering Recommendation is only applicable for single installations, either single or multi-phase, where the total installed PV generation capacity is 5 kVA or below.
The mechanism for implementing the legal documentation supporting the connection of a inverter-connected PV generator, e.g. a Connection Agreement is considered to be out of Scope, however in the context of providing information this Engineering Recommendation recognises that there may be a need for such documentation to exist.
Energy export, energy trading and metering are considered to be outside of the Scope of this Engineering Recommendation, however these issues are mentioned in the context of raising the awareness of the reader to the fact that these issues may need to be addressed.
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2. REFERENCES
Electricity Supply Regulations 1988
BS 7430 (1991) Earthing Code of Practice for Earthing.
BS 7671 (1992) Requirements for Electrical Installations IEE Wiring Regulations Sixteenth Edition.
BS EN 50081-1: 1992 Electromagnetic Compatibility Generic emission standard. Residential, commercial and light industry.
BS EN 50082-1: 1998 Electromagnetic Compatibility Generic immunity standard. Residential, commercial and light industry.
BS EN 61000-3-2: 2000 Limits for harmonic current emissions (equipment input current up to and including 16 A per phase).
BS EN 61000-3-3 Limitation of voltage fluctuations and flicker in low voltage supply systems for equipment with rated current < 16 A per phase and not subject to conditional connection.
BS EN 61000-3-4 Limitation of emission of harmonic currents in low-voltage power supply systems with rated current greater than 16 A per phase.
IEC 60255-5: 1977 (BS 5992 Part 3) Electrical Relays Electrical Relays: Specification for the Insulation Testing of Electrical Relays
Engineering Recommendation G.59/1, Amendment 1 (1995) Recommendations for the Connection of Embedded Generating Plant to the Regional Electricity Companies’ Distribution Systems.
Engineering Technical Report No. 113, Revision 1 (1995) Notes of Guidance for the Protection of Embedded Generating Plant up to 5 MW for Operation in Parallel with Public Electricity Suppliers ’ distribution systems.
Engineering Recommendation G5/4 :2001 Planning levels for harmonic voltage distortion and the connection of non-linear equipment to transmission and distribution networks in the United Kingdom.
Engineering Recommendation P28 (1989) Planning limits for voltage fluctuations caused by industrial, commercial and domestic equipment in the United Kingdom.
Engineering Recommendation P29 (1990)
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Planning limits for voltage unbalance in the UK for 132 kV and below.
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3. DEFINITIONS
Inverter A device for conversion from DC to nominal frequency AC.
Approved Inverter for PV Generators At this stage, until suitable national standards are developed, an Approved Inverter for PV Generators is one: • constructed and demonstrated to an accepted specification such as in the Approval and Type Testing Appendix; and • accepted by a DNO for connection to its distribution system
Inverter-Connected Photovoltaic (PV) Generators One or more single-phase inverter-connected photovoltaic (PV) generation systems up to 5 kVA total, connected to the DNO’s distribution system at the nominal voltage and frequency.
Nominal Voltage and Frequency Low voltage: 230 volts (+10/-6 %) single-phase, 50 Hz (+/- 1%).
Public Electricity Supplier(s) (PES) A public electricity supplier or suppliers who hold licences granted under section 6(1)(c) of the Electricity Act 1989 or the Electricity (Northern Ireland) Order 1992.
Distribution Network Operator (DNO) The company responsible for making technical connection agreements with consumers seeking connection of equipment to its distribution network. A DNO maybe a PES which owns and operates a distribution network.
Islanding Islanding of inverter-connected PV generator systems means any situation where the source of power from the DNO’s distribution system is disconnected from the network section in which the generator is connected, and one or more inverters maintain a supply to that section of the distribution system or consumer’s installation.
Direct Current (DC) A unidirectional current in which the changes in value are either zero or so small that they may be neglected. As ordinarily used the term designates a practically non-pulsating current.
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4. PROTECTION
4.1 Automatic Protection
Protection shall be provided to disconnect the inverter-connected PV generator from the DNO’s distribution system when:
a) operating voltage is greater than 253V phase to neutral (230V +10%) b) operating voltage is less than 207V phase to neutral (230V - 10%) c) operating frequency is greater than 50.5 Hz (50Hz +1%) d) operating frequency is less than 47 Hz (50Hz -6%) e) the mains supply is lost
The voltage and frequency limit settings should not be capable of adjustment by the user.
The inverter should incorporate a recognised technique for providing loss of mains protection e.g. frequency shift or vector shift. Active techniques that distort the voltage waveform beyond the limits specified in clause 4.1 or that inject current pulses into the DNO’s network are not approved.
This protection must ensure that the inverter disconnects from the DNO’s distribution system within 5 seconds, and does not reconnect until at least 3 minutes after the supply from the DNO’s system has been restored to within the voltage and frequency limits already specified.
As some distribution systems employ automatic reclosing, the inverter equipment might be re-energised from the mains within the 5 second period. The inverter must therefore be capable of withstanding connection to a non-synchronised mains supply - refer to clause A1.2.4.
4.2 Automatic Disconnection
The protection function can either be incorporated in the inverter or in a separate unit. In either case it shall be type tested for compliance with the above requirements and the Approval and Type Testing Appendix.
In response to a protection operation the inverter-connected PV generator shall be disconnected from the DNOs network, this disconnection must be achieved either by the separation of mechanical contacts or by the operation of a suitably rated solid state switching device.
Where a solid state switching device is used this can either be incorporated within the inverter or a stand alone item. In either case there shall be fail safe monitoring to check the output stage of the switch. In the event that the solid state switch fails to disconnect the inverter- connected PV generator, the output on the AC side of the inverter shall be reduced to a value below 50 volts within 0.5 seconds.
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The protection system, including the inverter and any ancillary equipment, shall meet the requirements of IEC 60255-5:1977 (BS 5992 Part3) Electrical Relays. Appendix 1 lists the tests that are of particular importance to DNOs.
5. POWER QUALITY
5.1 Harmonics
All equipment shall meet:
BS EN 61000-3-2 (1995) + A12 January 1996 Electromagnetic Compatibility (EMC) Part 3-2 Limits: Limits for harmonic current emissions (equipment input current <16 A per phase), Class C limits.
For equipment rated >16 A, the emission currents shall not exceed the limits quoted in Technical Report IEC 61000-3-4 when the PV inverter generator is supplying a purely resistive load of equal rating to the output of the PV inverter generator.
Note: for the purpose of assessing emission currents in accordance with 61000-3-4, the ‘Short Circuit Power’ Scc, shall be assumed to be 548 KVA - derived using maximum values for open circuit voltage and network impedance i.e. (253 2/0.35) x 3.
Connection of the equipment shall be subject to compliance with EA Engineering Recommendation G.5/4, or any superseding recommendation.
5.2 Power Factor
Power Factor shall be within the range of 0.95 leading to unity relative to the DNO’s supply, unless otherwise agreed with the DNO. Note: Leading power factor is VARs absorbed by the inverter.
5.3 Voltage Flicker
All equipment shall meet:
BS EN 61000-3-3 (1995) Electromagnetic Compatibility (EMC) Part 3 Limitations of voltage fluctuations and flicker in low voltage supply systems for equipment with rated current less than 16 A. Equiv. IEC 1000-3-3: 1994
Connection of the equipment shall be subject to compliance with: Engineering Recommendation P28 (1989) Planning limits for voltage fluctuations caused by industrial, commercial and domestic equipment in the United Kingdom.
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Note: the automatic protection settings of clause 4.1 can afford adequate immunity for operation of the PV inverter generator against: frequency dips, voltage dips and short supply interruptions - up to 5 seconds, dependent upon the protection time setting.
5.4 Electromagnetic Compatibility (EMC)
All equipment shall be CE marked in accordance with the UK EMC regulations and meet the relevant EMC standards:
BS EN 50081-1: 1992 Electromagnetic Compatibility Generic Emission Standard
BS EN 50082-1: 1998 Electromagnetic Compatibility Generic Immunity Standard
5.5 DC Injection
DC currents entering the AC distribution system can give rise to technical problems. G5/4 deprecates the existence of DC currents on the UK distribution system but does not specify levels.
It is recommended that an inverter with a transformer output stage be specified or that a transformer be installed between the inverter and the DNO’s distribution system to prevent DC from entering the distribution system. However if a DC detection device is installed at the point of connection on the AC side then the transformer may be omitted; provided that the output of the inverter(s) is disconnected if the level of DC injection exceeds 5 mA.
Where fitted, the DC isolation transformer will normally be located adjacent to the inverter, which will either be in close proximity to or an integral part of the PV array.
6. OPERATION & SAFETY
6.1 Connection Arrangements
For the purposes of disconnecting the inverter-connected PV generator from the DNOs network the generator should be connected via a double-pole manual isolation switch that is located in an accessible position on the ac side of the inverter. Where the inverter is located remote from this switch there shall be a second double pole ac switch fitted adjacent to the inverter to facilitate maintenance.
To reduce the risk of unbalance on multi-phase installations the PV generation should, as far as is reasonably practicable, be connected evenly on each phase.
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6.2 Labelling
There shall be labelling at the service termination, meter position and at all points of isolation to indicate the presence of on-site generation. The Health and Safety (Safety Signs & Signals) Regulations 1996 stipulates that labels should display the prescribed triangular shape, using black on yellow colouring. A typical label, for content and size, is shown below:
WARNING - DUAL SUPPLY
ISOLATE BOTH MAINS AND ON-SITE GENERATION BEFORE CARRYING OUT WORK
ISOLATE THE MAINS AT______
In addition to the safety labelling, Schedule 3 of the Electricity Supply Regulations 1988 requires certain information to be displayed at the point of interconnection. In the context of small single-phase generators, which will typically be installed in domestic environments, it is envisaged that this requirement can be met by displaying:
1) a circuit diagram showing the relationship between the inverter equipment and supply 2) a summary of the protection settings incorporated within the equipment 3) a contact telephone number for the supplier/installer/maintainer of the equipment
A typical single line diagram is shown in Figure 1.
6.3 Maintenance & Routine Testing
The DNO shall have the right to carry out tests pursuant to Regulation 27 of the Electricity Supply Regulations 1988. The DNO may require the customer to re-test the inverter equipment in association with supply quality and/or safety investigations.
6.4 Earthing
The PV installation shall meet:
BS 7430 (1991) Earthing Code of Practice for Earthing
BS 7671 (1992) Requirements for Electrical Installations IEE Wiring Regulations Sixteenth Edition
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In the UK, the majority of new low voltage (LV) electrical supplies are of the Protective Multiple Earthing (PME) type. These supply cables have a Combined Neutral and Earth (CNE) metallic outer conductor, which is earthed at multiple points on the supplier’s Terra- Neutral-Combined (TNC) distribution network. Separate earth and neutral terminals are then provided within the customer’s premises (TNC-S). Generally the PME earthing facility is not allowed to be extended outside of the equipotential zone.
In the case of older premises supplied from Terra-Neutral-Separate (TNS) networks or service lines, the requirements of the PME approvals do not apply, although all bonding should still comply with BS7671 1992.
7. COMMISSIONING / ACCEPTANCE TESTING
7.1 Connection Requirements
An ‘Approved Inverter for PV Generators’ may be connected without further testing subject to: • Satisfactory on site commissioning tests as agreed with the local DNO • Opportunity for a DNO representative to witness the commissioning tests • The installation is in accordance with IEE Wiring Regulations BS 7671 1992 and any other regulations specific to the installation in question.
Note: Prior to commissioning the customer and or installer will need to inform their electricity Supplier and their Meter Operator that a PV generator is to be installed. There may also be a need for the existing Connection Agreement to be modified or a new agreement to be put in place.
Non-approved inverter equipment may also be connected if additional commissioning and acceptance tests are carried out, as defined by the local DNO.
7.2 Interaction between PV Inverter Generators
The installer should declare to the DNO the method employed for detecting loss of mains (LoM). The DNO will need to satisfy himself that the LoM algorithm used will not adversely affect the operation of other equipment on the same network. Consideration should be given to the risk of interference between multiple inverters that employ contrary means of detecting for LoM, e.g. frequency shift up/down techniques. Test A1.2.3 in the Type Test Appendix of this document is designed to significantly reduce this risk.
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DNOs Customers Network Network Generator Isolating switch Local isolator if required
PV Array
Circuit PV Generator protective device Interface Inverter protection
Figure 1. Typical PV Inverter-Connected generator installation, single line diagram
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APPENDIX 1 APPROVAL & TYPE TESTING
For the purposes of this Engineering Recommendation the following assessments and tests will be carried out as necessary to establish if an inverter can be classed as an ‘Approved Inverter for PV Generators’
A1.1 CE MARKING AND SELF CERTIFICATION
In the first instance, the equipment should be CE marked and as such comply with requirements of the relevant European Directives.
In the absence of a product specification for PV inverters, it is necessary for the inverter manufacturer/importer to self-certify that the inverter complies with requirements of this Engineering Recommendation, namely the requirements of clause 4.2. The protection system, including the inverter and any ancillary equipment, shall meet the requirements of IEC 255 5:1977 (BS 5992 Part 3) Electrical Relays.' Attention is drawn to the test levels that are of particular importance to DNOs listed in Sect A1.4.
A1.2 TESTING OF AUTOMATIC PROTECTION
Trip times and settings can be tested as shown in the following clauses:
Note: The simulation of a PV array by a constant DC source in parallel with a diode presents some difficulties in performing some of these test procedures. The operation of the maximum power point tracker (all practical inverters include such a circuit) interferes with testing when a simulation is used. This can make the tests unduly severe, therefore it is recommended that a PV array is used whenever possible. The output of the source should remain stable within +/- 5% for the duration of the test.
A1.2.1 Over / Under Voltage The inverter equipment shall be tested by operation into a variable AC voltage test supply system, whilst being fed from a PV array or DC source. Correct protection operation shall be confirmed at three power outputs: 10%, 50% and 100% of full power rating of the inverter. The set points for over and under voltage at which the inverter system disconnects from the supply will be established by varying the AC supply voltage. These set points and trip times shall be within the requirements of clause 4.1.
Check reconnection feature as in A1.2.4.
PV Array or Variable AC DC Source Inverter Voltage Test Supply
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Al.2.2 Over / Under Frequency The inverter equipment shall be tested by operation into a low impedance; variable frequency test supply system, whilst being fed from a PV array or DC source. Correct protection operation shall be confirmed at three power outputs: 10%, 50% and 100% of full power rating of the inverter. The set points for over and under frequency at which the inverter system disconnects from the supply will be established by varying the test supply frequency. These set points and trip times shall be within the requirements of clause 4.1.
Check reconnection feature as in Al.2.4.
PV Array or Variable DC Source Inverter Frequency Test Supply
Note: It may be necessary to disable any Loss of Mains protection function built in to the inverter in order to perform this test.
Al.2.3 Loss of Mains Protection The inverter equipment shall be fed from a PV array or DC source. The inverter output shall be connected to a network combining a resonant circuit with a Q factor of >0.5 and a variable load; the value of the load is to match the inverter output. To facilitate the test for loss of mains there shall be a switch placed between the test load/inverter combination and the DNO’s distribution system, as shown below:
PV Array or DC Source Inverter Distribution Resonant Variable System Circuit impedance (Q>0.5) load
(To model local load and multiple parallel connected inverters)
The inverter equipment is to be tested at three levels of inverter output power: 10%, 50% and 100%.
Each test is to be repeated five times.
For each test the Load Match is to be within +/- 5%.
Load match conditions are defined as being when the current from the inverter-connected generator meets the requirements of the test load i.e. there is no export or import of supply frequency current to or from the DNO’s distribution system
The tests will record the inverter output voltage and frequency from at least 2 cycles before the switch is opened until the inverter protection system operates and disconnects itself from the DNO’s distribution system, or for five seconds whichever is the lower duration. The time G77/1 ver 4 Page 14 of 25 Jan 02 ENGINEERING RECOMMENDATION G77/1 from the switch opening until the protection disconnection occurs is to be measured and must comply with the requirements of this Engineering Recommendation under all conditions of output power and test load. If Island conditions persist for more than 5 seconds the unit will be deemed to have failed this test.
Check reconnection feature as in Al.2.4.
Al.2.4 Re-connection Further tests will be carried out with the three test circuits to check the inverter time-out feature prior to automatic network reconnection. This test will confirm that once the AC supply voltage and frequency have returned to their nominal values following an automatic protection trip operation there is a minimum time delay (as specified in 4.1 of this Engineering Recommendation) before the inverter output is restored (i.e. before the inverter automatically reconnects to the network).
To guard against the risk of a non-synchronised connection between the inverter and the DNO’s system (possibly as a result of the DNO’s system being re-energised after a system fault), the inverter shall be tested for connection to a mains supply which is 180 degrees out of phase and at peak voltage to ensure no damage occurs.
Note: This test is not required for inverters with trip times < 0.5 Seconds
A1.3 POWER QUALITY
Al.3.1 Harmonics The PV Inverter Generator shall comply with the limits specified in Class C of BS EN 61000- 3-2: Limits for harmonic current emissions (equipment input current < 16 A per phase).
Al.3.2 Power Factor For this test, the inverter can be fed by a DC source to simulate the DC output of a PV generator. The inverter generator supplies full load to the DNO system via the power factor (pf) meter and the variac as shown below. The inverter pf should be within the limits given in 5.2, for the three test voltages shown in the table below:
PV Array or Inverter Variac DC Source Distribution System
Note: for reasons of clarity the points of isolation are not shown
Test Voltage (supplied by variac) Inverter PF (measured) 230 V + 8% 230 V 230 V -8%
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A1.3.3 Voltage Flicker The PV Inverter Generator shall comply with the limits specified in BS EN 61000-3-3: Limits concerning voltage fluctuations and flicker for equipment having an input current up to and including 16 A per phase.
A1.3.4 Electromagnetic Compatibility The manufacturer shall ensure that the equipment is tested to BS EN 50081-1:1992 (emissions) and BS EN 50082-1: 1998 (immunity).
A1.3.5 DC Injection The level of DC injection from the inverter-connected PV generator in to the DNO network shall not exceed 5mA when measured during tests A2.1, A2.2, A2.3 and A3.2. This condition is satisfied by installation of a transformer on the AC side of the inverter- connected PV generator.
A1.4 TESTING TO IEC 60255-5
To ensure that the inverter will continue to operate safely when subject to overvoltages, the following tests are of particular interest to DNOs. These tests have been derived from IEC 60255-5. The inverter and the protection unit will have to pass these tests before a DNO will agree to connection. In the absence of self-certification they shall be performed as additional tests.
Test Standard Test level Radiated IEC 60255-22-3 10 V/m, 1 kHz, 80 to 1000 MHz sweep and 80, electromagnetic field 160, 450, 900 MHz spot frequencies. disturbance test Test Disconnect Function at Each Spot (RFI) Frequency Radiated IEC 60255-22-3 10 V/m, spot frequency electromagnetic field 900 & 1890MHz from digital radio Test Disconnect Function at Each Spot telephones immunity Frequency test Conducted IEC 60255-22-6 10 Vrms, 80% mod, 1 kHz. 0.15 to 80 MHz
electromagnetic field sweep and 27 and 68 MHz spot frequencies. disturbance tests Applied to all ports. Test Disconnect Function at Each Spot Frequency at Each Port Impulse tests (high IEC 60255-5 5kV, 0.5J L to N voltage, low energy) 5kV, 0.5 L+N to E Electrical fast IEC 60255-22-4 Level IV, 4 kV. Applied to all ports. transient/burst immunity Surge immunity test IEC 60255-22-5 Level 3, 2 kV common, 1 kV differential. Applied to all ports. The pass criteria for each test is that the Protection system is still operational or fails safe.
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A1.5 Self-Monitoring Function
To comply with section 4.2 & A1.1, and in the absence of self-certification, additional material shall be presented to the tester to allow an assessment to be made of the capability of the control equipment to monitor the output stage of the inverter to ensure that in the event of a protection initiated trip the output voltage is either disconnected completely or reduced to a value below 50 volts ac.
A1.6 STANDARDS
The manufacturer shall ensure that the equipment is tested to the relevant British standards.
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APPENDIX 2 TYPE TEST CERTIFICATE
TYPE TEST CERTIFICATE FOR SINGLE-PHASE LOW-VOLTAGE INVERTER
Note 1: This certificate is invalid if any of the test values are changed from those shown below, unless such changes have been agreed with the local DNO.
Note 2: The purpose of this Test Certificate is to demonstrate the compliance of one particular inverter with the test requirements of Appendix 1 of Engineering Recommendation G77/1, so that all other inverters of this type, with the same settings, will also be deemed to have complied with these requirements.
A2.1 INVERTER DETAILS
Manufacturer Tel: Address:
Inverter type Fax:
Serial number and Rating:
A2.2 TEST HOUSE DETAILS
Name and address of test house
Telephone number Facsimile number E-mail address
A2.3 TEST DETAILS
A2.3.1 GENERAL
Date of test Name of tester Test location if different from above
Protection settings are user adjustable Y or N. CE marking Y or N. Protection disconnection switch - electro mech or solid state
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A2.3.2 POWER QUALITY
Maximum permissible harmonic current expressed as a percentage of the input current at fundamental frequency (at 100% power). As per IEC 61000-3-2 Class C.
7 th 9 Harmonic 2nd 3rd th 11th -39th G77/1 Limit 2 30 * pf 10 7 5 3 Test value Pass / fail Comment
DC injection Power factor G77/1 Limit 5mA, tested at three power levels 0.95 - Unity at three voltage levels
Test level 10% 50% 100% 212 V 230 V 248 V Test value Pass / fail Comment
A2.3.3 UNDER / OVER FREQUENCY TESTS
Under Frequency Over Frequency Parameter Frequency Time Frequency time G77/1 Limit 47 Hz 5.0 sec 51 Hz 5.0 sec Output power % 10 50 100 10 50 100 10 50 100 10 50 100 Actual setting Trip value Pass / fail Comment
A2.3.4 UNDER / OVER VOLTAGE TESTS
Under Voltage Over Voltage Parameter Voltage Time Voltage time G77/1 Limit 207 V 5.0 sec 253 V 5.0 sec Output power % 10 50 100 10 50 100 10 50 100 10 50 100 Actual setting Trip value Pass / fail Comment
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A2.3.5 LOSS OF MAINS TEST
Note: the test is to be repeated five times at each power level, and the maximum trip value is to be recorded
Method used Output power % 10 50 100 Trip setting Trip value Pass / fail Comment
A2.3.6 RECONNECTION TIMES
Parameter Under/Over Under/Over Loss of mains voltage Frequency G77/1 max vlaue 180 seconds 180 seconds 180 seconds Actual Setting Recorded value
A2.3.7 SELF MONITORING - SOLID STATE SWITCHING
Test Voltage Confirm that the AC output voltage collapses to a value below 50 volts in the event that the solid state switch fails to operate.
A2.4 COMMENTS
Name and Signature:
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APPENDIX 3 GUIDE TO CONNECTION DESIGN PHASE
INITIAL SYSTEM PROPOSAL I DRAFT SYSTEM DESIGN
APPLICATION FORM (APPENDIX 3) & INVERTER TYPE-TEST CERT (APPENDIX 2). TALK TO DNO / STUDY
DNO ACCEPTANCE ALTERATIONS REQUIRED
INSTALLATION
FINALISE SYSTEM DESIGN
r------1 j Document pack to be enclosed with I | COMMISSIONG FORM | INSTALLATION
PROGRAM TO G77 PRINT-OUT TO DNO
INVERTER(S) NEED PROGRAMMING TO G77 ?
NO SCHEDULE OF SETTINGS TO DNO
NO AC ISOLATOR ? YES FIT SIGNS AS PER CLAUSE 6.2 COPY TO DNO
NO CONFORMS TO YES COPY OF INSTALLATION & TEST CERTS. TO DNO
_L t DISPLAY CIRCUIT DIAGRAM, PROTECTION SETTINGS & INSTALLER TEL. NO COPY TO I APPROVAL PHASE
COMMISIONING TESTS (MAY BE WITNESSED BY DNO) I COMMISIONING FORM (APPENDIX 5) TO DNO
OBTAIN CONNECTION AGREEMENT DNO I APPENDIX 4 APPLICATION FOR CONNECTION SWITCH ON
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Application for the connection of a photovoltaic Generator in parallel with the public distribution network - in accordance with Engineering Recommendation G77/1 2001 This form is intended for use at the planning stage of a grid connected PV system. This information to be provided to the DNO prior to installation of the system in order that a DNO can assess and make comment on the proposed system.
Site Details Site address (inc. post code)
Telephone number Customer supply number Distribution Network Operator (DNO) Contact Details System owner Contact person Contact telephone number PV System Details Installed capacity of PV array Location of PV array Type (manufacturer & model) of inverter(s) to be used Serial Number (if known at this stage) Proposed date for installation Installer Details Installer Contact person Name and Address
Telephone Number Fax Number
Other Information to be Enclosed
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Copy of inverter Test Certificate (ER G77/1 Appendix 2)
Copy of system schematic
Existing earthing arrangements Declaration - to be completed by applicant Comments
I declare that this installation has been designed to comply with the requirements of ER G77/1 2001
Applicant: Date:
DNO comments - to be completed by DNO representative following appication A representative of the DNO will wish to witness the commissioning tests yes/no
As a representative of the DNO, I give, in principle, permission for the connection yes/no of this photovoltaic generator
MPAN Number If NO, see comments below
DNO: Contact: Date:
APPENDIX 5 INSTALLATION COMMISSIONING
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Confirmation of commissioning of a photovoltaic generator connected in parallel with the public distribution network - in accordance with Engineering Recommendation G77/1 2001
This information to be supplied in order to arrange system commissioning / switch on date. NB. This form is provided for the purposes of providing information only. This form does not constitute a connection agreement.
Site Details Site address (inc. post code)
Telephone number Customer supply / M.P.A.N. number Distribution Network Operator (DNO) Contact Details System owner Contact person Contact telephone number PV System Details Installed capacity of PV array PV manufacturer / module type Location of PV array Type (manufacturer & model) of inverter(s) to be used Serial number of inverter(s) Serial number / version numbers of software (where appropriate)
Location of lockable isolator
Installer Details Installer Installer qualification / accreditation
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Address
Contact person Telephone Number Fax Number Information to be Enclosed Final copy of system schematic
Computer print out (where possible) or other schedule of inverter protection settings Connection Agreement (Signed)
Declaration - to be completed by installer The system has been installed in compliance with ER G77/1 2001:
Inverter operating parameters have been programmed to comply with Engineering Recommendation G77/1.
The inverter operating parameters are protected from alteration except by prior agreement with the DNO. That the system has been installed to comply with the relevant sections of BS7671 (1992) Requirements for Electrical Installations (IEE Wiring Regulations), BS7430 (1991) Earthing (Code of Practice for Earthing) and IEC 364-7-712. An installation test schedule is attached (where requested by the DNO). comments
Name: Signature: Date:
G77/1 ver 4 Page 25 of 25 Jan 02 APPENDIX B ER G77 COMMENTS SHEET
45 ER G77 Comment Sheet Summary, 9 October 01 Italic: Comments previously agreed for inclusion before the 09/10/01 meeting. Bold Italics: Adt itional items discussed for inclusion at 09/10/01 meeting. Comment ER Comment Proposed Change/ Response from ER G77 WG Editing Group Comments No. G77 Justification (to be agreed at review meeting) Section No. 1 Scope PV system connected to each phase of a ER G77 to include 1.5 Scope of ER three-phase installation which therefore falls for 3 phase connected This Engineering Recommendation is only • Included as 1.4 Steve G77 outside ER G77. Although each PV PV systems. applicable for single installations, either single Hayes, connected to each phase satisfied the ER or multi-phase, where the total installed PV GPU G77 principles we are not sure how to treat To formulate a generation capacity is 5 kVA or below. 10 th Oct the overall 3 phase connected system, national common • Included in 6.1 00 typically do we apply ER G77 or G59 and in approach with clear 5.1 Connection Arrangement particular what protection settings and at industry wide .... For multi-phase installations, to reduce the what clearance times etc? guidelines that are risk of unbalance, the PV generation should be • 'possible' changed to 'practicable' acceptable to DNO’s connected evenly on each phase. and PV installers. Add 'as far as is reasonably possible' (ER G77 Meet 10 Apr 01)
AGREED 30 Jan 01
46 Comment ER Comment Proposed Change/ Response from ER G77 WG Editing Group Comments No. G77 Justification (to be agreed at review meeting) Section No. 2 Scope We have been in discussion with some ER G77 to include Being discussed at Distribution Code Review of ER developers and suppliers of other inverter for other inverter Panel. • BEING PROGRESSED Steve G77 driven generation, typically micro CHP or driven generators. OUTSIDE ER G77 Hayes, wind power systems. For the lower capacity - Electricity Association OS GPU generators, single phase up to 5kW, should To formulate a Group, WG3 10 th Oct we apply the underlying principles of ER national common 00 G77 rather than G59 as it currently appears approach with clear that ER G77 could cover the necessary industry wide requirements and could easily lend its self to guidelines that are other forms of inverter driven generators. acceptable to DNO’s and PV installers. 3 Sect The type test is designed to test exactly this, Omit the requirement 7.2 Interaction between PV Inverter 6.2 by simulating the effect of other inverters on for a manufacturer’s Generators • Para inserted in 7.2 in place of old Martin the network. Is this paragraph still relevant statement. The installer should declare to the DNO the text Cotterell now that the type test is established ? Policing the issue is method employed for detecting loss of mains SunDog better achieved by an (LoM). The DNO will need to satisfy himself 9 Aug 00 actual test that the LoM algorithm used will not adversely affect the operation of other equipment on the same network. Consideration should be given to the risk of interference between multiple inverters that employ contrary means of detecting for LoM, e.g. frequency shift up/down techniques. Test A2.3 in the Type Test Appendix of this document is designed to significantly reduce this risk. AGREED 30 Jan 01
47 Comment ER Comment Proposed Change/ Response from ER G77 WG Editing Group Comments No. G77 Justification (to be agreed at review meeting) Section No. 4-8 DELETED 30 Jan 01 -
9 New Add example Type Testing Certificate to Add Type Testing Put in format familiar to Protection Engineers • 'Type' added to title Append Certificate Add comments from Mins Sect 3.1 (ER G77 • Add Sign -off box 'I certify..' new Appendix 2 ER G77 ix 2 Meet 10 Apr 01) • Note on 'validity' added - add Group, Standardise 'unless agreed with DNO' 24 Oct 00 Certificate for AGREED in principle 30 Jan 01 • Under voltage level remains at presenting 207V information to DNOs • 61000-3-2 harmonic limits added • Add serial number & rating • Reference to ER G77/1 added to header • Add 'box' to comments para • Reconnect time column added to 2.3.3 & 2.3.4 23.5% • 10%, 50%, 100% power levels added to 2.3.5 f&23.3, 23.4% • Add 'This inverter has settings that are adjustable' Yes/No • Add Note clarifying scope of test certificate.
48 Comment ER Comment Proposed Change/ Response from ER G77 WG Editing Group Comments No. G77 Justification (to be agreed at review meeting) Section No. 10 New Add example Application/ Commissioning Add Application/ (Changes: In Part 1& Part 2 ‘PV System Append Commissioning Details’ add Loss of Mains (LoM) method Appendices Renamed 4 & 5 Forms to new Appendices 3 & 4 ER G77 ices 3 Forms used. Group, & 4 Delete ROCOF from Part 1 ‘Other • References to 'Grid' connection 24 Oct 00 Standardise Forms Information’. changed to 'in parallel' for presenting Make computer printout a requirement under • Yes/No boxes deleted information to DNOs Part 2 ‘Information to be Enclosed’ Part 2 ‘Declaration’ add Ref to IEC364-7- • Delete 3rd box p22 (duplication) 712.) • In declaration change to '.has Add comments from Mins Sect 3.1 (ER G77 been designed...' Meet 10 Apr 01) AGREED in principle 30 Jan 01
11 Sect 1 In order to make the document look more Replace Sect 1 Retain 1.2 - 1.5. Introduction with like a Standard replace Sect 1 Introduction Move references in 1.1 to new Section 2, and • 'Introduction' replaced with 'scope' John 1 Scope and Delete 1.1 with 1 Scope and 2 References. and 'references' sections Sinclair, 2 References. (delete bold from titles of standards) Electricity (delete bold) • Add Supply Regs to Refs Associatio (Also to give consistency, do not use bold AGREED in principle 30 Jan 01 • Delete Ref to 61727 n, Make the document • Change all refs to G5/3 to G5/4 text for titles of Standards) 25 Jan 01 look more like a /5.1, 5.5, A1/? Standard • Change 'clause' to 'section' in appendix 1?
49 Comment ER Comment Proposed Change/ Response from ER G77 WG Editing Group Comments No. G77 Justification (to be agreed at review meeting) Section No. 12 Figure Clarify Earthing arrangements shown on Clarify note on The PV array shall be connected to earth in 1 Figure, as although ‘typical ’ the Figure is earthing accordance with BS7671: • 'Where appropriate' added Martin being misinterpreted Options include: Cotterell, Although ‘typical ’ • add PV array 'support structure' SunDog the Figure is being (1) - As before 26 Jan 01 misinterpreted (2) - As before • modify 6.4 to remove 'and so Clarify DC earthing as Mins Sect 3.1 (ER exposed metalwork..' to end of G77 Meet 10 Apr 01) para. AGREED in principle 30 Jan 01
13 Sect State minimum size for label State suggested size State suggested size from H&S Regs 1996. 5.2 from H&S Regs • Add that 'content and size shall be ER G77 1996. AGREED in principle 30 Jan 01 as shown below..' Working Group Prevent labels being Meeting, so small they are 30 Jan 01 overlooked
14 Inform Add Flow Chart to show process required Include Flow Chart Add Flow Chart before ‘Application for ative before ‘Application Connection’ forms • Added as Appendix 2 for ER G77 application ER G77 Annex for Connection’ Modify layout as Mins Sect 3.1 (ER G77 • typo of Appendix '3' & '4' on Working 5 forms Meet 10 Apr 01) chart Group • Retitle 'Guidefor Connection' Meeting, Clarify sequence of AGREED in principle 30 Jan 01 • Improve way it converts to .pdf 30 Jan 01 actions required to apply for ER G77 connection
50 Comment ER Comment Proposed Change/ Response from ER G77 WG Editing Group Comments No. G77 Justification (to be agreed at review meeting) Section No. 15 Append Clarify references to standards in table Delete table and ix 1 replace with • Table deleted and text para added Editing description in words • Add 'be' to first para p13 Meeting 25 May 01
16 Sect • Apply '255' test requirements to include Modify sect 4.2 as 4.2 Automatic Disconnection 4.2 control circuits next box • Change sect 4.2 to read as ER G77 The protection function can either be previous box. Only include last Working • Remove requirement for 'mechanical incorporated in the inverter or in a separate sentence if agreed by HSE Group, unit. In either case it shall be type tested for separation of contacts' (subject to 9 October compliance with the above requirements and endorsement by HSE) 01 the Approval and Type Testing Appendix.
The protection system (inverter and ancillary equipment) shall meet the requirements of IEC255-5:1977 (BS5992 Part 3) Electrical Relays. Annex A lists the tests that are of particular importance to the DNOs.
Disconnection may be achieved by either semiconductor or mechanical means (note subject to HSE endorsement). 17
51 52 APPENDIX C RESULTS OF DISCONNECT TESTS
53 Approval and Type Testing of PV Inverters - Inverter Disconnection Tests
Date: 8th October 2001
Objectives
The objective is to develop a generic, performance-based “black box ” type- test for the disconnection function of PV inverter systems which requires no assumptions to be made about the device under test (e.g. disconnection by semiconductor device or electromechanical relay). The key elements of this strategy are:
• the determination of appropriate performance criteria which reflect the appropriate level of safety protection, and • the definition of suitable test procedures which can be implemented in practice to verify the required level of protection.
Development of Tests
Performance tests which measure the current and voltage caused by leakage from the device under test when disconnected from the mains supply were proposed. These tests were based on existing standards for uninterruptible power supply (UPS) systems. These UPS tests have been adapted as appropriate for the purpose of testing grid-connected PV inverters.
However, it was identified that the performance tests needed to go beyond purely the functionality of the disconnect device itself, as failures in the related disconnection control circuitry could cause maloperation of the disconnect device. The network operator representatives therefore proposed that EMC and other tests as required for protection relays in substations should be applied. Those tests were reviewed and compared with equivalent standard IEC tests that could be expected to be applied to any electrical appliance for CE EMC testing purposes. Appropriate IEC tests and levels were then determined and specified, taking on board the criteria applied to substation protection relays, for application to the testing of the PV inverters.
Summary of Test Schedule
The following tests were identified as bring appropriate for the testing of the disconnection function of PV inverters, including testing of the inverter disconnection control circuitry:
• Leakage current/terminal voltage test • Susceptibility to radiated EMC (industrial level) tests • Susceptibility to conducted EMC • Impulse tests
54 • Surge immunity tests • Burst immunity tests
Details of these tests are contained in Appendix A of Volume II to this report ‘Working Group Report (ETSU S/P2/00400/REP)’.
The leakage current/terminal voltage test is the primary test of the disconnection function and is shown in Figure 1. The test was carried out at an approved EMC test house facility (CASS Industries, Manchester). It is also known that semiconductor leakage current increases with temperature and so this test is carried out at elevated temperature. The other EMC tests are not normally carried out at higher temperatures.
AC and DC current circuit and meter Inverter under test
DC supply to inverter
Power meter AC and DC voltmeter(s)
Mains connection
Figure 1: PV Inverter leakage test circuit
Compliance with EMC standards is already a requirement within ER G77. However, the susceptibility, impulse, surge and burst test specifications produced by the ER G77 sub-committee provide greater clarity in defining appropriate levels of EMC immunity for PV inverters. The susceptibility levels relate to possible continuous levels of EMC levels present in the operating environment and so the disconnection function is tested in this environment. The impulse, surge and burst tests are transient events and so it is appropriate to test the disconnection function after these tests have been applied. This ensures that any permanent effects caused by exposure to the
55 transient EMC phenomena has not caused the disconnection function to perform in an unsafe way.
Commentary on the Inverter Tests
The purpose of performing the disconnection tests was not to actually perform a “dummy-run” type test for any particular inverter, but rather to establish the practicalities of performing the tests in terms of implementation (e.g. equipment, etc.) and test time. The practicality of the disconnection tests were assessed by applying the test procedures to two commercially available inverters:
• SMA700 Sunny Boy Inverter • OK4E Inverter
The SMA 700 inverter (700W output power) has a valid ER G77 type test certificate and uses an electro-mechanical disconnection relay. The Sunny Boy inverter is manufactured in Germany and is one of the market leaders in Europe.
The OK4E inverter (100W output power) is from the Netherlands and is one of the new breed of PV inverters in that it relies on semiconductor technology for disconnection. This inverter has also passed the ER G77 “type test” as carried out at Southampton University. It also passed the IEC 255 “electrical relay” insulation and isolation tests carried out previously at EA Technology.
The disconnection tests are applied at various EMC spot frequencies. Normal EMC testing procedure calls for “swept frequency” testing followed by functional testing at spot frequencies. During the frequency sweep, the equipment is monitored for change in operation which could indicate a potential susceptibility. Functional testing is then performed at frequencies specified in the standard plus those at which an influence was seen during the sweep test.
Note that the disconnection test is not a test of the protection function itself (such as the loss of mains protection function) but does also confirm that the internal protection is triggered in order to activate the disconnection function. Also, inverters have a built-in delay prior to reconnection (3 minutes for application in the UK). This delay was re-programmed to a lower value in the Sunny Boy inverter in order to allow the disconnection function to be tested more quickly.
56 Practicality of Disconnection Tests
Two days were spent testing at CASS. Although some time was lost due to problems with the test equipment, most of the time was spent performing the tests. The two devices (SMA 700 & OK4E) were checked together for radiated susceptibility and serially for conducted susceptibility. The number of steps and dwell times for most of the frequency sweeps had to be reduced from the numbers originally planned in order to fit the testing into the time available. These omitted tests, including those carried out subsequently at EA Technology, would probably take half a day per device to perform. The complete test procedure should therefore take two days to perform at an EMC test house.
Summary of Test Results
The test results are shown in the appendix. Both devices passed all tests applied. Whilst not all tests were applied, the lack of disturbance shown in all measurements taken gives a fair degree of confidence that the tests are practical and realistic, and it is likely that the devices tested would pass the complete set. Notably the leakage measurements were all below 0.2% of the thresholds, and the largest readings were of the same order as the pickup from the variac of the DC supply.
Conclusions
The inverter disconnection tests described in this report are relatively straightforward to apply and can be seen as a natural extension to EMC tests that would have to be carried out in any case to comply with the European EMC directive. It therefore makes most sense to perform these tests at the same time as conventional EMC tests are applied. These tests are not intended to replace the LOM-related type tests for validating the functionality of the inverter ’s loss of mains protection function. The type tests as developed by Southampton University should still be applied. The LOM type tests should be applied to the SAME inverter that has been EMC-tested and the LOM tests should be applied AFTER the EMC tests.
Some of the EMC levels specified in the tests are based on DNO requirements for protection relays in electricity substations and are therefore higher than might be applied to other domestic electrical appliances. Since manufacturers develop products for global markets it is unlikely that inverter manufacturers will develop a product to meet a specific UK-only requirement. Thus, whilst it is possible that inverters could pass the higher test levels, it would be necessary for the European standards communities to take on board the UK requirements in the currently evolving international standards if it is expected that inverter manufacturers will take on board any additional UK requirement in the design of their equipment.
57 Inverter Disconnection Test Results
The measurements for leakage current are shown as follows: {oscilloscope peak voltage in mV, voltage measurement in mV AC, voltage measurement in mV DC, current measurement in uA AC, current measurement in uA DC}.
The measurements for disconnection functionality are shown as follows [low freq, high freq, low volts, high volts]. An indication of [0,0.1,0,-1] would indicate that under frequency disconnect was at nominal level, over frequency was at 0.1Hz above nominal, under voltage was nominal and over voltage was at one volt below nominal.
58 Test Standard Test level Comments and results
Leakage This document limits are OK4E: measured temperature 51.1C, internal indicated {25000mV,25000mV,2500 temperature 50C. 0mV,1000uA,1000uA} A{<10,4,2,0,2} Leakage is measured 3 B{<5,6,5,0,4} times during the test C{<5,10,1,0,2} PASS sequence, A,B and C SMA: measured temperature 45C A{<1,0,0,0,2} B{<1,0,1,0,2} C{<1,0,0,0,2} PASS Additional inverter: SOLADIN 120 A{<15,8,10,0,2} B{<5,1,2,0,2} C{X,X,X,X,X}
Live to neutral tested. 5 minute periods were reduced to ~30s. All signals were less than 0.2% of the limit thresholds. Signal due to pickup from the DC supplies (variac on/off) was responsible for the largest signals measured.
Radiated IEC 10 V/m, 1 kHz, 80 to 1000 CASS 25/9 electromagnetic 60255-22-3 MHz sweep and 80, 160, During sweep, generated power was monitored. As variations in field disturbance 450, 900 MHz spot power were seen around 90 and 326MHz, additional spot test (RFI) frequencies. frequency tests were added at these frequencies. TEST DISCONNECT 80MHz SMA:[0,0,0,0] FUNCTION AT EACH 80MHz OK4E:[0,0,0,1] SPOT FREQUENCY 90MHz SMA:[0,X,X,X] 90MHz OK4E:[0,X,X,X] 160MHz SMA:[X,0,X,X] 160MHz OK4E:[X,0,X,X] 326MHz SMA:[X,X,0,X] 326MHz OK4E:[X,X,0,X] 450MHz SMA:[X,X,X,0]
59 Test Standard Test level Comments and results
450MHz OK4E:[X,X,X,1] 900MHz SMA:[X,0X,X] 900MHz OK4E:[X,0X,X]
Radiated IEC 10 V/m, spot frequency CASS 24/9: 1890MHz electromagnetic 60255-22-3 900 & 1890MHz 200Hz pulse modulation field from digital TEST DISCONNECT During test: radio telephones FUNCTION AT EACH orientation 1: immunity test SPOT FREQUENCY SMA[-0.1,0,0,0.4] OK4E[0,0,0,-0.6] orientation 2: SMA[0,0,0.3,0.6] OK4E[0,0,-1.5,-1] CASS 25/9: 900MHz 200Hz pulse modulation During test: SMA[X,X,X,0] OK4E[X,X,X,1]
Conducted IEC 10 Vrms, 80% mod, 1 kHz. CASS 25/9 electromagnetic 60255-22-6 0.15 to 80 MHz sweep and SMA, injection DC side field disturbance 27 and 68 MHz spot Extra frequencies: 50+72MHz tests frequencies. Applied to all 27MHz:[0.5,0,-0.1,.0] ports. 50MHz:[X,0,X,0] 68MHz:[0,X,0,X] TEST DISCONNECT 72MHz:[0.7,X,X,0] FUNCTION AT EACH SMA, injection AC side SPOT FREQUENCY AT Extra frequency: 72MHz EACH PORT 27MHz:[0,X,X,0] 68MHz:[X,0*,-1*,X] 72MHz:[X,X,0,X]
OK4E, injection AC side. No extra frequencies required.
60 Test Standard Test level Comments and results
27MHz:[X,-0.1,0,X] 68MHz:[0,X,X,0]
Impulse tests (high IEC 60255-5 5kV, 0.5J L to N SMA inverter PASS (EATL, 27/9/01) after-test levels: voltage, low 5kV, 0.5 L+N to E [0,0,0,+1V ] energy) OK4E inverter - PASS (EATL)
Electrical fast IEC 60255-22-4 Level IV, 4 kV. Applied to X transient/burst all ports. These tests are standard EMC tests and equipment is routinely immunity made to pass these levels. Whilst the tests were not carried out, there is no reason to suppose that that the tests are particularly arduous.
Surge immunity IEC 60255-22-5 Level 3, 2 kV common, 1 X test kV differential. Applied to It is expected that these tests will already have been passed at a all ports. higher level by an inverter with CE certification.
61