NSE Ilaro Branch, 1st National Conference, Ilaro, 2-3 November, 2020.

Safety – Related Issues in Installation, Maintenance and Use of Electrical Equipment and Precautions Cletus Okoye & Samuel Omolola

Department of Electrical Electronics Engineering Federal Polytechnic, Ilaro, , . [email protected]; [email protected] ABSTRACT

Way back in 1993, the Defense Headquarters in Lagos was ravaged by fire attributed to electrical cause. Four years after, there was a deadly explosion at the 700 MW Afam Power Station which resulted in loss of lives and property. Besides, recent statistics have shown that a total of 146 electrical accidents occurred in Nigeria in 2017. Fires and explosions originating from electrical equipment constitute the bulk of all fire accidents in industrial, residential and commercial buildings. This study analyses the critical electrical equipment in power value chain likely to cause fire, explosion and subsequent destruction of lives and property. It provides useful guides to prevent such occurrences and further draws attention to best practices to assist technical personnel in the discharge of their duties as safely as possible.

KEYWORDS: Circuit breaker, electrical accident, explosion, fires, safety, transformer.

1. INTRODUCTION

According to Musa (2018), a total of 146 electrical accidents occurred in Nigeria in 2017. This resulted in the death of 113 persons with an additional 77 injured victims. Way back in April 2000, a technical personnel was electrocuted when he was replacing a ruptured J & P fuse element on the 11 kV side of 0.5 MVA, 33/11 kV Nasarawa Eggon injection substation, Lafia District, Abuja Distribution zone. Surprisingly the following day, the supervisor who instructed the late staff to clear the fault received severe burns on the 33 kV side of the injection substation (Nyong, 2004; Okoye, 2007) Besides, in September, 1997, there was yet another deadly explosion at the 700 MW Afam thermal power station, resulting in fire outbreak. Five persons lost their lives with considerable damage to station equipment and property (Okoye, 2000). And barely a week after the Afam incidence (Awosope & Okoye, 2008) another explosion rocked the 330 kV Ajah transmission station with yet another heavy losses in equipment and total blackout in Victoria , Lekki and other villages around Ajah.

Electrical accidents in industrial, residential and commercial environments are common in this day and agebut such accidents are hardly ever reported as appropriate. In particular, managers tend to be highly secretive when it comes to publication of accident statistics/records and when they do, the severity is suppressed. They do not want to portray their industries/organisations as an unsafe environment for workforce in order not to face some sanctions from the government, law enforcement agents and critical human rights organisations. The result is falsified or whole junk of unreliable accident data/statistics when they are made available. Such as was the experience in a study involving 73 companies/industries in Sango Ota town and Agbara Industrial Estates, Ogun State State, Nigeria (Okoye, 2002).

This study aims at assisting the utility board and end-users (consumers) to identify accident-prone situations and adhere to best practices in critical areas in energy value chain. This is to ensure safety in the installation, maintenance, operation and utilization of electrical equipment.

2. APPARATUS – BASED ELECTRICAL ACCIDENTS

There are much electrical equipment which are prone to presenting some electrical hazard. A few of them are given here as the list is inexhaustible.

 Oil circuit breakers and contactors.

 Portable tools, e.g. electric drilling machines.

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NSE Ilaro Branch, 1st National Conference, Ilaro, 2-3 November, 2020.

 Heaters, lamps, electric irons.

 Television, radio, and high frequency (HF) heating apparatus.

 Plugs sockets and adaptors.

 Cables and flexes and.

 Transformers and reactors (among others).

2.1 Risk Analysis by apparatus

(i) Very few electrical hazards can be caused by rotating machines. However, if a motor is overloaded, it will eventually catch fire. If the motor bearings collapse, causing the rotor to rub on the stator, sparks can be emitted which will cause spread of fire. Similarly, a three-phase motor which has no single- phasing protection can dangerously overheat, damaging a control gear and posing a safety problem. When a motor is rewound several times, its efficiency may be reduced by about 5% (Arora et al, 2002). So, whenever possible, a new motor should be preferred.

(ii) Connection of conductors of wrong phases to 3-phase motors makes them to run in the wrong direction. If a phase conductor is interchanged with the neutral line, explosion of equipment such as freezers, bulbs, and TV sets (among others) may occur.

(iii) Fires and explosions in oil immersed transformers can occur unexpectedly. If a naked flame is used at a substation for examining the transformer connections, one stands the risk of causing fire outbreak and subsequent explosion; neither is it safe to use an electric lamp for this purpose as this also may not be safe. However, an ordinary battery-operated torch-light will be safe enough to use.

(iv) Dropping bolts, nuts, and pieces of wire into transformers can lead to local stress condition, overheating and insulation breakdown. As a precautionary measure, when a transformer is switched off and isolated, the windings should be temporarily earthed since dangerous sparks may be slowly released by dielectric relaxation (Cooper, 1989).

(v) In certain transformers such as the 45 MVA, 132/33 kV; 150 MVA, 330/132/33 kV (NCC, 2018), the Sulphur Hexafluoride (SF6) gas may be leaking due to rusty gas pipes. The bad pipes should be quickly replaced with healthy ones to ensure grid stability and thus sustainable power supply to the consumer.

(vi) Opening of the secondary circuit of a current transformer while the primary is loaded would cause flashover and explosion.

(vii) Mechanical failure of ceramic insulators may displace conductors and cause short-circuit or may even spread the trouble once it has started. This must not be allowed.

(viii) Cranes working close to an overhead line may make contact with it, thus causing transient situations, severe arc and even death of the operator. It may also cut-off power supply. Similarly, TV poles near power lines and kites flown by children have been known to cause some accidents when they come in contact with the lines.

(ix) Transformers such as the 30 MVA, 132/33 kV should be checked for oil leakage points particularly on pressure vent and tap changer manhole to ensure continuity of system voltage transformation. Also, the associated diverter switches on grid transformers should be carefully examined for fault and if found deficient, should be replaced to maintain proper voltage transformation at various locations on the grid (NCC, 2017). From time to time, transformer oil circulating pump should be checked for fault to prevent unexpected transformer breakdown and system collapse.

(x) Some transformers while in operation emit an unusual “humn”. This shows that such transformers should be opened up and maintenance exercises such as clearing the windings of sludge carried out.

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NSE Ilaro Branch, 1st National Conference, Ilaro, 2-3 November, 2020.

Subsequent routine inspections involve observation for gas evolution, cleaning of insulators, evidence of rust, oil temperature and level.

(xi) Most of the disastrous fire incidents have been caused by switchgear (especially the oil-circuit breakers and associated equipment) which are also used as part of the control equipment for large motors and processes. According to Okoye (2019) and Idoniboyeobu et at, 2017, any circuit breaker or other high voltage switchboard failure is potentially very dangerous; the damage done to plants and buildings can be extensive and fatal. It is very important to periodically check the circuit breaker mechanisms of transformers such as the 30 MVA, 132/33 kV for fault before any dangerous situation could arise. In the same token, the hydraulic oil level of the 132 kV line breaker should be checked and topped up if it has reduced to ensure the much needed system protection.

(xii) As much as possible, fuses should not be preferred where circuit breakers will be more appropriate. This is because, a circuit breaker can disconnect simultaneously all the phases of a faulty line but a fuse can only protect one phase at a time.

(xiii) Sometimes, the spark or heat that starts a fire may result from a break in the insulation, partial grounding of a circuit, poor switch contacts, faulty splices and connections, improper fusing and overheating of equipment due to overloading. In fact, some people deliberately overfuse their circuits by as much as a factor of 10. Simply put, a blown fuse is replaced with one which current-carrying capacity is greater than that designed for the circuit. This situation must be avoided.

(xiv) A reactor in an electric grid can be out of service due to, for example, an exploded yellow phase of a current transformer, which can be instantly replaced. Similarly, the lightning protector on, for instance, the 30 MVA, 132/33 kV transmission substation should be examined frequently for rupture or some other technical defects and replaced accordingly.

(xv) Testing of electrical equipment ensures that no current-carrying part has come in contact with exposed metal work. Insulation resistance value expected should be several megohms. However, one megohms is acceptable provided the test is repeated at frequent intervals to prevent further degradation in value.

(xvi) Cables on their own require little maintenance but they may pose serious danger when they are trampled upon, run over by vehicles, barrows and forklifts. Wires are exposed and faults are developed at terminations, connections and joints.

(xvii) Fires may be caused by damage to insulation at sharp edges when conductors are drawn into conduit or nails driven into cables.

(xviii) Ducts and tunnels used for cable assemblies present serious risk in the event of faults, leading to arcing, fire or heavy earth-return currents. Hence, detectors for over-heating, smoke and/or fumes should be considered in association with automatic fire protection.

(xix) All doors and covers of sub-stations should be so secured that they cannot be opened except by means of a key or special appliance. There should be drainage sumps filled with clean pebbles or granites for absorption of oil which might leak or be released under fault conditions from transformers and circuit breakers. This restricts spread of fire when it occurs.

3. STANDARD PRACTICES TO ENSURE SAFE INSTALLATION AND USE OF ELECTRICAL EQUIPMENT

Non-adherence to best practices in installation of some electrical equipment is one of the major causes of electrical accidents. For instance, vehicles are known to have knocked down power lines passing across some streets because technical personnel violated the approved line clearances from the ground. Table 1 shows the permissible guide to be used when dealing with specific situation (CAP 106, 1996; Okoye & Olowofela, 2009).

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NSE Ilaro Branch, 1st National Conference, Ilaro, 2-3 November, 2020.

Similarly, these days, many rural communities indiscriminately use wooden poles of various types and sizes without regard to known standard. Table 2 shows pole lengths and burial lengths (depth of plantings) for identified lengths of Opepe wooden poles.

From Table 2 note that the depth of planting (burial length) for the local Opepe wooden poles ranges from 1.22 m to 2.44 m. It is also important that every 5th pole be provided with wind stays (for lines in high wind area). The portion of the pole below the ground should be painted with bitumen to prevent termite attack and subsequent deterioration. (Awosope & Okoye, 2003).

Table 1: Values of Electric line clearances to Ground

System voltage Over streets, roads, public open Along streets and roads In positions inaccessible between phases spaces and other places of and other places to vehicular traffic not (volts) vehicular traffic (m) accessible to traffic (m) streets or roads (m)

400 5.8 5.2 5.2

3,300 5.8 5.5 5.5

6,600 5.8 5.5 5.5

11,000 5.8 5.5 5.5

33,000 6.0 5.5 5.5

Table 2: Pole Length and Length of Planting for Opepe wooden poles. Source: PHCN (2001)

Pole Length (m) Depth of planting (m)

6.10 1.22

7.32 1.52

8.54 1.52

10.06 1.84

10.93 1.84

12.20 1.98

13.72 1.98

15.25 2.13

16.77 2.13

18.36 2.29

18.82 2.29

19.85 2.44

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4. CONCLUSION

A total number of 146 electrical accidents were recorded in Nigeria in 2017 alone. In a country where good record- keeping is poor, one would expect a much higher number. Most accidents that occur in industrial, residential and commercial buildings and markets are mainly attributed to electrical causes. Electricity-based accidents lead to devastating fires and explosions in most cases leading to a huge loss in lives and property. Rotating machines, oil circuit breakers, portable electric tools, transformers, reactors, electric iron and heater (among others) contribute largely to such accidents when not installed, maintained, operated or used according to specifications, or, at best, recognised best practices. Analyses of risks that may emanate from these electrical equipment have been detailed and necessary guides for safe handling and use have been provided. REFERENCES

Awosope C. O. A. & Okoye, C. U. (2008), Electricity-based Fires and Explosions in Industries: Technical Issues and Solutions, Journal of Engineering and Technology, 3(1).

Awosope C. O. A. & Okoye, C. U. (2003), Rural Electrification: Emerging Technical Considerations for Sustainability in a Developing Economy, Proceeding, National Conference, Nigerian Society of Engineers, Electrical Division.

CAP 106 (1996), Electricity Supply Regulations of the Laws of Nigeria.

Cooper, W.F. (1989), Electricity Safety Engineering, Butterworth, London.

Idinoboyeobu, D. C.; Bala T. K.; & Blue-Jack, K. T. (2017), Performance Evaluation of the 132 kV Sub-Transmission Lines in the Nigeria Power Network: A Case Study of Port-Harcourt Sub-Region, Nigeria, International Journal of Research in Engineering and Science; 5(12), December.

Musa, I. (2018), National Grid Stability: TCN/DISCOs Interface, Challenges Constraints and Solutions for Power Supply Improvement in Nigeria, Paper Presented at 2nd Stakeholders Forum on Enforcement of Technical Standards and Regulations, Safety, and Certification in Nigeria.

NCC (2017), Grid System Operations, Annual Technical Report, National Control Centre, Osogbo, Nigeria.

NCC (2018), Grid System Operations, Annual Technical Report, National Control Centre, Osogbo, Nigeria.

Myong, I. E. (2004), Learning from Accidents, NEPA News, March-May.

Okoye, C. U. (2019), Nigeria’s Electric Grid: Sharing Field Experience in Search of Grid Intergrity, Technical Paper presented at the Monthly Meeting of the Nigerian Society of Engineers, Ilaro branch, Ogun State, Nigeria.

Okoye, C. U. (2000), Averting System Failure and Explosion: An Appraisal of protective devices, Book of Readings, First National Conference, School of Applied Science, Engineering and Environmental Studies, Federal Polytechnic Ilaro, Ogun State, Nigeria.

Okoye, C. U. (2007), Practical Experiences Arising from Job Performance in Industries: An Electrical Engineer’s Account, Journal of Research in Engineering, 4(1), 21-25.

Okoye, C. U. & Olowofela, S. S. (2009), Towards Sustainable Electricity Distribution and Utilisation in Nigeria, International Journal of Electrical/Electronics Engineering, 1(1).

Okoye, C. U. (2002), Assessment, Analysis and Solution to Electric Energy Supply and Utilisation: A Case Study of Industries in Sango Ota and Agbara Industrial Estate, M.Sc. thesis, (unpublished), Department of Electrical/Electronics Engineering, , Nigeria.

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