TOPIC: DCE03.B Exported Transients Primary Power Lines

TECHNICAL GUIDANCE NOTE: DEF 004

ISSUE: Issue 1

FIRST DRAFT DATE: 20 May 2010

REVISION DATE: 26th October 2011

REFERENCE: DEF STAN 59-411, Part 3, Issue 1, Amendment 1, Publication Date 31.01.2008.

BACKGROUND: This guidance has been prepared to provide clarification of the DCE03.B test method and requirements in response to comments. This is interim guidance pending future revision of DCE03.B test method and limits in a future issue of Def Stan 59-411.

RATIONALE FOR CHANGE:

A study was performed for the sponsor of Def Stan 59-411 MOD DE3A (under Contract DCSA/2187 TAF057) to update the Defence Standard 59-411 test DCE03 exported transients.

A key finding of the study was that; DCE03 contactor switching limits should correspond to voltage spike characteristics given in power quality standards (duration typically less than a few milliseconds) and that DCE03 functional switching limits should correspond to voltage transient characteristics given in power quality standards (duration typically more than a few milliseconds). The study proposed a revised test method and new limits to ensure compatibility with power quality standards for voltage spike and voltage transients for the next issue of Def Stan 59- 411.

The existing limits in DCE03 are not drawn up in this way and therefore the method cannot be fully revised in this guidance but note is taken of the findings. In the interim the existing limits are retained but the guidance provided below on interpretation of the test method is intended to remove ambiguity as far as possible and provide a meaningful assessment.

GUIDELINES:

TGN DEF 004 Page 1 of 7 TECHNICAL GUIDANCE NOTE: DEF 004

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B.3.3 Test Layout

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Before commencement of this test Clause 6.25 should be studied which, defines the oscilloscope and oscilloscope probe parameters. The oscilloscope bandwidth shall be a minimum of 400 MHz. This value reflects the typical maximum bandwidth for power cable propagation of transients as indicated by test DCS02 frequency range for example. Reference to Annex C.9 should also be made. Figure 54 shows a typical test layout for this test method.

To enable the measurement of the transient voltage excursion relative to the power supply frequency waveform, a fast acquisition digital oscilloscope may be used to store the data. Although the power supply frequency is not filtered, measurement of all transient types can be made with reference to the AC waveform. This is achieved by reducing the time base, effectively zooming in on the transient using the data stored within the oscilloscope.

To ensure that all transients are captured the digital oscilloscope should be set-up and transient duration (for reference to the contactor switching limit voltage) measured as follows (note the exact settings are dependent on the oscilloscope type and model):

Typical settings for a DSO:

Connection: Differential probe or differential adapter Trigger: Positive & negative slope DC supply trigger: Single trigger AC supply trigger off to on event: Single trigger AC supply trigger on to off event: Run/Stop trigger & Window trigger. For 50/60 Hz supply, window time = 25 ms. For 400 Hz supply, window time = 5 ms Scale: Mains 230 V use 100V/div 28 V use 10V/div Timebase: 10 ms Trigger level: Midway between the supply peak to peak Acquisition: Select Horizontal Acquisition with maximum record length

Once the transient is captured, it can be examined in more detail to measure voltage excursion amplitude and duration using zoom or magnification functions and adjusting the horizontal time position.

Voltage excursion can be measured using amplitude cursors set to the level at the start of the departure of the transient excursion waveform from the normal supply waveform and set to the maximum amplitude of the voltage transient, see Figures 1 and 2.

Time duration of the transient is measured where it exceeds the contactor switching voltage excursion limit and can be measured using time cursors, see Figure 3.

B.3.4 Test Method

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Where the manufacturer or procurement authority specifies that the supply is controlled by an external switch or contactor For all EUTs, a switch or contactor of the type normally intended to control the supply to the EUT shall be connected into the power lines. If the contactor is not part of the EUT and its type is not known or available then an alternative, of suitable type and current rating may be used. The contactor shall be inserted at the LISN end of the lines 100mm from the LISN. Oscilloscope probe connections shall be made to the power lines at a distance of 50mm from the EUT connector and LISN. Figures 55 and 56 show typical test layouts for DC and AC lines respectively.

Where the manufacturer or procurement authority does not specify the use of an external switch or contactor then none shall be used. The exported transients due to switching of the EUT integral power switch and functional switching shall still apply.

The resulting switching mode, test position and applicable limits are shown below.

EUT Switching Mode Test Position Limits Applicable

External contactor/switch 50mm from EUT Contactor switching limit operated both ON to OFF and OFF to ON switching (where specified to be used). EUT power switch ON (if fitted). EUT integral power ON/OFF 50mm from LISN Functional switching limit switch operated both ON to OFF and OFF to ON (If transient fails functional switching (where fitted). switching limit and duration is Contactor turned ON. less than 5 ms also apply contactor switching limits (for voltage spikes) and report findings)

EUT Functional switching 50mm from LISN Functional switching limit operations likely to generate switching or load variations in (If transient fails functional supply voltage (all EUTs). switching limit and duration is EUT power switch ON (if less than 5 ms also apply fitted) and contactor ON (if contactor switching limits (for used). voltage spikes) and report findings)

The EUT is operated in each applicable mode (i.e. contactor switching, EUT power switch switching and functional switching modes) and the transient voltage measured. The maximum superimposed voltage excursion of the exported transient relative to the supply voltage waveform is compared against the limit (see Figures 1 and 2).

For tests against the contactor switch limit, the transient excursion duration is measured at the amplitude equal to the contactor switching limit, (see Figure 3).

It should be noted that different limits may apply for systems operating at power line frequencies or voltages other than those specified in this section. In these cases the Project Manager may adjust the limits accordingly to ensure compatibility with the relevant power quality standard.

±Vexcursion

Figure 1 AC Waveform Voltage Excursion Definition Diagram

±Vexcursion

VD C SU PPLY

±Vexcursion

Figure 2 DC Waveform Voltage Excursion Definition Diagram

±Vexcursion

Contactor Switching Duration Limit Voltage ±V Measurement

Supply waveform voltage level at start of transient

Figure 3 Waveform Duration Definition Diagram

For AC supplies, a twin ‘T’ notch filter may be used to filter the power supply frequency. Annex C, Clause C.9 describes the design of a twin-T filter, tuned to the supply frequency, which is connected at the oscilloscope input, in tandem with a voltage probe, which attenuates the power supply frequency response by at least 30 dB. With the power frequency filtered, any transients shown on the oscilloscope are relative to the AC waveform when measured between the transient's peak and the oscilloscope’s reference level. The test report (see Part 1 Clause 11 of this Standard) should give details of the filtering used showing how the input impedance requirements of Clause 6.25 have been met.

B.3.6 Test for Land Service Use (DC and AC Systems)

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The differential transient voltage appearing between the various power lines shall be measured as follows: a) For DC lines the transient voltage shall be measured between the positive line and zero volt return line, the positive line and the ground conducting bench and also between the zero volt return line and the ground conducting bench.

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