Conduct MOV test on surge protective devices of Type 1, Type 2, and Type 3 according to IEC 61643-11

Conduct MOV test on surge protective devices of Type 1, Type 2, and Type 3 according to IEC 61643-11

Created by: Glen Zhu | Updated Date: July 1st, 2024

Metal Oxide Varistor MOV for PV DC Solar Surge Protection Device SPD SLP-PV1000-S

General principles

The surge protective device (SPD) that meets the requirements of IEC 61643-11 must undergo one or more specified pulse tests, which are defined as Type 1, Type 2, and Type 3 SPD pulse tests.

Type 1 tests simulate situations where partial lightning current pulses are introduced into the line. Surge protective devices (SPDs) tested using Type 1 methods are typically recommended for installation in highly exposed areas, such as at the entrance of buildings equipped with lightning protection systems.

Surge protective device (SPD) tested using Type 2 and 3 methods only withstand pulses of shorter durations.

All test details are included in IEC 61643-11. This appendix outlines MOV testing used within surge protective device (SPD) compliant with IEC 61643-11.

MOV Selection

A single MOV or a combination of series-connected, parallel-connected, or both MOVs can be used to meet the rated pulse requirements of surge protective device (SPD) according to IEC 61643-11.

Abbreviations, Explanations, and Definitions Reference Table

Table A.1 lists abbreviations, explanations, and definitions related to IEC 61643-11 used in this standard.

Table A.1 Comparison between IEC 61643-11 and IEC 61643-331

IEC61643-11

IEC61643-331

abbreviation

explain

Definition/entry

abbreviation

explain

Definition/entry

Voltage-related abbreviations, descriptions, and definitions

Uc

Maximum Continuous Operating Voltage

3.1.11

Vm

Maximum sustained voltage

3.1.6, 3.1.6.1, 3.1.6.1

Uoc

Open-circuit voltage of composite wave generator

 

3.1.23

 

 

 

Ures

Residual pressure

3.16

Vc

Limit voltage

3.2.3

 

Composite wave limited voltage

 

Vc

Limit voltage

3.2.3

 

Measured limiting voltage

3.1.15

Vc

Limit voltage

3.2.3

Abbreviations, explanations, and definitions related to electric current.

In

Nominal discharge current for Type 2 tests

3.1.19

In

Nominal discharge current

3.1.2

Imax

Maximum discharge current

3.1.48

Imax

 

 

Iimp

Type 1 test pulse current

3.1.10

 

 

 

If

Continuation of flow

3.1.12

 

 

 

Ip

Expected short circuit current of power supply

3.1.38

 

 

 

Classification Definition of Pulse Testing

 

Experiment I

3.1.34.1

 

 

 

 

Experiment II

3.1.34.2

 

 

 

 

Experiment III

3.1.34.3

 

 

 

A.1 Action Load Test

General principles

The process overview of the action load test is shown in Figure A.1.

Figure A.1 Action Load Test Procedure

Figure A.1 Action Load Test Procedure

This test is carried out in accordance with the requirements of 8.3.4.2, where the surge protective device (SPD) is powered through an AC power system to its maximum continuous operating voltage, and a specified number of prescribed pulses are applied to simulate its usage conditions.

The test device should comply with the circuit shown in Figure A.2.

Figure A.2 Test setup for operation load test

Figure A.2 Test setup for operation load test

UC: Power frequency power supply that meets the requirements of 8.3.4.2;

D: Manufacturer-specified surge protective device (SPD) external disconnect device;

DUT: Device under test (SPD);

Surge: 8/20μs current for Type 1 and Type 2 SPD operation load tests according to 8.3.4.3; pulse current for additional load tests according to 8.3.4.4; composite wave for Type 3 operation load tests according to 8.3.4 .5.

Section 8.3.4.2.1 describes the characteristics of a power frequency power supply with a continuous flow not exceeding 500A used for SPD operation load testing.

The measured limiting voltage should be determined based on the test described in Section 8.33.

To avoid overloading the device, apply one positive polarity surge pulse and one negative polarity surge pulse as follows:

1- Type 1 test is conducted at a current peak equal to Iimp as per Section 8.3.3.1;

2- Type 2 test is conducted at In as per Section 8.3.3.2;

3- Type 3 test is conducted at Uoc as per Section 8.3.3.3.

Measured Limiting Voltage

A.1.1 General provisions

Conduct measured limiting voltage tests on various surge protective device (SPD) following the flowchart shown in Figure A.3.

A.1.2 Residual pressure of an 8/20μs impulse current (8.3.3.1)

If the surge protective device (SPD) only contains voltage-limiting components, then: Type 1 tests are carried out at a peak current of Iimp, and Type 2 tests are carried out at a peak current of In.

If the manufacturer claims Imax, an additional pulse test must be performed using an Imax peak value of an 8/20μs current, and residual pressure must be measured and recorded.

The surge protective device (SPD) must undergo both positive polarity sequence and negative polarity sequence pulse tests.

The interval between each pulse must be long enough for the device to cool to ambient temperature.

The residual pressure obtained when measuring during a peak current value of Iimp in Type 1 testing or during a peak current value of In in Type 2 testing determines the measured limiting voltage.

Residual pressure refers to the voltage peak value measured when surge currents pass through; all high-frequency interference and spike pulses generated before or during passage due to specific generator designs (such as crowbar generators) should be ignored.

Depending on different types of surge protective device (SPD) tests, Umax is determined by taking the highest residual pressure values obtained under In, Imax, or Iimp peaks into account.”

Figure A.3 Test process diagram for determining the voltage protection level Up

Figure A.3 Test process diagram for determining the voltage protection level Up

A.1.1.3 Limiting voltage of composite wave (8.3.3.3)

This test requires the use of a composite wave generator.

The time interval between each pulse should be long enough to allow the specimen to cool down to ambient temperature.

If surge protective device (SPD) only contains voltage-limiting components, this test only needs to be performed at Uoc.

After setting up the pulse generator, apply 4 pulses to surge protective device (SPD), 2 positive and 2 negative polarities.

The maximum recorded voltage value during the test is the measured limiting voltage value and Umax value.

Uoc is the open circuit voltage of the composite wave generator at the connection point with the test sample.

Type 1 and Type 2 SPD action load tests (8.3.4.3)

Apply 5 sets of positive polarity 8/20μs pulse currents per group in three groups of tests. The specimen is connected according to 8.3.4.2 with the power supply, and each pulse must be synchronized with power frequency starting from angle zero degree, and the synchronous angle increases step-by-step increase by 30°±5° for each pulse. The test process is shown in Figure A .4.

Figure A.4 Timing diagram for action load testing of Type 1 and Type 2

Figure A.4 Timing diagram for action load testing of Type 1 and Type 2 SPD

Surge protective device (SPD) should be applied with a voltage Uc. When applying each set of impacts, the expected short-circuit current capacity from the power supply shall comply with clause 8.4.3.2. After applying each set of impacts and after cutting off any subsequent follow-on current if present, SPD shall continue being energized for at least one minute to check its stability. After the last set impact or continuing energizing for one minute, surge protective device (SPD) remains energized or re-energized within less than thirty seconds up to Uc maintained fifteen minutes long checking its stability. For this purpose, the short-circuit current capacity from the power supply can be reduced down to five amperes when timing.

When conducting Type 1 impulse testing on MOVs, the peak value of applied 8/20μs current should equal Iimp;

When conducting Type 2 impulse testing on MOVs, the applied 8/20μs current should equal In;

If an MOV falls into both Type 1 & 2 categories, test only one category, but using parameters that are most severe among the two categories provided by the manufacturer.

Each impact time interval ranges from 55 seconds to 60 seconds; each group’s impact time interval ranges from 35 minutes to 45 minutes.

The specimen does not need electricity during intervals between groups’ impacts.

Additional action load tests for Type 1 SPD

In this test, the current flowing through surge protective device (SPD) gradually increases until it reaches Iimp.

MOV should be applied with a voltage Uc. The expected short-circuit current capacity from power supply shall be five amperes when applying every set impact. After applying every single impact, and after cutting off any subsequent follow-on current if present, it shall continue being energized for at least one minute, to check its stability. Once previous steps have been completed successfully, surge protective device (SPD) remains energized or re-energizes within less than thirty seconds up to Uc maintaining fifteen minutes long and checking its stability. For this purpose, the short-circuit current capacity from the power source (at Uc) shall also remain as five amperes.

For powered specimens, a positive polarity impulse current will be applied to corresponding work-frequency peak values in the following ways:

a) Apply an impulse electric flow equivalenting 0.1Iimp once; check thermal stabilization; cool down till ambient temperature;
b) Apply an impulse electric flow equivalenting 0.25Iimp once; check thermal stabilization; cool down till ambient temperature;
c) Apply an impulse electric flow equivalenting 0.5Iimp once; check thermal stabilization; cool down till ambient temperature;
d) Apply an impulse electric flow equivalenting 0.75Iimp once; check thermal stabilization; cool down till ambient temperature;
e) Apply an impulse electric flow equivalenting 1.0Iimp once; check thermal stabilization; cool down till ambient temperature.

The timing chart as shown in Figure A.5

Figure A.5 Additional Action Load Test Timing Diagram for Type I Tests

Figure A.5 Additional Action Load Test Timing Diagram for Type 1 SPD Tests

Load test of action for Type 3 SPD experiments

SPD is tested using three sets of impulses corresponding to Uoc:

4 – Trigger 5 positive polarity impulses at the positive peak value;

5 – Trigger 5 negative polarity impulses at the negative peak value;

6 – Trigger 5 positive polarity impulses at the positive peak value.

The timing diagram is shown in Figure 10.

Figure A.6 Timing diagram of action load test for Class III tests

Figure A.6 Timing diagram of action load test for Type 3 SPD tests

The criteria for the qualification of all action load tests and Type 1 additional action load tests.

The criteria A, B, C, D, E, F, G, and M in Table 4 of IEC 61643-11:2011 should be met.

A.4.7 Preferred value of impulse current Iimp for additional action load test in Type 1 tests

The impulse discharge current passing through the test sample (MOV) is defined by the peak current Iimp, charge amount Q, and specific energy W/R. The impulse current must not reverse polarity and must reach the Iimp value within 50μs. The transfer of charge amount Q must occur within 5ms, and the specific energy W/R should dissipate within 5ms.

The duration of the impulse shall not exceed 5ms.

Table A.2 provides values corresponding to certain values of Iimp (kA) for Q (As) and W/R (kJ/Ω).

Relationship between Iimp (A), Q (As), and W/R (J/Ω):

Q = Iimp x a where a = 5×10-4 s

W/R =I2imp x b where b=2.5×10-4 s

Table A.2 Preferred values for Type 1 tests

Iimp

within 50μs

kA

Q

within 50ms

As

W/R

25

12.5

W/R

20

10

W/R

12.5

6.25

W/R

10

5

W/R

5

2.5

W/R

2

1

W/R

1

0.5

W/R

The tolerances for the peak current Iimp, charge amount Q, and specific energy W/R should be:

7- Iimp -10%/+10%

8- Q -10%/+20%

9- W/R -10%/+45%

For further details refer to IEC 61643-11:2011 (Section 8.3.4.4 Additional action load test for Type 1 SPD tests)

Preferred values of surge currents for Type 1 and Type 2 SPD action load tests and residual voltage measurements

Table A.3 values are only applicable to the 8/20μs waveform.

Table A.3 Preferred values for Type 1 and Type 2 SPD tests

I (kA)

100

70

60

50

40

30

20

10

The allowable error of the current waveform flowing through the test sample is as follows:

10- peak value 10%

11- Wavefront time 10%

12- Half peak time 10%

Allow small overshoot or oscillation on the surge wave, but its amplitude should not exceed 5% of the peak value. The current value in any polarity reversal after the current drops to zero should not exceed 30% of the peak value.

For further details, refer to IEC61643-11:2011 (8.3.3.1 for residual voltage of 8/20μs impulse current and 8.3.4.3 for Type 1 and Type 2 SPD action load tests).

Preferred values for composite waves used in Type 3 SPD tests

The values in Table A.4 are used for a combination wave generator with a 1.2/50μs – 8/20μs waveform, where the standard impulse wave characteristics of the combination wave generator are represented by output voltage under open-circuit conditions and output current under short-circuit conditions. The rise time of open-circuit voltage should be 1.2 μs, and the time to half-value should be 50 μs; while the rise time of short-circuit current should be 8 μs, and the time to half-value should be 20 μs.

The maximum values for peak open-circuit voltage and peak short-circuit current are respectively 20 kV and 10 kA. If they exceed these values (20 kV /10 kA), a Type 2 test shall be conducted.

Table A.4 Preferred values for composite waves in Type 3 tests

Uoc (kV)

Isc (kA)

20

10

10

5

8

4

6

3

5

2.5

4

2

3

15

2

1

1

0.5

The allowable error of open-circuit voltage Uoc at the connection point of the Device Under Test (DUT) is as follows:

13- peak value 5%

14- Wavefront time 30%

15- Half peak time 20%

These tolerances are only for the generator itself, without connecting any MOVs or power lines. Whether to connect the power line depends on whether the test requires powering.

For more details, refer to IEC 61643-11:2011 (8.1.4 subclause – composite wave for Type 3 SPD tests, Figure a).

The allowable error of short-circuit current Isc at the connection point of the Device Under Test (DUT) is as follows:

16- peak value 10%

17- Wavefront time 10%

18- Half peak time 10%

Regardless of whether the power line is connected or not, the tolerance of these generators should be met. Whether to connect the power line depends on whether the test requires electrification.

For more information on this clause, see IEC61643-11:2011 (8.1.4 subsection – composite wave for Type 3 SPD tests, Figure b).

Test settings:

The nominal value of the virtual impedance or effective impedance zf of the generator should be 2 Ω, and virtual impedance is defined as the ratio of peak open circuit voltage Uoc to peak short circuit current Isc.

The above waveform and tolerance requirements are only used for tests at Uoc declared by manufacturers, which may require some adjustments to be made to the generator. For tests below Uoc (0.1, 0.2, 0.5, 1 times Uoc), no adjustment is required for the generator and the same settings can be used.

For more information on this clause, see IEC61643-11:2011 (8.1.4 subsection – composite wave for Type 3 SPD tests, Figure c).

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