IEC 17.5kV Circuit Breaker Test

IEC standards and GB standards are relatively close, with the vast majority of parameters requiring GB standards to be equivalent to or higher than IEC standards. However, there are also some parameters where IEC standards are more stringent, and it cannot be said that GB standard products can be used in the IEC standard market. At the same time, since GB standards do not define 17.5kV/27kV/36kV, GB standard products must meet the corresponding IEC standard test parameters at that voltage in order to be applied. Comparison of Short term Withstand Voltage Requirements between GB and IEC Standards:

It can be seen that due to different grounding methods, the power frequency withstand voltage specified by the IEC standard is smaller than the value specified by the GB standard, but some regions require a slightly higher impulse withstand voltage, such as Southeast Asia, Malaysia, and Australia. Although the rated voltage is 12kV, the impulse withstand voltage is required to be 95kV between phases and to ground.

17.5kV voltage is used in Spain, Portugal and Türkiye in Europe, Colombia, Mexico and Brazil in South America, South Africa in Africa, Saudi Arabia in the Middle East, the Philippines in Asia, etc. When meeting the above requirements, domestic manufacturers use 24KV switch cabinets and circuit breakers because they cannot meet the requirements of 95kV impulse withstand voltage. Such products are too large to meet customer requirements. The foreign 17.5kV circuit breaker switch cabinets are consistent with 12kV, that is, 650mm switch cabinets, and 150mm phase spacing.

In fact, the parameters of circuit breakers used abroad are not only different in impulse withstand voltage, but also in some parameters. Even with the same rated voltage, they still need to be verified through experiments.

1. Transient recovery voltage TRV

The above table shows that the amplitude coefficient calculated by TRV is different between IEC and GB standards, especially for T10. Under the same rated voltage, the TRV required by IEC is higher than that required by GB standards;

TRV is related to the rated voltage. A 17.5kV TRV is basically 17.5/12=1.458 times the value of a 12kV TRV. The opening speed of the circuit breaker needs to be fast in order to open through short-circuit current.

2. Different rated frequencies

The test of a 60Hz circuit breaker with a rated frequency needs to be conducted at a frequency of 60Hz, and the test at 50Hz cannot meet the requirements of 60Hz. a. The temperature rise test needs to be conducted at 60Hz, with a margin of 5% for the test at 50Hz; b. Dynamic stability needs to be tested at 2.6 times 60Hz, with a peak value of 31.5KA and 82KA; c. The following are the test requirements for circuit breakers to meet 50 and 60Hz applications during the breaking test.

3. Different control voltages

Some countries originally adopted the American standard NEMA, so the control voltage follows the range values specified in the American standard.

4. The difference in rated operating sequence according to IEC standards includes two operating sequences: O-0.3s-CO-3min-CO and O-0.3s-CO-15s-CO. European countries require a second time interval of 15 seconds, which requires the motor energy storage time to be less than 15 seconds and the switch operation to be reliable.

5. The testing items for neutral point grounded and ungrounded systems are also different and need to be tested according to laboratory requirements.

6. Requirements for operating environment: The maximum ambient temperature is 50 ° C, the maximum 24-hour average is 45 ° C, the annual average is 30 ° C, and the minimum is -10 ° C. The maximum relative humidity is 100%

There is a huge demand for IEC 17.5kV circuit breakers from foreign customers, but there are few IEC test reports available domestically. Customers in South America, the Middle East, and Southeast Asia are struggling with product sales, and those interested in the foreign market can develop in this area.