Application of IEC standard medium voltage switchgear in North American market

Does the GB KYN28-24 type test report meet the requirements of North American 15kV vacuum circuit breaker switchgear? Does the type test report of the 40.5kV vacuum circuit breaker cabinet meet the requirements of the American standard 38kV switchgear with GB and IEC standards?  

Firstly, we can clearly state that even if the 24/40.5kV domestic switchgear passes the type test of GB/IEC standards, it definitely does not comply with ANSI IEEE C37.20.2 standards, nor does it comply with IEEE C37.20.3 standards

This is because the IEEE standard has requirements for partition thickness greater than 3mm, no ventilation holes, ventilation hole design, and distance from charged bodies. Our general switchgear does not meet these requirements. In addition, the installation position of MOC circuit breaker opening and closing auxiliary switches, TOC circuit breaker handcart position auxiliary switch installation position are different from our conventional ones, which are clearly specified by IEEE standard 37.20.2.

IEEE C37.20.2 has clear testing requirements for insulation materials used in contact boxes, wall bushings, and other insulation components. The resistance to electrical traces follows the D2303 standard, with a 2500V rating and UL94 V0 rating for combustion. However, the conventional epoxy resin cast insulator contact box in China cannot pass the test, so all insulation components need to be cast with epoxy resin materials that meet the requirements, and the power frequency withstand and lightning impulse insulation withstand voltage tests of the switchgear need to be re verified.

Sections 90.7 and 110.3 of the NEC electrical regulations in the United States require products to be evaluated and listed by an accredited independent testing agency.

Secondly, can it be used in American standard projects? Theoretically, the parameters need to be met, and sufficient evidence verification is required to ensure the compliance of electrical parameters. Both domestic and IEC standards use 50Hz, while the North American frequency is 60Hz. The breaking performance of most circuit breakers needs to be re verified using 60Hz. Some test items such as L75/L90 tests, as well as the compliance of TRV and other parameters, must be strictly tested and verified in accordance with the North American IEEE C37.04 standard.

In terms of switchgear, a 60Hz temperature rise test is required, and ventilation holes are not allowed in the partitions between high-voltage compartments. The upper limit of temperature rise is 65k. Without testing, it is difficult to make accurate evaluations. Circuit breaker compartments and busbar compartments do not have air inlet ports, making it very difficult to pass the temperature rise test. Even with a large strip size, such as a rated current of 3000A instead of 2000A, it may not necessarily pass the test.

The peak withstand current is 2.6 times the effective value of the short-time withstand current, and the short-circuit current is 40kA 100kA instead of 31.5kA 82kA. In addition, if the internal arc test requires IEEE C37.20.7 standard Type 2B level, the original IEC standard IAC AFLR test report cannot be used and needs to be retested according to the standard because the indicator position is different, and 2B needs to be tested with the instrument room door open.

The mechanical operation test needs to be verified together with TOC, MOC, ASD, etc. Although it is 500 operation cycles, it still requires experimental verification.

In addition, safety requirements such as NEC must be met. The extraction of the circuit breaker from the switchgear requires energy storage to release the spring, which is a necessary safety requirement.

In addition, the American standard switchgear does not use grounding switches and instead uses the IEEE C37.20.6 standard grounding test trolley (G&T). It is required that the grounding contacts of the circuit breaker compartment can withstand short-circuit current for 2 seconds, which is a safety requirement and needs to be tested together with the switchgear.

There is also a contact short circuit test for the functional handcart that needs to be verified.