Medium voltage switchgear that complies with IEC and ANSI standards

Many manufacturers hope that their products can meet both the IEC standards used in most countries around the world and the ANSI standards used in North America.

The IEC standard specifies more performance and parameters, while the ANSI standard defines many structural and dimensional requirements, such as the absence of ventilation holes in compartments, the use of 11gauge plates between compartments, MOC (circuit breaker opening and closing position auxiliary switch fixed on compartments)/TOC (handcart position auxiliary switch fixed on compartments)/ASD (energy storage spring release extracted from compartments), and the use of C37.20.6 standard grounding test handcart (G&T) instead of grounding switch, etc. These are mandatory items for American standard switchgear, while the IEC standard does not have such provisions.

Electrical parameter compliance is necessary, as there are many voltage levels and system voltages around the world, such as 2.3/3/4.16/7.2/8.23/11/12/13.8/14.7 kV. The switchgear standard defines the highest voltage as the rated voltage, and the voltage levels defined by IEC62271-1 standard include sequence one and sequence two.

Therefore, the mainstream 17.5kV and North American 15kV are consistent, and many manufacturers use 17.5kV as the voltage level for switchgear to cover voltage levels of 17.5kV and below, in order to cover voltage levels of North American 15kV and below.

Regarding circuit breakers, they are quite complex. Generally speaking, the 17.5kV transient recovery voltage TRV can be used for voltage levels of 17.5kV and below. Many customers define TRV values in their technical specifications. At this point, it is necessary to verify the TRV value to confirm the TRV value at that voltage. The TRV value of the 17.5kV circuit breaker's short-circuit current is greater than the TRV value required by the IEEE 15kV circuit breaker standard.

For current and frequency, if 60Hz is required, the rated current of 50Hz needs to be reduced in capacity, as required by the project 1000A@60Hz At 50Hz, the current requires at least 1.05 times the current, which is 3000 * 1.05= 3150A@50Hz Therefore, if the project requires 3150A 60Hz, then products with 3150A 50Hz cannot meet the requirements 3150A@50Hz Calculate the temperature rise test report and confirm that a 5% margin can also be applied to 60Hz. For switchgear used in the North American ANSI standard region, the voltage and current levels are compared as follows,

Dynamic thermal stability test, main circuit, grounding circuit. The primary contact dynamic and thermal stability test of a functional handcart requires conducting dynamic and thermal stability tests on the primary contacts of auxiliary handcarts such as voltage transformers and power transformers. This is a mandatory testing project

The material of insulation components needs to meet the requirements of flame retardant V0 level, D2303 trace resistance 2.5kV 300min, thermal cycle test, D229 combustion level specified in IEEE C37.20.2 standard, and pass the tests specified in the standard. Material testing is also a mandatory test item specified by the standard, not optional.

The mechanical operation test frequency of American standard switchgear is relatively low, which can generally be covered by IEC standards. However, IEC circuit breakers such as TOC and MOC do not have this design and require 500 cycles of testing verification.

The protection level is different. The indoor NEMA 1 of the American standard switchgear is equivalent to IP2X. Therefore, if the temperature rise of our 60Hz switchgear is 10k lower than the IEC standard and there is no problem, it can also be done according to IP4X. A complete test is required for outdoor switchgear.

The internal arc fault test of the American standard is also very different from that of the IEC. The American standard internal arc level Type 2 is basically the same as the IAC B FLR. Generally, the A FLR does not meet the requirements for the arc test, but if Type 2B is required, in addition to the requirements of the B FLR, the instrument room door needs to be opened or removed to conduct the internal arc fault test.