Customization of American standard medium voltage switchgear

Domestic complete set manufacturers have become accustomed to buying ready-made cabinets for switchgear, which can be completed by assembling components, copper bars, secondary wiring, etc. Therefore, for American standard switchgear, many complete set manufacturers also want to buy ready-made cabinets and directly assemble them into American standard switchgear

Almost all domestic mid mounted cabinets have the same design, and the size of mid mounted circuit breakers is also basically the same. Insulation components, mechanical interlocking, etc. are also the same. Therefore, domestic switchgear can be divided and produced in batches through industrial cooperation.

Unlike the high homogenization of domestic switchgear, the products of major manufacturers in the United States are different. The external dimensions of the circuit breaker, handcart entry and exit mechanism, secondary plug connection, handcart position auxiliary switch TOC, circuit breaker opening and closing position auxiliary switch MOC, grounding contacts, etc. are all different.

The size of each contact is also different, so the manufacturers of the static contact, contact box, and current transformer on the contact box are different, so it is impossible to achieve a unified structural form and insulation components.

Taking the handcart entry and exit mechanism as an example, GE circuit breakers use two side screw nuts with the handcart entering and exiting the working position, while EATON and others use a middle arranged screw nut form, similar to low-voltage circuit breakers. After the circuit breaker is inserted into the cabinet, it engages with the nut and swings into the screw to drive the nut and move the handcart forward.

There are different products such as American standard circuit breakers, as well as crank arm rotation and propulsion mechanisms on both sides of the handcart.

Only ABB ADVAC/AMVAC has a chassis structure similar to that of domestic mid mounted circuit breakers, but with different widths and depths. It is designed with three stations and has two strokes of 250/370mm, which are 40mm to reach the test position, connected with a secondary plug, and then further 210mm to reach the working position.

Therefore, in general, it is necessary to purchase the circuit breaker together with its supporting compartment. The chassis and circuit breaker are used together, and only the circuit breaker is purchased without supporting drawings, making it impossible to produce supporting mechanisms such as circuit breaker rocking in and out. In addition, grounding contacts, secondary plugs, mechanical position indicators, level limit blocks, etc. also need to be coordinated with circuit breakers, which cannot be achieved simply by surveying.

Therefore, the ABB American standard ADVAC withdrawable circuit breaker is the easiest to design chassis components and cabinet front compartments. Some people say that it is almost impossible to design a universal compartment using American standard certified fixed circuit breakers with chassis and contact arms. The IEEE C37.20.2 standard is for withdrawable circuit breaker handcarts, and the accompanying circuit breakers are also withdrawable. There will be no fixed certified circuit breakers, and if they are not withdrawable, the circuit breakers will be equivalent to no American standard certification.

In addition, the primary contacts of the circuit breaker handcart are different, and the configurations of the contact box and static contacts are also different. The primary contact directly affects the core performance such as temperature rise and dynamic thermal stability, and cannot be randomly matched. The upper limit of temperature rise in the American standard is low, and it is not easy to pass the temperature rise test.

Choose appropriate (considering supply chain, price, delivery time, and performance parameters) circuit breakers and compartments as the front cabinet, and design the rear cabinet and busbar system independently. Customized design of American standard metal armored switchgear is the current solution.

The procurement of circuit breakers and their compartments also needs to consider the procurement of current transformers, voltage transformer handcarts, power transformer handcarts and their compartments. In addition, G&T grounding test handcarts that comply with IEEE C37.20.6 standards also need to be purchased as supporting equipment to meet project requirements.

The use of other switchgear accessories such as insulators and wall bushings must meet the non TYPE 1 insulation type requirements in IEEE C37.20.2 standard (i.e. the level of direct contact between insulation and live parts, and the level of live parts passing through insulation parts). The insulation material needs to pass the American standard D2303 trace resistance, D229 combustion, and UL94 V0 flame retardant tests, with high material and insulation part requirements. Compliant with American standard insulation component manufacturers, GE American standard medium voltage armored switchgear SECOGEAR suppliers, Zhejiang Jiangshan Jianghui Electric.