Electronics company Siemens reports that its Simetal Sivac-X 4K furnace switchgear has reliably switched a rated current of more than 4 500 A with a single circuit breaker during a successful type test according to IEC 62271.

Global testing services provider, the CESI group, performed the type test in Mannheim and Berlin, in Germany.

“This is significantly more than conven- tional furnace switchgears achieve. “The switchgear has a rated voltage of 40.5 kV and can supply electric arc furnaces (EAFs) with up to 300 MVA of power,” the company states.

The lightning impulse voltage is 200 kV, which makes the switchgear suitable for the North American market.

The switchgear has achieved the fault arc qualification of Internal Arc Classified A FLR of 40 kA/1s and also meets the highest demands for personnel safety.

The core component is the 3AH4 medium-voltage circuit breaker.

The Simetal Sivac-X 4K switchgear is designed to meet the extreme requirements of high-power EAFs and ensures a reliable power supply, as well as safe plant operation. Long maintenance intervals of up to 10 000 switching cycles increase availability and reduce operating costs.

The 3AH4 range of frequency circuit breakers are designed for use under extreme environmental conditions. These include high temperatures, high air pollution, unstable operating currents, frequent short-circuit releases and operating cycles with more than 100 switching cycles a day.

For this reason, the circuit breakers have a rugged, insulated support design and are equipped with freely accessible vacuum interrupters. This enables the interrupters to be replaced easily at the end of their life span of about 30 000 switching cycles.

The circuit breaker is specifically designed so that air can flow freely along the heat sinks. This enables the switching device to operate at up to 4 500 A in ambient temperatures of up to 40 °C without forced cooling.

The drive for the 3AH4 circuit breaker range is designed for up to 120 000 switching cycles over its entire life cycle.

About 400 furnace switchgear systems of the Simetal Sivac-X range are in use worldwide. Siemens offers switchgear for operating voltages ranging from 15 kV to 40.5 kV and rated currents from 1 250 A to meet the specific requirements of steelmakers.

According to the specific circumstances in the electric steel plant, the switchgear can be designed as an open unit with a permanently installed furnace circuit breaker, as a two-field system in a metal enclosure with a permanently installed circuit breaker, or as a single-field solution in a metal enclosure with a withdrawable furnace circuit breaker mounted on a traveling carriage.

The range of products also includes the customised protection circuit, which is essential for the operational safety of the vacuum circuit breakers and connected components.

The arcing-fault tested design, the metal encapsulation, interlocks, the capacitive voltage testing system and the IP4X degree of protection ensure maximum safety for personnel.

The first 3AH4 furnace circuit breakers, with rated currents of 3 150 A and 4 000 A respectively, are in use in steelworks in Germany and Turkey. The first US-bound 4 000 A switchgear is currently being delivered.

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