High-voltage circuit-breaker for 800 kv up to 1200 kv

Transmission of electrical energy at the highest voltages is constantly gaining in importance across the globe due to ever-increasing demands in load coupled with increasing diffculties in getting right of way to run additional lines at lower voltages.

The technical demands on high-voltage circuit-breakers have continued to increase in recent years. High levels of reliability under extreme climatic conditions and during earthquakes are essential prerequisites, as well as the ability to cope with high voltage loads, high breaking currents and fast break times.

Keeping in mind the reliability expected from circuit-breakers installed is systems with rated voltages over 550 kV, Siemens developed a circuit-breaker family with four interrupter units for 800 up to 1200 kV based on the established 3AP series. This series with self-compression type interrupting system and spring drive mechanisms now covers circuit-breakers in a voltage range of 72,5 kV to 1200 kV and a short-circuit breaking current of up to 63 kA. To face different environmental conditions the new circuitbreakers are available in LT design (currently 800 kV only) and different metal enclosed designs for use in DT, GIS or HIS installations.

This paper details the technical challenges in developing such ultra high voltage circuit-breakers and the solutions. The paper also describes the experiences of employing such devices and specifc features of the designs developed.

The new high-voltage circuit-breaker for 800 kV up to 1200 kV are extensions of themodular system of the 3AP2/3 circuit-breaker family for 420 kV and 550 kV with two interrupter units, closing resistors and spring drive mechanisms^[1].

With this development, all Siemens 3AP high-voltage circuit-breakers from 72,5 kV to 1200 kV have the same switching principle with self-compression system and spring drive mechanism ^{[2, 3]}.