13 / 2024-03-22 21:10:13

Design and Unit Test of a Dead-tank 550 kV Extria-high Voltage Multiple-break Fast Vacuum Circuit Breaker

fast vacuum circuit breaker,multiple-break,vacuum interrupter,unit test

The objective of this study is to present the design and unit test of a dead-tank 550 kV extra-high voltage multiple-break fast vacuum circuit breaker (FVCB). The FVCB consists of three units, with each unit comprising two parallel-connected circuit branches. Each circuit branch contains two series-connected modular 72.5 kV FVCBs. The modular 72.5 kV FVCB is designed to interrupt a nominated short-circuit current of 80 kA, by adopting a pair of cup-type axial magnetic field (AMF) contacts in the vacuum interrupter. The contact diameter is 100 mm. The contact material is arc-melting processed Cu50Cr50. An elaborately designed oil damper is used to achieve a high initial opening velocity v₁ of 5.2 m/s and a relatively low opening velocity v₂ of 1.7 m/s. Where v₁ is defined as an average velocity from the departure of the contacts to the first half contact gap of 30 mm in the opening operation; v₂ is defined as an average velocity across the full contact gap. In this way, an arcing time window from 3.8 ms to 12.8 ms is verified in a series 80 kA short-circuit current breaking test. Moreover, a prototype of 1/3 unit 550 kV FVCB is developed. The dielectric test is performed on the prototype with no disruptive discharge occurring. The test includes a short-time power frequency withstand test of 314 kV/ 1min and a consecutive lightning impulse withstand test of 615 kV with both polarities. The dielectric test takes consideration of a non-uniform distribution factor, 10%, of the stressed voltage across the 550 kV FVCB.