Development of a 126kV Single-break Vacuum Circuit Breaker and Type Test

High-voltage vacuum circuit breakers in transmission voltage, as their environmental friendly characteristics, are drawing more and more interests all over the world. The objective of this paper is to present experimental results of type-test for a 126kV/40kA-2500A single-break vacuum circuit breaker based on a standard of IEC 62271-100. Two kinds of test circuits were adopted in type tests for the 126kV 140kA-2500A single-break vacuum circuit breaker. One is direct test circuit for test duties such as out of phase making and breaking test duties OPI and OP2. The other is synthetic circuit for test duties, such as terminal fault test, capacitive current switching test, short-line fault test, out-of-phase test, double earth test and electrical endurance test. Type-test results, for the 126kV vacuum circuit breaker, presented in this paper are as follows: Dielectric test, 230kV Imin power frequency voltage withstand test and lightning impulse voltage withstand test, with IS times 550kV in both of polarities; Short time withstand current with 4s duration and peak withstand current test with 100kA; Terminal fault test, including test duties: TIO, T30, T60, TlOOs, TIOOa; Out of phase making and breaking test, including OPI and OP2; Short-line fault test L90 and L 75; Double-earth fault test as well as capacitive current switching tests of class CI with test duties of LCI, CCI and LC2, CC2; Electrical endurance tests; And assessment of condition after test with a 80% of dielectric test voltage; Temperature rise test under rated current of 2500A; Mechanical endurance test of class Ml. In summary, the 126kV/40kA-2500A single-break circuit breaker passed the type tests.