High-power testing of 1100 and 1200 kV circuit breakers

Circuit breakers for UHV (Ultra High Voltage, rated voltage ?? 800 kV) are required especially for various large-scale transmission projects, China (1100 kV) being the most recent focal point but India to follow soon with 1200 kV. The testing of these apparatus is a challenge in itself. Having experience with a large number of EHV breakers, among which 550 kV types including single break, KEMA now has developed test installations for high-power testing EHV and UHV switchgear. Given the fact that these breakers consist normally of at leat two breaking chambers, a part of the test that have to verify the (fault) current interruption capability, can be performed using only half (or a quarter) of the breaker. For livetank breakers equipped with grading capacitors this is generally true. However, in order to meet the requirements for metal enclosed switchgear (as laid down in IEC 61633) of having the correct dielectric stresses between live parts and enclosure also during the interruption process, tests other than on the complete circuit breaker are technically incorrect. This resulted in the design, realization and testing of new circuits for UHV. Key feature is the use of a double stage synthetic circuit, one stage of which is placed in the vicinity of the testobject. This has the advantage that the test-object's enclosure can remain on ground potential. Various full-scale tests have now proved this principle to be effective for 800 kV and 1100 / 1200 kV on a full-pole basis. Examples of tests are demonstrated.