Klaus Spitzenberg - Megger Support, Germany
Condition analysis of gas-insulated medium voltage circuit breaker systems is now practical and cost effective.
Working with energy distribution utilities Syna and Westnetz, Megger has developed techniques that make it possible to determine the condition of enclosed medium-voltage circuit breakers safely and cost-effectively. These techniques, which also allow first-trip testing to be performed, are based on connecting a Megger TM1800 or TM1700 circuit breaker analyser to the Voltage Detection System (VDS) via an adaptor. This opens up a whole range of new possibilities for system operators, as it means that it is no longer necessary to spend time isolating the circuit breakers for tests.
A definite need for testing
As gas-insulated medium-voltage circuit breaker systems are housed in enclosures, it is often impossible to use established condition analysis methods – the process would simply be too laborious, time consuming and uneconomical. However, there is a definite need to test these systems, as even components that are nominally maintenance-free need testing.Indeed, German law, and the law of most other countries, dictates that all work equipment must be tested regularly, using tests based on an assessment of the hazards that might arise from the equipment. And gas-insulated medium voltage circuit breakers most certainly fall into the category of work equipment. The new testing techniques make it easier for switchgear users to meet their legal obligations, as well as providing them with invaluable information to aid effective maintenance planning.
Isolation no longer needed
With the new techniques, it is no longer necessary to isolate the circuit breakers when evaluating their condition. The test instrument is connected to the capacitive Voltage Detection System via an adapter. It’s also connected to a trigger box and, via current clamps, to the medium-voltage circuit breaker system. A TM1700 circuit breaker analyser or a TM1800 analyser , shown in Figures 1 and 2, may be used. All key parameters can be measured and recorded without the time-consuming isolation and grounding procedures that are needed with other testing methods. In addition, no connections are needed to secondary circuits.