Most educational electrical power laboratories do not have access to a working 69-kV SF6 Puffer Circuit Breaker. At XXX, a utility consortium has donated a Siemens SP-72.5-40, 1200 A continuous, circuit breaker. The students perform travel time, insulation resistance, contact resistance, and power factor/dissipation factor testing on this breaker. This paper will discuss the problems encountered running these tests with undergraduates, including safety and power concerns. It will also discuss the student’s interactions and their impressions of the testing, and look at methods to evaluate how well they learned the testing methods and the circuit breaker operational concepts. The travel time test requires that both 120 Vac (for the compressor) and 125 Vdc (for the controls) be provided to the breaker. On the breaker tested, a large spring is used to open the interrupters, while a pneumatic system is used to close the breaker. A Doble TDR 900 is used to perform the test. This test instrument has inputs for 1) the linear transducer that measures the movement of the operating mechanism, 2) the status (open or close) of all three interrupters, 3) the current through the trip and open coils, and 4) the battery (or dc supply) voltage. It controls the circuit breaker tripping and closing so that trip, close, Trip-Free (CO), Reclose (O-C), C-O, O-CO, and O-C-O tests can be run. A Megger MIT525 is used to perform the insulation resistance and polarization index tests. Power to the breaker must still be provided for this test since the interrupters are tested in both open and closed positions. A DV Power Micro Ohmmeter RMO200G is used to perform the contact resistance test at 200 A. Finally, a Megger Delta 3000 is used to perform the power factor/dissipation factor tests at 10 kV. This test also requires that the circuit breaker is powered, since, again, the interrupters are tested both the open and closed position. In addition to learning how to use the test equipment safely, the students must also learn the software to run the tests and collect the data. It is hoped, that this paper provides insight in testing large circuit breakers and suggestions for others that are interested in running these tests.
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