Performing high voltage insulation diagnostic tests (power factor, tan delta) on large capacitive specimens like generators, motors, capacitive voltage transformers and long lengths of cable always presents a challenge. Typically, these tests are performed with the aid of a resonating inductor to neutralise the load presented to the test set by the capacitance of the specimen. Unfortunately, these inductors are expensive, heavy and complicated to operate, which means that an alternative approach is desirable.
Such an alternative is now available and involves making use of an insulation diagnostic analyser like the Megger DELTA4000 that supports variable frequency operation. With this test set it is possible to test four times the size of motor /generator by carrying out the test at 30 Hz with a test voltage of 8 kV, rather than carrying out the usual 60 Hz/12 kV test. And, of course, no resonating inductor is needed.
