The BM25 is designed for testing the insulation of high voltage electrical equipment and the wide voltage range also allows it to be applied to low voltage equipment.
Generators, motors, transformers, cables and switchgear require effective maintenance and the test techniques on the Megger range give valuable diagnostic information.
‘Spot’ Insulation tests that are the most widely used, check on the general condition of electrical insulation, called up in most standards covering equipment design, testing,installation and maintenance.
Insulation suffers from gradual steady decline, as well as occasional sudden damage; the effects of dirt, grease, moisture, vibration an chemical attack can be tracked through the recording of Polarisation Index tests which remove the temperature dependence of raw Insulation resistance measurements.
For finding more localised insulation problems, the BM25 includes both Step Voltage and Dielectric Discharge tests. Step Voltage identifies local weak spots because they respond differently as the electrical stress is increased, while the Dielectric Discharge test can show up a single bad layer in multilayer insulation. The key to Predictive Maintenance is the trending of diagnostic tests and this is facilitated on the BM25 by the ability to use a PC to store results over time for trend analysis.