A helping hand for insulation testing above 1 kV

Electrical Tester – 29 June 2018

Engineers throughout the electrical industry are discovering that insulation testing at 5, 10 or

 even 15 kV can be a very useful tool, particularly for fault detection on high voltage equipment, and for providing early indications of insulation degradation. But if it is to give dependable results, and if safety is to be assured, testing at these high voltages must be carried out in accordance with appropriate procedures. It is also highly desirable for those performing the tests and interpreting the results to have a good understanding of the basic principles involved.

With these needs in mind, Megger has produced an informative and comprehensive publication entitled A Guide to Diagnostic Insulation Testing Above 1 kV. This invaluable booklet can be downloaded free of charge from the Megger website at www.megger.com/support/technical-library.

Written by Megger experts with wide practical experience of high voltage insulation testing, the publication starts at a basic level, explaining what insulation is and what causes it to degrade, before proceeding to explain the ways in which insulation resistance can be measured, and how the test set should be connected to various types of equipment, including power cables, power circuit breakers, transformers and generators.

A whole section is devoted to the important and often misunderstood topic of the guard terminals which, when correctly used, reduce or even eliminate the effects of surface leakage on insulation measurements. Other sections explain the differences between and relative merits of spot reading, timed, polarization index (PI), step voltage, ramp voltage and dielectric discharge tests.

The guide also features useful appendices, the contents of which include potential errors sources and how to avoid them, a discussion of CAT safety ratings and details of the latest models in Megger’s extensive range of high-voltage insulation testers.

Illustrated throughout with clear and informative diagrams, graphs and tables, this 36-page publication is a useful – and cost-free – addition to the reference library of any engineer or technician whose work involves carrying out or analysing the results of insulation tests.