The aging of insulation leads to high losses, which can be determined with a power / dissipation factor (Tan Delta) measurement.

A wide frequency range from 15 to 400 HZ allows very reliable conclusions to be drawn about the insulation's condition. This allows you to identify wet and aged bushings, transformers, generators and other parts of high-voltage systems according to IEEE 62 (C57.152), IEC 60076-1 and -3, as well as the CIGRE "Guide for Transformer Maintenance". As recommended in the CIGRE Guide, testing is performed at variable frequencies to better diagnose signs of ageing in insulation.

Thanks to the measuring processes and selectable measurement bandwidths, exact measurements are even possible in areas with high levels of interference.


Tan Delta is an effective part of any condition monitoring regime for high voltage insulation. The information which can be captured during this test includes-

  • Capacitance
  • Dissipation factor tan δ (tan delta)
  • Power factor cos φ
  • Watt losses

If you require Tan Delta testing, call Megavar for professional service and advice.