Dissipation/Power Factor Measurement (Tan Delta) on Instrument Transformers

An insulation failure is often the reason for an instrument transformer (IT) malfunction. 

Factors which possibly accelerate the insulation's aging process:

  • Moisture ingression due to broken seals
  • Heat caused by the ambient temperature or sunlight

Older insulation can lead to high losses in the IT, which generates further heat. Since ITs are not actively cooled, old or degraded insulation can result in a failure or even an explosion. Fragments from the explosion represent a serious hazard for persons in the substation as well as for surrounding equipment.

Dissipation/power factor (tan(δ) delta) measurements help you determine the insulation condition. When using our testing systems, you will also be able to determine the dissipation factor at various frequencies and detect any signs of aging at an early stage. Thus, an IT can be replaced before any further damage occurs.

Expert recommends

CPC 100 + CP TD12/15 + PTM

With CPC 100 you can perform the most common electrical tests on power and instrument transformers, rotating machines, grounding systems, power lines and cables. CP TD12/15 completes your CPC 100 for dissipation/power factor and capacitance measurements.

The CP TD12/15 includes a high-voltage source (12 kV/15 kV, 300 mA), a reference capacitor and measurement electronics. It achieves laboratory precision even in environments with strong interferences.

Benefits of this solution

Other solutions


The portable TANDO 700 system offers high-precision measurement of dissipation/power factor (Tan Delta) and capacitance for high-voltage laboratory tests, such as routine and type tests, on instrument transformers. TANDO 700 also measures additional parameters such as power, current, voltage, impedance and frequency. TANDO 700 software shows you all measurement data in real-time, displays related trends and enables you to create customized reports. 


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