Due to partial discharges (PD), the insulation system of high voltage equipment is subjected to a series of stresses that, individually or combined, are responsible for insulation degradation.

These insulation stresses can be classified as follows:

The electric charges that are products of PD can increase the local electric field concentration.


The energy released by PD increases the local temperature, which can trigger the formation of new chemical bonds.


(i) Particles originating from PD can hit the insulation system's surface at considerable speeds, causing surface degradation.

(ii) Chemical bonds can be broken or altered due to the energy gain of the particles.


(i) Changes in chemical structure are caused by particles and thermal, mechanical, and impact stresses.

(ii) The possibility of exothermic reactions that can damage solid insulation.


(i) Charges released by partial discharges can interact with the electric field, causing mechanical vibrations.

(ii) Attraction and repulsion between trapped charges can cause local mechanical damage.

The different physical effects can be captured by sensor elements. The following figure summarizes the main effects and detection methods, making it evident that more than one method can capture the same occurrence by being sensitized in different ways.


In this context, the objectives of PD measurement are:

Insulation Degradation: Activators and Measurement Techniques

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