Abstract

Partial discharge measurements on transformers and rotating machines are an accepted tool of quality control, in factory and on site. Common methods to improve the quality of noisy PD data are filtering and gating. Recently a new method was introduced, which is able to clearly separate different PD sources within the DUT as well as separate PD from noise. This multi-channel synchronous measuring method compares amplitude relations of simultaneous PD sources of three phases (3PARD).

PD pulses propagate from its origin to the decoupling site, even cross-coupling to the other phases. PD from different locations inside the insulation will lead to unique pulse triples at the 3 decoupling positions. The amplitude relations of the 3 synchronous decoupled pulses of one pulse source will be nearly constant. That allows a classification of different noise sources and single PD failures within the DUT by comparison of these amplitude relations.

As a new approach of PD source separation the 3PARD method was adapted to the 3-Center-Frequency-Relation-Diagram 3CFRD. This technique allows PD and noise  separation by the comparison of the frequency spectrum of different PD mechanisms and noise pulses. In real-time a diagram can be constructed with similar clusters as the familiar 3PARD. As 3CFRD is not inevitably linked to 3-phase systems like power transformers it can also be applied on single phase transformers, VTs and CTs. This paper will present promising results from the latest multi-channel PD measurements.