Synchronous multi-channel PD measurements and the benefits for PD analyses

Partial discharge (PD) measurements on transformers, cable systems and rotating machines are a worldwide accepted tool of quality control in factories and under on-site conditions. Common methods to improve the quality of noisy PD data are filtering and gating. Recently a new multi-channel synchronous method has been introduced, capable of separating PD from noise by comparing the amplitude relationship of simultaneous PD of any three channels (3PARD). PD pulses propagate from their origin to the decoupling site, and generate cross-coupling to other phases. PD from different locations inside the insulation will lead to unique pulse triples at any 3 decoupling positions. The amplitude relationship of the 3 synchronously decoupled pulses of one pulse source will be nearly constant. That allows a classification of single PD failures inside the device-under-test (DUT) by comparison of these amplitude relations. As an extension of this 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 single clusters representing different PD sources in accordance to their discharge physics. Additionally, 3CFRD is not exclusively applicable to 3-phase systems like power transformers, it can also be applied on single phase transformers, VTs and CTs. This paper presents promising results from the latest multi-channel PD measurements.