PD 101 Series – #05: Advanced PD separation feature – 3PARD/3CFRD


3-Phase Amplitude Relation Diagram (3PARD)
Partial discharge (PD) events on one phase can be detected also on the other phases. Distinction between different PD sources and superimposed noise pulses is a challenge due to this coupling.
MPD 600, OMICRON high-end PD measurement and analysis system, provides powerful tools for separation of different sources of interference and easy visualization
The 3-phase amplitude relation diagram(3PARD) simplifies the differentiation of various PD sources and PD interferences. The three phases are measured synchronously. The results are displayed and combined in a single diagram, the 3PARD diagram. Figure 1 and Figure 2 exexmplify how the 3PARD diagram works.

In Figure 1, the transformer has PD source on phase L1 of 900pC. This PD signal is also coupled to other phases (L2 and L3) and measured at the same time, but at a lower value. Based on the amplitude on each phase, the cluster will be formed near Phase L1.

In Figure 2, external noise couples in every phase with an equivalent value. The vector addition will result with a cluster at zero. If the noise does not couple symmetrically in the test setup, the cluster will shift to around zero at the axis.

Figure 3 shows three different clusters in the 3PARD. The transformation of the clusters will allow users to distinguish PD signal from the disturbances and background noise.

3-Center Frequency Relation Diagram (3CFRD)
The 3CFRD characterizes PD sources by their frequency signature. Even for a single phase, or a single PD decoupling position, pulse triples can be acquired by using three different PD filter settings. The synchronous signal output from three filters with different center frequencies is visualized in a 3-Center Frequency Relation Diagram (3CFRD) for pulse waveform analysis.

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