OMICRON electronics

PD phenomena are defined by IEC 60270 as localized dielectric breakdowns of a small portion of a solid or liquid electrical insulation system under high voltage (HV) stress. PD causes the insulation to deteriorate progressively and can lead to electrical breakdown. Therefore, the integrity of the insulation of HV equipment should be confirmed using PD analysis during its manufacturing, its commissioning, and during its life time.

In power transformers, PD can lead to corrosion on solid insulating materials, which may lead to a breakdown of the concerned operating component. PD can also decompose and pollute the insulating oil, so that the insulation properties of the oil can no longer be guaranteed. Measuring the PD of transformers is therefore essential at the beginning of their life-cycle and at the time of major repairs.

PD measurement may be used to determine the ageing condition of transformers and so conclude its remaining lifetime. Here, specific phase-related diagrams (PRPD) or fingerprints can assist in identifying fault types and in localizing the PD source.

The 3PARD (3-Phase Amplitude Relation Diagram) evaluation method allows separating different PD sources inside a transformer, or separating PD activity from noise or other signals. It is widely accepted by clients all over the world who use it even under noisy on-site conditions. The 3CFRD (3-Center Frequency Relation Diagram) enhances the 3PARD method and has shown promising results in laboratory and field tests.

3PARD and 3CFRD requires synchronous multi-channel PD data acquisition. Powerful hardware, in the form of the MPD 600, is needed to allow synchronous PD acquisition within nanoseconds.