Partial Discharge (PD)
Localized electrical discharges in small insulation regions not bridging electrodes, indicating defects or aging.
PD is a localized discharge bridging only part of insulation between conductors. Occurs in voids, cracks, or surfaces where local field exceeds breakdown strength of gas-filled cavities.
Most important insulation condition indicator. Progressive erosion through oil/paper decomposition, electrical trees, gas generation detectable by DGA.
Measurement per IEC 60270: typically <100 pC at 1.5x rated for power transformers. Online monitoring enables predictive maintenance. Methods: electrical, acoustic, UHF.
QDTB ensures stringent PD limits through rigorous insulation design, vacuum oil filling, and comprehensive factory PD testing.
Related Products
Related Terms
Dielectric Strength
The maximum electric field an insulating material can withstand before breakdown, measured in kV/mm.
Dissolved Gas Analysis (DGA)
A diagnostic technique analyzing gases dissolved in transformer oil to detect internal faults before they become critical.
Insulation Class (A/E/B/F/H)
Standardized temperature ratings for transformer insulation materials defining maximum operating temperatures.
More Terms Starting with “P”
Power Transformer
A large transformer (>10 MVA) used in transmission networks for stepping voltage between system levels.
Power Factor
The ratio of real power (kW) to apparent power (kVA) indicating how effectively electrical power is utilized.
Prefabricated Substation
A factory-assembled complete substation integrating transformer, switchgear, and protection for rapid installation.
Phasor Diagram
A graphical representation of AC voltage and current relationships in a transformer showing magnitude and phase angle.
More in “Diagnostics & Maintenance”
Dissolved Gas Analysis (DGA)
A diagnostic technique analyzing gases dissolved in transformer oil to detect internal faults before they become critical.
Furan Analysis
A diagnostic measuring furan compounds in transformer oil to assess cellulose insulation degradation.
Moisture Content
The amount of water in transformer oil and solid insulation, critical for dielectric strength and insulation life.
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