IEC 60270: Partial Discharge Measurements

IEC 60270 – partial discharge measurements (previously high voltage test techniques) – is applicable to the measurement of partial discharge which occurs in electrical apparatus, systems, and components when tested with DC voltage or AC voltage up to 400 Hz.

Related Standards:

IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements

IEC 60060-2, High-voltage test techniques – Part 2: Measuring Systems

CISPR 16-1:1993, Specification for radio disturbance and immunity measuring apparatus and methods – Part 1: Radio disturbance and immunity measuring apparatus

Introduction to Partial Discharge Testing

Partial discharge is a major factor in insulation failure and the failure of electrical equipment like power transformers, HV cables, switchgear, motors and generators. PD measurement allowsoperators to perform effective and reliable insulation testing of these high voltage devices in applications like factory acceptance testing, on-site commissioning and routine electrical maintenance. PD analysis techniques must adhere to IEC 60270, the international standard for the measurement of electrical discharges in insulation.

Partial discharge testing, or PD testing, detects the presence of partial discharges in high voltage equipment. A partial discharge (PD) is a small spark within electrical insulation caused by insulation breakdown. PDs occur when an electrical insulation system experiences HV stress; a dielectric breakdown of a small portion of the insulation generates electrical discharges, which bridge the gap between two conducting electrodes. These dielectric breakdowns manifest across the surface of insulation material, in pockets found in solid insulation, within gas bubbles in liquid forms of insulation and proximal to electrodes in gases. As aging HV equipment continues to operate at high levels all around us, PD testing is more critical than ever to diagnose insulation failure before electrical stress shuts systems down and incurs expensive maintenance.

Basic Test Equipment Requirements:

Technical committees are recommended to use apparent charge as the measured quantity wherever possible. Other quantities may be used if the apparent charge is not appropriate for a given situation.
 

• High-voltage power supply with low background noise
• High-voltage connections
• Measuring system with known input impedance
• An impedance or filter for reducing background noise
• Coupling capacitor with low inductance
• Test object (usually denoted as a capacitor)

Partial Discharge (PD) – "Localized dielectric breakdown of a small portion of a solid or fluid electrical insulation system under high voltage stress, which does not bridge the space between two conductors. While a corona discharge is usually revealed by a relatively steady glow or brush discharge in air, partial discharges within a solid insulation system are not visible." [Retrieved February 11, 2013 from Wikipedia]

Partial Discharge Pulse (PD Pulse) – A voltage or current pulse resulting from a partial discharge occurring within the DUT (device under test). Appropriate detection circuits are introduced to the circuit to measure the pulse.

Discharge Mechanism – "PD usually begins within voids, cracks, or inclusions within a solid dielectric, at conductor-dielectric interfaces within solid or liquid dielectrics, or in bubbles within liquid dielectrics. Since PDs are limited to only a portion of the insulation, the discharges only partially bridge the distance between electrodes. PD can also occur along the boundary between different insulating materials. Partial discharges within an insulating material are usually initiated within gas-filled voids within the dielectric. Because the dielectric constant of the void is considerably less than the surrounding dielectric, the electric field across the void is significantly higher than across an equivalent distance of dielectric. If the voltage stress across the void is increased above the corona inception voltage (CIV) for the gas within the void, then PD activity will start within the void.