1、 The essence and harm of partial discharge

Early characterization of concealed insulation defects

Partial discharge occurs inside the insulation system (such as bubbles, impurities, cracks), and non penetrating discharge occurs when the electric field strength exceeds the local breakdown field strength. This type of discharge is invisible to the naked eye, but it continues to release energy, causing electrical corrosion (charged particle bombardment), chemical corrosion (generation of ozone and nitrogen oxides), and thermal effects (localized high-temperature carbonization) of insulation materials. If not detected in a timely manner, the insulation performance will deteriorate rapidly, ultimately leading to breakdown faults.

Chain failure risk

Equipment damage: Long term partial discharge may develop into phase to phase short circuit or ground short circuit, leading to serious accidents such as switchgear arc explosion and transformer burnout.

System paralysis: Equipment failure may cause voltage fluctuations in the power grid, unplanned power outages, industrial shutdowns, and socio-economic losses.

Security threats: Electromagnetic radiation, noise, and potential fire risks generated by discharge pose a threat to the safety of operation and maintenance personnel.

2、 Limitations of routine inspections

Partial discharge cannot be effectively identified through manual observation, touch, or conventional electrical testing (such as insulation resistance testing). The forms of energy release (sound, light, heat, electromagnetic waves) require professional sensors to capture, and the discharge signal is easily masked by environmental noise.

3、 The core value of professional testing

Basis for preventive maintenance

By using detection technologies such as ultrasound, ultra-high frequency (UHF), and transient earth voltage (TEV), the discharge source can be located and the discharge intensity (such as pC value) can be quantified. For example:

Ultrasonic method: captures mechanical vibration waves (>20kHz) generated by discharge, suitable for surface discharge positioning.

UHF method: detects GHz level electromagnetic waves, has strong anti-interference ability, and is suitable for monitoring gaps or glass windows in switchgear.

TEV method: By detecting nanosecond level electromagnetic pulses through metal shell gaps, live online monitoring is achieved.

By integrating multiple technologies, such as the APD300 online monitoring system, a baseline for equipment status can be established to achieve trend warning.

Standardized safety threshold

The test results can be compared with national standards to assess risks (such as air insulated cabinets with a partial discharge of ≤ 50pC at a voltage of 1.2Ur, which is considered high-quality), and guide operation and maintenance decisions:

Below 20dB: The equipment is functioning properly and undergoes regular inspections;

20-30dB: Shorten the detection cycle and track changes;

30dB: Immediately locate and repair.

Maximizing economic benefits

Early detection of partial discharge can avoid equipment replacement (such as switch cabinet replacement costs exceeding 100000 yuan), power outage losses (industrial users can lose tens of thousands of yuan per minute), and emergency repair costs.