Slot Partial Discharge Meaning
Slot Partial Discharge Definition
Slot Partial Discharge Symptoms

The phase resolved partial discharge (PRPD) patterns of slot discharge are analyzed using a PRPD analyzer and the variation law of slot discharge patterns with voltage variation is illustrated.
Partial discharge measurement is routinely carried out to assess the condition of the insulation system of rotating machines (motors and generators), transformers, and gas-insulated switchgear. Partial discharge measurement system. A partial discharge measurement system basically consists of: a cable or other object being tested.
Tiara Vibrasindo Pratama 15 Rentang deteksi PD terhadap kerusakan akibat mekanisme kegagalan. 10 tahun untuk mesin 18kV. 5 tahun untuk mesin 13.8 kV. 2 – 3 tahun untuk mesin 6 kV. beberapa bulan untuk mesin 4 kV Partial Discharge Partial Discharge (PD) is an electrical discharge that does not completely bridge the space between.

In electrical engineering, partial discharge (PD) is a localized dielectric breakdown (DB) (which does not completely bridge the space between the two conductors) of a small portion of a solid or fluid electrical insulation (EI) system under high voltage (HV) stress. While a corona discharge (CD) is usually revealed by a relatively steady glow or brush discharge (BD) in air, partial discharges within solid insulation system are not visible.

Slot discharge refers to the observation that partial discharges (PD) may occur on the surface of the bar (half-coil), either within the stator core slot, or just outside of the slot. Figures 1-2 show photos of bars experiencing slot discharge considered as fairly serious and corrective action would be considered necessary. There are three. Partial discharge and applied voltage sampled by the oscilloscope is sent to the computer to complete data storage and further processing and analysis. Phase Resolved Partial Discharge Based on partial discharge measurement data during the whole lifetime of PI films, phase resolved PD pattern under.

PD can occur in a gaseous, liquid or solid insulating medium. It often starts within gas voids, such as voids in solid epoxy insulation or bubbles in transformer oil. Protracted partial discharge can erode solid insulation and eventually lead to breakdown of insulation.

Discharge mechanism

A partial discharge within solid insulation. When a spark jumps the gap within the gas-filled void, a small current flows in the conductors, attenuated by the voltage divider network Cx, Cy, Cz in parallel with the bulk capacitance Cb

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 that 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, PD activity will start within the void.

PD can also occur along the surface of solid insulating materials if the surface tangential electric field is high enough to cause a breakdown along the insulator surface. This phenomenon commonly manifests itself on overhead line insulators, particularly on contaminated insulators during days of high humidity. Overhead lines use air as their insulation medium.

PD equivalent circuit

The equivalent circuit of a dielectric incorporating a cavity can be modeled as a capacitive voltage divider in parallel with another capacitor. The upper capacitor of the divider represents the parallel combination of the capacitances in series with the void and the lower capacitor represents the capacitance of the void. The parallel capacitor represents the remaining unvoided capacitance of the sample.

Partial discharge currents

Whenever partial discharge is initiated, high frequency transient current pulses will appear and persist for nanoseconds to a microsecond, then disappear and reappear repeatedly as the voltage sinewave goes through the zero crossing. The PD happens near the peak voltage both positive and negative. PD pulses are easy to measure using the HFCT method. The HFCT is a 'high frequency' current transducer which is clamped around the case ground of the component being tested. The severity of the PD is measured by measuring the burst interval between the end of a burst and the beginning of the next burst. As the insulation breakdown worsens, the burst interval will shorten due to the breakdown happening at lower voltages. This burst interval will continue to shorten until a critical 2 millisecond point is reached. At this 2 ms point the discharge is very close to the zero crossing and will fail with a full blown discharge and major failure. The HFCT method needs to be used because of the small magnitude and short duration of these PD events. The HFCT method is done while the component being tested stays energized and loaded. It is completely non-intrusive. Another method of measuring these currents is to put a small current-measuring resistor in series with the sample and then view the generated voltage on an oscilloscope via a matched coaxial cable.

When PD, arcing or sparking occurs, electromagnetic waves propagate away from the fault site in all directions which contact the transformer tank and travel to earth (ground cable) where the HFCT is located to capture any EMI or EMP within the transformer, breaker, PT, CT, HV Cable, MCSG, LTC, LA, generator, large hv motors, etc. Detection of the high-frequency pulses will identify the existence of partial discharge, arcing or sparking. After PD or arcing is detected, the next step is to locate the fault area. Using the acoustic emission method (AE), 4 or more AE sensors are placed on the transformer shell where the AE and HFCT wavedata is collected at the same time. Bandpass filtering is used to eliminate interference from system noises.

Discharge detection and measuring systems

With the partial discharge measurement, the dielectric condition of high voltage equipment can be evaluated, and electrical treeing in the insulation can be detected and located. Partial discharge measurement can localize the damaged part of an insulated system.

Data collected during partial discharge testing is compared to measurement values of the same cable gathered during the acceptance-test or to factory quality control standards. This allows simple and quick classification of the dielectric condition (new, strongly aged, faulty) of the device under test and appropriate maintenance and repair measures may be planned and organized in advance.

Partial discharge measurement is applicable to cables and accessories with various insulation materials, such as polyethylene or paper-insulated lead-covered (PILC) cable. Partial discharge measurement is routinely carried out to assess the condition of the insulation system of rotating machines (motors and generators), transformers, and gas-insulated switchgear.

Partial discharge measurement system

A partial discharge measurement system basically consists of:

a cable or other object being tested
a coupling capacitor of low inductance design
a high-voltage supply with low background noise
high-voltage connections
a high voltage filter to reduce background noise from the power supply
a partial discharge detector
PC software for analysis

A partial discharge detection system for in-service, energized electric power equipment:

a cable, transformer, or any MV/HV power equipment
Ultra High Frequency Sensor (UHF) Detection Bandwidth 300 MHz-1.5GHz
High Frequency Current Transformer (HFCT) Bandwidth 500 kHz-50 MHz
Ultrasonic microphone with center frequency 40 kHz
Acoustic Contact Sensor with detection bandwidth 20 kHz - 300 kHz
TEV sensor or coupling capacitor 3 MHz-100 MHz
Phase-resolved analysis system to compare pulse timing to AC frequency

The principle of

Slot Partial Discharge