Transient Earth Voltage Sensor Research Articles

Defect Localization Inside Simulated MV Switchgear Based on Cumulative Energy Curve Using Transient Earth Voltage Sensors

The partial discharge (PD) leads to catastrophic failure of the medium voltage (MV) switchgear insulation. Determination of the PD source (defect) location in high voltage (HV) equipment is very important in the maintenance procedures and in isolating the root cause of PD generation. In this paper, the transient earth voltage (TEV) detection method was used to acquire defect-initiated PD signals in a simulated MV switchgear model. An array of four TEV sensors were placed on the surface walls outside an MV switchgear tank to acquire the PD signals generated from the known location(s)/coordinates of sharp needle type defect inside the tank. The time difference of arrival (TDOA) between signals that are captured by the TEV sensors array was critically analyzed. Estimating the TDOA between PD signals generated by PD source at a known location with high accuracy is of great importance for accurate defect localization. The cumulative energy method (CEM) is used to estimate the onset time point of each TEV signal. The estimated TDOA by the cumulative energy method is compared with actual and expected TDOA based on known coordinates of PD source and TEV sensors. Experimental data are used as a basis for determining the TEV method accuracy for PD source localization. Experimental results show the average error of time difference is about 1.34 ns, which is equivalent to the propagation distance of 0.4 m.

Partial discharge detection method for vacuum leakage diagnosis of a vacuum interrupter

Vacuum circuit breakers (VCBs) have been widely used in the medium distribution voltage range of 12–38 kV for more than half a century. Recent interest for them is because of the loss of vacuum in a vacuum interrupter (VI). Generally, the leakage is an improbable event during the expected lifetime of typically 20–30 years, while there are some reports that VIs beyond their expected lifetime have a significantly higher leakage rate. To keep the high reliability of middle voltage VCB, even for the high voltage VCB, it is necessary to develop the earlier detection method of vacuum leakage from VI. In the present study, an experimental setup with a partial discharge (PD) detecting system for detecting vacuum leakage from a test VI was constructed. The internal pressure of VI was arbitrarily regulated in the range of 0.02–100 Pa through an insulating tube using several valves. A detecting resistor of 1 kΩ was connected to a plane electrode located outside 115 mm away from VI to measure the PD current due to discharges inside the VI. A current transformer (CT) was also placed below the plane electrode. Sensors with different specification for PD detection, such as a transient earth voltage sensor, a horn antenna, and an acoustic emission sensor, were investigated and characterized. As a result of pressure dependence of PD inception voltage, it follows the left side of Paschen's Law in the pressure range more than 2.0 Pa, while no discharges occurred below 2.0 Pa. To analyze the PD charge and rise time from measured waveforms, the PD mechanism in the medium voltage range inside the VI was discussed. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Study on Pattern Recognition of Partial Discharge Stage in Switchgear Using TEV Amplitude-Number Chart

Partial discharge is one of the main causes of insulation condition assessment. Transient earth voltage (TEV) method is widely used in partial discharge detection of switchgear. This article simulated the actual fault defects in the switchgear. A TEV sensor was designed to measure the TEV signal generated by internal partial discharge. The amplitude and number of triggers of the TEV signal pulse were counted. A method for TEV amplitude-number chart was proposed. The similarities of spectra at different voltages were compared and the support vector machine (SVM) algorithm for verification was used. The results show that the matrix similarity comparison method and support vector machine algorithm can be used to analyze the amplitude-number chart of TEV pulse under different voltages. The partial discharge stage can be recognized by using TEV amplitude-number and the state of the switchgear can be predicted.

Analysis of PD Signal for Condition Monitoring of MV Switchboards by the Measurement of Transient Earth Voltage

This paper dealt with the application of transient earth voltage (TEV) sensors for the online measurement and analysis of partial discharge (PD) in medium-voltage switchboards. To simulate the typical insulation defects in the switchboards, four types of artificial electrode systems, including high-voltage protrusion, low-voltage protrusion, particle-on-conductor, and void inside cast-resin potential transformer were fabricated. A TEV sensor with a frequency range of 1–150 MHz and a non-inductive resistor were used to detect the PD-induced TEV signal and the PD voltage pulse, respectively. The frequency spectrums of TEV signals were analyzed, and it was found that they had a mutual frequency range of 5–50 MHz. However, the amplitude of TEV signal was not proportional to the apparent charge specified in IEC 60270, resulting the difficulty of quantification of PD. The phase-resolved partial discharge patterns were acquired using the TEV sensor and the developed measuring algorithm, by which distinguishable patterns were obtained from different defects.

Transient Earth Voltage Measurement in PD Detection of Artificial Defect Models in $\hbox{SF}_{6}$

This paper mainly discussed the utilization of transient Earth voltage measurement (TEVM) in partial discharge (PD) detection of gas insulation switchgear. Four typical artificial defect models in SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> such as spikes fixed on high voltage (HV) conductor, suspended metals, voids in dielectric, and metal particles on the surface of dielectric had been used as test objects in ac PD experiments with the aid of the synchronized PD signals sampled from a transient Earth voltage sensor, photomultiplier, Rogowski monitor, and PDCheck system. The measuring results of TEVM results, which included the phase distribution of PD, the relative amplitude, and the pulse number of different voltage thresholds, showed good consistency with three other methods and had better sensitivity of detection in spark or corona PD patterns. For further study, the frequency distributions of the three PD patterns were analyzed and discussed for understanding the different measurement sensitivities showed in different typical defects in SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> . In addition, TEVM was applied to detect PD under oscillating impulse voltage. As an example, the needle-plane electrode with short gap was adopted under 613.2-kHz oscillating impulse, which showed the effectiveness in this kind of detection.