Partial Discharge Test System Research Articles

PD Characteristics and Parameter Extraction for EPR Cable Terminal in EMUs With Spike Defect at Low Temperature

Ethylene propylene rubber (EPR) cable terminals are widely used in high-speed railway trains. In the alpine environment, partial discharge (PD) and even breakdown failures caused by spike defects frequently occur in EPR cable terminals. To study the discharge development of cable terminals with spike defects in alpine regions, EPR cable terminal test samples with spike defects were made, and a low-temperature PD test system was built to simulate the environmental conditions in alpine regions. The characteristics of the lower PD spectrum were analyzed, and the influence mechanism of low temperature on the discharge activity was analyzed combined with the scanning electron microscope (SEM) scan. The research results show that the discharge development of the terminal spike defect can be divided into three stages: S1~S3. In S1 stage, the degree of PD at –30°C is weaker than that at 20°C dues to the low diffusion ability and weak polarization effect of carriers. In S2 and S3 stages, with the continuous discharge, low temperature makes the deterioration tolerance of ethylene propylene rubber material decrease more seriously, which promotes the development of discharge. The discharge phase interval is larger and the discharge activity is more intense at –30°C than at 20°C, and the breakdown time point is 11.6% earlier. By studying the characteristics of the spectrum, it is found that the deviation of PD φ- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q_ave</i> spectrum at –30°C from positive to negative is an important signal before the critical breakdown of cable insulation, which can provide a reference for judging the severity of terminal spike defects at low temperature.

Measurement and Diagnosis of PD Characteristics of Industrial Cable Terminations in Extreme Cold Environment

In the alpine region, there are many flashover failures of ethylene-propylene rubber (EPR) cable terminations due to cavity discharges in China high-speed railways (CHRs). The cable termination with cavity defects is used as test samples and a low-temperature PD test system is set up to study the characteristics of partial discharge (PD) of cavity defects in cable termination in those regions. Influences of the different temperatures on internal discharge in EPR insulation at −40°C and 20 °C have been analyzed. When the applied temperature dropped to −40°C, the PD initiation voltage and extinction voltage decreased by 31% and 28%, respectively, and the discharge pulse appeared at both positive and negative half-cycles. The results showed that, at 20 °C, the discharge was mainly caused by the internal discharge of the gas-filled cavity. Apart from the internal discharge of the gas-filled cavity, a marked trace of surface discharge was also detected at −40°C. Besides, the characteristics of PD development at −40°C are closely related to the discharge phase distribution and the asymmetry of the spectrum. The research can further reveal the development and evolution of PD of the gas-filled cavity and provides a basis for judging the severity of termination at low temperature.

Distributed Partial Discharge Detection Technology for High Voltage Cable Based on Ac Withstand Voltage

with the Development of Urbanization, It is More and More Urgent to Improve the Reliability and Stability of Power Supply. Due to the Consideration of Municipal Planning, Environment, Personal Safety and Other Factors, the Utilization Rate of Power Cables in Urban High-Voltage Transmission Channels Has Increased Dramatically. Accidents Such as Fire, Large-Area Power Failure and So on, Which Are Caused by Internal Insulation Defects of Cables, Defects in Joint Position Fabrication and Installation Process, Occur from Time to Time. This Paper Studies the Detection Method of Potential Insulation Defects in the Cable Interior and Joint Position Based on the Ac Withstand Voltage Partial Discharge Detection Technology, and Designs a Set of Distributed Partial Discharge Test System Based on the High Frequency Pulse Method to Detect the Interior, Middle Indirect Head and Terminal Head of the Cable. in the Field, the Distributed Pd Detection Technology Based on Ac Withstand Voltage Designed in This Paper Can Effectively Detect the Internal and Joint Insulation Defects of Power Cables, and Realize Fault Location, Which Has the Value of Practical Application and Promotion.

Effects of RTV Coating on the Discharge Characteristics of A Suspension Glass Insulator

DOI : 10.26650/electrica.2019.19024 The present study shows the effects of room temperature vulcanizing (RTV) silicone rubber high voltage insulator coatings on the discharge characteristics of a cap-and-pin type suspension glass insulator. The study covers both laboratory investigations and 3D electric field analysis, considering the coated and uncoated glass insulators. An ultraviolet corona camera is used to detect the location of the discharges, and a partial discharge test system is used to obtain the discharge patterns and pulse magnitudes. The experimental work is only conducted for 50 Hz power frequency voltage. In addition to the laboratory investigations, 3D electrostatic field analysis is performed to determine how the RTV coatings on the glass insulators affect the field distributions. Cite this article as : Ilhan S. Effects of RTV Coating on the Discharge Characteristics of A Suspension Glass Insulator. Electrica, 2019; 19(2): 173-181.

Study on Partial Discharge Performance Testing of High Voltage Cables for EMUs

EMU high voltage cable partial discharge detection is an important means that is to ensure the reliable operation of EMU. This thesis summarizes the causes of partial discharge of EMU high voltage cable, and the mechanism of its formation is analyzed, then the corresponding cable partial discharge model and its interference model are designed. The main components of the test system are introduced. The partial discharge test system for high voltage cable of EMU is tested on site, and corresponding test data is obtained and then analyzed. At the same time, measures of anti-interference on site are put forward. Partial discharge testing detects the potential risks through state detection, and handles this problem by taking some effective measures to reduce the operational risks of the power supply system and ensure the safety and stability of the vehicle operation.

Optical fiber‐triggered solid‐state switch applied in power cables damped AC voltages test system

The damped AC voltage (DAC) cable partial discharge test system is an effective approach to diagnose offline cross‐linked polyethylene (XLPE) power cables. The high‐voltage solid‐state switch, as its core component, should meet the requirements of withstanding the high voltage, short conduction time, and low resistance. This paper reports the development of a solid‐state switch for 35 kV DAC test system using insulated gate bipolar transistors (IGBTs) connected in series. To improve the synchronization of the trigger signal, a trigger circuit based on optical fiber is designed. In order to solve the unbalanced voltage distribution of multilevel IGBTs in series, an RCD (resistor–capacitor–diode) snubber circuit is designed and utilized. Especially, lithium batteries were used to drive the trigger circuit, thereby avoiding the problem of isolation of power supplies. Besides, the problem of high‐voltage insulation was solved by designing a reasonable structure and layout. Test results show that the proposed solid‐state switch, with partial discharge inception voltage &gt;62.5 kV, conduction time &lt;320 ns, and conduction resistance &lt;3.31 Ω, meets the special demands of the 35 kV DAC test system. It is demonstrated that the solid‐state switch based on optical‐fiber‐triggered IGBTs in series can be effectively applied in the DAC test system. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Partial discharge diagnosis by simultaneous observation of discharge pulses and vibration signal

Protrusion defects on inner conductor can seriously weaken the dielectric strength of gas insulated switchgear (GIS). In practice, pulse current method (IEC 60270) and vibration method sometimes are ineffective for this type of defect. Clarification of coincidence of partial discharge (PD) characteristics measured with both methods is very important for further application of the vibration method. In this paper, PD pulses and vibration signal recorded on enclosure generated from artificial protrusions mounted on inner conductor with different lengths and diameters were measured synchronously by using a 252 kV GIS PD test system. The test GIS was filled with the gas SF6 of the standard atmosphere pressure (i.e. 101 kPa), and the power frequency of the test voltage was 50 Hz. The pulse repetition frequency (PRF) characteristics and frequency-resolved vibration (FRV) characteristics under different discharge level were investigated. The dynamic response (DR) characteristics of the experimental GIS are also obtained by using the force hammer test. For a good understanding of PD vibration characteristics, the relationship between FRV, PRF and DR was analyzed in detail. To make more reliable operations of GIS, an improvement vibration method for protrusion defect detection was developed and applied.

Effect of repetitive square voltage frequency on partial discharge features

The inverter-fed motor is a key component of environmental-friendly hybrid cars, high-speed trains, and other industrial applications. After the widespread use of inverter-fed motors, the repetitive impulse surges from inverters were found to cause new insulation problems in inverter-fed motors that were linked to premature insulation failure. The partial discharge (PD) induced by the overvoltage inner stator windings was found to be the root cause of insulation reliability problems. To mitigate this problem, PD detection and life testing at repetitive square voltages should be performed on new types of insulation models and entire motor insulation systems. The obtained partial discharge inception voltage (PDIV) and lifetime of insulation in the tests can be used to evaluate the insulation status of inverter-fed motor insulation systems and thus to improve the insulation designs. At AC voltage conditions, the voltage frequency can significantly affect PD activity. At repetitive square voltage with rapid rise time, the influence of the square voltage frequency on PD activity should be investigated (1) to suggest values for the repetitive square voltage frequency selection for the PDIV and lifetime tests, and (2) to increase the signal-to-noise ratio when extracting PD pulses from strong disturbances generated by the operating switch of impulse generators. Therefore, the main purpose of this paper was to investigate the effects of repetitive square voltage frequency on PD events. Insulation models of both Type I (low-voltage inverter-fed motor) and Type II (high-voltage inverter-fed motor) were used to obtain single-PD and multi-PD statistical features, respectively. Experimental results indicated that higher frequencies caused less PD events with lower PD magnitudes and shorter delay times in one square voltage cycle. This phenomenon was attributed to the different surface charge decay ratios and the initial electron emission probabilities resulting from different square voltage frequencies. Finally, a number of considerations for PD measurements on inverter-fed motors were provided to improve the sensitivity of the PD test system and to obtain high objective insulation lifetime test results, which are used to assess the insulation status of inverter-fed motors.

Study of partial discharge characteristics at repetitive square voltages based on UHF method

Due to overvoltage produced by inverter output, inverter-fed motor insulation systems often experience fast electrical aging process, especially when partial discharge (PD) is incepted. Before putting into use, the PD detection should be performed on inverter-fed motors at repetitive square voltages to avoid the PD caused insulation deterioration when the motors are collected to inverters having specific characteristics. However, unlike PD tests at AC/DC voltages proposed in IEC 60270, the PD detection at repetitive square voltages is much more complex because of serious interference generated by impulse generator. To solve the problem, ultra-high frequency (UHF) method seems recommendable for its preferable signal-to-noise ratio (SNR). The chief aim of this study is to investigate PD pulse and statistical characteristics of turn-to-turn insulation for inverter-fed traction motors. A square-shaped Archimedes antenna, specially designed for the PD detection at repetitive square voltages of fast rise times, was used to perform PD tests on turn-to-turn insulation models. Time and frequency analysis results indicate that energy component of generator disturbance and PD pulses are mainly distributed in the 0–0.5 GHz and 0.6–1.5 GHz range, respectively. Based on the results, suitable filter was designed for power disturbance suppression. Additionally, resorting to the sensor unit (i.e. antenna and filter) and the PD test system, the PD statistical features at square voltages of different frequencies were obtained. Experimental results show that higher frequency will give rise, statistically, to PD of lower magnitudes distributing at smaller phases. A reasonable interpretation of this phenomenon was presented. Lastly, according to the PD statistical features, some suggestions for the PD detection system design, generator parameter optimization and the PD pulse extracting were given. The results of this work would be beneficial to the increase of the sensitivity when performing the PD detection on insulation systems for inverter-fed motors at repetitive square voltages and thus, improving the reliability of inverter-fed motors.