Partial Discharge Detection Method Research Articles

Defect simulation and state characteristic analysis of cable joints with tip defects

In recent years, the breakdown of the body and accessories of high voltage cables has increased gradually. Taking the tip defect of 110 kV high voltage cable joint as an example to carry out electric field simulation analysis, the distribution and change law of electric field under this defect are put forward. Based on full working condition detection platform of high voltage cable, the simulation test of the defect is carried out. The effectiveness of various charged detection methods and on-line monitoring methods has been studied, and the variation rules of cable state under different working conditions have been obtained. The results show that, when tip defect is between stress cone silicon rubber and main insulation of cable body, electric field distortion around the tip shows discharge, and the breakdown potential is 83 kV. The high frequency partial discharge detection method and ultrasonic partial discharge detection method can detect the defects effectively, among which anti-interference ability of high frequency partial discharge detection at the capacitive arm is the best, and detection sensitivity of the grounding current is higher in the on-line monitoring. The thermal efficiency of load current has little effect on development of tip defects. But with the increase of test voltage, the high frequency emission volume increases obviously and breakdown occurs easily at higher voltage.

Field verification of a novel and simple partial discharge detection method for generator applications

This study introduces a simple and novel partial discharge (PD) detection method for generator condition monitoring applications. The proposed method uses statistical operator ‘Variance’ which is proportional to the power of an electrical signal. It was validated by field measurement conducted at four in service hydro-generators: two having heavily aged windings and the other two having identical new. First, accuracy of detecting PD pulses was verified by comparing with wavelet-based method. The proposed method detected all the PD pulses with a ‘Precision’ higher than 90% and recall of 100%. As the second step phase resolved PD (PRPD) patterns generated using the proposed method were compared with commercial PD monitoring systems. It was found that the overall similarity was above 0.75. Finally, extracted PD pulses were used to calculate the polarity wise dissipated PD energies. The calculated energies were correlated with identified PD sources through series of off-line tests and visual inspections. It was observed that discharges due to loosen windings and corona activity were well correlated with estimated PD energies. All these validation processes indicated that the proposed method effectively and accurately detect PD pulses and can be used as a diagnostic tool for generator applications.

Evaluation of UHF Transfer Function in a Power Transformer for Real-Time Partial Discharge Detection

The UHF transfer function is significant for a short-range communication system, e.g., a real-time diagnosis of partial discharge (PD). Real-time diagnosis of the PD has become a challenging topic of improving the diagnosis of high voltage equipment, including a power transformer. Further, the PD detection in high voltage equipment is critical since the PD can cause severe damage to electrical systems. The PD detection methods are classified by a phenomenon of the PD. The PD detection by electromagnetic (EM) method is regulated by IEC TS 62478, which specified the UHF band for the PD detection in power transformers. Hence, an evaluation of frequency characteristics is essential to achieve an excellent diagnostic performance. In this paper, a complex form of channel analysis is applied with the PD detection method. The measurement model in a power transformer is proposed. The optimum receiver is introduced to maximize SNR and hence it is easy to analyze the results. The results were analyzed by using magnitude, phase, group delay, received waveform, and path loss parameters. The results show that the measured channel is affected by the structure of the power transformer. The contribution of this research is useful for improving the precision of the PD detection with EM method and building an accurate real-time partial diagnosis via a smartphone or laptop computer.

FEM based 3D modelling of partial discharge detection and localization in an oil-filled power transformer using piezoelectric acoustic sensor

Abstract The main cause of insulation degradation is due to partial discharges (PDs) occurring inside the transformer, and its detection and localization are the most effective, non-destructive methods to assess the insulation condition of the transformer. Among the PD detection methods, the acoustic PD detection technique is popular because of its various advantages. The acoustic PD detection method for accurate PD source localization becomes quite challenging when PD occurs inside the transformer core and windings. As the acoustic sound wave can be distorted and vibration with its distribution, so the type of PD sensors with their setting in the transformer should be thoroughly investigated and chosen. In this work, via simulation, the acoustic sound distribution inside the power transformer due to PD occurs is studied. Based on the knowledge of acoustic pressure wave distribution, a Lead Zirconate Titanate (PZT-5H) sensor is designed using Finite element method based COMSOL Multiphysics software and placed it on the outer walls of the transformer for PD detection and localization. The PD induction position has been recognized from the sensor signal using an artificial neural network. The results of PD detection and localization by the proposed piezoelectric sensor and COMSOL probe point are in good agreement.

Corrections to “A Novel Partial Discharge Detection Method for Power Transformers on Site Adopting its Component as Ultra-High Frequency Sensor”

Corrections to “A Novel Partial Discharge Detection Method for Power Transformers on Site Adopting its Component as Ultra-High Frequency Sensor”

Principles and Applications of UHF Method for Partial Discharge Detection in GIS

In this paper, the causes of partial discharge in GIS and the existing detection methods are described, and signal processing and pattern recognition method of insulation defect in UHF detection method are introduced emphatically.

Influence of PD source and AE sensor distance towards arrival time of propagation wave in power transformer

Partial discharge (PD) often begins with cracks or gas-filled voids in solid insulation or with gaseous bubbles in liquid insulation. These presences can degrade the quality of insulator. PD detection can identify these cracks at high voltage equipment such as power cables and power transformer at the early stage. One of PD detection methods is acoustic emission (AE) detection. PD produces an ultrasonic signal that can be captured by an AE sensor. The signal captured is then analysed by capturing the time of the receiving signal onto the sensor. The information related to time can be used for allocating the PD for maintenance purpose. This paper shows the influence of the distance between PD source and the AE sensor towards the arrival time of propagation wave in power transformer. In this study, the four placements of sensors were analysed by having three possible PD sources to represent the variety of distances between the PD source and the sensor. The simulated signal is generated by MATLAB and the arrival time is captured using time of arrival (TOA) method. The time captured and the distance between the PD source and arrival time showed that the relationship is proportional to one another.

A Novel Partial Discharge Detection Method for Power Transformers On Site Adopting Its Component as Ultra-High Frequency Sensor

A novel partial discharge (PD) detection method for transformers on site adopting its component as ultra-high frequency (UHF) sensor is proposed. The bushing tap, iron core, and high-voltage (HV) winding can be used as internal UHF sensor for UHF PD detection. The experiments are carried out on an 80-kV transformer model to prove the validity of this method. The results show that the proposed method has good detection sensitivity and anti-disturbance performance, and can measure the PD signals without additional sensor. It solves the problem of the lack of available unused valves for internal UHF sensor installation while the external sensor is susceptible to interference. It provides a novel method with application prospects for PD detection of transformers in field.

Partial discharge analysis through Lissajous figure at low air pressures

The condition of electrical insulation is significant to the safety of electric power systems, especially to the More Electric Aircraft (MEA) that carries hundreds of people. The property of insulation will be reduced by aging and degradation which caused by partial discharge (PD). This has become a topic of extensive research and investigation. This paper represents the PD detection in terms of Lissajous figures which is a composite of two orthogonal oscillations with integral proportional frequencies. It can be used to calculate the total charge of PD transferred per cycle and the total energy of PD per cycle, thus the average charge and energy of a single PD activity can be recognized accompany with the current pulse PD detection method based on IEC 60270. These parameters could be useful to evaluate whether the insulation was damaged or how badly the damage was, hence to provide references to engineers for insulation condition judgment and design service plan.

High Accuracy Insulation Fault Diagnosis Method of Power Equipment Based on Power Maximum Likelihood Estimation

Partial discharge (PD) detection is one of the most effective methods for electrical equipment insulation fault diagnosis. Most existing PD detection methods are based on the processing of PD waveforms. However, the PD waveforms can be severely disturbed by the complex environment noise in substations, which can lead to great drop in detection accuracy. In this paper, we propose a PD detection method based on power maximum likelihood estimation. This method does not rely on the PD waveforms but utilizes a statistical approach of maximum likelihood estimation to analyze the distribution characteristic of PD signals, transferring the traditional method of waveform processing to a new perspective of statistical analysis. Eventually, the direction of arrival of the PD source can be derived. The proposed method has greatly improved the PD detection accuracy, especially in low signal to noise ratio (SNR) conditions. In simulation tests, it shows a better capability of noise immunity with signal SNR in [–5 dB, 5 dB] range. Field tests performed in a 110-kV substation (SNR around 5 dB) showed that the PD detection accuracy can be improved by up to 70% compared to the traditional methods. Our results may further promote the practical application of substation PD detection system.

Generation of acoustic phase-resolved partial discharge patterns by utilizing UHF signals

Detection of partial discharges (PD) is of great importance in the monitoring of high voltage devices and their early fault diagnosis. The ultrasonic sensing is one of the PD detection methods proposed in the literature. Normally, the partial discharge signals are mapped onto the voltage waveform to generate the phase resolved partial discharge or PRPD patterns for the fault type recognition. However, the travel time of ultrasonic signals hinders using a similar process in the ultrasonic PD method. In order to avoid this problem and to improve the ultrasonic PD detection by generating corresponding PRPD, this paper presents a novel method that utilizes ultra-high frequency (UHF) and ultrasonic signals of PD, simultaneously. To show the performance of this method, a circuit is built for ultrasonic PD detection first. In the next step, a wideband antenna is utilized, and its signals are compared with the ultrasonic sensor output to compensate for the PD travel time error. Finally, the PRPD patterns are generated and analyzed for five different configurations. The electrical PRPDs are measured for these cases and compared with the acoustic ones. The experimental results demonstrated in this paper prove the potential of the proposed idea to generate acoustic PRPD for the purpose of PD type recognition.

Using ANN and SVM for the Detection of Acoustic Emission Signals Accompanying Epoxy Resin Electrical Treeing

Electrical treeing is one of the effects of partial discharges in the solid insulation of high-voltage electrical insulating systems. The process involves the formation of conductive channels inside the dielectric. Acoustic emission (AE) is a method of partial discharge detection and measurement, which belongs to the group of non-destructive methods. If electrical treeing is detected, the measurement, recording, and analysis of signals, which accompany the phenomenon, become difficult due to the low signal-to-noise ratio and possible multiple signal reflections from the boundaries of the object. That is why only selected signal parameters are used for the detection and analysis of the phenomenon. A detailed analysis of various acoustic emission signals is a complex and time-consuming process. It has inspired the search for new methods of identifying the symptoms related to partial discharge in the recorded signal. Bearing in mind that a similar signal is searched, denoting a signal with similar characteristics, the use of artificial neural networks seems pertinent. The paper presents an effort to automate the process of insulation material condition identification based on neural classifiers. An attempt was made to develop a neural classifier that enables the detection of the symptoms in the recorded acoustic emission signals, which are evidence of treeing. The performed studies assessed the efficiency with which different artificial neural networks (ANN) are able to detect treeing-related signals and the appropriate selection of such input parameters as statistical indicators or analysis windows. The feedforward network revealed the highest classification efficiency among all analyzed networks. Moreover, the use of primary component analysis helps to reduce the teaching data to one variable at a classification efficiency of up to 1%.

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.

A Partial Discharge Detection Method for SF6 Insulated Inverted Current Transformers Adopting Inner Shield Case as UHF Sensor

A partial discharge (PD) detection method for SF6 insulated inverted current transformers (SIICTs) adopting an inner shield case as an ultra-high frequency (UHF) sensor is proposed in this paper. The inner shield case is a component of the SIICT. Its structure is similar to that of an antenna and can be used as a UHF sensor to measure the PD UHF signal. A 110 kV current transformer is used as an experimental object and the voltage standing-wave ratio of the inner shield case is calculated. The validity and sensitivity of this method are proved by experiments with ac voltage. This PD detection method solves the problem that the UHF sensor is difficult to mount inside current transformers and provides a novel method for PD detection of SIICTs.

Study on localization of transformer partial discharge source with planar arrangement UHF sensors based on singular value elimination

The large-scale power transformer gap leakage electromagnetic wave partial discharge detection method belongs to the external UHF detection method. This method can perform partial discharge insulation detection on the large-scale power transformer that is running without any modification of the power transformer, and the principle is simple and convenient to use. We have studied the reliability and the leakage electromagnetic wave propagation characteristics. However, this method requires UHF sensors in the same gap plane. When performing PD localization, it has the shortcomings of large positioning error and easy deviation of positioning results due to on-site noise pollution. For this problem, this paper proposes a PD source localization method based on singular value elimination. This method maps the three-dimensional coordinate sample set of the PD source to one-dimensional coordinates, and uses the improved box-plot diagram method to eliminate the singular values. Then the least square method is used to find the optimal coordinate of the real PD source. The proposed method has the advantages of greatly improving the data utilization efficiency of the PD sample set and effectively eliminating the singular values. Finally, the experimental verification of the proposed new method is carried out. The experimental results show that the proposed localization method can effectively improve the localization accuracy of PD source.

PD measurements, failure analysis, and control in high‐power IGBT modules

Increased voltage blocking capability and the development of packaging technology for IGBTs can enhance the local electric field that may become large enough to increase partial discharges (PDs) within the module. The study presents a survey on (i) simulation the electric field within an IGBT module; (ii) current standards for evaluation of the insulation systems of IGBTs; (iii) PD detection and localisation methods as well as other diagnostic and quality control test methods about IGBTs; and (iv) various methods for PD control in an IGBT module. The survey shows remarkable technical gaps in all four areas. More sophisticated numerical and theoretical techniques are needed to model complicated geometries, e.g. extremely sharp edges of the copper metallisation and protrusions in the substrate, and composite non-linear field grading materials. There is no model to take into account defects in the gel and on the ceramic substrate. IEC 61287-1 cannot sufficiently assess the behaviour of PDs on IGBT module under the actual operating conditions exposing fast rise pulse-width modulation-like voltages. There is no agreement on the exact origin and location of PDs in the module with relying on measured phase-resolved PD patterns. PD control methods using non-linear grading materials are not mature enough.

A Novel GIS Partial Discharge Detection Sensor With Integrated Optical and UHF Methods

A novel gas insulated switchgear (GIS) partial discharge (PD) sensor with integrated optical fiber and ultrahigh frequency (UHF) method is developed in this paper. The integrated sensor is formed by placing an optical fiber on the surface of the UHF sensor. The novel sensor can be mounted inside the GIS and measure the PD through optical and UHF signals at the same time. The validity and sensitivity of the sensor are proved by experiments on a physical 110 kV GIS. This PD detection sensor solves the problem that the optical fiber is difficult to be mounted inside GIS and provides a novel method for PD detection in GIS.

Primary Differential Pulse Method for Partial-Discharge Detection of Oil-Immersed Inverted Current Transformers

This paper proposes the primary differential pulse method (PDPM) for the live partial-discharge (PD) detection of oil-immersed inverted current transformers. The PDPM is based on the differential current measurements that are taken at the high-voltage side of the current transformer under test. The proposed technique overcomes the problem of an internally grounded test tap and identifies the internal PD based on the polarities of current pulses. The PDPM detection system is composed of current sensors, a data-acquisition module, a fiber-optics-based data-transmission module, and an operation mechanism with an insulating rod. The testing results prove that the designed system is effective for the live PD detection and can also effectively differentiate between PD and outside interference for oil-immersed inverted current transformers.

Measurements on partial discharge in on‐site operating power transformer: a case study

This study presents the case study of a substation in-service power transformer referred to the on-site partial discharge (PD) detection and evaluation methods. An original methodology for simultaneous application of three methods is proposed: electrical, acoustic and ultra-high frequency. Transformer is powered by the power grid and no external generator is required according to the proposed methodology. Furthermore, several possibilities of applying these concurrent measurements and benefits of such solution in terms of result interpretation, interference resistance and on-site measurement applicability are indicated. The proposed methodology allows for a fast, accurate and secure PD diagnostics in a power transformer under on-site operating conditions. In the described example, a failure as a surface PD in the vicinity of the first phase of high voltage winding output is detected. The research results provide the basis for further works on a diagnostic expert system, which exploits automatic detection and evaluation of the PD phenomenon in power transformers under normal operating conditions.

On-line Monitoring Device for High-voltage Switch Cabinet Partial Discharge Based on Pulse Current Method

The pulse current method for partial discharge detection is generally applied in type testing and other off-line tests of electrical equipment at delivery. After intensive analysis of the present situation and existing problems of partial discharge detection in switch cabinets, this paper designed the circuit principle and signal extraction method for partial discharge on-line detection based on a high-voltage presence indicating systems (VPIS), established a high voltage switch cabinet partial discharge on-line detection circuit based on the pulse current method, developed background software integrated with real-time monitoring, judging and analyzing functions, carried out a real discharge simulation test on a real-type partial discharge defect simulation platform of a 10KV switch cabinet, and verified the sensitivity and validity of the high-voltage switch cabinet partial discharge on-line monitoring device based on the pulse current method. The study presented in this paper is of great significance for switch cabinet maintenance and theoretical study on pulse current method on-line detection, and has provided a good implementation method for partial discharge on-line monitoring devices for 10KV distribution network equipment.