Partial Discharge Location Research Articles

Localization of Multiple Partial Discharge Sources in Air-Insulated Substation Space by RF Antenna Sensors Array

This paper proposes a method to localize multiple partial discharge (PD) sources in air-insulated substation by using radio frequency (RF) antenna sensors combining with clustering algorithm, which solves the problem that multiple PD or interference sources are difficult to localize in air-insulated substation (AIS). Our research group made four omnidirectional RF antenna sensors, the detection frequency band was 250 MHz-3 GHz, the voltage standing wave ratio (VSWR) of the RF antenna in the detection frequency band was less than 2, which meets the detection requirements. The scenes of multiple PD sources in AIS were simulated in the laboratory, the time difference of arrival (TDOA) was collected through four RF antennas, and the clustering effects of K-means and Two Step algorithms were compared. Based on the normal distribution characteristics of TDOAs and the better Two Step algorithm, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma $ </tex-math></inline-formula> -Two Step algorithm was proposed to process TDOAs and output the centers of TDOAs. Newton iterative algorithm was used to solve the localization equations. The results show that the average localization error of two PD sources was 0.21 m and that of three PD sources was 0.45 m. The PD localization tests were carried out in an actual AIS in China, the proposed method localized a corona discharge on a post insulator and a corona discharge on a disconnector. Through the verifications with an ultraviolet camera, it was obtained that the localization errors at each position were within the range of 0.6-2 m.

Iterative method for partial discharges location in power transformers

In this paper an efficient and fast iterative method has been successfully used for detection and localization of partial discharges in a power transformer. It is mainly based on finite elements method solving in an isotropic medium. Current methods for localizing mechanical waves emitted by partial discharges are subject to the use of at least three acoustic sensors. A new numerical localization method based on the Newton-Raphson iterative method is presented. It reduces the number of sensors to only two. The propagation of an acoustic wave (AW), initiated by a Gaussian-type partial discharge inside a power transformer is analyzed. The wave equation was solved numerically by finite element using Comsol Multiphysics software. Two sensors made possible to follow the spatio-temporal distribution of the acoustic pressure of five partial discharges distributed in different positions of the transformer. The performance of the proposed method is demonstrated through a comparison with a direct resolution method.

3D Localization Method of Partial Discharge in Air-Insulated Substation Based on Improved Particle Swarm Optimization Algorithm

Partial discharge (PD) localization in an air-insulated substation (AIS) can be used to assess insulation conditions efficiently. Many localization methods have been reported during the past few years. However, the error of the localization results has been large or the localization algorithm too inefficient. The reason is that the localization equation set is nonlinear and non-symmetrical. In this paper, an improved particle swarm optimization (PSO) algorithm is proposed to improve the localization accuracy in 3D. Firstly, the proposed localization method is based on the symmetrical antenna array and the location error distribution is analyzed. Secondly, the objective function of PSO is constructed using the error distribution. Specifically, the 3D location target is divided into two steps—plane coordinates and height. The two targets are optimized respectively. To verify the method, a test is carried out by a prefabricated fault bushing in the laboratory to compare with the existing methods. According to the results, the localization error is 0.21 m, which can locate the PD source accurately. A complete calculation takes 42.29 s, and the efficiency is increased by 16.13 times under the same accuracy. The comparison results show that the proposed method can greatly improve the efficiency while ensuring accuracy.

Multi-terminal Detection and Localization of Partial Discharge in Transformer

The transformer is the key equipment in the power system, and partial discharge is the main reason for the deterioration of the insulation of the transformer. The existing partial discharge detection method cannot determine whether the discharge comes from the transformer body or the peripheral equipment of the transformer when the discharge signal is detected. In order to study the difference between the internal and external partial discharges of the transformer received signals at the detection end and form an effective positioning method, this paper injects high frequency small signals into the external leads, inside the windings and surrounding screens of the 110kV three-phase double-winding transformer to simulate the external discharge of the transformer, the discharge inside and outside of the windings. The research shows that the first wave polarity of the external discharge and the internal non-winding discharge of the transformer is the same at each detection terminal, and the first wave polarity of the winding discharge signal at each detection terminal is different. The polarity information can be used to judge whether the winding discharges; the external discharge is the same as the transformer internal discharge. Non-winding discharge has different proportions of high-frequency and low-frequency components in each detection terminal signal. The signal energy of each detection terminal of external discharge is concentrated in low frequency, and the signal energy of each detection terminal of non-winding discharge inside the transformer is concentrated in high frequency, which can be judged by frequency domain information. The external discharge and the internal non-winding discharge of the transformer provide a reference for the research on the multi-terminal detection and positioning of the transformer.

Bi-Long Short-Term Memory Networks for Radio Frequency Based Arrival Time Detection of Partial Discharge Signals

Partial discharge (PD) monitoring of electrical substations could provide early warning of insulation failures. Among the various technologies, Radio Frequency (RF) based PD monitoring system could be a promising solution. The RF-based monitoring system detects PD sources in the substation and can also localise the PD sources. The time difference of arrival (TDOA) based PD localisation system primarily require arrival time (AT) of the impulsive RF signal. Though many localisation algorithms have been proposed in the recent past to overcome the TDOA estimation errors, less attention has been given to the accurate estimation of RF PD signal arrival time. This paper presents the AT's automatic labelling in the RF PD signal using Bi-Long Short-Term Memory (Bi-LSTM) network applied on the continuous wavelet transformed (CWT) signal. Further, it also shows PD signal augmentation to overcome the problem of limited representative training data set. The behavior of the radiated RF signals is influenced by many factors and has almost stochastic characteristics. The proposed system has been validated with laboratory-based experimental signals and the data set obtained from different electrical substations. The results show that the improved performance is obtained from the combination of a multilayer Bi-LSTM model and an augmented training set.

Acoustic-Electrical Joint Localization Method of Partial Discharge in Power Transformer Considering Multi-Path Propagation Impact

Efficient and accurate localization of partial discharge (PD) is of paramount importance to ensure the safe operation of power transformers. However, the multi-path propagation effect introduced by the reflection, refraction and diffraction of the ultrasonic signal may add significant computational complexity to the localization process and degrade the localization accuracy. This paper proposes an acoustic- electrical joint method for partial discharge location in the power transformer with the full consideration of the multi-path propagation impact. Unlike the conventional error analysis methods, a partial discharge localization model is proposed for characterizing the multipath propagation impact without the prior knowledge of the transcendental error probability. Based on the matrix inequality transformation and relaxation, the high-dimensional nonlinear localization equations are transformed into a set of second-order convex optimization equations that can be solved using the convex second-order cone program (SOCP). The proposed solution can significantly reduce the computational complexity and improve the localization accuracy as well as avoid the local optimum and slow convergence. The solution is assessed through extensive experiments based on simulations, testbed and trial deployment in comparison with the existing solutions with the localization error of about 0.1 m.

Research on ultrasonic location method of partial discharge in switchgear based on TOA algorithm

Abstract In view of the problem that the partial discharge location of switchgear still needs to detect the amplitude of multiple cabinets, and then can be roughly located only through the calculation and review of workers, an ultrasonic receiver is placed in the switchgear to calculate and locate the ultrasonic location of partial discharge. In the experiment, the model simulation is used to verify that the ultrasonic receiver terminal maintains excellent positioning effect under different installation positions.

Partial discharge localization in power transformers using acoustic time reversal

The localization of partial discharges (PD) is important to monitor the conditioning of high voltage insulator materials. One of the key components in power grids is the high power transformer. Localization of PDs in these pieces of equipment can increase the reliability of power networks. One of the most commonly used methods to localize PDs is the time difference of arrival (TDoA) technique. Recently, time reversal (TR) techniques in the electromagnetic regime have been proposed to localize PD sources with a lower number of needed sensors compared to the TDoA technique. Contrary to TDoA, TR-based techniques do not need line-of-sight wave propagation from PD sources to the sensor(s). In this study, we extend the TR technique to localize PD sources in the acoustic regime for three-dimensional structures. Similar to the electromagnetic TR methods, a typical time reversal process includes three steps: 1) record the acoustic fields caused by a PD source using at least one sensor, 2) time reverse and back inject into the medium the recorded acoustic signal(s), 3) use a proper criterion to obtain the focusing point associated with the location of the PD source. The acoustic TR technique presented in this paper uses only one sensor. Numerical simulations are used to evaluate the performance of the acoustic TR technique for three-dimensional power transformer models. To do this, an open source MATLAB toolbox is used to solve the acoustic wave equation. The numerical results show that the TR technique can accurately localize the PD sources in three-dimensional power transformer models. Our analysis shows that the presence of windings inside the transformer tank does not degrade the efficiency of the acoustic TR technique.

Partial Discharge Localization in Oil through Acoustic Emission Technique Utilizing Fuzzy Logic

This study presents an examination of partial discharge (PD) localization in oil based on acoustic emission technique utilizing fuzzy logic. First, the PD measurement and localization systems are developed. In total, 2 coordinates of needle-plane electrodes that represent the PD location and 336 acoustic emission sensor (AES) coordinates are examined. The electrical PD is measured through an impedance matching circuit (IMC). The acoustic PD is acquired through AES and its signal is boosted by a preamplifier gain unit. The acoustic and electrical PDs are collected once the voltage reaches 30 kV. The data are first preprocessed by discrete wavelet transform (DWT) whereby it will be further analyzed by time of arrival (TOA), fuzzy logic Mamdani (FLM), and fuzzy logic Takagi&#x2013;Sugeno (FLTS) methods. The arrival of time and distance between PD and AES are calculated based on TOA to find the PD location. Next, TOA and distance to PD location are used to define the input and output membership functions for FLM and FLTS to determine the PD location. It is found that FLTS has a great potential to be used for localization of the PD in oil whereby it has the lowest errors between actual PD location and AES. The performance of FLM and TOA is inferior to FLTS whereby the errors between actual PD location and AES are quite high for both PD locations.

Research on cable partial discharge detection and location system based on optical fibre timing

Partial discharge (PD) is an important index to reflect the running state of cables. According to the characteristics and propagation mechanism of cable partial discharge signal, a cable partial discharge detection and location system based on optical fibre time synchronisation technology and travelling wave double terminal location principle is developed. The system has high detection sensitivity, high reliability, real-time detection, diagnosis and positioning of cable discharge power supply. The experimental results show that the positioning accuracy of the cable partial discharge source can be effectively improved based on the fibre timing and double terminal positioning technology, and the positioning accuracy can reach 1%; the method studied in this paper can meet the requirements of the accurate location of the partial discharge source of the cable, Gil and other equipment.

The Effect of the Ring Mains Units for On-Line Partial Discharge Location With Time Reversal in Medium Voltage Networks

The performance of a new on-line partial discharge (PD) location method based on the Electromagnetic Time Reversal (EMTR) theory and the Transmission Line Matrix (TLM) method are investigated for characterization of Medium-Voltage (MV) networks. The distortion of the PD signal during its propagation along a cable connection including network components modelled based on experimental data is reproduced in simulation and the effectiveness of the EMTR-based method to localize the PD source is analyzed. In particular, the effects of the ring main units (RMUs), that behave as a complex impedance, the variation with frequency of the MV cable impedance and the reflection patterns, due to impedance mismatches, are considered and investigated. Simulation results are given showing the performance of the EMTR method in two different networks configurations: the former one with a RMU at the end of a MV cable and the latter one with a second MV cable connected to the RMU of the first configuration having a distribution transformer at its far end. The results show that the EMTR method is able, with only a single observation point, to localize PDs also in the presence of RMU with a relative error, with respect to the line length, of approximately 1%.

Partial Discharge Localization on Power Cables Based on a Novel Signal Relay System

Time domain reflectometry (TDR) is an effective method used to detect partial discharge (PD) and localize PD sources on power cables. However, for long-length power cables, the attenuation and dispersion of PD signals are significant due to the propagated distance. The attenuation causes a serious reduction of the pulse amplitude, which makes the defects located far away from the PD detector difficult to find. The dispersion causes appreciable asymmetry in the PD pulse wave form. Thus, the localization accuracy is reduced. To solve the problem of long-length cable fault localization, a novel signal relay system is proposed in this paper. Once a weak PD pulse is captured in the signal relay system, another standard Gaussian pulse signal is initiated by a function generator. The Gaussian pulse signal is injected into the cable and travels along the cable. During this procedure, the weak PD pulse is likely to be amplified, and the fault localization accuracy is notably enhanced. To validate the effectiveness of the proposed method, an experimental platform is built in a laboratory, and PD detection of an artificial defective cable is performed. The experimental results show that the signal relay system can effectively “enlarge” the PD pulse on a long-length cable. For long-length power cables, PD detection can achieve a higher localization accuracy based on the proposed method.

Research on cable partial discharge detection and location system based on optical fibre timing

Research on cable partial discharge detection and location system based on optical fibre timing

Numerical and Experimental Investigations on Influence of Internal Defect Parameters on Partial Discharge Induced UHF Signals in Gas Insulated Switchgear

A detailed study of the influence of internal defect parameters on partial discharge (PD) induced ultrahigh frequency (UHF) signals propagated through an L section of metal encapsulated gas insulated switchgear (GIS) is presented. The study is carried out using PD defect model with varying rise time, defect size, location, and orientation, an ultrawideband UHF internal sensor, and 3 m long L-GIS with dielectric spacers, shorting plates, hand holes and bus bar with disconnector. Presence of higher order modes, multipath propagation, losses, and dispersion inside L-GIS were observed to influence the time and frequency domain characteristics of PD signals induced in the internal UHF sensor with 0.5 to 6.8 GHz operating bandwidth and directional radiation pattern. The rise time of PD signals significantly influenced UHF signal characteristics in time and frequency domains while PD defect size, location and angular orientation primarily affected the signal amplitude. UHF sensor measurements confirmed the complex behavior of PD induced electromagnetic wave propagation inside L-GIS for varying defect parameters in agreement with the simulations. Despite the complex behavior, it is concluded that PD sensing in GIS is possible using ultrawideband internal UHF sensor.

Acoustic Based Localization of Partial Discharge Inside Oil-Filled Transformers

This paper addresses the localization of Partial Discharge through a 3D Finite Element Method analysis of acoustic wave propagation inside a 3-phase 35kV transformer with the help of COMSOL Multiphysics software. Due to the complexity inside transformers, acoustic waves generated by PDs cannot simply be detected with typical acoustic sensors, especially when PDs happen inside inner windings. These waves are distorted and attenuated along with their propagation. The type, number, and position of sensors are essential factors in PD localization inside a transformer. A new installation arrangement of fiber-optic acoustic sensors inside the transformers is proposed with this information. This array of acoustic sensors has significant effects on PD localization accuracy and has immunity from on-site noise and interference; more importantly, they can be installed after transformer manufacturing. They are reachable if needed to be repaired or replaced. Several numerical studies have been carried out considering different PD source positions, and the Levenberge-Marquardt algorithm is employed for solving localization equations.

An Automatic Tool for Partial Discharge De-Noising via Short-Time Fourier Transform and Matrix Factorization

This paper develops a fully automatic tool for the denoising of partial discharge (PD) signals occurring in electrical power networks and recorded in on-site measurements. The proposed method is based on the spectral decomposition of the PD measured signal via the joint application of the short-time Fourier transform and the singular value decomposition. The estimated noiseless signal is reconstructed via a clever selection of the dominant contributions, which allows us to filter out the different spurious components, including the white noise and the discrete spectrum noise. The method offers a viable solution which can be easily integrated within the measurement apparatus, with unavoidable beneficial effects in the detection of important parameters of the signal for PD localization. The performance of the proposed tool is first demonstrated on a synthetic test signal and then it is applied to real measured data. A cross comparison of the proposed method and other state-of-the-art alternatives is included in the study.

Effect of Hydrostatic Pressure on the Propagation of Partial Discharge Acoustic Signals in Transformer Oil

In this research article an attempt is made to investigate the effect of hydrostatic pressure on the propagation behavior of Partial Discharge (PD) Acoustic Emission (AE) signals in a simple experimental tank. A mathematical model has been developed in the form of Partial Differential Equations (PDEs) for PD acoustic wave propagation in transformer oil in a steel tank. A Finite Element Analysis tool (FEMLAB), has been used to simulate the propagation of the acoustic waves. The simulation results show that the speed of the acoustic signal varies with the depth of the source location demonstrating hydrostatic pressure affects AE wave propagation. Furthermore, the effect of hydrostatic pressure was investigated and conformed experimentally. It is concluded that the propagation speed is not constant within the tank and increases with tank depth. If the effect of increased acoustic velocities due to hydrostatic pressure is ignored then the possibility of practical PD location algorithms inferring the incorrect location in high voltage assets, such as oil filled transformers, will be increased significantly.

Reliable detection of pulse arrival time for partial discharge location in HV cable based on improved Allen-Bear algorithm

In multi-sensor data based partial discharge (PD) source location in high voltage (HV) cable, poor reliability of detection of pulse arrival time against noises, waveform distortion, amplitude attenuation is the major barriers to practical application. In this paper, an improved Allen-Bear PD pulse detection algorithm, which combines the advantage of the characteristic functions of the two time-window energy ratio based detection algorithms, is proposed for robust PD location. The most critical contribution of proposed method is the extension of frequency domain component compared to the characteristic functions of the original algorithm. Simulation and physical experiment results demonstrate that the proposed method not only ensures the detection accuracy of the PD pulse arrival time, but also improves the reliability under harsh practical scenarios. It performs significantly better than the existing detection algorithm in terms of anti-noise, anti-waveform distortion, time window length variation, etc. It has significant value for practical applications.

Partial Discharge Location Through Application of Stationary Discrete Wavelet Transform on UHF Signals

The degradation level of high voltage equipment insulation systems can be estimated from the monitoring of partial discharge (PD) activity. The radiometric method stands out as one of the most promising methods for monitoring these discharges, however, in substations, the PD signals may be susceptible to external interference and, in some cases, hide by background noise. This work presents the application of the stationary discrete wavelet transform (SDWT) over PD signals measured by bio-inspired printed monopole antennas (PMA) operating at the UHF frequency range (300-3000 MHz). In addition to the filtering from the SDWT, the use of the SDWT scaling coefficients energy is evaluated as a support tool for the location of PD. The PD signals are investigated under low signal-to-noise ratio (SNR) and; high SNR with a high pulse repetition rate. These signals are obtained from a laboratory setup composed by a discharge generating oil cell, and acquired through a bio-inspired PMA. After the application of the SDWT over the evaluated signals, together with the energy calculation using different mother wavelets, it is verified that the proposed methodology provides an efficient filtering result, being appropriate for PD detection. From the energy of SDWT scaling coefficients, it is possible to highlight the constant delays between the detection of consecutive pulses, minimally interfering over the time differences of arrival and providing better location results.

Efficient and Low-Cost PD Monitoring and Locating System for MV Switchgears Using TEV Detectors

Identifying the location of partial discharges (PDs) and providing clear information on insulation vulnerabilities in power systems can help utility companies to improve their maintenance efficiency. This paper presents a PD monitoring and locating system for medium-voltage switchgears using a set of transient earth voltage (TEV) detectors. A time-of-flight methodology was used to identify the switchgear affected by PD among a row of switchgears. A time sharing access mechanism, which was implemented by multiple high-frequency surface mounting relays integrated into each TEV detector, was applied to automatically identify the site of PD and minimize the number of expensive high-speed acquisition cards. The operation principle and implementation of the modular system were formulated, and the efficiency of the proposed system in identifying the switchgear with PD among three 10 kV metal-clad switchgears was confirmed experimentally.