Partial Discharges

Partial discharge (PD) spectral response to variations in the supply voltage frequency was experimentally investigated through laboratory-based tests. The PD spectral content of each defect type responded uniquely to variations in the sinusoidal supply voltage frequency in the range 20 to 400 Hz. The findings are interpreted using the theory of space charge dynamics in PD mechanisms. Prospective diagnostic applications

Partial discharge testing of complete, low-voltage induction machines and dry-type convertor transformers for the More Electric Transportation is discussed. The current standard (i.e. IEC 60034-18-41, 60317-0-1 and 61378-1) offers very few answers to the new challenges posed to the insulating systems reliability of these increasingly electrified electrical machines. Based on tests performed on different kind of specimens and the literature, the most promising assessment technique to ensure a reliable insulation is based on optical sensors. In addition, this work seeks to give some precise, but simple, indications on how to take into account the effect of altitude and high frequency in the qualification of an insulation system for More Electric Transportation and the limits of the different standards involved are highlighted.

Distribution management system has been implemented and utilized by utilities around the world to support the system operators in their decision making process especially when emergencies occur in the distribution system. The system can vary from utility to utility due to the complexity of each system. This inevitably leads to the importance of the Distribution Management System design in order to get the system life cycle assessment. This paper presents an advantage of using a knowledge engineering technique along with knowledge management theory as an alternative approach in designing the Distribution Management System for Metropolitan Electricity Authority, Thailand. The results of this paper show that knowledge engineering technique is suitable to solve the designing problems of the Distribution Management System. Furthermore, this framework can also help utility capture, utilize and update their existing knowledge in designing their own system. Moreover, the comparison with consultant study is also introduced.

the pattern of partial discharge (PD) occurrence at a defect site within a solid dielectric material is influenced by the conditions of the defect site. This is because the defect conditions, mainly its size and location determine the electric field distributions at the defect site which influence the patterns of PD occurrence. A model for a spherical cavity within a homogeneous dielectric material has been developed by using Finite Element Analysis (FEA) software. the model is used to study the influence of different conditions of the cavity on the electric field distribution in the cavity and the PD activity. in addition, experimental measurements of PD in spherical cavities of different size within a dielectric material have been undertaken. the obtained results show that PD activity depends on the size of the cavity within the dielectric material. © 2009 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5252384

The detection and localisation of partial discharge (PD) activities is gaining importance in maintaining operational transformers and diagnosing those which are faulty. Ultra-high-frequency (UHF) techniques have been applied successfully to detection of PD activities in HV transformers because of their sensitivity to fast transient pulses. When an UHF PD monitoring system is applied, one of the crucial pieces of information

Measurement of partial discharge (PD) in high voltage equipment is widely used in condition assessment and performance maintenance of the insulation system. One of the methods to evaluate PD data from condition monitoring activities is by analysing PD signals captured from the PD detection equipment. In high voltage power cable, PD pulses originated from defect sites within cable insulation can propagate along the insulation. A better understanding of PD pulse propagation along cable insulation can be attained through simulation work. Therefore, in this paper, the propagation of PD pulses within cable insulation was simulated using finite element analysis (FEA) software and its velocity of propagation was calculated. The result was compared with the theoretical value and simulation results using PSCAD software. The effect of cable insulation parameters on the PD pulse propagation was also studied through the FEA model; these include variation of the permittivity and conductivity of the insulation material. © 2013 IEEE.

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=06554201

Pada sistem kelistrikan, peralatan tegangan tinggi merupakan elemen yang penting untuk menciptakan kehandalan pasokan listrik pada sistem listrik. Pada peralatan tegangan tinggi pasti ada suatu medan elektromagnetik dimana medan ini harus dipisahkan dari ground dan antar fasa menggunakan isolator. Ada beberapa jenis isolator yaitu isolator padat, cair, dan gas. Pada saat beroperasi isolator tersebut akan mengalami fenomena partial discharge yang mana fenomena ini harus bisa di indetifikasi dan di analisis agar tidak terjadi kegagalan pada sistem isolasi yang menyebabkan terhambatnya pasokan listrik. Fenomena partial discharge pada jangka Panjang dapat merusak isolator yang menyebabkan kegagalan sistem isolasi. Pada paper ini akan dijelaskan apa itu partial discharge secara umum dan apa yang dapat menyebabkan terjadinya partial discharge, dan apa saja sumber dari partial discharge. Selain itu akan ditunjukan bentuk gelombang dan bentuk pola fasa dari partial discharge baik pada isolator jenis padat, cair, maupun gas. Diagnosis partial discharge juga akan dibahas dalam paper ini. Paper ini merupakan rangkuman penyusun dari beberapa referensi paper maupun penelitian ilmiah tentang partial discharge. Kata Kunci-partial discharge; tegangan tinggi; isolator; pola pulsa; diagnosis. I. PENDAHULUAN Pada sistem kelistrikan, kita akan menemui beberapa peralatan tegangan tinggi seperti generator, kabel, trafo, dan isolator. Peralatan tegangan tinggi pasti dilengkapi oleh sistem isolasi atau isolator untuk memisahkan bagian yang bertegangan dengan bagian bertegangan lain dan bagian bertegangan dengan netral atau ground, karena pada suatu peralatan tegangan tinggi pasti terdapat medan elektromagnetik, isolator tersebut yang bekerja menahan medan tinggi. Isolator tersebut bisa berupa bentuk gas, cair maupun padat. Isolasi suatu peralatan listrik tegangan tinggi memegang peranan yang sangat penting bagi operasi normal peralatan tersebut. Pada beberapa kondisi di isolator peristiwa partial discharge atau peluahan sebagian dapat terjadi. Adanya partial discharge pada suatu isolator dapat mengindikasikan umur suatu isolator dan pada waktu yang cukup lama dapat berpengaruh dalam penurunan kualitas dari isolator dan akan menyebabkan kegagalan peralatan isolasi. Kegagalan pada peralatan isolasi dapat menyebabkan kegagalan sistem kelistrikan sehingga menyebabkan terhentinya pasokan listrik pada pelanggan dan dapat menjadi penyebab terjadinya blackout atau mati listrik seperti yang terjadi pada sistem kelistrikan jawa-bali pada 4 Agustus 2019 yang melumpuhkan kelistrikan di daerah DKI Jakarta, Jawa Barat, dan Banten. Interpretasi dari data kemunculan partial discharge dapat digunakan dalam diagnosis peralatan tegangan tinggi. Ketepatan analisis partial discharge pada suatu peralatan tegangan tinggi dilakukan untuk menentukan tindakan yang harus dilakukan agar peralatan dapat bekerja dengan benar. Pada laporan tugas 1 ini akan dijabarkan bagaimana PD dapat terjadi dan analisa gelombang dan bentuk pola pulsa dari partial discharge atau PD berdasarkan beberapa rujukan jurnal dan paper dari beberapa sumber. II. PARTIAL DISCHARGE SECARA UMUM Partial discharge (PD) atau dalam Bahasa Indonesia dapat diartikan sebagai peluahan sebagian adalah fenomena peluahan muatan elektrik yang bisa menjembatani sistem isolasi baik secara sebagian ataupun menyeluruh di dalam suatu isolator. Fenomena PD dapat timbul karena diakibatkan oleh beberapa sebab di antaranya adalah akibat kualitas bahan isolator tersebut, adanya celah atau rongga pada bahan isolator, atau adanya cacat atau kegagalan pada proses pembuatan di pabrik. PD juga dapat terjadi jika ada runcing atau tonjolan pada suatu isolator [1]. PD dapat digambarkan sebagai pulsa listrik atau peluahan pada suatu rongga berisi gas atau pada sebuah permukaan dielektrik dari sistem isolasi cair, padat maupun gas. PD menurut IEC 60270 adalah peluahan listrik lokal yang hanya menjembatani sebagian isolasi di antara konduktor dan yang mungkin terjadi dekat dengan konduktor [2]. A. Penyebab terjadinya Partial Discharge Menurut Prof. Suwarno partial discharge akan muncul ketika medan listrik dalam void atau gelembung melebihi kekuatan medan listrik gas dalam void atau gelembung tersebut [3], atau jika diasumsikan dalam suatu isolator padat ada cacat berupa rongga atau void maka medan listrik akan tembus ketika medan listrik melebihi kekuatan tembus udara, padahal isolator tersebut sudah diatur kekuatan medan listriknya diatas kekuatan tembus medan listrik udara. Partial discharge muncul akibat medan tinggi lokal pada bagian tertentu di dalam atau permukaan isolasi. Jika dilakukan penelitian pada kondisi arus bolak balik atau arus AC pada kondisi tertentu ada tegangan dimana PD tidak akan terjadi apabila ditetapkan pada tegangan dibawah tegangan tersebut. Tegangan ini disebut tegangan insepsi PD atau Partial discharge inseption voltage (PDIV). Meskipun

It is important to detect decomposition of insulating gas SF6 caused by partial discharges for gas-insulated switchgear (GIS). In the previous result, the author developed a novel partial discharges sensing using carbon nanotube (CNT) gas sensor. In recently, an application of high voltage DC for long distance electric power transmission has been often used in various countries as the interconnection system and overload demand. In this study we applied the CNT gas sensor to detect partial discharges generated by high voltage DC. There was polarity profile for DC compared AC discharges. It was found, response of the sensor in the case of negative discharges was much higher than positive discharges under the same experimental condition. And the decomposed gases for each case were identified by FT-IR spectroscopy. The result indicated absorption peaks correspond to SF4 and SOF2 of positive discharges was much higher than that of negative discharges.

Defect in a cable joint is one of the main reasons of a power system being faulty. A defect can cause the electric field in the cable joint to become higher than the material surrounding the defect. This may result in partial discharge (PD) activity to occur within the defect site. When PD is repeating at the defect site, the material surrounding the defect will be affected, where PD may extend its path in the material. This may result in a breakdown at cable joint and consequently causes breakdown on the whole system. Therefore, the purpose of this research is to study the electric field distribution in 132 kV one piece premolded cable joint with and without the presence of defects. A better understanding of the electric field distribution at a cable joint can be attained by modelling the cable joint structure using finite element analysis (FEA) method. Through modelling and simulation results obtained in this work, an understanding of the electric field distribution in defects within cable joint structure can be enhanced. © 2012 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6416227

For high-voltage components, the measurement of partial discharge (PD) is a useful tool for performance assessment of electrical insulation. In this study, experimental measurements of PD activity for different spherical cavity sizes and material temperatures have been performed. A simulation model representing PD behaviour within spherical cavities in homogeneous dielectric materials has also been developed. The model has been used to study the influence of cavity size and material temperature on PD activity. Comparison of measurement and simulation results has been undertaken. The model uses a finite element analysis (FEA) method along with MATLAB code. It has been found that certain parameters in the model are both cavity size and temperature dependent. Thus, critical parameters influencing PD behaviour for different cavity sizes within the material and material temperatures can be identified; these are the charge decay time constant, cavity surface conductivity, electron generation rate (EGR), PD inception and extinction fields and the cavity temperature decay time constant. © 2012 The Institution of Engineering and Technology.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6170034&tag=1

Partial discharge (PD) activity is always linked to insulation degradation, which can affect the performance of the insulation. Therefore, measurement of PD events can be used to assess the condition of the insulation. To assist the assessment of the performance of insulation materials, modelling of PD events can be used to attain a better understanding of this phenomenon. In this paper, a Finite Element Analysis (FEA) model for simulation of PD activity within a spherical cavity in a homogeneous dielectric material has been developed. The model has been used to study the influence of amplitude of the applied voltage on PD activity. Through comparisons of simulation and measurement results, some parameter values in the model are seen to be dependent on the applied voltage amplitude. ©2010 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5640733

As shown in recent papers, Partial Discharge activity has a fundamental role in the premature failure of electrical insulation of machine stator windings fed by PWM inverters. The existence of Partial Discharges can be easily explained if the presence of micro voids inside a composite insulation is considered to be unavoidable. Since such micro cavities are filled with a gas whose permittivity is generally several times lower than the permittivity of the surrounding dielectric, the electric field in such occlusions can be much higher than the local expected average stress. On the basis of a numerical study carried out by using a multi conductor transmission line model for the evaluation of the potential distribution inside the machine and a PD simulation model for the evaluation of the possible ensuing PD activity, in this paper, a new experimental approach to evaluate the effect of PD generated by inverter distorted voltages is proposed. PD measurements under 50 Hz -10 kHz quasi-sq...

Partial discharge (PD) measurement is an important diagnostic tool for insulation system assessment, which can be used to determine degradation of the insulation. Thus, PD monitoring has become an essential tool in assessing the performance of insulation materials and the modelling of PD events has been used widely to attain a better understanding of this phenomena. In this paper, a Finite Element Analysis (FEA) model for simulation of PD activity in spherical cavities of different diameters within a homogeneous dielectric material has been developed. The model has been used to study the influence of spherical cavity size on PD activity within a solid dielectric material by comparison of the simulation and measurement results. It was found that certain parameter values in the model vary for different cavity sizes. Critical parameters affecting PD activity for different spherical cavity sizes have been identified. ©2010 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5568109

Partial discharge (PD) is an electrical discharge within a dielectric which does not bridge the electrodes. PD measurement has been widely used for assessing performance of insulation systems. Modelling of PD activity gives an insight of this activity and can provide important information for insulation diagnosis. In this paper, a finite element analysis (FEA) method has been used to build a model of PD activity within a spherical cavity in a dielectric material. The model has been used to study critical parameters and physical mechanisms affecting PD activity as a function of temperature. Critical parameters from the model have been identified through comparison between simulation and measurement results. ©2010 IEEE.

http://umexpert.um.edu.my/file/publication/00009839_66587.pdf

Partial discharge (PD) activity within a void in a dielectric material is influenced by many factors. One of the factors is the applied voltage waveform on the material. In this paper, a two-dimensional (2D) model of a cylindrical void in polyethylene layers has been developed using finite element analysis (FEA) software. The model was used to simulate PD activity in the void under square waveform applied voltage. The obtained simulation results were compared with the measurement results from literature. It was found that both results are within reasonable agreement but with only slight disagreement. From comparison, critical parameters from the model affecting PD activity under square waveform applied voltage were identified; they include the inception and extinction voltages and electron generation rate. This finding may increase an understanding of PD behaviour within a void in a dielectric material under square waveform applied voltage. © 2012 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6378726&tag=1

The measurement of partial discharge is used in the performance assessment of insulation systems of high voltage components. This paper describes the development of a test object consisting of a single spherical cavity within a dielectric material. The test object is used to experimentally study the effect of variable applied frequency, applied voltage magnitude and size on PD activity. The obtained measurement data are analyzed and presented. The variations in the measurement results can be interpreted as changes in cavity parameters that can be used for PD modeling. The obtained data gives more information on how PD activity behaves under different stress conditions and the cavity conditions. © 2009 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5377831

Wide bandgap (WBG) power modules able to tolerate high voltages and currents are the most promising solution to reduce the size and weight of the power management and conversion systems. These systems are envisioned to be widely used in the power grid and the next generation of more (and possibly all) electric aircraft, ships, and vehicles. However, accelerated aging of silicone gel when being exposed to high frequency, fast rise-time voltage pulses that can offset or even be an obstacle for using WBG-based systems. Silicone gel is used to insulate conductor parts in the module and encapsulate the module. It has less electrical insulation strength than the substrate and is susceptible to partial discharges (PDs). PDs often occur in the cavities located close to high electric field regions around the sharp edges of metallization in the gel. The vulnerability of silicone gel to PDs occurred in the cavities under repetitive pulses with a high slew rate investigated in this paper. The objective mentioned above is achieved by developing a Finite-Element Analysis (FEA) PD model for fast, repetitive voltage pulses. This work has been done for the first time to the best of our knowledge. By using the model, the influence of frequency and slew rate on the magnitude and rate of PD events is studied.

This work concerns the optimization of the sizing of the insulating system of an actuator realized for the aeronautical sector in the framework of the MEA (More Electric Aircraft) and its qualification. Furthermore, the absence of a real standard that takes into account the most stressful conditions at high altitude is discussed. The objective of this article is to provide an easy to use model that allows a conservative choice of the characteristics of the insulation system, given the environmental conditions and the type of power supply installed. Moreover, the calculation methodology on which the tool is based can be a starting point for defining qualification criteria for electric motors used in the aeronautical field.

The purpose of the present work is to show the validation of a new model to simulate the physical phenomenon of partial discharge (PD) produced in air voids inside insulating epoxy resin. The model has been developed on the basis of a new approach that combines the known circuit model of three capacitors with a model used to describe the behavior of the ionized channel inside of the inclusion during the discharge phenomenon, short-circuiting the capacity that represents the void. The approach is based on time-variable conductance of the void, subjected to multistress conditions: voltage, temperature and pressure. The new approach has been developed from a time variable conductivity model used for the study of the discharge with dielectric barrier (DBD). The different parameters which influence the discharge phenomenon in the void are taken into account through an approach in which a lumped circuit is used to simulate the effects of global PD asset. The results of the multiple simulations have been compared with experimental and simulated behaviors found in the literature on the subject.

In this paper, a study of the propagation of partial discharge pulses in the stator winding of a synchronous machine is presented. This study was performed by injecting artificial partial discharge pulses in the stator winding of a 2.4 kV/210 kVA salient-pole synchronous machine. It was found that the propagation of the partial-discharge PD signals is presented in two modes: the slow mode, in which the coil acts as a transmission line; and the fast mode, in which the pulse propagates through the overhangs. The fast mode is due to capacitive and inductive couplings in the overhangs. In the slow mode, a PD signal manifests itself at the generator terminals after a transit time that depends on the distance traveled by the pulse. A strong positive linear correlation was observed between the arrival time in the slow mode and the length traveled by the pulse in this mode. The DC ohmic resistance between the injection point and the measurement point was used to represent the distance traveled by the pulse in the slow mode. The capacitive and inductive couplings also cause a crosstalk between the phases. As a consequence, a PD signal can be measured at different phases to the origin phase. In the slow mode, the signal will suffer attenuation in amplitude due to the dispersion and the absorption of energy while it propagates in the slow mode.

In this work, a model representing partial discharge (PD) behaviour of a spherical cavity within a homogeneous dielectric material has been developed to study the influence of cavity surface charge distribution on the electric field distribution in both the cavity and the material itself. The charge accumulation on the cavity surface after a PD event and charge movement along the cavity wall under the influence of electric field magnitude and direction has been found to affect the electric field distribution in the whole cavity and in the material. This in turn affects the likelihood of any subsequent PD activity in the cavity and the whole sequence of PD events. The model parameters influencing cavity surface charge distribution can be readily identified; they are the cavity surface conductivity, the inception field and the extinction field. Comparison of measurement and simulation results has been undertaken to validate the model. © 2011 IOP Publishing Ltd.

http://iopscience.iop.org/0022-3727/44/24/245202

Modeling of the partial discharge (PD) process allows a better understanding of the phenomena. In this paper, a simulation model for spherical cavities within a homogeneous dielectric material has been developed. The model is implemented using Finite Element Analysis (FEA) software in parallel with a mathematical package. This method provides many advantages over previous PD models because discharge events can be simulated dynamically and the electric field in the cavity can be calculated numerically. The model has been used to study the effect of different amplitudes and frequencies of the applied voltage and simulation results have been compared with experimental measurement results. It is found that certain model parameters are dependent on the applied stress and parameters that clearly affect PD activity can be readily identified, these parameters include; the electron detrapping time constant, the cavity surface conductivity, the initial electron generation rate and the extinction voltage. The influence of surface charge decay through conduction along the cavity wall on PD activity has also been studied. © 2011 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5699446

Partial discharge testing of complete, low-voltage induction machines and dry-type convertor transformers for the More Electric Transportation is discussed. The current standard (i.e. IEC 60034-18-41, 60317-0-1 and 61378-1) offers very few answers to the new challenges posed to the insulating systems reliability of these increasingly electrified electrical machines. Based on tests performed on different kind of specimens and the literature, the most promising assessment technique to ensure a reliable insulation is based on optical sensors. In addition, this work seeks to give some precise, but simple, indications on how to take into account the effect of altitude and high frequency in the qualification of an insulation system for More Electric Transportation and the limits of the different standards involved are highlighted.

Microbubble floating in liquid dielectric and subjected to an electric field may initiate partial discharge (PD). This paper studies the parameters that affect the initiation through a computer simulation. This study inspects how the type of gas inside the microbubble, the size of the microbubble, distance from an electric field, Eo, source and, the magnitude of source’s voltage affect the start of PD. For a prolate spheroid shape, there is an important parameter called ‘c’. This ratio is between the radius of the microbubble polar (‘a’) and the radius of the equator (‘b’). At constant Eo and c, different gases will initiate PD at different distances from source due to differences in a localised electric field inside the microbubble (Emax). Emax is one of the important factors for PD initiation. It is interesting to report that if the ‘a’ and ‘b’ values are chosen so that ‘c’ will be constant, changes in Emax are insignificant. On the other hand, changes in ‘c’ will result in significant changes in Emax. Finally, changes in source voltage certainly affect the Emax.

Wide bandgap (WBG) devices made from materials such as SiC, GaN, Ga2O3 and diamond, which can tolerate higher voltages and currents compared to silicon-based devices, are the most promising approach for reducing the size and weight of power management and conversion systems. Silicone gel, which is the existing commercial option for encapsulation of power modules, is susceptible to partial discharges (PDs). PDs often occur in air-filled cavities located in high electric field regions around the sharp edges of metallization in the gel. This study focuses on the modeling of PD phenomenon in an air filled-cavity in silicone gel for the combination of (1) a fast, high-frequency square wave voltage and (2) low-pressure conditions. The low-pressure condition is common in the aviation industry where pressure can go as low as 4 psi. To integrate the pressure impact into PD model, in the first place, the model parameters are adjusted with the experimental results reported in the literature an...