Cable Discharge Research Articles

System of Measurement and Analysis of Partial Discharges in Underground Power Cables

System of Measurement and Analysis of Partial Discharges in Underground Power Cables

Study on Characteristics of Partial Discharge in XLPE Cable under Damped AC Voltage at Different Frequencies

Damped AC (DAC) voltage method is widely used in partial discharge (PD) detection of power cable. The frequency of DAC voltage is changed due to different length of testing cable. To study the PD characteristics in the heat-shrinkable cable accessories under DAC voltage at different frequencies, four different cases of artificial defects in cross-linked polyethylene (XLPE) cables were investigated. These defects include termination without stress tube, incorrect use of insulation tape as the semi-conductive adhesive tape in the middle joint, void and metal particles on the surface of XLPE insulation. Furthermore, some characteristic PD parameters including the partial discharge inception voltage (PDIV), the partial discharge extinction voltage (PDEV), discharge magnitude, discharge times and so on were compared and analyzed. The results show that PD characteristics are different as the DAC frequency changes, which provides guidance for the practical application.

Characteristics of Partial Discharge in Cross-Linked Polyethylene Insulation Cable under Damped AC Voltage

Partial discharge (PD) diagnosis techniques are widely used in the insulation condition monitoring for power cables. In this paper, the damped AC (DAC) voltage method was used to study the PD characteristics in the heat-shrinkable cable accessories. Four different cases of artificial defects in cross-linked polyethylene (XLPE) cables were investigated, and these defects include termination without stress tube, incorrect use of insulation tape as the semi-conductive adhesive tape in the middle joint, void and metal particles on the surface of XLPE insulation. Furthermore, the PD inception voltage and patterns obtained under the DAC voltage are compared with the AC test results.

Development of Damped AC Voltage Generator for the Partial Discharge Detection of Distribution Power Cables

This paper presents the development of the Damped AC (DAC) voltage generator for the detection of partial discharge (PD) in distribution power cables. High voltage semiconductor switch (HVSS) and air-core inductor are the key units in the DAC test system. Series connection of insulated gate bipolar transistors (IGBTs) was used to achieve the 20kV HVSS. Based on the Neumanns formula, the inductance of the air-core inductor was investigated. Finally, the performance of the developed DAC system was tested on a 8.7/15 kV cross-linked polyethylene (XLPE) cable in the laboratory, where artificial defect of missing stress tube is made in the cable termination.

Quantitative Analysis of Rogowski CT Frequency Characteristics

Partial discharges in power cables will generate small currents with low frequencies in the ground cords. In cable PD online monitoring systems, CTs are usually used to obtain such PD signals. In this paper, by derivations based on theories of wave propagation, the frequency characteristics of Rogowski CTs (RCTs) and the effects of transformer parameters (size, core material, etc.) on its pass band B, sensitivity H(jω0), the lower cutoff frequency fL is acquired. The feasibility of such derivations is verified by experiments. By conducting comparative experiments, the effect of the use of screening box and the way of coil winding on the performance of a current transformer is acquired. A feasible plan to improve the frequency characteristics of CTs is presented, in order to acquire more stable gain and better anti-interference ability within their pass band.

Design of Broadband Planar Spiral Antenna for Partial Discharge in Cable

The detection of partial discharge in power cables is an effective method to diagnosis early fault of XLPE cable . When partial discharge occurs, it emits abundant frequency component in ultra-high frequency (UHF) band, and broadband planar spiral antenna is an effective sensor to detect UHF partial discharge signals. High frequency electromagnetic simulation software Ansoft HFSS is used to simulate and analysis planar Equiangular spiral antenna and Archimedean spiral antenna. The simulation results show that the two kinds of antennas work effectively in 400 MHZ ~ 1 GHZ frequency band and are high sensitivity and superior performance. Because of with smaller size and larger gain, the Archimedean spiral antenna is used to detect UHF signals of partial discharge in XLPE cable.

Fractal features-based pattern recognition of partial discharge in XLPE power cables using extension method

Partial discharge (PD) may cause insulation deteriorations in power facilities and may demonstrate impact on the reliability. Therefore PD detection with pattern recognition is seen as an effective approach in the high-voltage (HV) insulation diagnostics of power systems. Based on an extension method, a PD recognition system for HV power cables is proposed in this study. A PD detector is used to measure raw three-dimension PD patterns of cross-linked polyethylene (XLPE) power cables using an L sensor, according to which two fractal features (the fractal dimension and the lacunarity) and the mean discharge are extracted as critical PD features that form the cluster domains of defect types. The matter-element models of the PD defect types are then built according to the PD features derived from practical experimental results. The PD defect type can be directly identified by the correlation degrees between a tested pattern and the matter-element models. The recognition ability is investigated on 160 sets of PD patterns of XLPE power cables and compared with a multilayer neural network and K-means method. The results show that a high accuracy together with a high tolerance in the presence of noise interference is reached by use of the extension method.

Comprehensive 3‐capacitors model for partial discharge in power cables

PurposeThe paper proposes and presents a comprehensive and integrated circuit model for investigating the behaviour of partial discharges occurring in voids inside the solid insulations of medium and high voltage cables.Design/methodology/approachThe model is based on the well‐known three capacitors model, which is remarkably improved to handle physical parameters such as cavity size, position, shape and pressure, environmental parameters such as cable temperature, in addition to operational parameters such as the contributions of the avalanche of free electrons inside the cavity through considering stochastic time delays.FindingsA complete, flexible and reliable model for partial discharges in voids inside the solid insulation of medium and high voltage cables is presented whose output agrees with experimental reported results.Research limitations/implicationsThe proposed model deals only with single voids, and the semiconductor layers in the insulation of cables are not considered.Practical implicationsThe model can be used in different physical, environmental and operational conditions in order to investigate the characteristics of partial discharge signals to be used as the bases for partial discharge detection and classification in power cables.Originality/valueThis paper presents a novel comprehensive and integrated circuit model with controlling functions to propose the behaviour of partial discharge occurring in voids inside the solid insulation of power cables. The model provides the contribution of geometrical parameters of the void, and operational conditions such as cable temperature and source frequency in partial discharge analysis.

Triggering of Transient Latch-up by System-Level ESD

This paper investigates the influences of temperature and the trigger parameters (width and rise time) on the threshold of transient latch-up (TLU). It is shown that temperature is a much more critical parameter than transient trigger parameters. For high discharge currents which are typical for system-level surges as, e.g., seen in cable discharge events, even very short trigger pulses can cause TLU.

Experimentally determining the voltage of inception and extinction of partial discharges in cable lines

The voltage of inception and extinction of partial discharges in cables with polyethylene, polyvinylchloride, and impregnated paper insulation for medium voltage is determined experimentally with use of the oscillating wave test system. It is shown that particle discharges are observed in more than half of cable lines.

Phase Difference Method for Two-end Partial Discharge Locating System of Power Cables

A method to locate partial discharges in power cables is presented in this article. The method is based on the phase difference between the first arriving waves of a partial discharge pulse at the cable terminals. The phase difference as a function of frequency is obtained using the cross-Fourier spectral density function. The partial discharge location can be determined from the slope of the unwrapped phase difference. The performance of the method is tested using the electromagnetic transient program on a 20 kV, 2-km underground cable, which takes into account the frequency-dependent parameters. The statistical results indicate high location accuracy.

Detection and Localization of Transient Sources: Comparative Study of Complex-Lag Distribution Concept Versus Wavelets and Spectrogram-Based Methods

The detection and localization of transient signals is nowadays a typical point of interest when we consider the multitude of existing transient sources, such as electrical and mechanical systems, underwater environments, audio domain, seismic data, and so forth. In such fields, transients carry out a lot of information. They can correspond to a large amount of phenomena issued from the studied problem and important to analyze (anomalies and perturbations, natural sources, environmental singularities, ). They usually occur randomly as brief and sudden signals, such as partial discharges in electrical cables and transformers tanks. Therefore, motivated by advanced and accurate analysis, efficient tools of transients detection and localization are of great utility. Higher order statistics, wavelets and spectrogram distributions are well known methods which proved their efficiency to detect and localize transients independently to one another. However, in the case of a signal composed by several transients physically related and with important energy gap between them, the tools previously mentioned could not detect efficiently all the transients of the whole signal. Recently, the generalized complex time distribution concept has been introduced. This distribution offers access to highly concentrated representation of any phase derivative order of a signal. In this paper, we use this improved phase analysis tool to define a new concept to detect and localize dependant transients taking regard to the phase break they cause and not their amplitude. ROC curves are calculated to analyze and compare the performances of the proposed methods.

Investigation on Robustness of CMOS Devices Against Cable Discharge Event (CDE) Under Different Layout Parameters in a Deep-Submicrometer CMOS Technology

Cable discharge events (CDEs) have been found to be the major root cause of inducing hardware damage on Ethernet ICs of communication interfaces in real applications. Still, there is no device-level evaluation method to investigate the robustness of complementary metal-oxide-semiconductor (CMOS) devices against a CDE for a layout optimization in silicon chips. The transmission-line pulsing (TLP) system was the most important method used to observe the electrical characteristics of semiconductor devices under human-body model (HBM) electrostatic discharge (ESD) stress. To understand the physical characteristics and CDE robustness of on-chip protection devices, the long-pulse transmission-line pulsing (LP-TLP) system is proposed in this paper and used to simulate the influence of CDE on Ethernet-integrated circuits. The secondary breakdown characteristics of the CDE protection devices under different layout styles and parameters can be measured and analyzed by the proposed LP-TLP with pulsewidths of 500 or 1000 ns. Furthermore, measured results using the LP-TLP system are compared with results measured by the traditional 100-ns TLP system. The experimental results with silicon devices in 0.18-mu m CMOS process have shown that the CDE robustness of n-channel metal-oxide-semiconductor (NMOS) and p-channel metal-oxide-semiconductor (PMOS) devices in deep-submicrometer CMOS technology is much lower than their HBM ESD robustness. By using the proposed LP-TLP system, one set of design rules for I/O devices to sustain high CDE robustness in a given CMOS process can be evaluated and built up for chip layout.

Analysis of ground fault current distribution along nonuniform multi-section lines

In case of a substation supplied by a combined overhead-cable line, most of the ground fault current flows through the cable sheaths and discharges into the soil surrounding the point of discontinuity, where cables are connected to the overhead line. In the paper a new method is presented for computing the ground fault current distribution in case of feeding line consisting of two or more different sections, i.e. part overhead and part underground cable. Besides the calculation of the earth current at the fault location, the leakage current at the transit/transition stations as well as at the overhead line towers can be evaluated, in order to ensure proper safety conditions. Based on the two-port theory, the method allows to take into account all the relevant conductively and inductively coupled parameters which take part to the fault current distribution. A computer program based on the proposed method has been developed and some application examples are reported.

Studies of Elastic Waves in Ethylene Propylene Rubber Using Acoustic Emission Sensor

The aim of our study is to investigate the relationship between lowering of the insulation performance of cross-linked polyethylene (CV) cable and partial discharges (PDs) followed by the dielectric breakdown and to establish a diagnostic technique using an acoustic emission (AE) sensor.In this study, we focused on characterization of AE signals detected from ethylene propylene rubbers (EPRs) used as insulating materials of CV cables. Elastic waves with various frequencies were added to the surface of the EPR, and then characteristics of the detected AE signals due to the elastic waves propagated in the EPR were evaluated. We showed characteristics of Lamb waves whose low frequency components around 100 kHz were large and their small attenuation characteristics.

Design automation to suppress cable discharge event (CDE) induced latchup in 90 nm CMOS ASICs

Design automation tools have been developed to suppress CDE-induced latchup in CMOS ASICs. The tools govern the placement of I/Os and cores subject to CDE and automate the insertion of well and substrate contacts with varying periodicities around CDE susceptible cells according to rules derived from an analytical latchup model.

Auto-detection of partial discharges in power cables by discrete wavelet transform

One of the serious problems that can occur in power XLPE cables is destruction of insulator. The best and conventional way to prevent this is ascertaining partial corona discharges occurring at small voids in organic insulators. However, there are some difficulties in detecting those partial discharges due to the existence of external noise in detected data, whose patterns are hardly identified at a glance. For this reason, there have been a number of researches into detecting partial discharges by employing a neural network (NN) system, which is widely known as a system for pattern recognition. We have been developing an NN system for auto-detection of partial discharges, and have input numerical data of the waveform itself and obtained appropriate performance. In this paper, we employed the discrete wavelet transform (DWT) to acquire more detailed transformed data in order to use them in the NN system. Employing the DWT, we were able to express the waveform data in time–frequency space, and achieved effective detection of partial discharges by the NN system. We present herein the results using DWT analysis for partial discharges and noise signals which we obtained. Moreover, we present results out of the NN system which dealt with those transformed data. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(1): 24–30, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10315

A novel calibration method for PD measurements in power cables and joints using capacitive couplers

Partial discharge (PD) measurements are universally accepted as a technique giving some indication of the state of the insulation in high-voltage apparatus. Cable end users are keen to adopt online PD monitoring during commissioning of systems. However, because of noisy environments and the problems of interference the conventional methods are difficult to implement. As a consequence, ultra-high frequency (UHF)/very high frequency (VHF) techniques of on-site detection of partial discharges have been developed. A technique based on capacitive coupling has received much attention. It has been demonstrated that it is possible to use the technique to monitor the partial discharge in cables, particularly in joints/terminations. However, in order to obtain quantitative information about PD, calibration is required for this technique. Existing calibration methods are difficult to implement on-site. In this paper, a novel method is proposed and compared with the conventional method on a short piece of cable. It has been shown that an individual capacitive coupler can also be accurately calibrated on-site and online using the new method, therefore it provides quantitative information about the amount of apparent discharge. In practice, this is important for electricity utilities as the quantitative information about PD can be used to determine the quality of the cable system and to decide whether the system needs to be repaired or replaced.

The cyclic AMP receptor promoter DNA complex:A comparison of crystal and solution structure by quantitative molecular electrooptics

The complexes formed between the cyclic AMP receptor and three different promoter DNA fragments, including a synthetic 30 bp fragment with the sequence used for determination of the crystal structure, have been analysed in solution by measurements of the electric dichroism (ED) at an ionic strength of 105 mM, using a special instrument based on cable discharge. The ED of the protein is negligible and, thus, the ED of the complexes is determined by the DNA and its orientation relative to the protein. The complex formed between the cyclic AMP receptor with the 30 bp fragment is characterized by a positive ED, indicating that the electric dipole is perpendicular relative to the direction of the helix; moreover, the dipole changes its nature from an induced one for the free DNA to a permanent one of 3.0×10−27 Cm for the complex; both the limiting value of the ED +0.3 and the dichroism decay time constant of 62 ns found for the complex (free DNA: 52 ns; 20°C) demonstrate bending of the DNA double helix. All these parameters are calculated quantitatively from the crystal structure: bead model simulations are used to derive the coefficients of rotational diffusion and to define the center of diffusion, which is the reference for calculation of the dipole vector; the dipole vector is then the basis for calculation of the limit value of the dichroism; the time constants are derived from the diffusion coefficients of the bead model The calculated parameters are in very satisfactory agreement with the experimental ones, demonstrating agreement of the structures in the crystal and in solution with respect to their essential features. These results also demonstrate the utility of electrooptical procedures for a quantitative comparison of crystal or model structures with structures in solution. While the crystal structure has been determined only for the complex with the 30 bp promoter fragment, it has been relatively simple to extend measurements of the ED to complexes formed with a 40 bp and a 203 bp promoter fragment: the data obtained for a 40 bp fragment with the consensus binding sequence are quite similar to those obtained for the 30 bp promoter, whereas the data obtained for the 203 bp promoter clearly show a much higher degree of protein induced bending with a bending angle of ∼180°.

Examination and location of partial discharge sites in severely aged underground distribution cables

This paper presents the results of laboratory investigations of partial discharge (PD) in field aged XLPE underground power cables. PD measurements were made on sixty-one cable samples over a three year period. When PD was detected, the magnitude was measured and a site location was determined. PD site locations were predicted using time delay estimations between PD pulses arriving at opposite ends of the test cable. Fourteen of the samples tested had detectable levels of PD. Some of these PD sites extinguished during the measurement period and were returned to rated voltage aging. When samples had continuously active PD sites, they were either dissected or returned to the aging test. Four sites of this type were found allowing two for dissection and two for aging. Seven of the samples failed after PD measurements. All seven failed near the predicted PD location. During the PD testing, no test cables contained PD which initiated at or below operating voltage. When PD detection equipment was monitoring cables which failed, the failures occurred from 2 to 80 minutes after the presence of PD pulses was detected. >