Different partial discharge (PD) detection and measurement procedures suitable for use on cables, capacitors, transformers and rotating machines are examined and compared. Both narrow and wide bandwidth PD detectors are considered; particular attention is given in regard to their suitability to different types of electrical apparatus and cable specimens under test as well as their applicability to discharge site location and their capability to detect different forms of PD. A rather substantial portion of the discussion is devoted to the use of intelligent machines as applied to PD pattern recognition in terms of either PD pulse-height/discharge epoch (phase) distributions or discharge pulse shape attributes.

Partial discharges. Their mechanism, detection and measurement

The author presents a bibliography and survey of the literature concerned with theory and measurement of the stochastic behavior of pulsating partial-discharge (PD) phenomena that can occur when insulation is subjected to electrical stress. The types of PD phenomena considered include AC and DC generated electron avalanches, pulsating positive and negative corona in gases, and PD that occur in liquid media and in the presence of solid dielectric surfaces. The basic physical mechanisms of discharge initiation, growth, and memory propagation that determine the probability distributions for pulse occurrence times and pulse amplitudes are discussed. Consideration is also given to special problems associated with the measurement and interpretation of data on the various statistical properties of PD phenomena. >

Stochastic properties of partial-discharge phenomena

An instrument capable of detecting and locating partial discharge sites and faults in shielded power cables was developed on behalf of a group of US electric utilities. The instrument uses state-of-the-art electronic hardware and advanced digital signal processing techniques. The partial discharge signals are reconstructed using the cable traveling wave characteristics (transfer function), and noise is reduced both through choice of hardware and by modern signal enhancement techniques. An adjunct instrument was also developed to correlate the location of a partial discharge site along the cable to the position along the surface of the cable burial trench. The principle and the implementation of the instrumentation package are described, and results obtained in the laboratory on a 175 m, 15 kV URD cable are discussed. >

Location and characterization of partial discharge sites in shielded power cables

There are several techniques that can be used to estimate the location of partial discharges in cables, however, certain technical obstacles need to be overcome before acceptance of this type of testing becomes widespread. A review of the theory of signal propagation in power cables is presented along with its relation to partial discharge site location. Fundamental limitations affect the detectability and location accuracy of partial discharges in power cables. The sources of these errors are discussed along with methods that minimize their effects. The advantages and disadvantages of alternative methods for locating partial discharge sites are presented along with a calibration method that improves the accuracy of these methods. >

Estimating the location of partial discharges in cables

A critical review is presented on the various electrical methods available for partial discharge detection and measurement in terms of their chronological development and application on cable, capacitor, transformer, and machine insulation specimens. A substantial portion of the effort is devoted to corona pulse detection techniques, because these constitute the most popular forms of corona measurement. It is pointed out, however, that under some conditions discharges may assume a pulseless or pseudo-glow type character and that in such circumstances pulse detection procedures become ineffective and must be replaced by appropriate bridge methods.

A Commentary on Partial Discharge Measurement and Detection

Todays partial discharge (PD) detection and location methods in high voltage cables are limited by the influence of external interferences as well as by the type and properties of the cable and by the nature of PD impulses. The problems of the existing methods could be overcome by the development of a new electronic PD detection and location method of high sensitivity and accuracy. It allows the recording and evaluation of partial discharges in HV cables even under the influence of external interference. The accuracy of location is 99.8% yielding a sensitivity down to 1 pC.

M. Beyer

Papers

A New Method for Detection and Location of Distributed Partial Discharges (Cable Faults) in High Voltage Cables Under External Interference

Analysis of significant tornado events in Central Europe: synoptic situation and convective development

A new method for detectionand locationof distributedpartialdischarges (cablefaults) in high voltage cablesunder externalinterference