For pt.XIII see ibid., vol.8, no.4 (July/August 1992). The finer points of acoustic partial discharge (PD) detection systems and their common applications are treated. The PD source, propagation path of the waves, the acoustic sensor, and system noise are described. The design of acoustic PD instrumentation, the location of discharges, and the detection and evaluation of signals are discussed. Applications to outdoor insulation, medium-voltage air-insulated switchgear, capacitors, transformers, and cables are covered. >

Partial discharge. XIV. Acoustic partial discharge detection-practical application

The authors have developed digital instrumentation that can measure the amplitude, shape, phase, and number of pulses per cycle. Examples are given of results obtained from an induction motor, a hydrogenerator, a polymeric cable system with a defective joint, and a high-voltage current transformer.

A new approach to the diagnosis of solid insulation systems based on PD signal inference

Industrial implementation of pulsed electric field electro-technology (PEF) for food preservation has been rather slow, despite its potential to produce safe, nutritious and high-quality products. Several research groups around the world are in a race to validate and optimize the operation of PEF systems. Insufficient kinetic studies and inaccurate treatment delivery assessment are some of the main obstacles to the implementation of this technology. Equivalency among PEF systems, treatment delivery and control variables need to be clearly defined before actual industrial implementation takes place. Limited commercial availability of PEF systems, mainly due to the complexity and high cost of pulsers, and to technical and economical limitations of the scaling-up process, reflects into high initial investment and operation costs. This paper reviews the state of the art on the above-mentioned issues, and also discusses engineering, biological, and regulatory aspects that should be considered for optimization and commercial implementation of PEF as a food preservation technology.

Food Processing by Pulsed Electric Fields: Treatment Delivery, Inactivation Level, and Regulatory Aspects

After referring briefly to the earlier developments of computer-based PD measurements in the 1970s, the paper outlines how the introduction of new technology has resulted in the design and production of a number of digital systems for use in test laboratories and on site. In order to avoid overgeneralization, the basis of the hardware required for detection and recording of the PD pulses is described by reference to a particular system, it being understood that many detailed variations are possible depending on the application. The paper describes a number of parameters that can be calculated by software and used to characterize the PD behavior. These include the IEC-270 integrated quantities, statistical moments and other fingerprints for recognizing the PD patterns within the power frequency cycle. Examples are given of the patterns obtained on equipment and samples. These are necessarily selective and are intended to indicate how the techniques may be applied. It is concluded that these new methods will become valuable in procedures for assessing the condition of electrical insulation, in particular faults or defects, but must be used in conjunction with existing techniques until improved confidence is achieved in interpreting results, especially in respect of the various phase-resolved distributions and calibration procedures. >

Development of computer-based measurements and their application to PD pattern analysis

A theoretical approach to partial discharge transients is presented. This approach is based on the relationship between the charge induced on the measurement electrode by those created in the interelectrode volume during partial discharge activity. The primary sources for these induced charges are the charges which, as a result of partial discharge activity, are distributed within the voids of the insulation medium. These charge relationships are derived, and their application to the measured transients associated with the time dependence of the induced charge is presented. The application to multiple electrode systems of practical interest is illustrated. A discussion of the salient features and practical aspects of the theory is included. >

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The theory and measurement of partial discharge transients

Electrical discharges that do not completely bridge the electrodes are called partial discharges Although small, these discharges have been known for more than fifty years to cause progressive deterioration Since 1945 the use of new high voltage dielectrics has required the use of sophisticated detection techniques Discharge detection has grown into an indispensible tool for the evaluation of modern insulation The subject has received little attention in books on high voltage techniques although a good deal is scattered in various papers and reports The object of this book is to collect this knowledge and present it as a coherent study Topics covered include the behaviour detection and measurement of discharges, the choice of detection method and procedure, the location of discharges and discharge detection in practice

F. H. Kreuger

Papers

Partial Discharge Detection in High Voltage Equipment