Showing papers on "Partial discharge published in 1973"

Device for detecting corona discharge in an enclosed electric device

Abstract: In an enclosed electric device in which a conductor to be charged with a voltage is supported by an insulation support in its enclosing metal case, an electrode is disposed on or in the insulation support so as to provide a first static capacitance with respect to the conductor and a second static capacitance with respect to the metal case. A corona discharge detector is connected between the electrode and the metal case and adapted to detect, with the first static capacitance used as a coupling capacitor, a corona discharge occurring from the conductor and the insulation support.

Charges on insulators generated by breakdown of gas

Abstract: The conditions for the occurrence of partial discharges are analysed and shown to be governed by the trapping of charged particles on the insulation surface. According to the instant of trapping, each discharge is constituted either by a series of single avalanches or by a sort of degenerated spark which constitutes the partial discharge. Charge deposits form a sharply defined site which is visible on powdering. If the deposited charge is positive, the site is star-shaped and its shape and size strongly depend on the electronegativity of the gas. If the discharge is negative, the site is circular in all the gases. By measuring the site diameter it is possible in several cases to calculate the capacity involved in the discharge, and consequently the energy of it. This technique is used to study the explosivity of vapours in spaces bounded by charged insulators.

Use of a Multichannel Analyzer for Corona Pulse-Height Distribution Measurements on Cables and Other Electrical Apparatus

Abstract: A method in which use is made of a multichannel analyzer to measure the distribution of the corona pulse heights of insulating systems of various electrical apparatus such as transformers, capacitors, and cables is described. Suitable pulse-shaping circuitry is used in conjunction with an RCL-type corona pulse detector to provide a basic sensitivity level of 1 pC and corona pulse resolution limit of about 10-15 ,?s. A calibration technique is described and particular attention is given to the interpretation of calibration results obtained under high ambient noise conditions normally prevalent in electrical apparatus production areas. It is shown that electrical interference may degrade the corona charge resolution of the analyzer display to as much as 4.0 pC as compared to the half-peak width value of about 0.5 pC in the near absence of noise. Typical corona pulse-height distribution spectra obtained on solid dielectric insulated power cables are presented.

The Relationship Between the Picocoolomb and Microvolt for Corona Measurements on HV Transformers and Other Apparatus

Abstract: Historically in North America, partial discharge or corona measurements in MV have been used for transformer quality control and customer acceptance, but in the future it is anticipated the pC unit may also be used.

Glow discharge tube ignition circuit for electric discharge tube

Abstract: Apparatus for starting and operating a gas discharge tube comprising a glow discharge starter connected to preheatable electrodes of the tube. An auxiliary circuit including a thyristor produces a voltage to ignite the glow discharge starter which then provides a path to heat the tube electrodes and subsequently aids in generating a voltage peak to ignite the discharge tube. The ignition voltage of the glow discharge starter is chosen to be higher than the AC supply voltage but lower than the voltage produced by the auxiliary circuit.

Static plate for power transformers

Abstract: A static plate constructed for the enhancement of partial discharge characteristics by the elimination of foil to oil interfaces. The conducting foil of the static plate is positioned between two relatively flexible electrical insulating members and uniformly bonded thereto by a suitable adhesive. The relatively flexible insulating members are disposed between relatively rigid insulating members and bonded thereto by an adhesive which allows some relative movement between the rigid and flexible insulating members. Dimensional changes of the conducting foil and of the rigid insulating members produce irregularities in the surface of the conducting foil. Since the tightly bonded flexible insulating members conform to the shape of the conducting foil, a solid insulating material is always positioned between the conducting foil and the oil dielectric of the transformer. Thus, irregularities in the conducting foil of the static plate do not produce foil to oil interfaces which are conducive to partial discharge.

Electrical apparatus with high voltage electrical conductor insulated by material including high dielectric constant inserts

Abstract: A high voltage, insulated conductor for electrical equipment such as dynamoelectric machines where non-uniform electric stresses occur. The insulation has inserts of a material of high dielectric constant incorporated in the insulation in regions of maximum stress to change the stress distribution in a manner to reduce the maximum stress.

Corona discharge apparatus for particle collection

Abstract: In corona discharge apparatus of the class including a source of high voltage and a corona discharge device energized therefrom, the source of high voltage is comprised by a source of alternating current and a piezoelectric transformer including a piezoelectric body, a pair of driving electrodes applied on the opposite surfaces of one end of the piezoelectric body and connected across the source of alternating current and an output electrode mounted on the other end of the piezoelectric body and connected to the corona discharge device and an electrostatic particle collector.

High voltage component testing systems

Abstract: Apparatus and method for testing electrical components for partial electric discharges which occur in such components, but which do not bridge the electrodes of such components. The electrical components to be tested are connected to monitoring units whose outputs are in turn connected to a comparator circuit, such as an AND gate. The comparator circuit compares the outputs from the monitoring units to determine whether a predetermined polarity or time relationship indicative of a partial discharge has been satisfied. Such relationship is dependent upon the configuration of the testing circuit.

Technique for charging dielectric surfaces to high voltage

Abstract: A technique for charging a stationary dielectric surface by corona discharge is described in which the voltage applied to a stationary corona wire is steadily increased over a time period to cause the gradual increase in voltage level on the dielectric surface over the same time period. The dielectric surface voltage increases with the wire voltage. The potential difference between wire and plate is kept below the sparking or arcing voltage and above the threshold voltage. In an arrangement employing a moving dielectric surface, plural corona wires are maintained at successively higher voltages to increase the charge on the dielectric in steps, each step being such as to maintain the potential difference between wire and surface below the arcing voltage.

Voltage stabilizers and their mechanisms in solid dielectrics

Abstract: The actual dielectric breakdown of PE cables or PE sheet specimens often occurs through treeing. Primarily, slight damage to the PE surface accelerates treeing, Significantly reducing dielectric breakdown voltage (Figure 1).

An Informative Method for Recording Partial Discharges in Insulating Materials

Abstract: A method of recording large numbers of partial discharge pulses graphically as a function of specimen voltage on a linear time base is described. The conventional method, using a Lissajous figure synchronized with the specimen voltage, does not show a graphic relation between the pulse occurrence and specimen voltage, and is limited by the repetitive nature of the Lissajous figure. Examples of the discharge pulse patterns obtained with the new method are given to illustrate the versatility of the technique. The method provides useful information in the study of partial discharge characteristics and causes.

Cellular Plastics for High Voltage Electrical Insulation

Abstract: Cellular plastics, in particular rigid closed cell foams, have always been attractive for electrical insulation. The obvious advantages of lightweight, high strength to weight ratios, chemical resistance, and fabrication versatility, offer improved design flexibility and lower costs. Certain dielectric properties; however, were not predictable, especially dielectric breakdown and corona resistance under high voltage stress. In fact, lack of knowledge in these areas gave foam a poor reputation. Electrical tests showed failures in the low voltage region before or after aging, and application was usually restricted to less than 5 kv. The rigid foams proved themselves quite capable in this voltage range especially in the aerospace industry where they were used to encapsulate antennas, modules, etc. Since the dielectric properties did not follow

Influence of Inorganic Fillers on the Voltage Endurance of Solid Dielectric Power Cables

Abstract: Results of work undertaken to evaluate solid dielectric materials containing inorganic fillers with respect to voltage endurance are reported. The results obtained are associated with degradation caused by the growth of dendrites within the solid dielectric when under voltage stress.

Partial discharge and treeing phenomena of polyethylene in liquid nitrogen

Abstract: The inevitable problem associated with the use of a cryogenic liquid in an insulation system is the bubble formation and subsequent partial discharge in the bubble. The first half of the paper describes the pressure dependence of partial discharge in liquid nitrogen (LN 2 ) and Lichtenberg figures of surface discharges along a color negative film in LN 2 . The following part deals with the treeing phenomena of low density polyethylene at LN 2 temperatures.

Initiation and growth of trees in polymeric dielectric materials

Abstract: Recently, as a result of the use of a great variety of polymeric dielectric materials as the insulation for high voltage electric devices, the importance of treeing breakdown has been established. This paper describes some results of a study on tree initiation and growth using the short time supply of voltage and the single needle and direct ground system in polystyrene and polyvinylchloride over the temperature range from 20° to 80°C.

Discussion of Practical Value of Internal Partial Discharge Measurements on High-Voltage Insulation Systems for Rotating Machines

Abstract: The application andinterpretation ofpartial discharge measurements on HV coil insulation are discussed. When internal partial discharges aredeveloped inan insulation systemcontaining voids, rapidchangesinvoltage distribution over thesolidand gaseousdielectrics takeplace. Themeasured total changes incharge transfer andlosses oftheinsulation areprobably more dependent on thedielectric properties andconfiguration ofthesolid thanon the actual coronadischarge pulses occurring inthevoids. Therefore, the analysis andinterpretation ofpartial discharge testdatamustbe basedon a complete knowledge oftheinsulation systemsandits intended function ina rotating machine. A better understanding oftheeffects ofinternal ionization inHV coils canonlybegained byfunctional endurance testing atvoltages abovecoronainception points. Quality control methodsforHV coil insulation systemsandcontrol standards mustbebasedon such experiences.

Partial discharge analysis in a Pb(Ti, ZrO 3 ) dielectric

Abstract: The sources of partial discharges in piezoelectric power transducers must be minimized if the corona discharge specifications are to be met. This paper describes some of the results of an investigation into the causes of partial discharges in sonal power transducer elements using a new method of discharge pulse display. The objective of the work was to provide greater insight into the factors leading to corona with the expectation that better methods of quality control in the fabrication of devices might follow.

In this issue - Technically

Abstract: The application and interpretation of partial discharge measurements on HV coil insulation are discussed. When internal partial discharges are developed in an insulation system containing voids, rapid changes in voltage distribution over the solid and gaseous dielectrics take place. The measured total changes in charge transfer and losses of the insulation are probably more dependent on the dielectric properties and configuration of the solid than on the actual corona discharge pulses occurring in the voids. Therefore, the analysis and interpretation of partial discharge test data must be based on a complete knowledge of the insulation systems and its intended function in a rotating machine. A better understanding of the effects of internal ionization in HV coils can only be gained by functional endurance testing at voltages above corona inception points. Quality control methods for HV coil insulation systems and control standards must be based on such experiences.