Dieter Koenig

Influence of grading capacitors on the breaking performance of a 24-kV vacuum breaker series design

This paper deals with the breaking capability of a series design consisting of two 24-kV vacuum circuit breakers (VCB) with grading capacitors. The investigations were done under worst-case conditions with regard to the rate of rise of the transient recovery voltage (TRV) exceeding the values given in the relevant IEC standard. In previous publications it was shown that the breaking capability of the series arrangement is higher than doubling the voltage of a single tube. In addition to these results it is shown that in some cases grading capacitors can increase the breaking capacity even more. Tests with simultaneous opening of the contacts of both tubes are presented with the application of different grading capacitors as well as the choice of different arcing times. In the case of reignition of one of the tubes the current circulating between the two tubes is shown. As a result of the tests the breaking capability of the arrangement depending on the arcing time and the value of the grading capacitors can be classified into three zones: area of reignition of the arrangement, scatter area and area of successful arc quenching.

Peculiarities of the switching performance of two 24 kV-vacuum interrupters in series

The breaking capability of two vacuum interrupters in series and their behaviour with added grading capacitors has already been reported in preliminary publications. In the first part of this paper, the breaking capability of the series arrangement in dependency of arcing time, recovery voltage and test current is compared with the performance of a single tube. Within these investigations the influence of the test current on the breaking capability of the double arrangement is shown. The second part of the work deals with the performance of the series arrangement during the re-ignition of one of the tubes. Tests with simultaneous openings of the contacts are presented which demonstrate that even one of the two tubes is able to withstand the total TRV in case of re-ignition of the other tube. Immediately after arc-extinguishing the previous re-ignited tube is able to recover and to take its part of the total TRV again. As a result the double arrangement is able to interrupt the test current.

Switching performance of two 24 kV vacuum interrupters in series

The breaking capability of two vacuum interrupters in series and their behaviour with added grading capacitors has already been reported in preliminary publications. In the first part of this paper the dependence of breaking capability of the series arrangement on arcing time, recovery voltage and test current is compared with the performance of a single tube. Within these investigations the influence of the test current on the breaking capability of the double arrangement is shown. The second part of the work deals with the performance of the series arrangement during the re-ignition of one of the tubes. Tests with simultaneous openings of the contacts are presented which demonstrate that even one of the two tubes is able to withstand the total transient recovery voltage (TRV) in case of re-ignition of the other tube. Immediately after arc-extinguishing the previous re-ignited tube is able to recover and to take its part of the total TRV again. As a result the double arrangement is able to interrupt the test current.

Switching and transient phenomena in a series design of two vacuum circuit breakers

This contribution deals with the investigation on the switching process of a series arrangement consisting of two 24-kV-vacuum circuit breakers and the assessment of the relevant transient phenomena occurring between the two chambers and their grading capacitors. In the first part of the paper the switching capability of the double arrangement is compared to a single tube of the same design. The physical behaviour of the series design in case of reignition of one of the tubes is presented in the second part of the paper. The observation of the transient oscillating currents between the vacuum tubes and their grading capacitors in the range of some μs shows the decisive influence of this parameter on the reignition processes and the resulting breaking capability.

Electrical Surface Discharges on Wet Polymer Surfaces

This paper tackles the problem of the influence of water droplets on the surface of HV insulators on the electric field distribution. During the lifetime of such a high voltage component, the surface of the solid insulation is very often stressed with layers of water droplets. These droplets tend to deform the electric field. Local field enhancements ensue. Field forces causing a deformation of the droplets may be produced as well as surface discharges starting from these droplets. Chemical deterioration of the insulator surface may follow.

Fundamental studies on vacuum circuit breaker arc quenching limits with a synthetic test circuit

The aim of this work is to demonstrate the use of a synthetic test circuit with LC resonant circuits for fundamental experimental work on CB (vacuum circuit breakers). Studies have been performed on a 36 kV-model CB at test currents of 5 and 10 kA r.m.s. aimed at separating the influence of different parameters of the transient recovery voltage such as average rate of rise and peak value on the breaking capability. Furthermore, the effect of the arcing time on the measured arc quenching limit is presented.

Arc tracking properties of the aging wires in aircraft

A modern commercial aircraft contains hundreds of miles of wiring. This vastly increased use of wiring, in conjunction with decreased insulation thickness, has increased the incidence of wire-related aircraft safety problems. Due to thermal, electrical, mechanical and chemical overstress, the aircraft wiring will be aged and the wire insulation will be decreased. Microscopic cracking occurs in wire insulation as the insulation ages. The Cracking in the wire insulation can lead to arc burning between metal conductors in aircraft wiring system. Aging wiring and associated deterioration of the insulation increases the potential for arc fault phenomenon to occur in aircraft. In order to investigate fault arc behaviour of the aging wire, the arc tracking tests have been performed with typical aircraft wire BMS 13-60. The video of the arc burning and the waveform of the fault arc have been recorded. The primary test results indicate that wire aging has an important influence on the fault arc behaviour.

Fundamental studies on vacuum circuit breaker arc quenching limits using a synthetic test circuit

The aim of this work is to demonstrate the use of a synthetic test circuit with L-C resonant circuits for fundamental experimental work on vacuum circuit breakers (CB). Studies have been performed on a 36 kV-model CB at test currents of 5 and 10 kA rms aiming at separating the influence of different parameters of the transient recovery voltage (TRV) such as average rate of rise and peak value on the breaking capability. Furthermore the effect of the arcing time on the measured arc quenching limit is presented.

Phenomena of fault-arc propagation on cables and wires for space applications in vacuum and oxygen-enriched atmosphere and air

Investigations of fault arc propagation on spacecraft cables under spacecraft specific conditions, e.g. vacuum, normal and oxygen enriched atmosphere have been performed. Typical patterns of fault arc extinction have been identified and their consequences with respect to causes of damages are discussed. The results indicate that for a given test current and test voltage the behavior of the arc and the damages caused in a cable bundle depend strongly on the kind of insulation material, cable size and design as well as on the environmental conditions. For some cables the arc propagation effects are increased at higher oxygen partial pressure and significantly increased under vacuum. In many cases vacuum has turned out to be an important worst-case parameter. It was found that the amount of damage assessed by post-test measurements increases substantially, if the value of the test current grows.

Breaking performance of a capacitive-graded series design of two 24-kV vacuum circuit breakers

This contribution deals with the breaking capability of a series design consisting of two 24-kV vacuum circuit breakers (VCB) with grading capacitors. In previous publications it was shown that the breaking capability of the series arrangement is higher compared to the double of a single tube. In addition to these results it is shown that in some cases grading capacitors can increase the breaking capacity even more. Tests with simultaneous opening of the contacts of both tubes are presented with the application of different grading capacitors as well as the choice of different arcing times. In case of reignition of one of the tubes the current circulating between the two tubes is shown. As a result of the tests the breaking capability of the arrangement depending on the arcing time and the value of the grading capacitors can be classified into three zones: area of reignition of the arrangement, scatter area and area of successful arc quenching.