Lightning is always a major cause of outages in power systems during these years, the description of insulator string breakdown process is a key part in lightning back flashover analysis. This paper builds a model to accurately depict the insulator breakdown process, which is applied to typical porcelain insulator or typical composite insulator under positive or negative impulse. The breakdown experiments of insulators of different string lengths for 500-, 220-, and 110-kV transmission lines are carried out under short-tail impulse. For comparison, the insulator breakdown experiments under standard lightning impulse are done as well. Then, utilizing the records of voltage, current data, and photos taken by high-speed cameras, the leader progression model is developed. Finally, the models are validated by being embedded in PSCAD software.

Breakdown Process Experiments of 110- to 500-kV Insulator Strings Under Short Tail Lightning Impulse

A technique is presented for the generation of short-tailed lightning impulses with an acceptable degree of efficiency for use in power system protection studies. The method consists in connecting an in-air inductance in series with the tail resistance in one of the standard configurations of the Marx circuit. The validity of the solution has been ascertained experimentally, and a criterion is provided for the analytical determination of the most suitable value of this parameter. >

An inductance on the Marx generator tail branch-new technique for high efficiency laboratory reproduction of short time to half value lightning impulses

The main objectives of this work are of two folds: the first is the design of impulse voltage gen- erator and impulse testing of a standard disc type insulator experimentally. The second is the development of MATLAB Simulink model of the above mentioned experimental setup. Investigation shows that this soft- ware is very efficient in studying the effect of parameter changes in the design to obtain the desired impulse voltages and wave shapes from an impulse voltage generator for high voltage applications.

Simulation of Impulse Voltage Generator and Impulse Testing of Insulator using MATLAB Simulink

Surges resulting from lightning strikes could propagate not only into the power line but also into a low voltage line such as the telecommunication system and could cause damage to the equipment. In order to protect this highly sensitive equipment, a telephone lightning protector (MOV) has to be installed in the telephone set. Since the natural characteristics of lightning are a multiple stroke/flash, the response of the protector under this condition has to be investigated. This paper presents the experimental studies on the voltage and current characteristic of the MOV under the application of multiple lightning impulse voltage and current.

Voltage-current characteristics of metal oxide varistors for low voltage telephone lightning protector under the application of multiple lightning impulse

The behaviour and performance of lightning protective devices such as the metal oxide varistor (MOV) under the application of multiple lightning impulse are different from that of the standard single stroke test. Since the MOV is the most common, economical and reliable device for low voltage and telecommunication systems lightning protection, a precise method of testing has to be adopted based on natural characteristics of lightning to accurately determine its performance and capability. In this work, a Multiple Lightning Impulse Generator (MIGe) with new electronic delay triggering technique with a voltage capability of 5 kV and a current capability of 1 kA has been designed, constructed and developed in the laboratory to conduct impulse testing based on natural lightning parameters. The generator can produce up to five sequences of impulse voltage and current with variable characteristics such as impulse waveshapes and time interval between impulses. This system also incorporates an electronic triggering and delay circuit to initiate and delay the breakdown process of the sphere gaps. Laboratory studies are then being carried out on 2 kV and 5 kV voltage and 1 kA current ratings metal oxide varistors. The electrical and thermal responses of the device are then being analyzed to determine the effect on the varistor characteristics. From the results it has been found that material degradation has occurred on the MOV test samples when multiple lightning impulse are being subjected as compared to the standard testing procedures. The degradation is shown by reduction in the electrical characteristics where the DC voltage at 1 mA current value reduces more than the tolerable limits of Â±10%. The other parameters being studied which are the temperature, insulation resistance, capacitance and partial discharge also showed a considerable effect whereby the percentage change is significant when the multiple impulse is applied.

The behaviour and performance of metal oxide varistor under the application of multiple lightning impulses

When impulse voltages of very short time to half-value are generated with a standard Marx circuit, there may be a considerable decrease in efficiency.

A. Carrus

Papers

Very Short Tailed Lightning Double Exponential Wave Generation Techniques Based on Marx Circuit Standard Configurations