ARCLESS TESTS OF THE HIGH VOLTAGE OIL-FILLED ELECTRICAL EQUIPMENT ON EXPLOSION SAFETY

摘要

Explosions of the high voltage oil-filled electrical equipment (OFEE) lead to a significant material damage. These explosions occur as a result of action of the arc discharge (AD) which arises at internal short circuit. In AD there is an intensive decomposition of transformer oil (TO) and liberation of great volume of gaseous decomposition products. It leads to significant growth of pressure in a place of occurrence of short circuit. The perfection of design of OFEE and protection systems is the possible way to achieve significant reduction of probability of explosion occurrences and essentially decrease the material losses. The examination of perspective explosion-proof OFEE designs and new systems of protection against explosion due to pulse pressure from AD demands the effective test methods. In present work results of development and application of an arcless source of pulse pressure (ASPP) are described. In ASPP the testing impulse is produced by the jet of powder gases (JPG) which arises at the combustion of explosive materials. In this work results of experimental researches of AD in TO at the conditions typical for an initial stage of AD are presented: current rise time was 3-5 ms, the maximal current of an arc - up to 30 kA, time of AD burning - 3-20 ms. The energy which has been released in AD amounted to 0.1 MJ. It is established, that electric field strength in AD column is about 0.2 kV/сm, gas producing factor in AD is of 110 l/MJ, a growth rate of pressure in TO is about 0.5 MPa/ms. It was established from experiments that TO flow under action of AD and of JPG are similar if at equal influence duration the energy which has been released in AD is equalled enthalpy of JPG on an input in a liquid. It was also shown that the action of JPG on TO and water is quite similar. In this work the tests of serial instrument transformers of 110 and 330 kV for the explosion safety, executed by means of ASPP, are described. In such transformers expected energy of AD can amount to 1 MJ. By means of ASPP the tests of breadboard models of two known methods of OFEE protection from explosion were carried out. In the first method it is assumed that the protection is reached due to fast dump of pressure inside of OFEE case when special membranes are opened. In the second method of protection it is offered to establish porous coverings on internal surfaces of OFEE cases. Experiments were carried out on model of OFEE with the characteristic size of 1 m at action energy up to 1.5 MJ. Observed destructions of the case of OFEE model are described.