Abstract
When an arc fault occurs in a medium-voltage (MV) metal enclosed switchgear, the arc heats the filling gas, resulting in a pressure rise, which may seriously damage the switchgear, the building it is contained in, or even endanger maintenance personnel. A pressure rise calculation method based on computational fluid dynamics (CFD) has been put forward in this paper. The pressure rise was calculated and the arc tests between the copper electrodes were performed in the container under different gap lengths by the current source. The results show that the calculated pressure rise agrees well with the measurement, and the relative error of the average pressure rise is about 2%. Arc volume has less effect on the pressure distribution in the container. Arc voltage Root-Mean-Square (RMS) has significant randomness with the change of arc current, and increases with the increase of gap length. The average arc voltage gradients measure at about 26, 20 and 16 V/cm when the gap lengths are 5, 10 and 15 cm, respectively. The proportion (thermal transfer coefficient kp) of the arc energy leading to the pressure rise in the container is about 44.9%. The pressure is symmetrically distributed in the container before the pressure wave reaches the walls and the process of the energy release is similar to an explosion. The maximum overpressure in the corner is increased under the reflection and superimposition effects of the pressure wave, but the pressure waves will be of no importance any longer than a few milliseconds in the closed container.
Highlights
Switchgear plays a very important role in electrical energy transport, which has wide application in the power system [1]
If an arc fault occurs in the medium-voltage (MV) switchgear, a considerable amount of energy will be released within a short period of time
The appropriate calculation methods and the small-scale tests were designed and carried out to get the pressure effect caused by the arc fault in the closed container
Summary
Switchgear plays a very important role in electrical energy transport, which has wide application in the power system [1]. If an arc fault occurs in the medium-voltage (MV) switchgear, a considerable amount of energy will be released within a short period of time. Parts of the released energy will increase the thermal energy of the gas in the switchgear and cause the pressure to build-up, which may cause catastrophic consequences to the switchgear, the building it is contained in, or even the maintenance personnel [2]. In order to evaluate the pressure stress on the wall, the internal arcing classification (IAC) tests have been put forward to verify the quality and safety of the switchgear [3]. The arc tests require a long test period, as well as substantial manpower and material resources. The appropriate calculation methods and the small-scale tests were designed and carried out to get the pressure effect caused by the arc fault in the closed container
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