Before delving into the details of how to prevent arc flash for MV switchgear, we will first take a look at the characteristics of an arc flash in MV switchgear.
Characteristics of an Arc Flash in MV Switchgear
Engineers should be well aware of design alternatives and mitigation techniques that can reduce arc flash hazards in medium-voltage systems. In an arc-flashover, the current always travels where it is not intended to be in the first place, it may protrude from one phase to another phase or even from one phase to the ground/earth.
Reasons for an Arc Flash in MV Switchgear
There are several reasons for an arc flashover taking place in a medium voltage switchgear, few of which are summarized below:
1. Loose soldering of connections
2. Defective equipment insulation
3. Technicians accidentally leaving behind metallic tools near energized parts
4. Rodents entering the enclosure
5. Incorrect alignment of terminals in protective devices
6. The corona effect
Since a medium voltage switchgear supplies power to LV feeds therefore a blackout on the switchgear could mean a blackout on a major portion of your facility. Concurrently, all medium voltage protective devices are operated with a relay which must be set to operate with a greater time delay in order to ensure optimal coordination with the downstream feeders. Moreover, medium voltage circuit breakers have a higher contact opening time which, when added to the relay signaling time, makes up a fault current opening time which is significantly higher when compared to low voltage circuit breakers. It is therefore imperative for facility owners to look for the best methods available for arc flash mitigation.
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Some of the effective methods of mitigation are discussed in detail here.
Let us know if you have any queries regarding this topic and do provide us with your feedback in the comments.
About The Author
Abdur Rehman is a professional electrical engineer with more than eight years of experience working with equipment from 208V to 115kV in both the Utility and Industrial & Commercial space. He has a particular focus on Power Systems Protection & Engineering Studies.
Abdur Rehman is the CEO and co-founder of allumiax.com and creator of GeneralPAC by AllumiaX. He has been actively involved in various roles in the IEEE Seattle Section, IEEE PES Seattle, IEEE Region 6, and IEEE MGA.