Several large-scale projects in India, non-standard methods are being used in subjects related to electrical safety, and reliability. Compliance to national reguations are violated.
One classic example is the use of Earthing for Signaling and Telecom application in metro rail projects. The following case study is from the tender documents of a leading metro railways.
Tender specification
Tender specifications can be downloaded from the following links.
Note: refer the tender specifications and calculations included in the above documents to understand the below figure.
According to the calculations included in the tender an earth fault in Low Voltage powerline (230 volt) produces a GPR of above 15kV. Two large sized earth mats are constructed under the metro railway station, one for LV electrical system and another for clean earth (S&T application).
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