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Should the Earthing System of PLC or Communication Rooms in High Voltage / Transmission Substations be electrically seperated from other parts of the Substation? Please reference the standards.

Hi EA Jamshidi,

Thank you for your question regarding the standards requiring PLC’s and communication equipment at utility substations to be bonded to the same ground potential.  It is our pleasure to help.

We see in your original question that you would like us to reference which standards require that PLC & Communication equipment at substations be bonded together.  We are tempted to say “All of them”, but we will start with simply listing just a few: Title 29 of the Code of Federal Regulations Part 1910.269 (29 CFR 1910.269), NFPA 70 National Electrical Code, IEEE Std-80 Guide for Safety in AC Substation Grounding, IEEE Std-487 Recommended Practice for the Protection of Wireline Communication Facilities Serving Electric Supply Locations, and IEEE Std-1590 Recommended Practice for the Electrical Protection of Optical Fiber Communication Facilities Serving, or Connected to, Electrical Supply Locations.  And this is to name only a few.  Clearly every single possible standard one could ever reference will mandate that not only are PLC’s and Communication equipment bonded to the same ground source at substations, but that equipment of ANY kind is bonded to the same ground source whether it is high-voltage or not, but ESPECIALLY at a substation. 

Any equipment, PLC’s and Communication equipment included, that are not bonded to the same ground source will present a difference in potential.  This is a bad scenario even for low-voltage conditions, but in high-voltage conditions it could be lethal.  Differences in potential from one piece of equipment to another will allow hazardous voltages to form which can result in injury or death from shock.  It is also very bad for the equipment itself.  Most people think that tying their sensitive electronic equipment into the same ground grid that handles high-voltage electrical faults, could cause damage to their gear.  But nothing could be further from the truth.  Your sensitive gear being installed with a different ground source will actually allow the destructive voltages to form due to the difference in potential.

Think of a bird landing on a high-voltage wire.  Why doesn’t the bird get electrocuted?  The reason is that the entire bird is at the same potential as the high-voltage wire.  Now, if part of the bird were to be at a different potential, than current would flow and the bird would be killed.  The same is true for your electronics.  As long as your electronic equipment raises in voltage along with everything else around it, there will be no voltage differential and therefore no current will flow and your gear will be safe.

We hope you have found this information helpful.  If you should have any further questions, please do not hesitate to contact us again.

Best regards,

The Engineering Team at E&S Grounding Solutions

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