High Voltage Ground Grid Modifications
High Voltage Ground Grid Modifications
(OP)
I would like to obtain some suggestions on addressing possible safety hazards associated with making modifications to high voltage (115kV) switchyard buried grounding grids such as when new equipment is planned to be installed and/or the yard expanded. Common sense tells me that any connections between bare copper conductors should be made with the yard de-energized or while wearing voltage rated gloves. Does anyone know of any specific procedures for this type of work? I don't see anything within NFPA 70E.






RE: High Voltage Ground Grid Modifications
Also, this would be a good opportunity to check the condition of ground rods and the grounding grid and fix anything that is wrong. A lot of things can deteriorate. There are some places here in Ohio where the well water eats copper tubing and all water heater warranties are VOID! The acid water is caused mostly by a source of sulphur and sulphur-metabolizing bacteria that convert hydrogen sulfide into sulfuric acid. Yet, a mile away or so there is nothing wrong with the ground water.
Using exothermic welding to make the tap or splice would be the best way for several reasons:
1. The amount of time spent handling the existing conductor is minimized which helps with safety problems.
2. Crimping really only makes contact with the outside wire strand layer. Exothermic welding gets around that problem particularly with older cables.
3. You do not have to cut the existing ground cable when doing exothermic welding. I would run a temporary bypass cable just in case a ground fault occurs while the joint is cooling.
Hot line gloves would help but you also need an insulated rubber mat when setting up the exothermic welding mold. For your situation, there could be up to 40 KV of voltage drop if the existing ground grid has old age defects.
RE: High Voltage Ground Grid Modifications
In general, the buried ground wire is at the same potential as all of the substation steel, the fence, and equipment frames. Would you use insulated mats and gloves, or de-energize the station when working on steel structures or the fence from the ground?
RE: High Voltage Ground Grid Modifications
RE: High Voltage Ground Grid Modifications
RE: High Voltage Ground Grid Modifications
I may be wrong, but I don't think that most electricians would use high voltage insulating gloves while laying and connecting ground grid conductors.
RE: High Voltage Ground Grid Modifications