Ground Cable for Ground Switch

[cwhite6]

I have a question about a 27kV ground switch we are installing in a HV yard. My substation technicians are having an issue with a ground cable we are being made to use. This company's standard is to use copper clad cable, which makes the cable OD much bigger than it would be with soft drawn copper. My question is are you required by any IEEE or other standard for the cable that runs from the ground blade on the ground switch to the grid beneath the soil to be one, continuous piece of cable like you are required to do for operating handles to switch pads? They are having hell trying to figure out how to bend the massive cable we are being made to use. We could make it work by using a high ampacity braid from the blade to the ground connector that holds the ground cable coming up the structure.

 

[bacon4life]

A moving part is subject to different conditions than the rest of the grounding system. Moving connections are usually a highly flexible braid that is hard to splice because of fine stranding. A splice in the middle of a braided conductor would also create a node that would concentrate the bending stresses adjacent to the joint, eventually braking strands.

The riser portion from the soil level to the switch level is not generally subject to repetitive motion, so it can have much coarser stranding. We do not have restrictions on where splice can be. Replacing a few feet of wire might be cheaper than using extra splice, not to mention it would look better. That being said, we routinely have a spice near the soil level and a second one up about 2 meters. The soil level one is sometimes intentional, but the second is the result of thieves stealing the copper wire. We are not going to put a new continuous cable all the way up to the switch level.

We do require all to meet IEEE standard for grounding, which requires that they be permanent and irreversible (e.g. compression or exothermic).

 

[cwhite6]

Thanks for the response. Can you direct me to the IEEE standard you are referencing?

 

[bacon4life]

IEEE 80 is the substation grounding standard and refers to IEEE 837 for details on the application of permanent connections used in substation grounding. IEEE 837 is a test standard for permanent connectors, and doesn't actually discuss proper application of connectors. Rereading IEEE 80, braised connections are also OK, but soldered connections should be avoided.

 

[cwhite6]

Thanks! I have IEEE 80. I must have missed the section you are referring to.