Control Cable Size and Length
Control Cable Size and Length
(OP)
How do you determine control cable length and size for a cable that runs from a DC source (125V) to some relay inputs like SEL or GE Multilin?
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
Download nowINTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
Control Cable Size and Length
|
RE: Control Cable Size and Length
Size? - If it is a power wire to deliver power to the relay, a #12 or #14 AWG size wire is probably more than large enough to carry the load without appreciable voltage drop. If it is just an input signal, like breaker position indication, the current draw is so small that a #18 awg is large enough but it might not have the physical strength to withstand the wire pulling stresses during installation.
Your question leaves a lot of assumptions to be made or questions unanswered. What are you worried about? Voltage drop to the relay input? Voltage drop during tripping? How much wire or cable to order for the new substation?
RE: Control Cable Size and Length
First of all thanks for your response. What I am worried about is the distances wires have to cover in high voltage yards to reach from control center to equipment in the yard. Sometimes these distances can be in upwards of 1000ft and my question is at what point do you go with a size higher than let's say #14 or #12. For example if you run a #12 wire from the breaker to the control center for tripping, closing and auxiliary contacts then at what distance would it become unreliable, where something like a #10 would be required. I am not running a single conductor from the yard to the control house to be worried about pulling strength, it would be more like an 8 to 12 conductor cable.
RE: Control Cable Size and Length
For signal circuits where operating time is critical, you should evaluate the affect of capacitance of the wiring.
Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.