Will the load contribute to the SC damage damage of the cable
Will the load contribute to the SC damage damage of the cable
(OP)
As it's said, the degree of the short circuit damage depends on the impendance. If the fault location is close to the current source (substation), then the damage will be more severe.
My question is, if the cable is 100% loaded and has a fault, compare to the cable that is 20% loaded under same fault condition, will the damage be the same?
Thanks
My question is, if the cable is 100% loaded and has a fault, compare to the cable that is 20% loaded under same fault condition, will the damage be the same?
Thanks






RE: Will the load contribute to the SC damage damage of the cable
1. Cable operating at design temperature (60C, 75C, 90C) prior to short circuit. (XLPE insulation = 90C)
2. All heat generated by short cicuit current stays inside the cable. (Not enough time for the heat to dissipate.)
3.Cable is OK if the resulting temperature is less than the cable insualtion damage temperature. (XLPE = 250C)
These assumptions or similar statements should be noted on the chart.
By loading the cable to only 20%, assumption #1 is probably violated and the starting temperature is less. The cable can take more heat before it is damaged. Check the Buff Book or Okonite website for the temperature damage equation, estimate your starting temperature, and calculate the allowable short circut time.
RE: Will the load contribute to the SC damage damage of the cable
This assumes that the fault itself was not caused by the overloading (overheating).
Rafiq Bulsara
http://www.srengineersct.com
RE: Will the load contribute to the SC damage damage of the cable
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RE: Will the load contribute to the SC damage damage of the cable
Also holds true for cable insulation overheating which is normally caused by loose connections. A loose connection will eventually cause enough heat to damage the insulation, whether it is fully loaded or partially.
Rafiq Bulsara
http://www.srengineersct.com
RE: Will the load contribute to the SC damage damage of the cable
RE: Will the load contribute to the SC damage damage of the cable
Depends on how much closer and the protection at the sub.
Closer to the sub should mean higher fault currents and hopefully faster clearing times, given proper protection.
Who said "As it's said"?
Alan
RE: Will the load contribute to the SC damage damage of the cable
When the engineer performs the GPR study, the distant from sustation is the main factor to consider, then the fault clearing time (and other factors of course). Doesn't matter how the fault is closer to the substation, the clearing time would not be less than 5 cycles for most of utilities, due to the speed of circuit breaker.
Same thing applies to the cable splice fault.
WOuld you tell why some damage caused by cable splice failures (fault) were hardly visible except the substation circuit breaker was tripped. But others caused the explosion even even vault fire?
RE: Will the load contribute to the SC damage damage of the cable
What do you mean by damage? Cable damage, damage at the site location or some other damage.
A solid ground fault will be fed from the source and may be fed by regenerating motors. Regenerated current may increase the damage at the site of the fault, but may not be seen by the cable ahead of the fault.
Bill
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"Why not the best?"
Jimmy Carter
RE: Will the load contribute to the SC damage damage of the cable
THanks
RE: Will the load contribute to the SC damage damage of the cable
To see the effects of loading, you must consider the existence of regenerating loads and then analyse the failure circuit to see if the regenerating current adds to the supply current, has no effect or subtracts from the supply current.
In some instances an open may do much more damage at the failure location than a short or partial short. This may be even more so in the event of a far out failure where the open is not immediately detected or the open arcs for a time before going to ground and initiating ground fault protection.
Bill
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"Why not the best?"
Jimmy Carter
RE: Will the load contribute to the SC damage damage of the cable
Regards
Marmite
RE: Will the load contribute to the SC damage damage of the cable