incoming Supply 11kv failed, new 11kv switch fitted by electricity supplier, before powering back on/and switch repair.........switchfuse to building 1500A per phase was isolated and locked OFF.....on the building incoming busbars (lv side)carried out resistance tests between phases...phase/neutral...phases/earth...all return values of 1.6 ohms.......there is the standard LV board monitoring amp/volts/earth leakage alarm,lamps, this is a 40 year old panel...on further inspection throughout building no signs of ANY damage issues on site...so went ahead and switched on???? everything worked AOK????......can anyone explain this???:?
LV busbar resistance/IR test after supply 11kv switch fail then repaired
- Thread starter ronkyote
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thinking about this...........an inductor/coil would oppose the increase in current in its physical dimension, a megger+resistance meter uses dc 250/500/1000 so capacitance is out of the equation)unless faulty??), electronically speaking the low resistance would show.......untill the ac pressure is applied then @ 50 hz uk, but the switching to block would be <microsec to mon cct??? disabling low ohms issue>>> wot do you think?:thumbsup:
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
I suppose that a low line to line DC resistance measurement might result from relay coils, transformer primaries, and motor windings that are connected but have a VERY high inductance, so that the normal current, even at 50Hz, would be much lower than you would calculate from the measured resistance.
In fact, since the measurements were on the low voltage side the increase in impedance with AC applied would not even have to be that great.
Am I interpreting what you say correctly: The 11kV incoming goes to a building feed transformer and you measured on the low voltage side of that transformer, where the building load would be seen? Was the transformer secondary disconnected at that time or did you only open the HV (primary) side?
In fact, since the measurements were on the low voltage side the increase in impedance with AC applied would not even have to be that great.
Am I interpreting what you say correctly: The 11kV incoming goes to a building feed transformer and you measured on the low voltage side of that transformer, where the building load would be seen? Was the transformer secondary disconnected at that time or did you only open the HV (primary) side?
zog
Senior Member
- Location
- Charlotte, NC
Have any volt or power meters in that gear? I am willing to bet you forgot to pull the PT fuses before testing
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