rcwilson, I like the two independent charger & battery and trip coil systems you recommended. It is a simpler and more secure trip system, with no common point of failure, besides the ac supply to battery chargers, assuming separate sources not available. I would keep the DC undervoltage...
Check the Manual on the Roof-Top unit (I assume an HVAC unit). It usually tells you the maximum rating of the Overcurrent Protective Device(OCPD) required for the unit. It also indicates that the OCPD should be UL listed as Type HACR (Heating, Air-Conditioning and Refrigeration).
Would current limiting fuses installed in series with each source help reduce the through-fault current contribution to downstream faults on the buses connected via the bus-ties? The fuses can be selected for operation within their current limiting range, for faults on the buses connected by the...
I suspect that the electronic governor for your turbine was powered by 110VDC, and the loss of 110VDC caused your turbine steam valve to go closed, resulting in the flow of reverse power into your turbine.
Normally, I have seen DC undervoltage alarms (27DC) on DC control voltage systems. Was...
If your 4160V Transformer winding has its star point solidly grounded, then using a CT on the star-point connection to ground in conjunction with a 50G protection relay, you can trip the generator breaker on the 480V side of the transformer within 50 msec. This would allow you to select your...
edison 123 Quote:"If there is a double ground on the rotor, he cannot run the machine at all."
The location of the double grounds can be within the same pole, just a few turns apart, so only a few turns are shorted out. I agree, if grounds involve large portions of the same pole winding or more...
Did you perform pole drop tests and rotor insulation-to-ground test on the rotor to check for turn-to-turn shorts and grounds? If you have a double-ground (at two locations) on the rotor winding, you will require more field current to generate a given voltage.
Does your 13.8kV Bus-Tie auto-close if you lose power on either the 'A' or 'B' incomer? If yes, the the closure of the Bus-Tie should be permitted by a 27R (Bus residual Undervoltage relay) located on the de-energized 13.8 kV Bus,to ensure that all motor back-emf has decayed before closure of...
Zogog, thanks for the feedback. Do you work with the Manufacturer or its representative? How did you upgrade so many breakers? Have you been able to track their performance for years after installation, or is your comment based on the number of retrofits you have commissioned?
I would think that if a single conductor (Core # 1) in a 3-core multicore cable is energized at 120VAC, 60 Hz, then there exists multiple capacitance paths between the energized core and the core (#3) carrying the start signal back to the contactor. Core # 2 will also be energized at 120VAC if...
Nightfox, are you still having the UPS problem with transfer to Bypass when energizing the rectifier? Can you check the manual on the Static switch to determine what the threshold limts are for transfer to Bypass? These can be a low inverter output voltage threshold (Undervoltage), high Inverter...
What were your Generator Stator Winding Insulation Resistance and Surge Test results prior to and after the event? Were generator stator cables disconnected & re-connected during the repair? If yes, was synch check done across Generator Breaker terminals with breaker removed from cell, using a...
Quote by Waross: "Even at that size, when the A/C starts, the UPSs may react due to the frequency dip and/or the voltage dip"
What is the response of the UPS to frequency/voltage dip? The Generator supply is powering the rectifier, which is recharging the battery and also powering the inverter.
