Hello:
I work for a US government agency.
We recently replaced our 30 year old substations in our administrative building.
Quite recently a grounded\shared neutral situation caused a feeder ground fault relay to trip the feeder breaker.
To remedy the situation we will have to revise the...
Hello:
A small pump house building was recently connected to our 4.16kV overhead distribuition system. Basicall the system consists of a 150kVa pad mounted transformer (4.16kV Delta Pri - 208Y/120V Sec.
At the pole cutouts the surge arresters are tied to a ground rod at the pole base. The...
Hello:
In the US the two main fire codes (IFC and UFC)impose a limitation of 50 gal of electrolyte for UPS VRLA battery systems.
Apparently the official interpretation is that the 50 gal of electrolyte is the aggregate sum of the battery systems in a specific space (data center, battery room...
Hello:
A decision was made by my management to install surge arresters at every other pole of a 69kV line thats 3200 feet long between the utility metering point and the main substation 69kV incoming switch. The distance between poles is 200 ft. The line has a guard wire.
Also the surge...
Hello:
We recently specified Doble testing (tip-up) on a 750/1000kVA dry-type transformer (20+ years old) as part of a comprehensive test regimen. Our NETA certified test company said that they would do it, but would not be able to get any useful information because the transformer is a...
Who can legally perform power systems and arcflash studies?
Can they be performed by technicians who will then use the study results to set protective relays and select fuses.
Sundale,
Just a reminder that there are people of all races in Mexico, Panama, Cuba, Puerto Rico and the majority of Central and South American countries.
Hidalgoe
...a 12.47kV load while a new feeder is being installed. It will take approximately 12 hrs to install and commission. Two question have been asked.
* Is it prudent to use a step down power transformer as a step up transformer?
* Will the 50/51 relay protection still work if the current flows...
Hello:
We have Westinghouse Power Centers in one of our buildings. These centers have ASLR dry type transformers (12.47kV,500/666kVA, 150 degree C rise, Sharon Plant, 1978)). Recently one of these transformer caught fire and released a lot of smoke over a period of 1/2 hour. Our fire dept...
Hi:
Our local utility does not transpose its HV lines (as far as I can see by looking at its transmission and subtransmission lines).
Is there a need to be worried about this as far as overcurrent relaying is concerned?
Thank you kindly,
hidalgoe
HellO:
What have been the results of recent engineering debacles, like Boston's Big Dig concrete section that fell and killed some folks in a car or Katrina meant for PE's as far as liability and ethics are concerned?
davidbeach,dpc,jghrist,stevenal:
I called a colleague who was familiar with the SEL 351S and discussed this relay's multi-functionality. We came to the conclusion that what I need is separate OV/UV protection; a relay that will provide the time-voltage characteristics that I want for OV/UV...
rbulsara:
I appreciate your concern.
I have over 35 years of experience as a PE and power systems engineer. I have done projects for small and large industrial plants and for colleges, universities, hospitals and a few medium sized utilities.
My motivation was obtaining advice on a relay I...
dpc:
We have no load shedding scheme implemented at this time or other frequency relaying
When I set the old 27/59 electromechanical devices I had access to time-voltage curves, but with the 351S I have not been able to locate any.
Yes, I would appreciate advice on settings for this advanced...
Hello:
We recently replaced our old main substation electromechanical relaying system with a SEL 351S/351A system. The 351A relays are for feeder protection and the 351S relays serve as main secondary breakers.
Our substation consists of 2ea power transformers (69kV/12.47kV, 15/20MVA ABB)...
The CTs are protecting the transformer. The 69kV lines feeding the transformers have load break switches up stream of the Trans-Rupter. The lines can be de-energized using these switches. We also have a tie switch at our main substation to parallel the transformers in case we want to shut down...
Our Main Substation transformers (15MVA, 69kV/12.47kV)have S&C Trans-Rupters with overcurrent protection on the 69kV side. What would be the best placement for the CTs used with the overcurrent relays: on the line side of the Trans-rupters or on the load side of the Transrupters.
dpc:
The company tested the OLTC was tested thoroughly and given a clean bill of health. The tripping did occur on phase instantaneous (set at highest settings) and a .3 sec additional time delay added.
