Dear Folks,
Is there a way to wire a Form 6S meter to accommodate Form 5S Meter requirements. The Switchgear instrumention available are 2 PT's and 3 CT's, the PT's are connected A-B & B-C while the three CT's are connected in star configuration. We only have Form 6S meter which if I understand...
Dear Folks,
I'm trying to figure out how the analysis dist. software we use calculate the impedance values for our system. My calculations match the software except for one area.
System/Source Information:
R1 (Utility-Per Unit)=0.0096 @100 MVA Base, @115 kV Base
X1 (Utility-Per Unit)=0.0761...
Folks,
SEL 351S Relay Settings started to confuse me, they use the 67 Directional Overcurrent element and the 32 Reverse Power element backward, in my opinion.
Have any of you worked or dealt with setting this kind of relay. My application is for dual-feed industrial substation and I want to...
Folks,
I'm hoping you share your opinion with me on this.
Do you consider the Minimum Utility Fault Current on the transformer primary side when setting the instantaneous element for the protective relay (115 KV side) or you need to be concerned only with the Maximum Fault Current??
Should...
Dear Folks,
May someone please explain to me the difference between MV circuit breaker auxiliary contacts versus spare ones.
I got a little bit confused after looking at the GE-Power VAC PVDB breakers schematics, they list all auxiliary contacts that are equipped with the breaker (for example...
Dear Folks,
We are about to replace an old oil MV Circuit Breaker with new MV Vacuum one.
The old breaker trip circuit coil is rated 12.7 amps @ 48VDC, close coil and charge motor was 240 VAC.
The new breaker trip circuit coil is rated 17 amps @ 48VDC, The close coil (17 amps) and charge...
Dear folks,
What is the most effective method to confirm and check the phase angle relationship for the load and source side CT's for a transformer differential relay?
The transformer is 30 MVA, 115/12.47 kV, Delta/Wye with 30 degree phase shift. The CT's are connected Wye (on TX delta side)...
Dear Folks,
what are the recommended commissioning tests on replacement of medium voltage circuit breakers?!
I made a list that included CT ratio and polarity tests, hipot test for the bottles, resistance tests for the contacts, megger test for the insulation, finally, functionality test for...
Dear folks,
Scenario:
We have 3 peak-only generation units, 1000 kw, 1250 kVA, 4160-2400 volts each. All generate to a common bus then to a 3750 kVA step-up transformer to 12.47 kV dist. level. They tie to utility through NO breaker on the 12.47 kv TX side. The TX is Star on gen. side and Delta...
We're about to replace old oil CB with new GE-VAC CB. Control dwgs for new CB shows two outputs to each of Remote Trip Ckt. and Remote Close ckt. Any advice on how best to utilize each of these 4 ckts (to the two remote trip and two remote close ckts)?
In the old breaker we had a Low Pressure...
Dear Folks,
I went over Bussmann's SPD Book and Cooper's Electric Distribution Protection Handbook, they all seem to explain how to protect individual TX primary. I would like to know how to incorporate that with Tap Line fuses (in case having more than one TX's down the tap line). Do you...
Dear Folks,
We've calculated the available fault current at our substations (points of delivery) using the Per Unit method. I got a bit confused on how to calculate the SC current at the Sub TX secondary knowing the available SC current at the Sub TX Primary (where we used the MVA/KV base)...
folks,
does any of you know the basic empirical equations used to calculate arc-flash energy produced by fault currents on 13.8 kV system. I've calculated the SC current on our system but I don't know how to convert the results into arc energy required to specify protection cloth/tools.
I...
Hi folks,
is sizing secondary metering CT's 25% above normal load is sufficient to accomodate for any short-term overload? in this case what role does the Thermal Rating Factor play, should it be conisdered when sizing the CT's and how?
Thanks for your input.
We know the Utility Available Fault Current on the 115 kV Substation Side (@100 MVA base), also, source impedances are known as well as the Substation Transformer Z% (%8).
How do I Calculate the Fault Current on 13.2kV Secondary Side of the Substation Transformer (115/13.2, 21 MVA, %Z=8)...
We are hi-pot testing our 4.16 kV distribution circuit breakers at 15 kV (AC) for two-three minutes, I was reading the circuit breaker spec. manual and it says test the breakers for 5-20 seconds!!! I'm seeking your opinion for the reasonable testing duration in order not to deteriorate the...
We're working on new installation for an airport facility in northern Virginia. The load current for the facility is about 400 amps, the line-line voltage is 208 volts, and the CTs will be used for metering purposes only. I was wondering what is the accuracy class for availble CTs that fit into...
