We are currently inplementing a design with a backup diesel generator which is used to backup critical loads in a facility. The generator is a CAT C32 PMG 1MW Standby, 1.25MVA. The generator is coupled to a traditional ATS with open transition transfer. When utility power is lost, the ATS will...
Hello,
I had a question with regards to utilizing the arc flash mitigation maintenance mode switch on a low voltage circuit breaker. Should the maintenance mode setting take into consideration the energization of a large load downstream? For example, the MCC main breaker has the maintenance...
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We have several 4000v 3000HP motors which are fed from a Siemens MCC FVNR cells. My understanding is that medium voltage equipment is suitable for 90degC terminations where the ampacity of the conductor can be based on 90deg ampacities. How about the motor end? These are API 541 motors...
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We have a few medium voltage motors with a 50:5 core balance current transformer for each phase. Are there any issues with connecting the neutral of each CT together at the motor end so that you only run 4-wires back to the relay, where the fourth wire is the common neutral wire? Are...
Hi Folks,
I am carrying out a motor starting study. I have a 3100HP 4000V motor being started across the line at a system voltage of 4160V. Motornis a centrifugal with closed valve start. The main transformer is a 12MVA transformer. The voltage dip is 13% for 1.5s. This dip is also seen on the...
Hello All,
We have a several 4kV motors, horsepower range is anywhere from 2000HP to 3500HP. These motors come with 50:5 self balancing differential CT. The accuracy class of these CT's is C10. The worst case distance of the motor from the Multilin 469 Motor Protection Relay is 180 meters. I am...
Hi All,
I have run into an existing installation where a 4.16kV Fused Contactor (360A) with 100E fuses feeds a 500kVA 4.16kV/480V transformer. There is a zero sequence CT and ground fault relay for the feeder which trips the contactor but there isn't any overload relay nor phase CT's. This is...
Hi Everyone,
I have been trying to determine the proper ampacity derating for TECK Single Conductor cables when arranged in a trefoil arrangement in Cable Tray with 2x the cable diameter spacing between in each trefoil. I cannot seem to apply the 12-2210 rules. Out of all the rules in Rule...
Hello All,
When implementing a differential protection for a transformer is there a problem if the accuracy class for the transformer primary CT is class C400 and the secondary CT at the switchgear is C200?
Hi Everyone,
We have a main-tie-main configuration for our system. When reverting back to normal service we want to use a closed transition re-transfer so that we don't have stop all the motors in the facility and cause a process upset. Both A and B sources on the M-T-M are fed from a utility...
