MTUgEEk
Electrical
- Dec 7, 2006
- 5
Looking to see if anyone has any experience in substation main breakers tripping when a utility switches nearby.
I currently work at a petrochemical style plant with many 480V main substations. Recently we had the utility switch at a yard not to far from our facility and had 3 main breakers trip off-line. The utility was switching at a 345kV to 138kV yard. We have 2 additional transformers isolating this activity(138kV to 34.5kV and 34.5kV to 480V) from the main substations affected. Both main breakers tripped on a double ended substation (cuttler-hammer w/ digitrip) as well as one other main breaker tripped elsewhere in the plant with the same isolation on a separate double ended substation (Siemens RL w/ Static trip III). When approaching each it looked as if someone just pushed the trip button. No indication of a pick-up or trip on the trip units, the 86 LO relay did not roll, and the auto-bus transfer (ABT) did not throw over. The ABT initiates when a Basler BE3-47N/27 and starts an Agastat relay to throw over. We know the Basler is sensitive to high frequency false activation but this does not appear to be the case. The 86LO relay is rolled when Basler 87T goes, but that was fine as well. Some power meters in the plant did pick up a 90% sag for ~2 Sec, but nothing else in the plant was affected. During the sag a slight DC offset is apparent on the waveforms, not sure if this is transformer inrush from the utility or built into the metering at our site. We are scratching our heads and production is hesitant to run because we do not know what could cause this type of interruption. All things in the electrical prints say this cant happen.
Looking for any help
MTUgEEk
I currently work at a petrochemical style plant with many 480V main substations. Recently we had the utility switch at a yard not to far from our facility and had 3 main breakers trip off-line. The utility was switching at a 345kV to 138kV yard. We have 2 additional transformers isolating this activity(138kV to 34.5kV and 34.5kV to 480V) from the main substations affected. Both main breakers tripped on a double ended substation (cuttler-hammer w/ digitrip) as well as one other main breaker tripped elsewhere in the plant with the same isolation on a separate double ended substation (Siemens RL w/ Static trip III). When approaching each it looked as if someone just pushed the trip button. No indication of a pick-up or trip on the trip units, the 86 LO relay did not roll, and the auto-bus transfer (ABT) did not throw over. The ABT initiates when a Basler BE3-47N/27 and starts an Agastat relay to throw over. We know the Basler is sensitive to high frequency false activation but this does not appear to be the case. The 86LO relay is rolled when Basler 87T goes, but that was fine as well. Some power meters in the plant did pick up a 90% sag for ~2 Sec, but nothing else in the plant was affected. During the sag a slight DC offset is apparent on the waveforms, not sure if this is transformer inrush from the utility or built into the metering at our site. We are scratching our heads and production is hesitant to run because we do not know what could cause this type of interruption. All things in the electrical prints say this cant happen.
Looking for any help
MTUgEEk