- #1
Fisherman199
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Seeking the guidance of the Physics forums gurus, I was told this would be a good question to contribute to the community. Perhaps it will lead to an in-depth discussion of harmonics: Their creation, implications to power quality, and how to mitigate them.
I've been looking at some power quality captures I've gotten from the O&M department of my utility. We have a customer who's experiencing loss of power. I get these fairly regularly and usually it's an issue within the customer's electrical work. In some cases customers are tripping on three-phase when it's not needed or wanted, others issues have been the result of old cabling, others due to transformer insulation breakdown, and some are even caused by perturbation on the transmission system if the customer has a singularly sensitive tolerance. This particular instance is giving me some trouble mainly because they're having significant harmonic issues but I'm unfamiliar with LV filters enough so that making a recommendation is difficult. I always hesitate to place the blame on the customer's electrical work, despite that being the issue more often than not.
Does anyone have recommendations of LV harmonic filters?
Below are some details for those feeling adventurous.
Issue:
A utility customer is experiencing outages on sporadic days. The outages are complete losses of power and always occur between 11:00 and 11:15. There are not indicative brightening of lights.
Power Quality Details (55 day capture):
Current THD% (secondary of transformer): Ranges between 10% - 32%. Average of ~25% per phase
Voltage THD% (secondary of transformer): Ranges between 0.1% - 0.5%, Average of ~0.15% per phase
Harmonic component contribution (most prevalent): 3rd
Maximum return imbalance (non-faulted): ~4.2 Amps, 0.2 volts
Faulted instances (unknown cause): 2 with maximums at 700 amps at 19:32 EST and 230 amps at 12:51 EST
CBEMA impulses: 202
CBEMA impulses (outside thresholds): 15
Average Vrms (phase to phase): 282 volts rms
Details:
Service: 3 phase, 480 volts phase-phase, 277 volts phase-ground, #2/0 cable (assumed)
Transformer: 3 phase, Grounded-Wye/Grounded-Wye, core-form, non-tap changing, %z = 4.7%, x/r = 7
Location Electrical Drawings: Not Available
Predominate loading: Ordinate Non-Linear load percentage. Electric heater and water.
(can't place a percentage on it without the electrical drawings, which I don't have)
Circuit (upstream utility):
Max fault capability at service location (primary of transformer) (3 phase, bolted fault): 3200 Amps (apprx. by system computational model)
Resonant order of upstream, switched capacitor bank: ~9
Size of the capacitor bank: 900 kVAR
Conducting leading to service location (primary side of transformer): 397.5 ACSR Overhead (~4.6 miles worth, #4/0 neutral), #1000 XPLE Underground (~1045 feet worth, triplexed, conduit buried)
Station (transmission or distribution) interruptions during time-period of interest (55 days): None
EDIT: (OF NOTE): There are two other capacitor banks on this customer's circuit.
I've been looking at some power quality captures I've gotten from the O&M department of my utility. We have a customer who's experiencing loss of power. I get these fairly regularly and usually it's an issue within the customer's electrical work. In some cases customers are tripping on three-phase when it's not needed or wanted, others issues have been the result of old cabling, others due to transformer insulation breakdown, and some are even caused by perturbation on the transmission system if the customer has a singularly sensitive tolerance. This particular instance is giving me some trouble mainly because they're having significant harmonic issues but I'm unfamiliar with LV filters enough so that making a recommendation is difficult. I always hesitate to place the blame on the customer's electrical work, despite that being the issue more often than not.
Does anyone have recommendations of LV harmonic filters?
Below are some details for those feeling adventurous.
Issue:
A utility customer is experiencing outages on sporadic days. The outages are complete losses of power and always occur between 11:00 and 11:15. There are not indicative brightening of lights.
Power Quality Details (55 day capture):
Current THD% (secondary of transformer): Ranges between 10% - 32%. Average of ~25% per phase
Voltage THD% (secondary of transformer): Ranges between 0.1% - 0.5%, Average of ~0.15% per phase
Harmonic component contribution (most prevalent): 3rd
Maximum return imbalance (non-faulted): ~4.2 Amps, 0.2 volts
Faulted instances (unknown cause): 2 with maximums at 700 amps at 19:32 EST and 230 amps at 12:51 EST
CBEMA impulses: 202
CBEMA impulses (outside thresholds): 15
Average Vrms (phase to phase): 282 volts rms
Details:
Service: 3 phase, 480 volts phase-phase, 277 volts phase-ground, #2/0 cable (assumed)
Transformer: 3 phase, Grounded-Wye/Grounded-Wye, core-form, non-tap changing, %z = 4.7%, x/r = 7
Location Electrical Drawings: Not Available
Predominate loading: Ordinate Non-Linear load percentage. Electric heater and water.
(can't place a percentage on it without the electrical drawings, which I don't have)
Circuit (upstream utility):
Max fault capability at service location (primary of transformer) (3 phase, bolted fault): 3200 Amps (apprx. by system computational model)
Resonant order of upstream, switched capacitor bank: ~9
Size of the capacitor bank: 900 kVAR
Conducting leading to service location (primary side of transformer): 397.5 ACSR Overhead (~4.6 miles worth, #4/0 neutral), #1000 XPLE Underground (~1045 feet worth, triplexed, conduit buried)
Station (transmission or distribution) interruptions during time-period of interest (55 days): None
EDIT: (OF NOTE): There are two other capacitor banks on this customer's circuit.
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