Working on a manufacturing client in Cleveland who's been getting hammered on demand charges. Got their 15-minute interval data from FirstEnergy and I'm seeing negative kW readings during several intervals in October. We're talking -45kW to -120kW which makes no sense for this facility. They don't have any generation on site. Anyone seen data corruption like this before? Client is on rate schedule GSU-3 and these bogus readings are throwing off the whole billing demand calculation.
FirstEnergy interval data shows impossible negative kW readings?
Frank, I've seen this with APS here in Phoenix. Usually it's a CT polarity issue or meter programming error. The negative readings often correlate with times when large motors are starting up. Have you checked if there's a pattern to when these negatives occur? Also worth requesting raw pulse data if they still have it.
Had Alabama Power give us similar garbage data last year. Turned out their AMI system was dropping packets during transmission and the billing system was filling gaps with interpolated values that went negative. Mobile Bay Electric Coop had the same issue. You need to demand they provide the actual meter register readings, not the processed interval data.
Check the multiplier on those intervals too Frank. LG&E had a case where the CT ratio was programmed wrong and creating negative demand when it rolled over the register. Cost my client $8,400 in excess demand charges before we caught it. FirstEnergy should be able to pull the event logs from that meter.
Frank, you might want to cross-reference those negative intervals with any power quality events. National Grid up here had similar issues when voltage regulators were switching during low load periods. The negative kW readings were actually real backfeed from the customer's power factor correction capacitors. Not saying that's your case, but worth checking the kVAR data too.
Good catch Gail - pulled the kVAR data and you're right, there's leading power factor during those negative kW intervals. Looks like their old capacitor bank is switching at the wrong times. Still arguing with FirstEnergy that these shouldn't count toward billing demand since it's their voltage regulation causing the issue. This could save my client about $15K annually if I can get them to adjust the rate calculation.
Frank, document everything and file a formal complaint with PUCO if FirstEnergy won't budge. Had PSO here in Tulsa try to bill negative demand as positive until the commission stepped in. The interval data is supposed to reflect actual consumption, not utility system artifacts. You've got a solid case for adjustment.
Ed's absolutely right. I've won three cases like this with the NY PSC. The key is proving the negative readings are system-induced, not customer equipment malfunction. Get FirstEnergy to provide the voltage and frequency data for those same intervals. If they can't or won't, that's grounds for questioning the whole dataset.