Sorry for yet another question on this topic.
I have got sub metering installed on all outgoing submains, I also have a meter on the incoming main
Between the main meter and sub meters, I have my power factor correction
over a week, I'm getting about 1,500kWh of difference, the sub meters total being higher by that amount compared to the incomer meter.
I'd like to say that the power factor correction has effectively saved that number of kWh, is that correct?
davezawadi (David Stone):
Ok Johno, can you supply the reactive power readings on the TX feed (overall) and after the PF corrector. I would expect the Tx to be very low (comparatively) as the PF reads 0.99. The readings on the outgoing feeders will show the reactive power and the total will be about how much you are saving. It may be about the 1500 kVAh you mention, presumably over a period, but a significant amount of money. The TX primary meter will be reading KVAh, and should approximately agree with the TX secondary meter, less 2-3% for TX loss etc. The PF correction could well be saving several hundred pounds over your metering period, and choosing a day for this would certainly help others understand the savings. Another saving may well come from the replacement of the main transformer, modern high-efficiency types may well save their cost reasonably quickly. Taking daily and hourly readings may also isolate more savings from the use of particular plant, or lighting loads that would benefit from changes or replacement.
Regards
David
I cant monitor the PF on the TX feed, I don't think its feasible to get it really. All I can really say is that the bill, which is obviously from the TX feed shows a PF of, usually, .99.
What I might do is take the bill reading, take the incomer reading which will give me something like the TX losses, then take the sum of the sub-meters, which seems to be higher, and that should be what the PFC is saving, with the uncertainty of measurement. Its going to take about six weeks to get a full months of data to do this, its all an interesting learning curve.
the main focus is on the sub mains, as we can see loads switching in and out on timers. Armed with some good site knowledge and the size and duration of the load, you can make a good guess of what equipment is turning on and whether a more effective system is needed to shut it down
The transformer is from about 2005, a Schneider ONAN air cooled one, I'd like to think because of its age, its reasonably efficient.
davezawadi (David Stone):
Ok Johno, can you supply the reactive power readings on the TX feed (overall) and after the PF corrector. I would expect the Tx to be very low (comparatively) as the PF reads 0.99. The readings on the outgoing feeders will show the reactive power and the total will be about how much you are saving. It may be about the 1500 kVAh you mention, presumably over a period, but a significant amount of money. The TX primary meter will be reading KVAh, and should approximately agree with the TX secondary meter, less 2-3% for TX loss etc. The PF correction could well be saving several hundred pounds over your metering period, and choosing a day for this would certainly help others understand the savings. Another saving may well come from the replacement of the main transformer, modern high-efficiency types may well save their cost reasonably quickly. Taking daily and hourly readings may also isolate more savings from the use of particular plant, or lighting loads that would benefit from changes or replacement.
Regards
David
I cant monitor the PF on the TX feed, I don't think its feasible to get it really. All I can really say is that the bill, which is obviously from the TX feed shows a PF of, usually, .99.
What I might do is take the bill reading, take the incomer reading which will give me something like the TX losses, then take the sum of the sub-meters, which seems to be higher, and that should be what the PFC is saving, with the uncertainty of measurement. Its going to take about six weeks to get a full months of data to do this, its all an interesting learning curve.
the main focus is on the sub mains, as we can see loads switching in and out on timers. Armed with some good site knowledge and the size and duration of the load, you can make a good guess of what equipment is turning on and whether a more effective system is needed to shut it down
The transformer is from about 2005, a Schneider ONAN air cooled one, I'd like to think because of its age, its reasonably efficient.
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