Is there some level of "free" KVARH tolerated by Electric Ireland.

Calahonda52

Looking at 4 months bills. jan to April
MIC is 400kVA, costing c 2,500/month
max actual c 250kVA/month
monthly usage c 60,000kWh
Its an office with full gas heated aircon so don't expect KVA to vary that much

Reactive Power Charge (RPC) is c 16,500 per month at zero cost.

Just wonder why the RPC is "free", hence this post
Tariff is 7 Band Seasonal time of day

Thanks as always

brightspark

https://www.electricireland.ie/business/help/efficiency/wattless-charges-for-business---explained


Not sure if figures apply to everyone or are current

Calahonda52

Thanks for this, much obliged.

would be interesting to know how this formula is arrived at
"If your consumption of wattless units increases above one-third of your general units per bill, the power factor will drop below 0.95, and the excess wattless units will incur a charge."

Stoner

This is useful

http://docs.wattics.com/2016/03/03/analysing-electrical-demand-and-supply-kw-kvar-kva-pf-v/
There's a simple one with a pint of beer and the head analogy if you want it

brightspark

Calahonda52 wrote: »

Thanks for this, much obliged.

would be interesting to know how this formula is arrived at
"If your consumption of wattless units increases above one-third of your general units per bill, the power factor will drop below 0.95, and the excess wattless units will incur a charge."

Power factor = KW/ (sqr root (kW*kW+kVA*kVA)

(Not sure how to write formulas here)

But in your example (figures divided by 1000)

60/(Sqr root (60*60+16.5*16.5)

60/(Sqr root(3600+272.25)

60/(Sqr root(3872.25)

60/62.2274

= 0.964

As it's above 0.95 you don't get charged

If the wattless was exactly a third of the watts value then using the formula PF = 0.948683298 so it's close enough to the point where you get penalised.

Bruthal

Probably the KVA x KVA in the formula there should in fact be KVAr x KVAr, if im looking right.

The 62.274 is in fact the KVA, or apparent power.

If the power triangle is drawn, with real power at bottom being 60 long, at 90 degrees straight up we have reactive power, at about 16.5 long, then the apparent power will be the final line of the triangle, being about 62.2 long, giving a pf of about 0.95

brightspark

Correct Bruthal!

Surprised no one spotted it sooner



I think the autocorrect removed the "r"

Thanks

Incidentally I wonder what old Pythagoras would have made of his theorem being used to calculate electrical values?

Calahonda52

Thanks to all here!
Stoner, I found the beer analogy, thanks.

So, looking at another bill with a MIC of 170kVA, does that imply a max current of c 246 A [246A*400V*1.732)/1000 =170 ?

ps
Meant to ask, if you correct the PF to inside the 0.95 - 1.00 band, are you actually saving energy as well in terms of kWh or is it just the Excess fees paid being saved.
Am looking at a bill where PF is 0.86, thanks to the math above!, and a 4 month cost in 2017 of euro 350

My gaffer is of the view that I am only paid to identify kWh savings and not euros, hence the question.

Bruthal

brightspark wrote: »

Incidentally I wonder what old Pythagoras would have made of his theorem being used to calculate electrical values?

It would be interesting alright.

ted1

Your MIC charge is different than watt less charges.

If your MIC exceeds the rated MIC at any one stage throughout the month you'll be charged an MIC fee of about 7 euro per kvarh over your MIC.

Your wattless charge is if your KVarh is greater than a third of your KWH

Calahonda52

ted1 wrote: »

Your MIC charge is different than watt less charges.

If your MIC exceeds the rated MIC at any one stage throughout the month you'll be charged an MIC fee of about 7 euro per kvarh over your MIC.

Your wattless charge is if your KVarh is greater than a third of your KWH

Ted thank you for that
what about this?
Meant to ask, if you correct the PF to inside the 0.95 - 1.00 band, are you actually saving energy as well in terms of kWh or is it just the Excess fees paid being saved.
Am looking at a bill where PF is 0.86, thanks to the math above!, and a 4 month cost in 2017 of euro 350

brightspark

Calahonda52 wrote: »

Ted thank you for that
what about this?
Meant to ask, if you correct the PF to inside the 0.95 - 1.00 band, are you actually saving energy as well in terms of kWh or is it just the Excess fees paid being saved.
Am looking at a bill where PF is 0.86, thanks to the math above!, and a 4 month cost in 2017 of euro 350

A poor PF will affect the MIC as it's based on kVA, which increases as the PF gets lower (the reason why there is a charge is because more amps are required to supply a given wattage, necessitating larger cables etc)

There is an energy saving on the I^2 R losses but that is primarily an issue for the network.

It does not affect the kWh, however why pay extra when it's possible to reduce the charge unless the cost of installing the PF correction equipment is excessive. But the ESB website seems to indicate that a four year payback is typical.

Bruthal

Calahonda52 wrote: »

Ted thank you for that
what about this?
Meant to ask, if you correct the PF to inside the 0.95 - 1.00 band, are you actually saving energy as well in terms of kWh or is it just the Excess fees paid being saved.

Less energy is used at the generation end, and lost in transmission, to provide the same KWhs at the user end, the better the pf is.

2011

+1 to the above post.

Just to add, there is a heat loss during transmission. This loss is equal to the current squared multiplied by the resistance of the cabling. A better power factor results in a reduced current for the same power output and therefore reduced power loss. Volt drop is also reduced (I x R) and of course smaller current can result in smaller cable sizes.