Cost Implications Of Low Power Factor

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Discussion Overview

The discussion revolves around the cost implications of operating a three-phase, 11kV network without power factor correction (PFC) equipment. Participants explore how to calculate the increased electricity costs incurred during a period when PFC was switched off, considering a constant load of approximately 2.5MW.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks to calculate the cost of running without PFC, emphasizing the need to include these costs in an insurance claim.
  • Another suggests using a power meter capable of measuring power factor to assist in the calculations.
  • A participant provides context on how uncorrected loads affect utility costs, noting that utilities may charge based on distribution demand and energy supplied, with specific reference to Dominion Power's billing practices.
  • One participant mentions reviewing earlier bills that include charges for kVAr, anticipating a significant increase due to the PFC being turned off.
  • Another confirms that the purpose of PFC is to reduce kVAr, supporting the previous participant's concerns about increased charges.
  • A question is raised about the possibility of installing a kvar-hr meter to measure the reactive power consumption more accurately.

Areas of Agreement / Disagreement

Participants generally agree on the implications of operating without PFC and the potential for increased costs, but there is no consensus on the exact calculations or methods to quantify these costs.

Contextual Notes

Participants mention various factors that could influence costs, such as utility-specific billing structures and the impact of uncorrected power factor on distribution demand charges. There are also references to specific utility practices that may not be universally applicable.

Who May Find This Useful

This discussion may be useful for electrical engineers, facility managers, and professionals involved in energy management or utility billing analysis.

BIGEYE
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We operate a 3 phase, 11kV network with automatic power factor correction equipment installed. Over the last four weeks we have had the PFC switched off due to an electrical incident.
How can I calculate the cost of running without PFC for this period of time, our load is fairly constant at around 2.5MW. Our manager wants to include the increased electricity cost on the insurance claim due to operating without PFC.

TIA
 
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A power meter that can measure power factor? Something from Fluke (345B), http://www.amprobe.com/cgi-bin/pdc/searchprod.cgi?category=195&type=elec&tid=1&action=search", or your favourite instrumentation supplier.
 
Last edited by a moderator:
Background:
To see this from the Utility's point of view, remember what your uncorrected load is doing: forcing the Utility to supply you surplus current for the same power draw. This doesn't immediately cost them anything, unless it happens to force them to up the current rating of their distribution equipment in the locale of your facility.

Details:
You should have some idea of the uncorrected power factor from the rating on the correction equipment installed. The cost, if any, will depend on the particular utility. Typically total cost is broken down into Distribution Demand in kw (power rating of the distribution to your facility) and another part reflecting actual energy supplied. Dominion Power for instance has an http://www.dom.com/customer/pdf/va/vab8.pdf" Stay above that and there's no penalty. Drop below it and for your Distribution Demand cost, they charge a minimum of 85% of your maximum KVA demand. If your facility's max VA demand peaks up to, say, 3000 KVA, they may charge you for 2.55MW worth of distribution regardless of actual load. If your utility invokes such a trigger it will be no doubt be reflected in the next bill as a new floor for your 'Distribution Demand' as it is called with the supply portion remaining at the 2.5MW average. The cost difference between that bill and earlier ones, with the reason indicated on the utility bill, should be easy to demonstrate for your insurer.
 
Last edited by a moderator:
I have managed to get a look at earlier bills and there is a charge for kVAr, it varies quite a bit, but I'm expecting a big jump due to PFC being turned off. I am thinking along the correct lines?
 
Yes, you are. The purpose of the power factor correction is to reduce the kVAr.
 
Would there be a way to install a kvar-hr meter?
 

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