Auxiliary Consumption and limits

[jan63]

The topic of recent discussion in our Power system is the auxiliary consumption.
In our power stations meters are installed at generator terminals,at source of Auxiliary for power station and at exit points for power evacuation i.e transmission line.
Our Audit party says that the difference between reading of generator terminals and transmission lines(difference between generation and net electrical output) is our Auxiliary consumption.While our plea is that this difference includes losses in bus ducts,losses in excitation system,losses in power transformers which can not be counted towards Auxiliary consumption.
I want to know opinion of forum.
Also are there any standards set for these losses

 

[cranky108]

Sounds like accounting problems. Is there a real difference between aux load and other losses?
Unless there is an accounting difference, say such as amount billed in the accounting, there is no difference.

May I ask if you are using revenue class metering? Or just relaying class CT's?

Is the accounting for play money, or actual money?

 

[RRaghunath]

Audit party is right.
All losses within the plant are counted as part of plant auxiliary consumption.
Power generated minus power that is billed is auxiliary consumption to put it simply.

 

[bacon4life]

The exact handling of losses versus auxiliary consumptions likely depends on your local market conditions.

Keep in mind that meters have some inaccuracy. In an application with very low auxiliary loads (i.e. hydro, solar, wind), the actual auxiliary losses might be smaller than the the error between two different meters placed at the same location. In low loss situations, the best accuracy is actually achieved by measuring the electrical parameters of each component (i.e. resistance, excitation currents) during factory testing, then calculating losses.

In my region, the market organization has somewhat different requirements for auxiliary losses depending on the magnitude of losses. No much is gained by detailed modeling of losses less than one percent, whereas modeling losses for plants with 10+ percent losses has more impact on the system.

 

[crshears]

OP: I am confused; you begin your thread speaking of your Power System, then seem to segue into generating stations . . .

If you limit your total losses to those on-site, they will generally be negligible compared to auxiliary consumption, and can conveniently be lumped together with the site consumption.

Grid losses on the other hand can be substantial; my utility applies a rule-of-thumb value of ~ 9% losses of all power generated, separate and distinct from the auxiliary power consumption of our transformer and switching stations [ our system's generating units are owned by various entities and account for their losses internally and on their own balance sheets.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[Hoxton123]

Traditionally the station power was considered at the generator terminals. The advent of private power as opposed to state owned or controlled generation, resulted in a significant change to attitude, especially with subsidised renewable generation. There came a realisation that nett generation (station terminals) was important, not gross (generator terminals).

Despite station losses sometimes only being a few percent of station capacity, power purchases wanted the station to provide its own auxiliary power, at its own cost…

In addition, the problem of metering arose. When energy (and money( flows are high, minor differences in metering tolerance can result in a large annual financial difference. Billing meter position can become the subject of detailed contractual discussions.

 

[cranky108]

"Billing meter position can become the subject of detailed contractual discussions."

That's a bit of an understatement. Throw in there ACE and BA zone of authority then the discussions become very heated. As well as discussions about testing, and who owns the meter, and maybe the need for more than one meter.

A good meeting to be a fly on the wall.

 

[Hoxton123]

Been there, done that. Real fun when you are stood in a 132 kv outdoor switchyard with a pair of binoculars trying the read the nameplate on a VT to determine the accuracy!

 

[cranky108]

Use a gopro on a hot stick. Works much better.

 

[Hoxton123]

Good idea! The tallest thing I had to hand at the time was a giraffe, and they can out run me!