Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Auxiliary Consumption and limits

Auxiliary Consumption and limits

Auxiliary Consumption and limits

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

RE: Auxiliary Consumption and limits

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?

RE: Auxiliary Consumption and limits

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.

RE: Auxiliary Consumption and limits

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.

RE: Auxiliary Consumption and limits

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.


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

RE: Auxiliary Consumption and limits

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.

RE: Auxiliary Consumption and limits

"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.

RE: Auxiliary Consumption and limits

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!

RE: Auxiliary Consumption and limits

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

RE: Auxiliary Consumption and limits

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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close