×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Definition of Reactive Power
2

Definition of Reactive Power

Definition of Reactive Power

(OP)
The IEEE Standard 1459-2000, section 3.1.1.3 defines reactive power as the contour integral of v*di divided by 2*PI.  Does anyone know the origins of this definition?

RE: Definition of Reactive Power


...Does anyone know the origins of this definition?

Reactive power (Q) is usually calculated using RMS value from the conventional power triangle relationship.
                
                        Q=SQRT(S2-P2)   or Q= S.Sin[cos-1(PF)]

This relation may contain significant error in unbalance or waveforms other than perfect sinusoidal conditions.

The formula proposed in the IEEE Std 1459 is intended for not only perfect sinusoidal waves, but also to distorted sinusoidal and non-sinusoidal waves in balance or unbalance conditions.

This definition  provide a challenger benchmark for manufacturers of new digital revenue meters and monitoring devices to measuring reactive power (Q) and total power (S) with better accuracy than conventional methods.

RE: Definition of Reactive Power

The countour integral applies to a complex function. If we are considering non-sinusoidal waveforms, we cannot consider v a vector. So I don't understand mathematically what that expression represents.

One sanity check though. Using the chain rule:
integral v di /(2Pi) = integral v(t) * (di/dt) dt / (2Pi)

If we looked at the pure sinusoidal case, di/dt will be 90 degrees ahead of i(t).  If v(t) and i(t) were in phase, then v(t) and di/dt will be 90 degrees out of phase and integral over one cycle will be zero as expected.

If v(t) led i(t) by 90 degrees such as inductive power, then then v(t) and di/dt will be in-phase and the integral over one cycle would be positive.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: Definition of Reactive Power

Note that this standard is a "trial use" standard and does not have ANSI approval. The approved ANSI standard for revenue meters is C12.1 from NEMA. This standard uses a sum the harmonics approach. Even with a wider definition, the tests described in the standard are all at or very near the fundamental with no harmonics.

There is a bibliography in 1459. Sorry I cannot narrow it down.

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!


Resources