Watt-Hour/VAR Meter Calibration

[bmodrow]

A typical calibration for a this type of meter calls for calibration to be performed 1.0 PF(unity), 0.5-lag, and 0.5-lead for watts and this makes perfectly good sense to me.

However, for the VAR function the points are 0-lag, 0-lead, .5-lag, .5-lead, .87-lag, and .87-lead.

My first question is what is the difference between 0-lead and 0-lag? (I inherently assume 0-lag and 0-lead are the same which is unity power factor, but why are two specific calibration points(0-lead, 0-lag) called for?)

My second queston realates to both watts and vars. The leading and lagging reference points are referring to power factor are they not?

Thank you in advance to all for any replies, I know I am missing a simple concept here and just cannot seem to grasp it.

 

[jstickley]

0-lead and 0-lag are definitely not the same as unity PF. Unity power factor (100% PF) is defined as a load made up of purely "real" power (a resistive load). 0% power factor loads must be either leading or lagging (either purely capactive or purely inductive).

 

[bmodrow]

See, I knew it was so simple it was eluding me. My problem stemmed from the fact that I was thinking 0-degrees leading or lagging and not of power factor itself.

Thanks for the quick and simple answer jstickley!

 

[ECHU]

FOR THE LEADING POWER FACTOR 0, THE LOAD SHOULD BE SOLELY CAPCITANCE WHEREAS LAGGING SHOULD BE SOLELY INDUCTIVE.
PLEASE READ THE FOLLOWING PHASOR DIAGRAM


VOLTAGE
1
1
1
LEADING-----------o------------LAGGING
CAPACITANCE INDUCTION
CURRENT CURRENT

PHASE ROTATION SHOULD BE CCW

BY THE WAY CAN ANYBODY TELL ME IS IT POSSIBLE TO USE SINGLE PHASE INJECTION TO CALIBRATE AN THREE PHASE VAR METER

 

[jbartos]

Suggestion to the original posting bmodrow (Electrical) May 16, 2003 marked ///\\A typical calibration for a this type of meter calls for calibration to be performed 1.0 PF(unity), 0.5-lag, and 0.5-lead for watts and this makes perfectly good sense to me.

However, for the VAR function the points are 0-lag, 0-lead, .5-lag, .5-lead, .87-lag, and .87-lead.

My first question is what is the difference between 0-lead and 0-lag? (I inherently assume 0-lag and 0-lead are the same which is unity power factor,
///True, in the unity power factor context.\\ but why are two specific calibration points(0-lead, 0-lag) called for?)
///VAR calibration context calls for these to distinguish between capacitive VARs for 0-lead, and inductive VARs for 0-lag. This is in agreement with the above postings.\\My second queston realates to both watts and vars. The leading and lagging reference points are referring to power factor are they not?
///Yes, since the Power Factor is affected by VARs, e.g.
PF=Watts/VAs=Watts/{[(Watts**2 + (VARsind - VARscap)**2]**0.5}\\\

 

[busbar]

1.0PF and 0.5PF produce 100% and 50% registration in a watthour function. Similarly, 0.0PF and 0.866PF produce 100% and 50% registration in a varhour function.

As for lead and lag, typical {Radian/S-C} standards produce no registration in a leading condition—though that could be a regional custom.