Novatech Bitronics M87X Series, Manual

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ML0021 August 15, 2018
36
Copyright 2018 Bitronics, LLC
There is also a relationship to the Total Power Factor, which is described in Section 4.3.
Total Power Factor calculations using the Arithmetic VA method will still indicate a "1" on a
system with phase amplitude imbalance, but not with canceling leading and lagging loads.
For example, on a system with a lagging load on one phase and an equal leading load on
another phase, the value of the Arithmetic VAs will not change relative to a balanced
system, but the Total Power Factor will be less than "1". The Total Power Factor
calculated with Arithmetic VAs will "see" the reactive elements in this system, while the
Total Power Factor calculated with Geometric VAs will not.
4.4.3 Equivalent VA Calculations
2 2 2 2 2 2
2 2 2 2 2 2
3
  
  
     
    

TOTAL A N B N C N A B C
A B B C C A A B C
TOTAL
EQUIVALENT WYE VA V V V I I I
V V V I I I
EQUIVALENT DELTA VA
The Equivalent VA calculation has not been as commonly used as other approaches, but
has been discussed extensively in technical papers. It is also referred to as "System
Apparent Power". This approach to the VA calculation may yield results which are
surprising to those used to more traditional methods. A system with amplitude imbalance
will yield a greater value of Equivalent VAs than a balanced system.
There is also a relationship to the Total Power Factor, which is described in Section 4.3.
Essentially, Total Power Factor calculations using the Equivalent VA method will not
indicate a "1" on any system unless the loads are purely resistive, and the amplitudes are
balanced. Further, the Equivalent VA method may yield better results in the presence of
harmonics, where Total Power Factor will also be reduced from "1". Refer to industry
standards for more information.
4.5 Energy (1-Cycle Update)
Separate values are maintained for both positive and negative Watt-hours, positive and
negative VAR-hours, and VA-hours, (for each feeder in the M872). These energy
quantities are calculated every cycle from the Total Watts, Total VARs, and Total VAs, and
the values are stored into non-volatile memory every 15 seconds.
Energy values may be reset. All values are reset simultaneously. Refer to the appropriate
protocol manual for details.