Frequency; Demand Measurements - Novatech Bitronics PowerPlex II User Manual

reset. All values are reset simultaneously. Refer to the appropriate protocol manual
for details.

5.9 Frequency

Frequency is calculated every cycle for every input. The PPX II monitors the change
in Phase Angle per unit time using the Phase Angle measurement for the fundamental
generated by the FFT. The System Frequency is the frequency of the input used for
synchronizing the sampling rate.

5.10 Demand Measurements

The traditional thermal demand meter displays a value that represents the logarithmic
response of a heating element in the instrument driven by the applied signal. The
most positive value since the last instrument reset is known as the maximum demand
(or peak demand) and the lowest value since the last instrument reset is known as the
minimum demand. Since thermal demand is a heating and cooling phenomenon, the
demand value has a response time T, defined as the time for the demand function to
change 90% of the difference between the applied signal and the initial demand value.
For utility applications, the traditional value of T is 15 minutes, although the PPX II can
accommodate other demand intervals (Section 6.10.5).
The PPX II generates a demand value using modern microprocessor technology in
place of heating and cooling circuits, it is therefore much more accurate and
repeatable over a wide range of input values. In operation, the PPX II continuously
samples the basic measured quantities, and digitally integrates the samples with a
time constant T to obtain the demand value. The calculated demand value is
continuously checked against the previous maximum and minimum demand values.
This process continues indefinitely, until the demand is reset or until the meter is reset
(or power removed and reapplied). The demand reset and power-up algorithms are
different for each measurement. These routines are further described in following
paragraphs. The maximum and minimum demand values are stored in non-volatile
memory on the Host Processor module.
NOTE: Changing VT or CT ratios does NOT reset demand measurements to zero.
Demand Quantity
Amperes
Fundamental Amperes
Volts (Bus 1 only)
Total Watts (A, B, C, Total)
ML0047 December 1, 2017
Phase Reference
Phase, Residual
Phase, Residual
Phase - Neutral,
Phase - Phase
Phase, Total
92
Function
Present, Max
Present, Max
Present, Max, Min
Present, Max, Min
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