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Programmable Min/Max Log
For the real-time harmonic quantities, the PM295 provides 16 programmable
Min/Max log registers. The user can allocate these registers to any of the 16
harmonic parameters, and the instrument will continuously monitor them allowing
the corresponding minimum and maximum values to be logged.
Programmable Min/Max registers operate in the same manner as standard registers,
and can be accessed and cleared in the same way.
Resetting the Min/Max Log
All the minimum/maximum keeping registers, either for real-time parameters or
extreme demands, can be cleared separately via the front panel, communications, or
by a programmable setpoint. Through communications, reset can be made
concurrently in all instruments connected to a master computer, if the broadcast
mode is used.
4.3 Demand Measurements
4.3.1 Demand Readings
The PM295 provides demand measurements for active (kW), reactive (kvar) and
apparent (kVA) power over all three phases, and volt and ampere demand s per
phase. All demand readings are represented by a positive number.
Active power demand is calculated for positive power only. When the instrument
detects reverse energy, no demand calculations are made (negative demand is not
taken into consideration).
Reactive power demand is calculated for bi-directional power, without taking into
consideration power sign, and will represent integral energy flow through load,
either inductive or capacitive.
Voltage and ampere demand calculations are always made using the sliding window
technique. Power demands are calculated using block interval, sliding window and
thermal averaging techniques.
4.3.2 Block Interval Demand
For block interval demand, calculations are completed at the end of each subsequent
demand interval (see Section 4.2.3), and the result is used as the new present value
for the extreme demands evaluation. This method is similar to the way mechanical
demand meters operate. The billing demand period is defined for block interval
demand by the
For long demand intervals, block
DEMAND PERIOD parameter.
58
Operation Techniques
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