ND MultiCube Single Phase, Инструкция по установке и эксплуатации

Страница: 6 / 32

Meter Operation
Page 6 Single Phase MultiCube
2. Meter Operation
2.1 Measurements
The MultiCube makes use of a high speed micro-processor and an Analogue to
Digital converter to monitor input signals. The phase voltage, current and power (kW)
are measured directly and a number of other parameters derived from these in
software. The measurement process is continuous with all signals scanned
simultaneously at high speed ensuring that all input cycles are detected. Distorted
input waveforms, with harmonics to the 20th are therefore detected accurately.
Derived parameters are calculated and displayed once a second, scaled by user
programmed constants for current and voltage transformers.
Instantaneous power parameters are integrated over long time periods providing a
number of energy registers. System frequency is detected by digital processing of
the voltage input signal.
2.1.1 Rolling Demand (Amps and kW Demands)
Average values of Amps and kW are calculated over a user programmable time
period (10 - 2500 seconds for Amps, 1 - 60 minutes for kW). The displays show the
averages for the most recent time period ending at the time the display was last
updated. The demand period is continuously updated as time progresses hence the
term “
Rolling Demand ”.
2.1.1.1 Calculating Rolling Demand
Each user set time period is split into smaller sub-periods (10 for Amps, 15 for kW).
An average value for measurements taken every second during a sub-period are
calculated for each parameter. The most recent 10 (15 for kW) sub-period averages
are stored in memory as an array. An average of the data in each of these arrays is
displayed as MD (rolling demand).