Aggregation intervals, Demands – SATEC PM180 Operation Manual User Manual
Page 22
Chapter 2 Device Description
Metering
20
PM180 Substation Automation Unit
The device provides individual voltage and current harmonic measurements both in
percent of the fundamental component, and in corresponding engineering units.
Quantities in engineering units are calculated only for odd harmonics.
Angles for phasor vectors are given relative to the V1 phase voltage.
Aggregation Intervals
The device provides electrical measurements using a number of fixed aggregation
time intervals from 1/2 cycle to 2 hours. The demand measurements use
programmable aggregation intervals of up to 2.5 hours. The following table shows
aggregation intervals available for different electrical quantities.
Parameter
1/2 cycle
1 cycle
200 ms
1 sec 3 sec
10 min
2 hours
RMS volts and currents
Ч
Ч
Ч
Ч
Ч
Ч
Ч
Powers
Ч
Ч
Zero-sequence
Ч
Ч
Ч
Ч
Ч
Ч
Ч
Unbalance
Ч
Ч
Ч
Ч
Ч
Ч
Ч
DC Voltage
Ч
Ч
Ч
Ч
Ч
Ч
Ч
Frequency
Ч
Ч
Ч
Ч
Ч
Ч
Total
Harmonics/Interharmonics
Ч
Ч
Ч
Ч
Individual Harmonics
Ч
Ч
K-factor
Ч
Ч
Ч
Ч
Crest factor
Ч
Ч
Ч
Ч
Symmetrical components
Ч
Ч
Phasors
×
The 200 ms RMS and unbalance quantities are integrated over a 10-cycle time for 50
Hz and 12-cycle time for 60 Hz power system. The data for the 3 sec time interval is
aggregated from fifteen 200 ms time intervals. All RMS quantities aggregated from
lower time intervals represent true RMS readings over the entire aggregation interval.
Demands
Demand measurements are provided for volts, amps, total harmonics and powers.
Two different demand measurement techniques are used: block interval demand and
sliding window demand.
Block Interval Demand
The block interval demand is calculated by aggregation of measurements over
contiguous and non-overlapping fixed time intervals. Volts, amps and total harmonic
demands are produced by averaging 1 sec RMS aggregates. Power demands are
evaluated using integration of energies and averaging power over the demand time
interval.
For volt, ampere and total harmonic demands, the demand period time is
programmed from 1 second to 2.5 hours (see
For power demands, the demand period can be selected from 1 min to one hour.
Sliding Window Demand
The sliding window (rolling) demand technique is applied to power demands. The
sliding window demand is calculated by averaging block interval demands over a
number of adjacent demand intervals, which produce a sliding window. The number
of time intervals for a sliding window can be selected from 1 to 15. When the present
block demand interval expires, the sliding window moves one step forward by
replacing the oldest entry with the most recent calculated block interval demand.
Accumulated and Predicted Demands
For power demands, the device provides an indication of two additional parameters:
the accumulated block interval demand and predicted sliding window demand. Both
accumulated and predicted demands can be effectively used for load shedding on
the substation feeders.