Arbiter Systems Portable Power Sentinel 933A, Руководство по эксплуатации

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9.17 Voltage Fluctuations
Voltage fluctuations are monitored by classifying the 20/second voltage
data, per phase, with a 256-step linear classifier covering a range of
±
20%
of nominal voltage. These data are then summarized as a cumulative
probability table over a specified interval
−
typically 15 minutes. In
addition, the minimum, maximum, mean and standard deviation are
calculated. The data may be recorded in flash memory either continuously
or on demand.
Voltage fluctuations corresponding to system stability
events may also be monitored and a trigger generated using Schulz-Laios
filtering of the voltages.
9.18 System Time Deviation
System time deviation, which is the accumulated error of a clock using
the system frequency as its reference, compared to an absolute reference
such as UTC, is determined from the 20/second phase data described
earlier. System time deviation is accumulated as integer cycles of error
plus fractional phase, and is converted to seconds as needed. The positive-
sequence voltage phase angle is used for this measurement. Since this is
an integrated value, the constant of integration (initial time offset value)
must be specified by the user.
9.19 Phasor Measurements
Phasor data are formatted and output in accordance with IEEE Standard
1344-1995.
Phasors consist of the real and imaginary component of
magnitude for the voltages and currents at a particular point in a power
distribution system, along with suitable time synchronization fields and
other information. This information is available in real time, and is based
on the measured fundamental voltage, current, and phase angle described
above, at a rate of 20 records per second. There is a measurement delay
due to the data acquisition delay of 50 ms, signal processing time of
approximately 15 ms, and data transfer time which depends on the data
rate.
9.20 Phase Balance
The 933A measures phase balance by calculating the symmetrical sequence
components (positive, negative, and zero sequence) for the three-phase
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