Rms Variation Limit - Dranetz Energy Platform User Manual

RMS Variation Limit

RMS variation
setup properties
RMS trigger
parameters
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RMS stands for root mean square, a mathematical formula used to compute the
equivalent value of the voltage and current. Voltage and current changes are measured
and checked against the programmed limits. Thresholds are preset as high limits
(threshold above the programmed limit) and low limits (threshold below the
programmed limit). RMS variations result whenever voltage or current rms value rise
above or fall below the threshold limits.
The Energy Platform limits are fixed at IEEE 1159 standard default values of 90% of
normal for sag (dip), 110% for swell, and 10% for interrupts. However the user has the
option to enable/disable rms variations.
In order for the instrument to trigger on rms variation, any one of the measured
quantities for which a trigger is enabled must go above the High Limit or below the
Low Limit for a period of at least one rms sample point (which are taken twice per
cycle with a one cycle sliding integration window).
The disturbance end point is defined as the cycle when all channels for which triggers
are enabled have come back within limits (plus hysteresis). Until this criteria is met,
any subsequent excursions beyond the thresholds are considered part of the original
disturbance. To minimize the number of triggers recorded for a sequence of closely
spaced disturbances, hysteresis is employed in both voltage and time for the begin-
event and end-event thresholds.
NOTE: Hysteresis values assigned to limits are set by the system and not
programmable by the user.
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