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Chapter 3 Paramters/Functions Innovation Series Medium Voltage GP Type - G Drives GEH-6385
Phase Imbalance Monit or

The Phase Imbalance Monitor function mon itors the con dition of the phase

imbalance on the ac lin e as well as the status of the phase lock loop.

Function inputs

The following table specifies the input parameters of the Phase Imbalance Monitor

function.
Variable Description
PLL error This is the error signal of the phase lock loop.
X axis line voltage The demodulated, x-component of the ac line voltage. This
variable is also used in the Phase Lock Loop function.
AC line magnitude This is the magnitude of X axis line voltage and Y axis line
voltage (square root of squared sums). It represents the
magnitude of the ac line..
Phase imbalance sqr This signal is basic in the determination of phase imbalance
or phase lock loop goodness for the sour ce. It is the filtered
sum of two squared signals. The first is PLL error and the
second is the difference between X axis line voltage and AC
line magnitude.
Phase imbalance ref This signal represents the allowed amount of imbalance for
the source. It has units of volts squared. It includes an
allowance for noise and is compensated by the magnitude
of the ac line.
Phase imbalance avg This signal is the amount by which Phase imbalance sqr
exceeds the allowed threshold, Phase imbalance ref.
Phs imbalan ce limit Clamp thresh old that the int egrator
Phs imbalance time Seconds.
Function outputs

The following table specifies the output variables of the Phase Imbalance Monitor

function.
Variable Description
Phase imbalance int Integrator that accumulat es the amount by whi ch the line
imbalance (variable Phase imbalance sqr) exceeds its
allowed threshold (variable Phase imbalance ref). This
variable drives the AC line transient alarm and the AC line
watchdog trip fault. S ee Faults and alarm s section.
AC line loss I f the ac line drops below 10% of nominal for 5msec, AC line
loss will be set True, declaring that the ac line has been lost.
This variab le drives the AC line transient alarm.
Diagnostic variables

The following table specifies the diagnostic variables of the Phase Imbalance

Monitor function.

Variable Description
PLL proven This boolean indicates the status of the Phase Lock Loop function. The
Phase Imbalance Monitor function has a direct effect on PLL proven.