GE UR Series C70, Instruction Manual

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GE Multilin C70 Capacitor Bank Protection and Control System 5-67
5 SETTINGS 5.4 SYSTEM SETUP
5
The phase sequence of the power system is required to properly calculate sequence components and power parameters.
The
PHASE ROTATION
setting matches the power system phase sequence. Note that this setting informs the relay of the
actual system phase sequence, either ABC or ACB. CT and VT inputs on the relay, labeled as A, B, and C, must be con-
nected to system phases A, B, and C for correct operation.
The
FREQUENCY AND PHASE REFERENCE
setting determines which signal source is used (and hence which AC signal) for
phase angle reference. The AC signal used is prioritized based on the AC inputs that are configured for the signal source:
phase voltages takes precedence, followed by auxiliary voltage, then phase currents, and finally ground current.
For three phase selection, phase A is used for angle referencing ( ), while Clarke transformation of the
phase signals is used for frequency metering and tracking ( ) for better performance dur-
ing fault, open pole, and VT and CT fail conditions.
The phase reference and frequency tracking AC signals are selected based upon the Source configuration, regardless of
whether or not a particular signal is actually applied to the relay.
Phase angle of the reference signal will always display zero degrees and all other phase angles will be relative to this sig-
nal. If the pre-selected reference signal is not measurable at a given time, the phase angles are not referenced.
The phase angle referencing is done via a phase locked loop, which can synchronize independent UR-series relays if they
have the same AC signal reference. These results in very precise correlation of time tagging in the event recorder between
different UR-series relays provided the relays have an IRIG-B connection.
FREQUENCY TRACKING
should only be set to “ Disabled ” in very unusual circumstances; consult the factory for spe-
cial variable-frequency applications.
The frequency tracking feature will function only when the C70 is in the “Programmed” mode. If the C70 is “Not Pro-
grammed”, then metering values will be available but may exhibit significant errors.
V
ANGLE REF
V
A
=
V
FREQUENCY
2 V
A
V
B
–
V
C
–
( )
3
⁄
=
NOTE
NOTE