GE C70 Instruction Manual page 224

5.4 SYSTEM SETUP
The phase sequence of the power system is required to properly calculate sequence components and power parameters.
The
PHASE ROTATION
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
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 (
phase signals is used for frequency metering and tracking (
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 always displays zero degrees and all other phase angles are relative to this signal. 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. This results in very precise correlation of phase angle indications between different
UR-series relays.
FREQUENCY TRACKING
frequency applications.
NOTE
The frequency tracking feature functions only when the C70 is in the "Programmed" mode. If the C70 is "Not Pro-
grammed", then metering values are available but can exhibit significant errors.
5
NOTE
5-100
setting matches the power system phase sequence. Note that this setting informs the relay of the
setting determines which signal source is used (and hence which AC signal) for
is set to "Disabled" only in unusual circumstances; consult the factory for special variable-
C70 Capacitor Bank Protection and Control System
V V ), while Clarke transformation of the
=
ANGLE REF A
(
V 2V V V
= – –
FREQUENCY A B
5 SETTINGS
) 3 ⁄
) for better performance dur-
C
GE Multilin