GE T35 UR Series, Instruction Manual

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GE Multilin T35 Transformer Protection System 5-85
5 SETTINGS 5.4 SYSTEM SETUP
5
5.4.2 POWER SYSTEM
PATH: SETTINGS

SYSTEM SETUP

POWER SYSTEM
The power system
NOMINAL FREQUENCY
value is used as a default to set the digital sampling rate if the system frequency
cannot be measured from available signals. This may happen if the signals are not present or are heavily distorted. Before
reverting to the nominal frequency, the frequency tracking algorithm holds the last valid frequency measurement for a safe
period of time while waiting for the signals to reappear or for the distortions to decay.
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. This results in very precise correlation of phase angle indications between different
UR-series relays.
FREQUENCY TRACKING
is set to “ Disabled ” only in unusual circumstances; consult the factory for special variable-
frequency applications.
The frequency tracking feature functions only when the T35 is in the “Programmed” mode. If the T35 is “Not Pro-
grammed”, then metering values are available but can exhibit significant errors.
Systems with an ACB phase sequence require special consideration. Refer to the Phase relationships of
three-phase transformers sub-section of chapter 5.

POWER SYSTEM

NOMINAL FREQUENCY:
60 Hz
Range: 25 to 60 Hz in steps of 1
MESSAGE
PHASE ROTATION:
ABC
Range: ABC, ACB
MESSAGE
FREQUENCY AND PHASE
REFERENCE: SRC 1
Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6
MESSAGE
FREQUENCY TRACKING:
Enabled
Range: Disabled, Enabled
V
ANGLE REF
V
A
=
V
FREQUENCY
2 V
A
V
B
–
V
C
–
( ) 3 ⁄
=
NOTE
NOTE
NOTE