Power System - GE 869 Instruction Manual

SYSTEM
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Power System

4–70
AUX. VT CONNECTION
Range: Van, Vbn, Vcn, Vab, Vbc, Vca, Vn
Default: Van
Select the voltage type corresponding to the one applied to the Aux VT relay terminals
from bank J2. Select Vn (neutral voltage), if the neutral voltage is applied to the relay
auxiliary VT.
AUX. VT SECONDARY
Range: 10.0 to 240.0 V in steps of 0.1 V
Default: 120.0 V
Select the output secondary voltage of the aux. VT connected to the aux. VT input from
bank J2.
AUX. VT RATIO
Range: 1.00 to 5000.00 in steps of 0.01
Default: 1.00
Select the aux. VT ratio to match the ratio of the VT connected to the aux. VT input from
bank J2.
The nominal PHASE VT SECONDARY and the AUX VT SECONDARY voltage settings are the
voltages across the phase VT terminals and the auxiliary VT terminals correspondingly
when nominal voltage is applied.
For example, on a system of 13.8kV nominal primary voltage, and a 14400:120 volt VT in a
Delta connection, the secondary voltage would be 115V, i.e. (13800/14400)*120. For a Wye
connection, the voltage value entered must be the phase to neutral voltage which would
be 115/√3 = 66.4 V.
On a 14.4 kV system with a Delta connection and a VT primary to secondary turns ratio of
14400:120, the voltage value entered would be 120 V, i.e. 14400/120.
Path:
Setpoints > System > Power System
NOMINAL FREQUENCY
Range: 60 Hz, 50 Hz
Default: 60 Hz
The power system NOMINAL FREQUENCY is used as a default to set the digital sampling
rate if the system frequency cannot be measured from available AC signals. This may
happen if the signals selected for frequency tracking are not present, or a valid
frequency is not detected. 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.
FREQUENCY TRACKING
Range: Disabled, Enabled
Default: Enabled
The frequency reference is provided by composite signal derived by the Clarke
transformation (V
FREQUENCY
open pole, and VT and CT fail conditions.
• If present, the three-phase voltages are used for frequency tracking. Phase A voltage
is used as a phase reference.
• Frequency tracking is switched automatically by an algorithm, to the three-phase
currents (or auxiliary voltage signal for the tie-breaker configuration), if the frequency
= (2V – V – V ) / 3) for better performance during fault,
A B C
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS