Signal Sources - GE L90 Instruction Manual

CHAPTER 5: SETTINGS
The power system
NOMINAL FREQUENCY
cannot be measured from available signals. This can 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 setting matches the power system phase sequence and informs the relay of the actual system phase
PHASE ROTATION
sequence, either ABC or ACB. CT and VT inputs on the relay, labelled as A, B, and C, must be connected 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 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 (V
signals is used for frequency metering and tracking (V
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.
is set to "Disabled" only in unusual circumstances; consult GE Grid Solutions for special variable-
FREQUENCY TRACKING
frequency applications.
The frequency tracking feature functions only when the L90 is in the "Programmed" mode. If the L90 is "Not
Programmed," then metering values are available but can exhibit significant errors.
Select the nominal system frequency as 50 Hz or 60 Hz only. The
a reference for calculating all angles, must be identical for all terminals. Whenever the 87L function is "Enabled," the
frequency tracking function is disabled, and frequency tracking is driven by the UR algorithm. Whenever the 87L
function is "Disabled," the frequency tracking mechanism reverts to the UR-series mechanism that uses the
FREQUENCY TRACKING

5.5.3 Signal sources

SETTINGS  SYSTEM SETUP  SIGNAL SOURCES  SOURCE 1(4)
 SOURCE 1

Identical menus are available for each source. The "SRC 1" text can be replaced by with a user-defined name appropriate
for the associated source.
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
value is used as a default to set the digital sampling rate if the system frequency
setting determines which signal source is used (and hence which AC signal) for
FREQUENCY
setting to provide frequency tracking for all other elements and functions.
SOURCE 1 NAME:

SRC 1
SOURCE 1 PHASE CT:

None
SOURCE 1 GROUND CT:

None
SOURCE 1 PHASE VT:

None
SOURCE 1 AUX VT:

None
= V ), while Clarke transformation of the phase
ANGLE REF A
= (2V - V - V ) / 3) for better performance during fault,
A B C
FREQUENCY AND PHASE REFERENCE
Range: up to 20 alphanumeric characters
Range: None, F1,... up to any 6 CTs. Only Phase CT
inputs are displayed.
Range: None, F1,... up to any 6 CTs. Only Ground CT
inputs are displayed.
Range: None, F5, L5
Only phase voltage inputs are displayed
Range: None, F5, L5
Only auxiliary voltage inputs are displayed
SYSTEM SETUP
5
setting, used as
5-139