GE Multilin g60 Instruction Manual page 233

5 SETTINGS
The first letter in the source identifier represents the module slot position. The number directly following this letter repre-
sents either the first bank of four channels (1, 2, 3, 4) called "1" or the second bank of four channels (5, 6, 7, 8) called "5" in
a particular CT/VT module. Refer to the Introduction to AC sources section at the beginning of this chapter for additional
details on this concept.
It is possible to select the sum of all CT combinations. The first channel displayed is the CT to which all others will be
referred. For example, the selection "F1+F5" indicates the sum of each phase from channels "F1" and "F5", scaled to
whichever CT has the higher ratio. Selecting "None" hides the associated actual values.
The approach used to configure the AC sources consists of several steps; first step is to specify the information about each
CT and VT input. For CT inputs, this is the nominal primary and secondary current. For VTs, this is the connection type,
ratio and nominal secondary voltage. Once the inputs have been specified, the configuration for each source is entered,
including specifying which CTs will be summed together.
User selection of AC parameters for comparator elements:
CT/VT modules automatically calculate all current and voltage parameters from the available inputs. Users must select the
specific input parameters to be measured by every element in the relevant settings menu. The internal design of the ele-
ment specifies which type of parameter to use and provides a setting for source selection. In elements where the parameter
may be either fundamental or RMS magnitude, such as phase time overcurrent, two settings are provided. One setting
specifies the source, the second setting selects between fundamental phasor and RMS.
AC input actual values:
The calculated parameters associated with the configured voltage and current inputs are displayed in the current and volt-
age sections of actual values. Only the phasor quantities associated with the actual AC physical input channels will be dis-
played here. All parameters contained within a configured source are displayed in the sources section of the actual values.
DISTURBANCE DETECTORS (INTERNAL):
The disturbance detector (ANSI 50DD) element is a sensitive current disturbance detector that detects any disturbance on
the protected system. The 50DD function is intended for use in conjunction with measuring elements, blocking of current
based elements (to prevent maloperation as a result of the wrong settings), and starting oscillography data capture. A dis-
turbance detector is provided for each source.
The 50DD function responds to the changes in magnitude of the sequence currents. The disturbance detector scheme
logic is as follows:
The disturbance detector responds to the change in currents of twice the current cut-off level. The default cut-off threshold
is 0.02 pu; thus by default the disturbance detector responds to a change of 0.04 pu. The metering sensitivity setting (

UCT SETUP DISPLAY PROPERTIES
accordingly.
GE Multilin
ACTUAL
SOURCE 1
CURRENT PHASOR
_1
_2
_0
ACTUAL
SOURCE 2
CURRENT PHASOR
_1
_2
_0
ACTUAL
SOURCE 6
CURRENT PHASOR
_1
_2
_0
Figure 5–18: DISTURBANCE DETECTOR LOGIC DIAGRAM

CURRENT CUT-OFF LEVEL
G60 Generator Protection System
SETTING
PRODUCT SETUP/DISPLAY
PROPERTIES/CURRENT
CUT-OFF LEVEL
_1 - _1' >2*CUT-OFF FLEXLOGIC OPERAND
_2 - _2' >2*CUT-OFF OR SRC 1 50DD OP
_0 - _0' >2*CUT-OFF
Where ' is 2 cycles old
SETTING
PRODUCT SETUP/DISPLAY
PROPERTIES/CURRENT
CUT-OFF LEVEL
_1 - _1' >2*CUT-OFF FLEXLOGIC OPERAND
_2 - _2' >2*CUT-OFF OR SRC 2 50DD OP
_0 - _0' >2*CUT-OFF
Where ' is 2 cycles old
SETTING
PRODUCT SETUP/DISPLAY
PROPERTIES/CURRENT
CUT-OFF LEVEL
_1 - _1' >2*CUT-OFF
FLEXLOGIC OPERAND
_2 - _2' >2*CUT-OFF SRC 6 50DD OP
OR
_0 - _0' >2*CUT-OFF
Where ' is 2 cycles old
827092A3.CDR
) controls the sensitivity of the disturbance detector
5.4 SYSTEM SETUP
5
PROD-
5-73