Supervising Elements - GE L90 Instruction Manual

5 SETTINGS
a) MAIN MENU

PATH: SETTINGS GROUPED ELEMENTS
 SUPERVISING
 ELEMENTS
MESSAGE
b) DISTURBANCE DETECTOR

PATH: SETTINGS GROUPED ELEMENTS
 DISTURBANCE
 DETECTOR
MESSAGE
MESSAGE
MESSAGE
MESSAGE
The disturbance detector (50DD) element is an 87L-dedicated sensitive current disturbance detector that is used to detect
any disturbance on the protected system. This detector is intended for such functions as trip output supervision and starting
oscillography The disturbance detector also signals the 87L function that a disturbance (possible fault) occurred and to
resize the operating window to remove the pre-fault current. It is essential to have the disturbance detector enabled for
applications where the 87L operating time is critical.
If the disturbance detector is used to supervise the operation of the 87L function, it is recommended that the 87L trip ele-
ment be used. The disturbance detector FlexLogic operand must then be assigned to an
50DD SV
The disturbance detector function measures the magnitude of the negative-sequence current (I_2), the magnitude of the
zero-sequence current (I_0), the change in negative-sequence current (I_2), the change in zero-sequence current (I_0),
and the change in positive-sequence current (I_1). The disturbance detector element uses net local current, computed as
a sum of all sources configured in the current differential element, to detect system disturbances.
The adaptive level detector operates as follows:
• When the absolute level increases above 0.12 pu for I_0 or I_2, the adaptive level detector output is active and the
next highest threshold level is increased 8 cycles later from 0.12 to 0.24 pu in steps of 0.02 pu. If the level exceeds
0.24 pu, the current adaptive level detector setting remains at 0.24 pu and the output remains active (as well as the
disturbance detector output) when the measured value remains above the current setting.
• When the absolute level is decreasing from in range from 0.24 to 0.12 pu, the lower level is set every 8 cycles without
the adaptive level detector active. Note that the 50DD output remains inactive during this change as long as the delta
change is less than 0.04 pu.
The delta level detectors (I) detectors are designed to pickup for the 0.04 pu change in I_1, I_2, and I_0 currents. The I
value is measured by comparing the present value to the value calculated 4 cycles earlier.
• DD FUNCTION: This setting is used to enable/disable the operation of the disturbance detector.
• DD NON-CURRENT SUPV: This setting is used to select a FlexLogic operand which will activate the output of the dis-
turbance detector upon events (such as frequency or voltage change) not accompanied by a current change.
• DD CONTROL LOGIC: This setting is used to prevent operation of I_0 and I_2 logic of disturbance detector during
conditions such as single breaker pole being open which leads to unbalanced load current in single-pole tripping
schemes. Breaker auxiliary contact can be used for such scheme.
GE Multilin
 
SETTING GROUP 1(6)

SUPERVISING ELEMENTS

 DISTURBANCE
 DETECTOR
 87L TRIP

 
SETTING GROUP 1(6)
DD
FUNCTION: Disabled
DD NON-CURRENT SUPV:
Off
DD CONTROL LOGIC:
Off
DD LOGIC SEAL-IN:
Off
DD
EVENTS: Disabled
L90 Line Current Differential System
5.6 GROUPED ELEMENTS
5.6.16 SUPERVISING ELEMENTS
See page 5-229.
See page 5-231.

SUPERVISING ELEMENTS DISTURBANCE DETECTOR
Range: Disabled, Enabled
Range: FlexLogic operand
Range: FlexLogic operand
Range: FlexLogic operand
Range: Disabled, Enabled
87L TRIP SUPV
5
setting.
5-229