GE L90 Instruction Manual page 484

GROUPED ELEMENTS
5.7.15.3 87L trip
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  SUPERVISING ELEMENTS  87L TRIP
 87L TRIP

5
The 87L trip element must be used to secure the generation of tripping outputs. It is especially recommended for use in all
single-pole tripping applications. It provides the capability of maintaining the trip signal while the fault current is still
flowing, to choose single-pole or three-pole tripping, to employ the received direct transfer trip (DTT) signals, and to assign
supervising trip elements like the disturbance detector. The logic is used to ensure that the relay
• Trips the faulted phase for a single line to ground fault, as detected by the line differential element
• Trips all three phases for any internal multiphase fault
• Trips all three phases for a second single line to ground fault during or following a single pole trip cycle
For maximum security, it is recommended that the disturbance detector (plus other elements if required) be assigned to
see a change in system status before a trip output is permitted. This ensures the relay does not issue a trip signal as a
result of incorrect settings, incorrect manipulations with a relay, or inter-relay communications problems (for example,
extremely noisy channels). The open pole detector provides forcing of three-pole tripping for sequential faults and close-
onto-fault if wanted. The open pole detector feature must be employed and adequately programmed for proper operation
of this feature. The
autoreclosing.
If a direct transfer trip (DTT) is not required for the 87L trip scheme to operate, disable it at the remote relay via the
GROUPED ELEMENTS  SETTING GROUP 1(6)  LINE DIFFERENTIAL ELEMENT  CURRENT DIFFERENTIAL
menu.
87L TRIP FUNCTION
— Assigns a source for the seal-in function.
87L TRIP SOURCE
— Selects either three-pole or single-pole mode of operation.
87L TRIP MODE
— Assigns a trip supervising element. The
87L TRIP SUPV
enabled); otherwise, elements like instantaneous overcurrent, distance, and so can be used.
5-298
87L TRIP FUNCTION:

Disabled
87L TRIP SOURCE:

SRC 1
87LP TRIP MODE:

3-Pole
87LG TRIP MODE:

3-Pole
87LP TRIP SUPV:

Off
87LG TRIP SUPV:

Off
87L TRIP FORCE 3Φ:

Off
87L TRIP SEAL-IN:

Disabled
87L TRIP SEAL-IN

PICKUP: 0.20 pu
87L TRIP TARGET:

Self-reset
87L TRIP EVENTS:

Disabled
and
87L TRIP 1P OP 87L TRIP 3P OP
— This setting is used to enable or disable the element.
Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 3-Pole, 1-Pole
Range: 3-Pole, 1-Pole
Range: FlexLogic operand
Range: FlexLogic operand
Range: FlexLogic operand
Range: Disabled, Enabled
Range: 0.20 to 0.80 pu in steps of 0.01
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
operands are provided to initiate single-pole or three-pole
FlexLogic operand is recommended (the element has to be
50DD SV
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
settings