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CHAPTER 4: SETPOINTS
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
LEFT BLINDER
Range: 0.10 to 500.00 ohms in steps of 0.01 ohms
Default: 2.00 ohms
This setting defines the left blinder position of the blinder characteristic along with the
resistive axis of the impedance plane, expressed ins secondary ohms. The angular
position of the blinder is adjustable with the use of the BLINDERS RCA setting.
BLINDER RCA
Range: 40 to 90° in steps of 1°
Default: 90°
This setting defines the angular position of the left and right blinders.
PICKUP DELAY
Range: 0.000 to 1.000 s in steps of 0.001 s
Default: 0.100 s
This setting should be set to detect the fastest expected unstable power swing and
produce out-of-step tripping in a secure manner. This timer defines the interval that the
impedance locus must spend between the left and right blinders to establish the out-of-
step tripping signal. This time delay must be set shorter than the time required for the
impedance locus to travel between the left and right blinders during the fastest
expected out-of-step. Setting the delay too long can reduce dependability.
TRIP MODE
Range: Blinder Exit, MHO Exit
Default: MHO Exit
Selecting "Blinder Exit" results in an instantaneous trip after the last step in the out-of-
step tripping sequence is completed (the impedance locus leaves the opposite blinder).
The Blinder Exit trip mode stresses the circuit breakers as the currents at that moment
are high (the electromotive forces of the two equivalent systems are close to 180° apart).
Selecting "MHO Exit" results in a trip at the moment when the impedance locus leaves
the mho characteristic. The MHO Exit trip mode relaxes the operating conditions for the
breakers as the currents at that moment are low, preventing the breakers from a
maximum recovery voltage during interruption. The selection should be made
considering the capability of the breakers in the system.
POS SEQ CURR SUPERVISION
Range: 0.05 to 10.00 x CT in steps of 0.01 x CT
Default: 1.00 x CT
A common overcurrent pickup level supervises the left and right blinder characteristics.
The supervision responds to the positive sequence current.
SEAL-IN DELAY
Range: 0.000 to 1.000 s in steps of 0.001 s
Default: 0.100 s
The out-of-step trip FlexLogic operand (OOS OP) is sealed-in for the specified period of
time. The sealing-in is crucial to the MHO EXIT trip mode, as the original trip signal is a
very short pulse occurring when the impedance locus leaves the mho characteristic
after the out-of-step sequence is completed.
BLOCK
Range: Off, Any operand from the list of FlexLogic operands
Default: Off
OUTPUT RELAY X
Range: Do Not Operate, Operate
Default: Do Not Operate
PROTECTION
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