GE UR Series L90 Instruction Manual Download

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5-324

L90 Line Current Differential System

GE Multilin

5.7 CONTROL ELEMENTS

5 SETTINGS

BASIC RECLOSING OPERATION:

Reclosing operation is determined primarily by the

AR MODE

and

AR BKR SEQUENCE

settings. The reclosing sequences are

started by the initiate inputs. A reclose initiate signal sends the scheme into the reclose-in-progress (RIP) state, asserting
the

AR RIP

FlexLogic operand. The scheme is latched into the RIP state and resets only when an

AR CLS BKR 1

(autore-

close breaker 1) or

AR CLS BKR 2

(autoreclose breaker 2) operand is generated or the scheme goes to the Lockout state.

The dead time for the initial reclose operation is determined by either the

AR 1-P DEAD TIME

AR 3-P DEAD TIME 1

, or

AR 3-P

DEAD TIME 2

setting, depending on the fault type and the mode selected. After the dead time interval the scheme asserts the

AR CLOSE BKR 1

AR CLOSE BKR 2

operands, as determined by the sequence selected. These operands are latched until

the breaker closes or the scheme goes to Reset or Lockout.

There are three initiate programs: single pole initiate, three pole initiate and three pole, time delay initiate. Any of these
reclose initiate signals start the reclose cycle and set the reclose-in-progress (

AR RIP

) operand. The reclose-in-progress

operand is sealed-in until the Lockout or Reset signal appears.

The three-pole initiate and three-pole time delay initiate signals are latched until the

CLOSE BKR1 OR BKR2

or Lockout or

Reset signal appears.

AR PAUSE:

The pause input offers the possibility of freezing the autoreclose cycle until the pause signal disappears. This can be done
when a trip occurs and simultaneously or previously, some conditions are detected such as out-of step or loss of guard fre-
quency, or a remote transfer trip signal is received. The pause signal freezes all four dead timers. When the ‘pause’ signal
disappears the autoreclose cycle is resumed by continuing the shot timer it was left at when paused.

This feature can be also used when a transformer is tapped from the protected line and a reclose is not desirable until the
transformer is removed from the line. In this case, the reclose scheme is ‘paused’ until the transformer is disconnected. The

AR PAUSE

input will force a three-pole trip through the

3-P DEADTIME 2

path.

EVOLVING FAULTS:

1.25 cycles after the single pole dead time has been initiated, the

AR FORCE 3P TRIP

operand is set and it will be reset only

when the scheme is reset or goes to Lockout. This will ensure that when a fault on one phase evolves to include another
phase during the single pole dead time of the auto-recloser the scheme will force a 3 pole trip and reclose.

RECLOSING SCHEME OPERATION FOR ONE BREAKER:

•

Permanent Fault

: Consider Mode 1, which calls for 1-Pole or 3-Pole Time Delay 1 for the first reclosure and 3-Pole

Time Delay 2 for the second reclosure, and assume a permanent fault on the line. Also assume the scheme is in the
Reset state. For the first single-phase fault the

AR 1-P DEAD TIME

timer will be started, while for the first multi-phase fault

the

AR 3-P DEAD TIME 1

timer will be started. If the

AR 3P TD INIT

signal is high, the

AR 3-P DEAD TIME 2

will be started for

the first shot.

AR MAX NO OF SHOTS

is set to “1”, upon the first reclose the shot counter is set to 1. Upon reclosing, the fault is again

detected by protection and reclose is initiated. The breaker is tripped three-pole through the

AR SHOT COUNT >0

oper-

and that will set the

AR FORCE 3P

operand. Because the shot counter has reached the maximum number of shots per-

mitted the scheme is sent to the Lockout state.

AR MAX NO OF SHOTS

is set to “2”, upon the first reclose the shot counter is set to 1. Upon reclosing, the fault is again

detected by protection and reclose is initiated. The breaker is tripped three-pole through the

AR SHOT COUNT >0

oper-

and that will set the

AR FORCE 3P

operand. After the second reclose the shot counter is set to 2. Upon reclosing, the

fault is again detected by protection, the breaker is tripped three-pole, and reclose is initiated again. Because the shot
counter has reached the maximum number of shots permitted the scheme is sent to the lockout state.

•

Transient Fault

: When a reclose output signal is sent to close the breaker the reset timer is started. If the reclosure

sequence is successful (there is no initiating signal and the breaker is closed) the reset timer will time out returning the
scheme to the reset state with the shot counter set to "0" making it ready for a new reclose cycle.

RECLOSING SCHEME OPERATION FOR TWO BREAKERS:

•

Permanent Fault

: The general method of operation is the same as that outlined for the one breaker applications

except for the following description, which assumes

AR BKR SEQUENCE

is “1-2” (reclose Breaker 1 before Breaker 2)

The signal output from the dead time timers passes through the breaker selection logic to initiate reclosing of Breaker
1. The Close Breaker 1 signal will initiate the Transfer Timer. After the reclose of the first breaker the fault is again
detected by the protection, the breaker is tripped three pole and the autoreclose scheme is initiated. The Initiate signal
will stop the transfer timer. After the 3-P dead time times out the Close Breaker 1 signal will close first breaker again

GE UR Series L90, Instruction Manual

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