GE Multilin L60, Instruction Manual

Page: 421 / 752

GE Multilin L60 Line Phase Comparison System 5-291
5 SETTINGS 5.6 CONTROL ELEMENTS
5
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
or
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.
If
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.
If
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