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IB02602004E
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Instructional Literature
Effective: May 2008
Page
169
Instructions for the FP-6000 Protective Relay
The auto zone coordination is included in the autoreclose logic,
but it can work independently or be bound with the autoreclose
logic. It is the user's choice to decide if both the functions are
bound together or not. The user can activate the auto zone
coordination feature even if the autoreclose is disabled; as long
as the settings of the four reclose shots are specified as if the
autoreclose were enabled. Regardless the autoreclose logic
being enabled or not, the auto zone coordination logic, if
enabled, will only be active when the autoreclose logic is either
in the Off or Ready mode.
When the auto zone coordination is active, the maximum
number of shots is determined with the breaker off time settings,
but not with the breaker operation history. If the autoreclose
logic is disabled, the breaker off time settings in the intended
shots can be any non-zero value. For example, if an intended
maximum shot number is two, the breaker off time settings in
shot 1 and shot 2 must be non-zero; and the breaker off time
setting in shot 3 must be zero.
The auto zone coordination logic shares Run-To-Ready timer with
the autoreclose logic. Once the auto zone coordination logic
senses the falling edge of the overcurrent protection pickup
signal, the shot sequence will be incremented and meanwhile
the Run-To-Ready timer is initiated. The autoreclose failure timer
has no effect on the auto zone coordination logic. Figure 66 (or
Figure 67), another way to represent overcurrent coordination)
depicts how the upper and down stream relays are coordinated
to each other, with the solid lines at both relays being paired to
form a fast trip sequence coordination while the dashed lines
form a slow trip sequence coordination. When a fault occurs
beyond the down stream relay, because the down stream relay is
more sensitive to the fault, it should trip first. If, for some reason
such as the local breaker failure, the down stream relay cannot
trip the fault, the upper stream relay would trip the fault with
some delay if the fault is within the upper stream relay protection
range. As is seen from this example, if two relays are well
coordinated, it can ensure the selectivity of the system
protections.
The anti-pumping feature is incorporated in the autoreclose
logic. The breaker pumping refers to when the fault current is
between the normal overcurrent pickup and the shot protection
pickup such that the relay would trip once the autoreclose logic
returns to normal from Run mode. Without the anti-pumping
function, the autoreclose logic will be initiated after a trip that is
initiated by the normal overcurrent functions, and then the
autoreclose logic returns to normal form Run mode again, and
the normal overcurrent functions will trip again. This process
will continue until the breaker wears out. Because the fault
current is below the overcurrent pickup level, the autoreclose
logic will never advance to next shot stage; as a result, it will
never go to lockout mode. With the anti-pumping logic, the
autoreclose logic will switch the settings from the shot protection
settings to the normal settings after the Run-to-Ready timer is
expired but it will not reset from Run mode to Ready mode until
ten cycles later. If the fault is sensed with the normal overcurrent
protections during the period of ten cycles, the shot stage will
advance to next level. If this type of fault persists, the
autoreclose logic with the anti-pumping feature will repeat this
process until it reaches the Lockout mode. At this point, the
breaker will not be allowed to automatically reclose, thus
preventing the breaker from wearing out.
The Sync Check function is a stand-alone logic. When it is
enabled, its output can be used to supervise autoreclose. A Sync
Supervision setting is added to bridge Sync Check and
autoreclose functions. When it is disabled, the autoreclose logic
will ignore the sync condition; while if it is enabled, a reclose is
only possible when two systems are in sync. The Sync Failure
timer setting in the Sync Check logic can be used for indicating
Sync Failure.
There are three general programmable gates, PLC Block, PLC
RInit, and PLC Lockout, added under the general PLC setting
category, which can be used in the autoreclose logic if they are
enabled. There are three shot sequence specific programmable
gates to terminate the autoreclose sequence, Shot 1 PLC to
Lockout, Shot 2 PLC to Lockout, and Shot 3 PLC to Lockout.
These gates allow the user to lockout the breaker from reclosing
if some conditions are met after shot "X" run sequence. All these
logic gates, just like other general-purpose logic gates, can be
programmed the same way and take the same input options.
The only difference is that they are dedicated to the autoreclose
logic, so they cannot be fed into other general-purpose logic
gates. These logic gates give the user a great deal of flexibility to
meet application needs.
Note that the cold load pickup logic, if it is enabled, has the
similar capability of adjusting the protection settings. Although
the cold load pickup logic is independent of the autoreclose
logic, if both the logics are enabled, once the autoreclose logic
enters the Run mode, the cold load pickup condition will be
override. This means that whenever the autoreclose logic is in
action, its shot protection settings will take over the cold load
pickup protection settings.
The autoreclose (AR), maximum shots adjustment (MSA), and
auto zone coordination (AZC) may generate the following events,
alarms and indications:
The AR Operation Flag has the following bits:
AR_Bkr_Pumping_flag:
Breaker pumping.
AR_Shot_4_flag:
AR logic in shot 4 run sequence.
AR_Shot_3_flag:
AR logic in shot 3 run sequence.
AR_Shot_2_flag:
AR logic in shot 2 run sequence.
AR_Shot_1_flag:
AR logic in shot 1 run sequence.
AR_PLC79RI_flag:
General programmable reclose
initiate logic gate active.
AR_PLC79RL_flag:
General programmable reclose
lockout logic gate active.
AR_PLC79RB_flag:
General programmable reclose
block logic gate active.
AR_79VB_Pickup_flag:
Undervoltage block pickup.
AR_Fail_flag:
AR run sequence takes too long.
AR_79VB_Trip_flag:
Undervoltage block timeout.
AR_Lockout_flag:
AR logic in Lockout mode.
AR_Blocked_flag:
AR logic is blocked in either Ready
or Run.
AR_Run_flag:
AR logic in Run mode.
AR_Ready_flag:
AR logic in Ready mode.
AR_Off_flag:
AR logic in Off mode.