24 S&C Instruction Sheet 1041-540
Switch Control Operation
The
Shots to Lockout
feature allows the field technician or SCADA operator to test a
potentially faulted line by reducing the counts to trip to either one or two for a specified
time period. If the circuit is then de-energized by a source-side protective device (recloser,
breaker, etc.) and the switch control sees the transition from voltage present to loss of
voltage, the switch control opens the switch immediately. This allows the faulted line
segment to be isolated and prevents the source-side device from reclosing into a fault
multiple times.
Note:
If the source-side device opens and recloses very quickly, sensors on the load
side of the switch may not have enough time to sense both the voltage increase (when
the switch closes) and the voltage loss (when the source-side device opens) before the
source-side device recloses. Under these conditions, the switch control cannot carry
out shots-to-lockout except during a transfer event. For best results, always position
the switch so the sensors are on the source side.
NOTICE
It is very important that the end of the
Shots to Lockout timer and the source
breaker operation are coordinated . Operation of the breaker at the same time the
switch opens could result in personal injury and damage to the switch .
The
Shots to Lockout
feature can also be enabled when the line switch is closed.
This feature is useful for extending the shots-to-lockout functionality to a load-side
manual switch. The feature is enabled indefinitely (“latched”) until disabled by toggling
the faceplate REMOTE/LOCAL switch to
Remote
mode.
When the
Shots to Lockout
feature is enabled:
(a)
When the line switch is open:
If closing the switch into a fault and the source-
side protective device (recloser, circuit breaker, etc.) detects the fault, the
source-side device opens and voltage is lost on all phases.
When the line switch is closed:
If a load-side manual switch on the circuit
closes into a fault and the source-side protective device (recloser, circuit breaker,
etc.) detects the fault, the source-side device opens and voltage is lost on all phases.
(b) The switch control recognizes that the source-side device opened. If the Number
of
Shots Required for Lockout
value is set to “One,” the switch control trips
open the switch right away. If it is set to “Two,” the switch control waits until the
source-side device recloses and opens a second time. Then, the switch control
trips open its switch. If the “Overcurrent Required before
Shots-To-Lockout
Operation
setpoint is also enabled, the switch control only opens the switch if
the three-phase voltage loss was preceded by an overcurrent.
Setting the
Number of Shots to Lockout
value to “Two” prevents the switch
control from trying to open the switch at the same time as the source-side device
is performing its instantaneous reclose. If the
Overcurrent Required Before
Shots-To-Lockout Operation
setpoint is also enabled, the relationship between
the detection of overcurrent and voltage losses follows the
Fault Current
Required Before First/All Voltage Loss(es)
setpoint.
(c) The switch remains open until it is closed with a SCADA command or manually
from the switch control faceplate.
Shots-to-Lockout