Using TCC Shifting With PulseFinding Fault Location
As stated above, the PulseFinding technique is used for series-connected IntelliRupter
fault interrupters that cannot be selectively time-current coordinated, enabling some or
all of them to trip open when downstream faults occur. The fault is quickly located by
sequential
PulseClosing Technology
operations, starting at the open device closest to
the source. Each successive downstream device will perform a
PulseClose Technology
operation, find no fault and, quickly close. But the device nearest the fault will perform
a
PulseClosing Technology
operation, sense the fault, and stay open.
In some areas, local vegetation can produce faults known as reinitiating faults because
they require time to redevelop after a circuit is reenergized and can result in multiple
PulseFinding technique sequences occurring for a single fault. TCC shifting mitigates this
condition by ensuring the device using PulseClosing Technology has a faster response
than the upstream devices that have already closed. See Figure 40 on page 57 for an
example TCC. Depending on the conditions, after being reenergized, a reinitiating fault
can take from a couple of cycles to a few seconds to reach fault levels. A few cycles may
be adequate, but historical data (if available) are the best reference when determining a
reasonable time frame for use on the system. The example on pages 57 and 58 assumes
the majority of these faults reinitiate in 5 cycles. Therefore, 5 cycles is used as the baseline
for setting this feature in this example. See Figure 41 on page 58.
56 S&C Instruction Sheet 766-530
Protection Setup
