200E
400E
300E
250E
100E
150E
125E
175E
80E
40E
30E
50E
65E
25E
MINIMUM TRIPPING TIME-CURRENT CHARACTERISTIC CURVES
VISTA™ OVERCURRENT CONTROL — TAP FAULT INTERRUPTER — S&C STANDARD SPEED
(For use in place of conventional “-E” rated power fuses.)
BASIS—The total clearing time-current characteristic curves shown APPLICATION—The maximum continuous current-carrying capa- clearing times are included in the curves; additional adjustments are
above are applicable to 60-Hz systems. For 50-Hz systems, add 4 bility of S&C Vista Underground Distribution Switchgear is 1200 not required.
milleseconds to the total clearing curve under consideration. This amperes. The overcurrent control is capable of sensing current in
Since the time-current characteristics are electronically derived,
adjustment is not necessary when coordination with the source- the range of 50 to 25,000 amperes RMS.
they are not subject to change due to aging, transient overcurrents,
side circuit breaker, recloser, or fuse is not particularly tight. In addi-
The total clearing time-current characteristic curves shown above or fault currents. It is, therefore, only necessary to reset the fault
tion, these curves are applicable over the entire S&C Vista Under-
represent the total time required for the S&C Vista Underground interrupters following a fault-clearing operation.
ground Distribution Switchgear operating temperature range of
Distribution Switchgear to both detect and interrupt the fault current.
-40°C to +40°C. No adjustments need to be made to these curves CONTROL SETTINGS—Curves are set using a laptop computer.
These curves should be followed for coordination problems where a
for ambient temperatures within this temperature range.
tap fault interrupter is applied as a “protecting” device with respect to
TOLERANCES—Curves are plotted to maximum test points; all a main fault interrupter (if present) or with respect to a source-side
variations are minus. relayed circuit breaker or recloser. Fault interrupter operating and
February 16, 2009 © S&C Electric Company TCC Number 680-9
