Superconducting
Current Fault Limiters (SCFL)
"Cryo-Pinch"
Superconducting
Fault Limiters by Power Superconductor Applications with
AC excitation of the superconductor represents a quantum leap
in fast power
regulation, efficient control and protection automation as they combine
the following features:
-
Cryo-Pinch operates on the
differential inductive principle and
inserts a variable inductance into
the power system timed over a programmable period such as a quarter cycle.
Inductance ranges
from 10 mH
to 50
mH are designed specific to each utility.
-
SCFLs obviate the need for large
interrupting (transient recovery voltage
producing) circuit breakers- they
eliminate air-core reactors for fault limiting; they replace current limiting
fuses and pyrotechnic
devices.
-
SCFLs allow remote control of the
power system for
limiting high current faults with a programmable sub-cycle
(4 ms) response time. Cryo-Pinch damps-out crest values of
inrush
current and surge current on the power system or ship.
This permits the power system operator
to use smaller rated electrical
equipment elsewhere in the system, with
economic savings. For example a 42 kA station breaker can now be
used instead of a
63 kA unit. For example, the SCFL is placed in series with a conventional breaker of 1000 MVA rating rather than having to purchase
a 2500 MVA breaker.
-
SCFLs permit the system operator
to fully
automate the distribution system by commanding the SCFL to ramp
in terminal inductance through a SCADA controller or RF communication
link.
View of 4160 Volt Fault Limiter built under
U.S. Patent No. 5,642,249
The programmable current limiting
feature of the SCFL results in the utility
being able to add load base
or customers without purchasing new breakers, new transformers or transmission
lines - a quantum savings
for the utility T&D departments.
The range of voltage application for 60 Hz systems is 480 Volts to 38 kilovolts.
The
programmable current limiting feature of the SCFL
Cryo-Pinch
is 3 times as fast in response time than DC excited
superconducting limiters
with 57% of the investment in superconducting wire as the competition.
Figure I shows three response curves
available: 1) sinusoidal inductance
insertion versus time after fault, 2) linear inductance ramp and 3) quasi-exponential
inductance ramp.
Cryo-Pinch
limiters have a 60:1 inductance ratio; for example if a non-fault state
inductance of 100 mh
(.038 ohms) is specified, the limiting inductance of the device is 6.0
mH (2.26 ohms) at a quarter cycle. On a 7.6 kV power system this
limit faults to 3,300 amps rms rather than the prospective current of 40,000
amps rms.
The reset
time for the Cryo-Pinch is 10 milliseconds in contrast to DC excited
devices which have 90 second reset times. A 2-stage Gifford-McMahon
refrigerator and cryostat provide a 20 K cryogenic environment for the
magnetics. Service intervals are 12 months. The LX series Cryo-Pinch
limiters are available in 150 kV BIL ratings in hermetically-sealed, stainless
steel units for
underground vault, pole-top or pad-mount applications.
Manufactured in the United States of America with 100% US
components.
POWER SUPERCONDUCTOR APPLICATIONS CORPORATION
930 Cass Street
New Castle, PA 16101
Laboratory Telephone: 724-652-8610
Office Telephone: 412-824-5062
E-Mail: psacorp@peoplepc.com
Click here to
see Superconducting Current Fault Limiter Specifications
