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These ratings are in accordance with:
ANSI/IEEE C37.04-1979 Standard Rating
Structure for AC High-Voltage Circuit
Breakers Rated on a Symmetrical
Current Basis
ANSI C37.06-1987 AC High-Voltage Circuit
Breakers Rated on a Symmetrical Current
Basis - Preferred Ratings and Related
Required Capabilities
ANSI/IEEE C37.09-1979 Standard Test
Procedure for AC High-Voltage Circuit
Breakers Rated on a Symmetrical
Current Basis
ANSI/IEEE C37.010-1979 Application
Guide for AC High-Voltage Circuit Breakers
Rated on a Symmetrical
Current Basis.
Footnotes:
"xxxx" in type designation refers to the continuous
1.
current rating 1,200 A, 2,000 A or 3,000 A,
as appropriate. The 4,000 A fan-cooled rating
is achieved using a 3,000 A circuit breaker, in
combination with fan cooling as indicated in
Footnote 4.
Maximum design voltage for which the circuit
2.
breaker is designed and the upper limit for
operation.
K is the ratio of the rated maximum design voltage
3.
to the lower limit of the range of operating voltage
in which the required symmetrical and asymmetrical
interrupting capabilities vary in inverse proportion
to the operating voltage.
4,000FC indicates that fan cooling is included in the
4.
switchgear structure for this rating. 4,000 A rating
is not available in outdoor equipment.
To obtain the required symmetrical interrupting
5.
capability of a circuit breaker at an operating
voltage between 1/K times rated maximum design
voltage and rated maximum design voltage,
the following formula shall be used: Required
symmetrical interrupting capability =
rated short-circuit current (I) x [(rated maximum
design voltage)/(operating voltage)]. For operating
voltages below 1/K times maximum design voltage,
the required symmetrical interrupting capability of
the circuit breaker shall be equal to K times rated
short-circuit current.
Within the limitations stated in
6.
ANSI/IEEE C37.04-1979, all values apply to
polyphase and line-to-line faults. For single phase-
to-ground faults, the specific conditions stated in
clause 5.10.2.3 of ANSI/IEEE C37.04-1979 apply.
Current values in this row are not to be exceeded
7.
even for operating voltage below 1/K times rated
maximum design voltage. For operating voltages
between rated maximum design voltage and
1/K times rated maximum design voltage, follow
Footnote 5.
Current values in this row are independent of
8.
operating voltage up to and including rated
maximum voltage.
Nominal three-phase MVA class" is included for
9.
reference only. This information is not listed in ANSI
C37.06-1987.
Standard duty cycle is O - 15s - CO.
10.
Standard rating interrupting time is five-cycles
11.
(83 ms). Optional rated interrupting time of three-
cycles (50 ms) is available (except with 24 Vdc
tripping).
67
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