Appendix
Table 13: Type 38-3AH3 vacuum circuit breaker ratings (historic "constant MVA" ratings basis)
Measured parameter
Units
Circuit breaker type
1
38-3AH3-1500
General
Nominal voltage class
kV
38.0
Nominal three-phase MVA class
9
MVA
1500
Rated
values
Rated
voltage
Maximum design voltage (V)
2
kV rms
38.0
Voltage range factor (K)
3
----
1.65
Insulation
levels
Withstand
voltage levels
Power-frequency
kV rms
80
Lightning-impulse (BIL)
kV peak
150
Rated
current
Continuous
4
A rms
1,200, 2,000, 3,000FC
Short-circuit (at rated maximum design voltage) (I)
5, 6, 10
kA rms sym
21
Interrupting time
11
Cycles/ms
5/83
Permissible tripping delay (Y)
Sec
2
Related
required
capabilities
Current
Rated maximum design voltage (V) divided by K = (V/K)
kA rms
23.0
Maximum symmetrical (sym) interrupting (K x I)
kA rms sym
35
Short-time current (K x I) (three-seconds)
kA rms sym
35
Closing and
latching
(momentary)
Asymmetrical (1.55 x I)
8
kA rms
56
Peak (2.6 x I)
8
kA peak
95
Footnotes:
1
“xxxx” in type designation refers to the
continuous current rating 1,200, 2,000, or
3,000 A, as appropriate. The 3,000A fan-cooled
rating is achieved using fan cooling as
indicated in Footnote 4.
2
Maximum design voltage the circuit breaker is
designed for and the upper limit for operation.
3
K is the ratio of the rated maximum design
voltage 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
3000FC indicates fan cooling is included in the
switchgear structure for this rating. 3000 A
rating is not available in outdoor equipment.
5
To obtain the required symmetrical
interrupting 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)].
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.
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.
6
Within the limitations stated in 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.
7
Current values in this row are not to be
exceeded 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.
8
Current values in this row are independent of
operating voltage up to and including rated
maximum voltage.
9
"Nominal three-phase MVA class" is included
for reference only. This information is not listed
in ANSI/IEEE C37.06-1987.
10
Standard duty cycle is CO - 15s - CO.
11
Three-cycle (50 ms) interrupting is optionally
available.
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