GE SecoGear Application Guide

DET-882 SecoGear Medium-voltage Switchgear Application and Technical Guide
Circuit Breaker Selection
©2017 General Electric All Rights Reserved 11
Table 2-1: SecoVac VB2+ Vacuum Circuit Breaker Characteristics
Characteristic
1200/31.5 Rating
1200/40 Rating
2000/40 Rating
Rated current
1
1200 A
1200 A
2000 A
Rated voltage (max.)
4.76 kV, 8.25 kV,
15 kV
4.76 kV, 8.25 kV,
15 kV
4.76 kV, 8.25 kV,
15 kV
Nominal ANSI voltage class
4.16 kV, 7.2 kV,
13.8 kV
4.16 kV, 7.2 kV,
13.8 kV
4.16 kV, 7.2 kV,
13.8 kV
Rated frequency
50 Hz, 60 Hz 50 Hz, 60 Hz 50 Hz, 60 Hz
Rated dielectric
withstand test voltage
Power frequency rms voltage
36 kV 36 kV 36 kV
Crest impulse voltage
95 kV
95 kV
95 kV
Rated short-circuit current (max interrupting capability)
2
31.5 kA
40 kA
40 kA
Rated interrupting time
3 cycles 3 cycles 3 cycles
Rated permissible tripping delay
2 s
2 s
2 s
Short time current carrying capability
31.5 kA
40 kA
40 kA
Close and latch current peak (2.6 x short-circuit current rating)
82 kA
104 kA
104 kA
Notes:
1. Maximum voltage for which the breaker is designed and upper limit of operation.
2. At system operating voltages equal to or less than rated maximum voltage.
Closing and Latching Current
The function of any circuit breaker is to close and stay
latched, during which the breaker goes through a first-
cycle maximum asymmetrical rms current. In common
applications, the standard close and latch capability meets
the requirements and specification of the circuit.
However, in certain applications that can include large
motor loads, the first-cycle asymmetrical short-circuit
current exceeds the closing and latching capabilities of the
selected breaker. If this situation arises, the circuit breaker
selection will be based, in most cases, on the closing and
latching capability of the next higher short-circuit current.
The closing and latching capability (kA, rms) of the circuit
breaker is expressed in peak amperes. The value is equal to
2.6 times rated short-circuit current for 60 Hz and 2.5 times
for 50 Hz.
Continuous Current
To select the proper SecoVac VB2+ breaker, calculate the
continuous current duty based on the loads of the feeders
and main breaker and identify a continuous current rating
equal to or greater than the load current.
SecoVac circuit breakers are 100% rated with no
continuous overload rating. For special applications with
long-time overload rating such as motors, generators or
transformers, it is important to consider that all of the
switchgear equipment (including circuit breakers) must
have a continuous current rating at least equal to the
overload rating of the special apparatus. Consult ANSI
C37.20.2 for overload current capability guidelines.
Rated Interrupting Time
SecoVac VB2+ circuit breakers are available only with
interrupting ratings of 3 cycles, as stated in Table 2-1.
Duty Cycle
SecoVac VB2+ circuit breakers have a rated duty cycle of
O - 0.3s – CO - 180s – CO.
SPECIAL SWITCHING APPLICATIONS
Application of power circuit breakers for switching duty
may require derating of the circuit breaker, or increased
maintenance. SecoVac VB2+ circuit breakers do not require
derating when applied in automatic reclosing duty. For
these applications, like capacitor switching, the usual
practice is to first select a circuit breaker based on the
criteria provided under “Selection Considerations,” above.
Then, consider the switching duty and, if necessary, re-
determine the circuit breaker capabilities (continuous-
current rating, interrupting rating, etc.). Also, factor in any
modified operating or maintenance requirements.
Recheck the circuit breaker’s evaluation capabilities
against all the basic duty requirements under “Selection
Considerations.” If the circuit breaker selected initially, and
as derated (or otherwise modified), no longer meets the
duty requirements of the application, choose the next-
higher-rated breaker. Repeat the derating or rating
adjustment process to confirm that the new breaker has
adequate capability.
Automatic Transfer
To improve system reliability and ensure supply to critical
loads, primary or secondary selective system designs are
often utilized. In these configurations, two or more
otherwise typical radial buses are connected together via

GE SecoGear Specifications

General

Brand	GE
Model	SecoGear
Category	Switch
Language	English