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2
Product Summary
The purpose of this book is to provide instructions for
the unpacking, storage, installation, operation and
inspection of W-VACi IEC vacuum circuit breakers for
qualified personnel. Reliable control and protection of
short circuit current can be achieved through the
application of W-VACi vacuum circuit breakers in 12 /
17.5 / 24kV air insulated switchgear. Legal and other
regulations and documents pertaining to accident
prevention, personal safety and environmental
protection must be observed. Operations involving the
repair of the breaker are to be carried out by or under
the approval of Eaton. Information with respect to
these operations is, therefore, not included in this
manual. If further information is required by the
purchaser regarding a particular installation,
application or inspection activity, an Eaton
representative should be contacted.
2.1
Standards and Specifications
W-VACi IEC circuit breakers are designed and third
party tested to the latest IEC 62271-100 and IEC
62271-1 standards. All W-VACi circuit breakers meet
or exceed the electrical and mechanical endurance
requirements of E2 and M2, in accordance with IEC
62271-100.
2.2
Altitude Correction Factor
The main external insulation of the 12 / 17.5 / 24 kV W-
VACi vacuum circuit breakers is air. The insulation
capabilities of air change relative to altitude above sea
level. Customers should always consider this
phenomenon when designing / specifying new
switchgear installations. Eaton uses and specifies a
correction factor (K
) to address this phenomenon. This
a
correction factor is shown in Figure 2.2A. The source
is the IEC 62271-1 standard. One factor that is not
hindered by this property is the internal insulation of
the vacuum interrupters.
Figure 2.2A: Altitude Correction Factor
K
= Correlates to the correction factor in regards to the altitude.
a
H = The value of Altitude (in meters).
M = A fixed value, in terms of power frequency, lighting impulse, and phase to phase switching impulse voltages; m=1.
6
ALTITUDE CORRECTION FACTOR- EXAMPLE
Installation altitude
Operation at the rated voltage
Power frequency withstand voltage
Lightning impulse withstand voltage
Correction Factor (K
In this example, the above information would compute the
withstanding capabilities of the unit to be:
Focusing on the values determined above, it can be
concluded that this unit at 3000 m above sea level, with 17.5
kV of available service voltage must use a 24 kV rated
voltage breaker. The resulting breaker selection is due to
the 125 kV modified Lightning impulse requirement. The
minimum circuit breaker with the required capabilities for this
application is the 24kV circuit breaker, which also provides
the 50kA Power Frequency Withstand Voltage (see section
2.6, Technical Parameters 24 kV W-VACi IEC Circuit
Breaker). Referencing the above calculations, these values
are influenced by the Correction factor (K
factor (K
height above sea level (3000 m). The insulation levels must
also conform to a power frequency rating of 50 kV with a
125 kV lightning impulse withstand voltage.
2.3
Charts on the following pages include all technical
parameters for the IEC standard 12 / 17.5 / 24kV W-
VACi vacuum circuit breakers.
65A7355H01 November 2011 www.eaton.com
) obtained from graph
a
Power frequency withstand voltage equal to:
38 kV x 1.28 = 48.64 kV
Lightning impulse withstand voltage equal to:
95 kV x 1.28 = 121.60 kV
) is obtained from the graph, by using the known
a
Technology Parameters
3000 m
17.5 kV
38 kV
95 kV
1.28
). The correction
a
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