Drawout; Information On This Booklet; Principle Of Extinction Of The Vacuum Interrupter; Application Of The X-Ray Emission Standards - ABB VM1 Installation And Service Instructions Manual

1.3. Drawout

A Drawout circuit-breaker is a breaker that may be removed
from a cell without unbolting connections or mounting
supports. It is intended for use in ABB PowerCube modules.
It contains primary and secondary disconnects and provides
two operating positions: Disconnect and Connect.

1.4. Information on this booklet

This booklet provides information for the VM1/A/P circuit-
breakers as described below. Not all sections of the bulletin
apply to all types of VM1/A/P circuit-breakers. For example,
the racking and interlock sections do not apply to the fixed
mount breaker styles. All information in this booklet was
current at the time of printing. Unless otherwise noted, all
references in this booklet are determined by viewing the
circuit-breaker from the front.
The purpose of this manual is to provide instructions for
unpacking, storage, installation, operation, and maintenance
for VM1/A/P vacuum circuit-breakers. This manual should be
carefully read and used as a guide during installation, initial
operation, and maintenance.
The specific ratings of each model circuit-breaker are listed on
the individual nameplates. The VM1/A/P circuit-breakers are
protective devices. As such, they are maximum rated devices.
In no event should they be applied outside of their nameplate
ratings.
1.5. Principle of extinction of the
vacuum interrupter
Given the relatively low static pressure of the interruption
chamber (between 10 and 10
-4
distance between the contacts is required to obtain high
dielectric strength. The vacuum arc is extinguished on the first
passage of the current through natural zero.
Considering the limited distance between the contacts, the
high conductivity of the plasma of metallic vapours, the
drop in voltage of the arc and, moreover, the short arcing
time, the energy associated with the arc is extremely limited,
therefore producing benefits for the useful life of the contacts
obtained and, consequently, for the useful life of the vacuum
interrupters.
hPa), a relatively limited
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1.6. Application of the X-ray emission
Standards
One of the physical properties of vacuum insulation is the
possibility of X-ray emission when the interrupter contacts are
open.
The specific tests carried out at the PTB laboratories
(Physikalisch-Technische Bundesanstalt, in Brunswick -
Germany) show that local emission at a distance of 10 cm from
the interrupter or pole surface, does not exceed 1 mSv/h.
it follows that:
– at the rated service voltage the use of vacuum interrupters
is absolutely safe;
– application of the withstand voltage at industrial frequency,
according to the IEC 62271-100, VDE 0670 and IEEE
C37.04 Standards, is safe;
– application of a voltage higher than the withstand voltage
at industrial frequency or of a direct current test voltage
in direct current, specified in the IEC, VDE and ANSI/IEEE
Standards, cannot be used;
– limitation of the above-mentioned local phenomena, with
interrupters with open contacts, depends on keeping the
specified distance between the contacts.
This condition is intrinsically guaranteed by correct operation
of the operating mechanism and by adjustments of the
transmission system.
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