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III. 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 and
VDE 0670 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
and VDE 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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