ABB VM1 Installation And Service Instructions Manual page 57

M E D I U M V O LTA G E P R O D U C T S
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12. 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 power
frequency, according to the IEC 62271-100 and VDE
0670 Standards, is safe;
• application of a voltage higher than the withstand
voltage at power frequency or of a direct current
test voltage, 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 specific distance between
the contacts.
This condition is intrinsically guaranteed by
correct operation of the drive and by adjustments
of the transmission system.
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