Page 694 - Industrial Power Engineering and Applications Handbook

I4 Trend\ Thcw breaker\ wcre cxten\i\elq used until a tern 3nly hreaket for all LT In lower range\. say. up This has become the This has the latot
year5 ago (say, 1970s) hut are non fast losing thcit- ~pplication\ to 66 kV. this breaker IS iiiobt preferred breaker technology in the at-c
hold in favour of SF, and VCB\ for HT and ACBs now fast lo\ing it\ hold with thc wide\t voltage interruption and suitable
for 1.T \y\tetn\ in favour of SF,, duc to range and suitability for for all applications a\
cost considerations arid all application\ noted above, particularly
the cumbcrsome dry air in view of having
preswre sy\tem. In achieved a very low
higher ranges. say. 120- chopping current, of the
765 kV, however. they order of just 2A and even
are \till being used hut le\s. In view of current
only rarely chopping and limited
voltage range. however,
it is facing limitations in
its extensive application.
The development work
on higher ranges is still
under way and not many
breakers above 36 kV
have been produced so
far. Tendency to a cold
weld, during closing and
change in the arc
chamber pressure, during
an interruption which
may damage the metallic
bellows (Figure IY.24),
have also been noted as
disadvantages in their
extensive use
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"These comparisons relate only to HT interrupters.
"For LT systems only.
'Referred to at power frequency (SO or 60 H7) and ratcd current. These figures are approximate and for a general reference only. They may vary with rating, loading and manufacturer. For
lower voltage ratings. they may he shightly higher.