2.10.3
SF6 Interrupters
SF6 interrupters shall be of the puffer type where the movement of the
contact plunger will initiate the puff of SF6 gas across the contact to
extinguish the arc at zero gauge tank pressure (atmospheric pressure). The
puff of SF6 must be sufficient to clear an arc for [15 kV] [_____] or lower
class equipment and remain operational without damage or requiring
maintenance or repair except for gas leaks. Breakers shall be provided
with a loss-of-pressure alarm remote as shown on the drawings. Before the
pressure in the container drops below the point where the breaker or switch
cannot open safely without damage, the breaker shall activate the
loss-of-pressure alarm, open automatically, and remain in the locked open
position until repaired. If located inside a structure, breakers shall be
located in a closed room with access only from outside, and provided with
direct outdoor ventilation and a sensor unit which activates a vent fan and
an alarm when a SF6 leak had occurred. The alarm will automatically be
silenced when the oxygen in the room is above 19.5 percent. The SF6 shall
meet the requirements of ASTM D 2472, except that the maximum dew point
shall be minus 60 degrees C 140 degrees F(corresponding to 11 ppm water by
volume), with only 11 ppm water by volume, and the minimum purity shall be
99.9 percent by weight. Circuit breakers shall have provisions for
maintenance slow closing of contacts and have a readily accessible contact
wear indicator. Tripping time shall not exceed five cycles.
2.10.4
Vacuum Interrupters
Vacuum interrupters shall be hermetically-sealed in a high vacuum to
protect contact from moisture and contamination. Circuit breakers shall
have provisions for slow closing of contacts and have a readily contact
wear indicator. Tripping time shall not exceed five cycles.
2.10.5
Ratings
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NOTE: ANSI C37.06, Table 2 lists preferred ratings
for indoor oilless circuit breakers. A
short-circuit study is required to specify ratings.
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Main buses shall be three-phase [three-wire] [four-wire] with a continuous
current rating of [_____] amperes rms. [The neutral bus shall be rated for
[_____] amperes, continuous.] Switchgear ratings at 60 Hz shall be in
accordance with ANSI C37.06 and as follows:
Maximum voltage...................................[_____]
Nominal voltage class.............................[_____]
BIL...............................................[_____]
Maximum symmetrical interrupting capacity.........[_____]
3-second short-time-current carrying capacity.....[_____]
Rated continuous current...............[as shown] [_____]
2.11
OIL CIRCUIT BREAKERS FOR SUBSTATIONS
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SECTION 16475A
Page 20
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