Download - Daman and Diu Electricity Department, Government of ...
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1.4.2 Temperature Rise :-<br />
1.4.2.1 The temperature rise <strong>and</strong> the maximum temperature on any part <strong>of</strong> the<br />
breaker when in service under continuous full load conditions <strong>and</strong> exposed<br />
continuously to the direct sun-rays shall not exceed the permissible limits as per<br />
relevant ISS. When the st<strong>and</strong>ard specifies the limits <strong>of</strong> temperature rise. This shall not<br />
be exceeded when corrected for the difference between ambient temperature at site<br />
<strong>and</strong> the ambient temperature specified in the relevant specification. The correction<br />
proposed shall be stated in <strong>of</strong>fer <strong>and</strong> shall be subject to the approval <strong>of</strong> the purchaser.<br />
1.4.3 General Features <strong>of</strong> Circuit Breakers :-<br />
1.4.3.1 The circuit breakers shall be suitable for outdoor operations under the climatic<br />
conditions specified in section-II <strong>of</strong> this specification.<br />
1.4.3.2 The circuit breakers operating mechanism shall have two nos. <strong>of</strong> tripping coils <strong>and</strong><br />
one no. <strong>of</strong> closing coil for better reliability.<br />
1.4.3.3 Exposed live parts shall be placed high enough above ground to meet the<br />
requirements <strong>of</strong> local safety codes.<br />
1.4.3.4 All similar parts, particularly removable one <strong>and</strong> shall be interchangeable with one<br />
another.<br />
1.4.4 Insulation <strong>of</strong> the Circuit Breaker :-<br />
The insulation to ground, the insulation between open contacts <strong>and</strong> the insulation<br />
between phases <strong>of</strong> the completely assembled circuit breaker shall capable <strong>of</strong><br />
withst<strong>and</strong>ing satisfactorily die-electric test voltage corresponding to BIL specified in<br />
Clause –2.4.2 <strong>of</strong> his specification.<br />
1.4.5(a) The minimum clearances in open air shall be as under,<br />
1.4.5(b)<br />
Minimum clearance between phase : As per relevant IS.<br />
Minimum clearance between live parts : As per relevant IS.<br />
And grounded objects.<br />
Adequate clearance in air shall be provided between phase <strong>and</strong> from phase to ground.<br />
The clearance shall be such that the breaker shall withst<strong>and</strong> the BIL specified in the<br />
specification. The minimum clearance from live parts to ground level shall not be less<br />
than 3000m – including plinth height as 150mm.<br />
1.4.5 Contacts <strong>of</strong> Circuit Breaker :-<br />
1.4.6.1 The main contacts shall have adequate area <strong>and</strong> contact pressure for carrying the rated<br />
currents <strong>and</strong> the short time rated breaking currents <strong>of</strong> the breaker without excessive<br />
temperature rise. Contacts shall be easily replaceable <strong>and</strong> shall be first to open <strong>and</strong><br />
last to close so that burning <strong>of</strong> the contact may be negligible.<br />
1.4.7 Operating Mechanism <strong>of</strong> Circuit Breakers :-<br />
1.4.7.1 Circuit breakers shall be power operated by a motor compressed spring charging<br />
mechanism, the mechanism will be trip-free electrically <strong>and</strong> mechanically. The<br />
mechanism shall be strong, quick in action <strong>and</strong> shall be removable without disturbing<br />
other parts <strong>of</strong> the circuit breakers. All the working parts in the mechanism shall be <strong>of</strong><br />
corrosion resistant materials <strong>and</strong> all bearings which require greasing, shall be<br />
equipped with pressure grease fittings. The mechanism <strong>and</strong> breaker shall be such that<br />
the failure <strong>of</strong> any spring will not prevent tripping <strong>and</strong> will not cause tripping or<br />
closing.<br />
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