3AT4/5 SF6 CIRCUIT BREAKER
 

The 3AT4/5  breaker permits 765kV system voltage to be built with only four Interrupter Units per pole.

The 3AT4/5 type circuit breaker is of Puffer design and has a hydraulic operating mechanism for each pole and is suitable for both single and triple pole auto re-closing  duties. Breaker has four series connected  interrupter units per pole and are insulated from ground by two support insulator columns housing  operating  rods connected to hydraulic drive units actuated by common hydraulic valves assembly located in base unit.

A smaller number of Interrupter units also means fewer of the other active elements, e.g., Operating mechanism, Bell crank mechanism and Grading capacitors. Extensive studies have shown that the reliability of a breaker increases as the number of active components decreases. In addition to the breaker being less susceptible to faults, it is simpler to erect, control, monitor and maintain.

A further aspect which is of considerable importance for 765kV switchgear is that the breakers shall be completely independent as regards their operation. The electro-hydraulic mechanism of 3AT4/5 SF6 breakers fully meets this requirement. They dispense with the need to provide compressed air systems which, owing to the large size of such switching stations, are particularly extensive and thus both costly and susceptible to breakdown.

The 3AT4/5 conforms to Latest IEC standards.

3AT4/5 SF6 CIRCUIT BREAKER

3AT4  :- With out Pre-Insertion Resistor (PIR)

3AT5  :- With Pre-Insertion Resistor (PIR)

 

TECHNICAL  DATA  
RATED  VOLTAGE  800 kV
RATED  NORMAL CURRENT 3150 A
RATED  SHORT  CIRCUIT  BREAKING CURRENT 40 kA
RATED  DURATION  OF  SHORT CIRCUIT  BREAKING  CURRENT 3 sec
RATED  MAKING  CURRENT 100 kA
RATED POWER FREQUENCY WITHSTAND VOLTAGE  FOR  1 min. 830 kV 
RATED LIGHTNING IMPULSE WITHSTAND VOLTAGE  1.2/50 m sec 2400 kVp
RATED SWITCHING IMPULSE WITHSTAND VOLTAGE   250/2500 m sec 1500 kVp
RATED  DUTY  CYCLE O-0.3sec-CO-3min-CO
TOTAL  BREAK  TIME 40 ms  max.
RATED  TRV  FOR  TERMINAL FAULTS 624  kVp
NO. OF  BREAKS  PER  POLE 4
FIRST  POLE  TO  CLEAR  FACTOR 1.3
RATED  FREQUENCY 50 Hz
TYPE OF OPERATING MECHANISM ELECTRO-HYDRAULIC