DESIGN
Kian Tajhiz’s circuit breaker uses superior arc quenching performance and the insulation characteristics of the SF6 gas and adopts the puffer-type, which has a simple operation principle and structure. With the double trip coil, it guarantees reliable circuit breaking and its few parts allow for simple maintenance.
Disconnecting switch is a device used to segment the charge current section partitioned by the circuit breaker. It is operated by an electric motor; however, it can be manually operated for maintenance tests. In addition, the user can check the switch status since the switch status display is connected to the control shaft in the control box.
The earthing switch is classified into two types according to its role. 1-Device earthing: manually and electrically controlled for maintenance 2-Line earthing: controlled at high-speed. It has an input capacity even when the line is energized. For preventing any unforeseen accidents, it is interlocked with associated circuit breaker and disconnecting switches.
Most busbars up to 362kV use three-phase batch tank for reducing the number of parts and installation period. The conductors are automatically connected via the tulip contactor when the housing of the busbars is assembled. The expansion or shrinkage of conductors due to temperature changes can be compensated.
Current transformer protects the system by sensing any abnormal current in the line and measuring the usual conductive current. Insulation by high-voltage is not required since this is in the enclosure grounded at both ends of the circuit breaker and isolated by the first conductor and SF6 gas.
Voltage transformer is a small-sized transformer using high-reliable gas insulated winding. It monitors the voltage of the line or the busbar. Voltage transformer is classified into two types: Metering Out Fit (MOF) and general meters.
The lightning arrester protects the power utilities from overvoltage due to lightnings or surges and prevents the utilities from breakdowns and blackouts. It uses Zine-Oxide Lightning Arrestor (ZLA) which removes the series gap using Zinc Oxide element.
The interface is classified into three types: 1- Gas-to-Oil Bushing: when the interface is directly connected to the transformer, the bushing separates the gas and insulation oil. The bellows compensates the tolerance and minimizes vibration. 2- Gas to Air Bushing: when the interface is directly connected to the feeder, the bushing filled with the SF6 gas is used. 3- Cable Sealing End: when the interface is directly connected to power cable
- Design Process
- Breaking Performance Analysis
Low current breaking performance: analyze changes in SF6 gas density cause by arc heat generated between the poles of the circuit breaker by the charge current of transmission line. High current breaking performance: analyze changes in SF6 gas density by the high arc heat which is generated when the circuit breaker blocks the abnormal current. For maximizing the breaking performance, phoenics and fluent, the arc analysis tools, are used for analyzing the SF6 gas density and flow