Gas Insulated Switchgear (GIS) refers to the general equipment of a substation in a metal enclosure filled with high-insulation SF6 gas and connected to the ground, which includes a circuit breaker, disconnecting switches, earthing switches, and peripheral devices (e.g., current transformer, voltage transformer, and lightning arrester). It can be installed in a small space in cities or buildings. Ensuring reliable and stable operation and good maintainability, it is especially suited for polluted and/or salty seashore areas

Our GIS ensures reliable and stable operation along with simple maintainability. We offer GIS with rated voltages ranging from 72.5kV to 800kV and rated short-circuit breaking current up to 63kA and have acquired international certificates from KERI (Korea Electrotechnology Research Institute), CESI (Italy) and KEMA (Netherlands). Kian Tajhiz has now become synonymous as the most trusted GIS supplier in the world.

• Compact Design



The installation space that is required is about 1/10~1/20th than that of conventional air-insulated substations which makes it possible to install GIS within a building.



• Safety



Enhanced insulating properties and reduced long-term operational costs by means of a sealed metal enclosure filled with SF6 gas which assures first-rate reliability, thus making it suitable for highly populated and urban areas.



• Superior Reliability



Personnel safety is ensured by an earthed enclosure, numerous interlocks, and lockout devices. Greater stability is provided during earthquakes and the perfect enclosure protects from loss or damage from salt, dirt, weather, and lightning. While the SF6 gas insulation prevents deterioration, the partition of the gas prevents accidents from occurring.



• Elimination of periodic maintenance



Virtually eliminates long-term maintenance costs and contamination of critical components by means of SF6 gas-filled metal enclosures, automatic monitoring of operating mechanisms, and the SF6 gas system.



• Installation & transportation



Installation time and costs are reduced since the system is shipped in a completely assembled bay or by unit.

Components

• Circuit Breaker



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



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.



• Earthing Switches



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.



• Busbars



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 Kian Tajhiz of the busbars is assembled. The expansion or shrinkage of conductors due to temperature changes can be compensated.



• Current Transformers



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 SF ₆ gas.



• Voltage Transformer



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.



• Lightning Arrester



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.



• Interfaces



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

hree-Dimensional Electric Field Analysis

• Because high voltage is applied in the SF6 GIS, a very precise electric field analysis is needed. Therefore, Kian Tajhiz uses a three-diemensional analysis program to design a product that analyzes the electric field distribution of all parts of the GIS including the busbar and insulating materials.

Mechanical Performance Analysis

• To maximize the optimum mechanical performance of the conductor, enclosure, and controller of the GIS, values (mass, shape, stress, transformation, etc) of all parts of the GIS are precisely analyzed using the structure analysis programs and three-dimensional design.

Three-Dimensional Design & Assembly

• Solid Edge, the latest three-dimensional design tool, is used for basic GIS design to assembling parts in order to minimize any possible design errors. It is also used to model the final installation so that the installation site is optimized by the assembled parts.

Seismic & Vibration

• To verify the seismic and vibration at the design stage, the latest seismic and vibration analysis tools, which consider all loads resulting from gravity (both the vertical load and the wind load), have been used for ensuring overall structural safety.