Gas Insulated Switchgear (GIS) 145kV solution for HV transmission networks

Switchgear (GIS) 145kV

145kV Gas Insulated Switchgear (GIS) is a high-voltage switchgear system used in 132/138kV class transmission networks. It uses SF6 gas or alternative environmentally friendly insulating gases as the insulation medium and combines major high-voltage equipment—including circuit breakers, disconnectors, earthing switches, current transformers, voltage transformers, and busbars—inside a sealed, grounded metal enclosure.

Compared with conventional Air Insulated Switchgear (AIS), 145kV GIS provides a compact, highly reliable solution for transmission substations where space, environmental conditions, and operational reliability are critical.

Main Functions
·Circuit Switching: Connects and disconnects transmission circuits under normal operating conditions.
·Fault Interruption: Clears short-circuit currents through high-voltage circuit breakers.
·Electrical Isolation: Provides safe isolation of equipment for maintenance.
·Protection and Measurement: Integrates CTs and VTs for relay protection, metering, and monitoring.
·Substation Optimization: Reduces installation area and improves system reliability.

Typical Applications
·132kV / 138kV transmission substations
·Urban substations
·Underground substations
·Hydropower plants
·Wind and solar power substations
·Industrial power receiving stations
·Railway traction substations
·Coastal and polluted environments
·Space-limited high-voltage installations

Typical Technical Specifications
·Rated Voltage: 145 kV
·Highest System Voltage: 145 kV
·Rated Frequency: 50 Hz / 60 Hz
·Rated Current: 1250 A – 4000 A
·Short-Time Withstand Current: 31.5 kA – 50 kA
·Peak Withstand Current: 80 kA – 125 kA
·Lightning Impulse Withstand Voltage: Up to 650 kV
·Power Frequency Withstand Voltage: Up to 275 kV
·Insulation Medium: SF6 / alternative gas
·Installation: Indoor or outdoor enclosure
·Enclosure Material: Aluminum alloy / stainless steel
·Protection Degree: Gas-tight sealed compartments

Main Components
1.) Gas Insulated Busbar
·Transfers power between GIS bays
·Fully enclosed in grounded metal housings
·Provides compact and reliable connection
2.) High Voltage Circuit Breaker
·Interrupts load and fault currents
·Uses high-performance arc extinguishing technology
·Controlled by protection and automation systems
3.) Disconnector (DS)
·Provides visible electrical isolation
·Enables safe maintenance work
4.) Earthing Switch (ES)
·Grounds isolated sections
·Ensures operator safety during maintenance
5.) Current Transformer (CT)
·Used for:
·Distance protection
·Differential protection
·Overcurrent protection
·Energy metering
6.) Voltage Transformer (VT)
·Provides voltage signals for:
·Protection relays
·Metering systems
·Synchronization
·SCADA monitoring
7.) Gas Compartments
·Divide GIS equipment into isolated sections
·Reduce gas loss during maintenance
·Improve system availability

Operating Principle
Normal Operation
·Conductors are enclosed inside sealed gas compartments.
·High dielectric strength gas provides insulation between live parts and grounded enclosure.
·Electrical power flows through GIS busbars and switching equipment.
Fault Operation
·Protection system detects abnormal current.
·Circuit breaker receives a trip signal.
·Arc is extinguished inside the breaker chamber.
·Faulted section is isolated by disconnectors.
·Earthing switches discharge and ground isolated equipment.

Advantages
·Extremely compact compared with AIS
·Excellent insulation performance
·High reliability in harsh environments
·Low sensitivity to pollution, dust, and humidity
·Reduced substation footprint
·Lower maintenance requirements
·Improved operator safety
·Long service life
·Suitable for indoor, underground, and coastal substations

Typical GIS Configurations
Single Busbar GIS
·Simple and economical
·Used for standard substations
Double Busbar GIS
·Provides operational flexibility
·Allows load transfer and maintenance switching
Ring Bus GIS
·Improves supply continuity
·Used in important distribution networks
Breaker-and-a-Half GIS
·Used in critical transmission substations
·Provides high reliability and operational flexibility

Applicable Standards
·IEC 62271-1 – High-voltage switchgear and controlgear common specifications
·IEC 62271-100 – High-voltage AC circuit breakers
·IEC 62271-102 – Disconnectors and earthing switches
·IEC 62271-203 – Gas-insulated metal-enclosed switchgear above 52 kV
·IEEE C37.122 – Gas-Insulated Substations

Typical Applications by Industry
·Electric Utilities: 132/138kV transmission substations
·Renewable Energy: Large wind and solar grid connection
·Hydropower: Generator step-up substations
·Industrial Plants: High-voltage receiving substations
·Railways: Traction power substations
·Urban Infrastructure: Compact indoor substations
·Oil & Gas: Reliable high-voltage electrical systems

Key Features
·Rated voltage 145kV
·Designed for 132/138kV transmission systems
·Metal-enclosed gas-insulated construction
·Integrated CB, CT, VT, DS, and ES modules
·Compact footprint compared with AIS
·High dielectric strength and insulation reliability
·Excellent resistance to environmental conditions
·Low maintenance requirement
·High operational safety and availability
·Suitable for digital and smart substations
·Compliant with IEC 62271 and IEEE C37.122 standards