What is MV Switchgear?
MV switchgear, also known as medium voltage switchgear, refers to the complete set of switching, protection, control, and measurement equipment used in electrical distribution networks with voltage levels up to 36 kV. These modular units play a critical role in transformer substations, industrial distribution centers, renewable energy plants, and both step-down and step-up substations. They ensure safe operation, fault isolation, load switching, and reliable power supply in medium voltage systems.
Modern MV switchgear is designed as compact, modular metal-enclosed or metal-clad panels. They integrate several essential components into a single, safe, and easy-to-operate unit. Typical components include vacuum or SF6 circuit breakers, disconnectors, earthing switches, current and voltage transformers, protection relays, busbars, cable terminations, surge arresters, and low voltage compartments for control and auxiliary circuits.
Types of MV Switchgear: Air Insulated vs Gas Insulated
MV switchgear is primarily divided into two main categories based on the insulation medium:
1. Air Insulated Switchgear (AIS) In air insulated switchgear, the busbars and main current-carrying parts are insulated by air. Circuit breakers and disconnectors are usually installed inside SF6 gas-filled compartments for arc quenching. This design is widely used because it offers easy visual inspection, straightforward maintenance, and lower initial cost. Air insulated switchgear is preferred in applications where space is not a major constraint and regular maintenance access is available.
2. SF6 Gas Insulated Switchgear (GIS) / RMU Gas insulated switchgear uses SF6 gas as the primary insulating and arc-quenching medium for all active parts. These units are extremely compact and are commonly known as Ring Main Units (RMU) in distribution networks. GIS switchgear provides superior dielectric strength, smaller footprint, and higher reliability in harsh environments. It is the preferred choice for urban substations, underground installations, and projects where space is limited.
Both air insulated and gas insulated MV switchgear can be configured with different functional units such as incoming/outgoing feeders, transformer protection panels (with circuit breaker or fuse), bus coupler panels, metering panels, and cable connection panels.
Classification of MV Switchgear
MV switchgear is classified according to international standards (mainly IEC 62271) using the following key parameters:
- Internal Arc Classification (IAC): Defines the accessibility during an internal arc fault. Classes include A (authorized personnel only), F (front), L (lateral), and R (rear).
- Loss of Service Continuity (LSC):
- LSC-1: All equipment in one compartment — full shutdown required for maintenance.
- LSC-2A: Switching devices can be accessed while busbars remain energized.
- LSC-2B: Both cable and busbar compartments can remain energized while working on the switching device compartment.
- Partitioning Type: PM (metal partitions) or PI (insulating partitions).
In Turkey, most standard MV switchgear is supplied with PI partitioning, A-FL internal arc class, and LSC-2A service continuity.
Typical Technical Specifications in Turkey
In the Turkish market, the most commonly used MV switchgear ratings are:
- Rated voltage: 36 kV (also 24 kV and 12 kV)
- Rated current: 630 A (up to 2500 A in some designs)
- Short-circuit breaking capacity: 16 kA, 20 kA, or 25 kA
- Internal arc withstand: 16 kA for 1 second
Air insulated switchgear requires larger phase-to-phase and phase-to-ground clearances. For 36 kV systems, the minimum air clearance between busbars is typically 35–36 cm. Gas insulated switchgear achieves the same insulation level in a much smaller volume thanks to the high dielectric strength of SF6 gas.
Design and Safety Features
High-quality MV switchgear from manufacturers such as ABB MV switchgear and Schneider MV switchgear incorporates several advanced safety and operational features:
- Mechanical interlocks to prevent incorrect operation
- Visible isolation and earthing
- Pressure relief devices for internal arc faults
- Integrated protection relays with advanced communication (IEC 61850)
- Modular design allowing easy extension of switchgear lineup
- Conformal coating on electronic modules for harsh environments
These features ensure personnel safety, equipment protection, and high service reliability.
Applications of MV Switchgear
MV switchgear is used in a wide range of applications including:
- Primary and secondary distribution substations
- Industrial plants and factories
- Renewable energy plants (wind and solar)
- Commercial buildings and infrastructure projects
- Mining and oil & gas facilities
The choice between air insulated and gas insulated switchgear depends on factors such as available space, maintenance strategy, environmental conditions, and total cost of ownership.
Standards and Regulations in Turkey
In Turkey, MV switchgear must comply with TEDAŞ technical specifications:
- Air insulated switchgear → TEDAŞ-MYD/95-007.E
- SF6 gas insulated switchgear → TEDAŞ-MYD/95-002.B
Internationally, the equipment is designed and tested according to IEC 62271 series standards.
MV switchgear is one of the most critical components in medium voltage power distribution systems. Whether you choose air insulated switchgear or compact SF6 gas insulated switchgear, selecting the right type, correct classification (LSC and IAC), and reputable manufacturer ensures long-term reliability, personnel safety, and operational efficiency.
Proper engineering, correct protection coordination, and compliance with local standards such as TEDAŞ are essential for successful project implementation.
Looking for MV Switchgear for your project?
Looking for high-quality MV switchgear, medium voltage switchgear, air insulated switchgear, SF6 switchgear, or metal clad switchgear solutions from leading brands such as ABB MV switchgear and Schneider MV switchgear? We provide expert technical support and genuine products tailored to your project requirements.
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