Medium Voltage Switchgear

Definition of Medium Voltage Switchgear

Do you wonder what is medium voltage switchgear? Essentially, it’s a distribution system that integrates circuit breakers, disconnect switches, fuses, and protective devices within a metal enclosure. Primarily used to control, isolate, and protect each electrical circuit, it ensures your entire system remains stable and secure during power supply and fault handling.

How does Medium Voltage Switchgear Work?

ZHONGSHAO’s medium voltage switchgear typically controls, disconnects, and protects medium-voltage distribution systems through three key steps.

Step 1: Control

By integrating draw-out circuit breakers, disconnect switches, earthing switches, and instrument transformers within a metal enclosure, mechanical interlocks and five-prevention mechanisms enable control, switching, and isolation of each medium-voltage circuit.

Step 2: Distribution

Under normal operating conditions, vacuum circuit breakers reliably connect circuits, distributing electrical energy stably to transformers, feeders, or equipment loads.

Step 3: Protection

When your system experiences a short circuit, ground fault, or overload, relay protection devices detect abnormal currents, phases, or voltages and send a trip signal to the circuit breaker.

Upon receiving the signal, the vacuum circuit breaker completes the opening operation within milliseconds, isolating the faulty circuit from the system. This prevents accident escalation and safeguards personnel and equipment.

Key Components of Medium Voltage Switchgear

All medium voltage switchgear components​ of ZHONGSHAO comply with ANSI and IEC standards, ensuring you a stable and safe power distribution experience under various working conditions.

Enclosure

The equipment is equipped with a high-strength metal enclosure, suitable for both indoor and outdoor environments. It not only protects the internal components but also ensures reliable operation of the entire system in damp, dusty, high-temperature or slightly corrosive environments.

Load Switch and Circuit Breaker Units

These components determine whether the system can operate safely and isolate circuits, and they are one of the core modules of medium voltage equipment. According to your application requirements, ZHONGSHAO can provide various switch configurations, including:

• Load Circuit Breaker

• Fusible Load Switch

• Grounding / Isolating Switch

• Oil-immersed Switch

• Air Switch

• Vacuum Switch

Take ZHONGSHAO General Electric medium voltage switchgear as an example. We usually adopt withdrawable vacuum circuit breakers. This structure is convenient for maintenance and replacement, and has excellent breaking capacity, effectively enhancing the reliability of the equipment operation.

Busbar System

The busbar is the main conductive channel of the medium voltage system. ZHONGSHAO uses tin-plated or silver-plated copper busbars to improve conductivity, reduce heat generation and lower the risk of long-term oxidation. A high-quality busbar system not only affects energy efficiency but also directly influences the overall lifespan of the equipment.

Communication and Remote Monitoring

ZHONGSHAO medium voltage switchgear supports mainstream communication protocols such as Modbus TCP/IP, DNP3, and IEC 61850, enabling real-time integration with SCADA or Building Management Systems (BMS).

The medium voltage switchgear panels integrate HMI, human-machine interface buttons, indicator lights, and status display areas, providing you with clear and intuitive operation information and supporting one-click operation.

Through the intelligent panel and communication system, you can achieve:

• Remote monitoring of circuit breakers, trolleys, and circuit status
• Online diagnosis and alarm
• Smart relay and HMI diagnostic interface
• IoT data collection and cloud monitoring

This entire system enables your switchgear to have the capability of “always visible and always controllable”, making it suitable for unmanned sites, high-reliability factories, and projects sensitive to operational data.

Protection Devices

To ensure timely response before a system failure, ZHONGSHAO is equipped with microcomputer protection relays, intelligent sensors, and monitoring units with HMI from brands such as ABB, SEL, Siemens, and GE. They monitor current, voltage, temperature, and circuit status, achieving rapid protection and precise location, reducing your downtime risk.

Cables and Insulation System

Epoxy insulation parts, bushings, connectors, and other components can provide necessary electrical isolation, ensuring stable operation of the equipment under high voltage. A good insulation system can also effectively prevent flashover and creepage, enhancing your overall safety level.

Types of Medium Voltage Switchgear

1. Compact Switchgear

Compact design is especially prevalent in the gas-insulated medium voltage switchgear market. Its high integration in layout dramatically reduces footprint, which makes it ideal for high-density urban distribution networks or space-limited building distribution rooms where complete protection and operation functions are needed.

2. Metal-enclosed Switchgear

It has an enclosure made of metal covering all the live parts, giving it a medium-grade level of protection and isolation. Being robustly constructed and of low maintenance, it finds outdoor applications in medium voltage switchgear: park power supply, road distribution points, or public utility systems.

3. Metal-enclosed Air-insulated Switchgear

It offers complete compartmentalization for the circuit breaker compartment, busbar compartment, and cable compartment, with independent grounding and protection designs. The metal-enclosed air-insulated switchgear is highly suitable for high-safety scenarios. This makes it a typical choice for power plant medium voltage switchgear, hence, operating under extremely high reliability even in continuous high-load operations.

4. Floor-mounted Switchgear

Floor-mounted switchgear is normally used outdoors and mounted directly onto a foundation platform. It was designed to withstand environmental challenges like rain, dust, and temperature fluctuations. Its design is usually more for public utility distribution networks, which happen to be the most common configuration in outdoor distribution systems.

5. Underground or Basement Switchgear

The underground or basement medium voltage switchgear is appropriate for areas beneath the road, in urban core areas, or where facilities of distribution should be hidden. By structure, it is sealed and waterproof; therefore, stable operation in underground spaces is possible. It is one of the popular choices for the vacuum-insulated medium voltage switchgear market​. Especially, it excels in places where space is limited and environmental humidity is high.

6. Metal-enclosed + Metal-enclosed Combination

These usually are large industrial or substation projects where both structures have their place within the installation: armored construction for high-reliability areas, and metal-enclosed construction for lower-load branch units. The combination approach will provide the right balance of flexibility, cost, and reliability in large distribution systems involving several circuits.

How to Install Medium Voltage Switchgear?

The installation of medium-voltage switchgear must be performed by a qualified electrical engineering team to ensure the system’s safety and long-term stable operation. If you have selected ZHONGSHAO’s medium-voltage switchgear, our technical personnel can provide remote installation guidance to assist your team in successfully completing on-site assembly.

Step 1: Verify the Installation Environment

Before installation, please ensure the area in which the equipment will be installed is clean, dry, and free of condensation, and that good ventilation is available. Generally, the ambient temperature remains at about 70°F (21°C). If the installation must be done in cold areas, a temporary heater of no less than 200 W is used, but flammable materials are kept away from the heater. Ensure continuous ventilation in the entire area to keep the temperature around the equipment below 40°C (104°F).

Step 2: Prepare for Construction

Before the installation of medium-voltage switchgear, it is necessary to check whether the construction site provides appropriate conditions for electrical installation. First, the passage should be bright enough and have facilitating power sockets for normal use by electric tools during installation. Meanwhile, the ground should have good drainage capability, and necessary floor drains should be set up to avoid water accumulation during construction or afterward in operation.

Step 3: Preparation of Power Supply and Heating Equipment

Prior to installation, the external power should be connected to the cabinet heater, and the main current-limiting fuse to the control power transformer should be removed. Particular attention should be given not to using greasy or smoking heating equipment to avoid depositing carbon particles on the insulation surface, leading to leakage or reduced insulation performance.

Step 4: Preinstallation and Positioning of Transport Sections

When there are many transport sections that make up the medium-voltage switchgear, only the middle section should be unloaded and installed first, then pushed to both sides in sequence in order to reduce the accumulation of conduit position errors.

In the process of operation personnel, every section of the equipment should be moved together with the base; if rollers are used, the base must be fixed. Only when accurately landing on the base can the transport base be removed, and the equipment cannot be adjusted by prying structural components, door panels, or covers.

Step 5: Alignment of Equipment

After the first section is in place, check that the conduit is centered in the opening, the back of the equipment is perpendicular to the base pad, and adequate maintenance clearance is reserved. Check at the same time that installation holes align with base angle steel. Then push the next transport section into the mating position and add steel shims under the base as required to make it level.

After installation of each section, check its level and alignment, and fit between sections. If there is no fit, lift the section, clear the bottom obstacles, and reinstall the section.

Step 6: Between Sections Adjustments

After the sections are aligned, the bolts connecting adjacent sections should be fixed in sequence. It is necessary to tighten all the sections before performing the operation of fixing the equipment to the angle steel beam or connecting to the horizontal main busbar.

Step 7: Verify the Position

After the fixation of all sections, the overall final position of the switchgear should be cross-checked against the construction drawings once more to ensure that there is no deviation or cumulative error and all the mechanical structures are in the designed state.

Step 8: Install the Cable Room Base Plate

After all structures are fixed and the position is confirmed, you also need to install the cable room base plate in order to form an effective barrier between the cable room and the equipment bottom space to prevent foreign objects from getting in and ensuring safety and tidiness of subsequent cable installation.

How to Maintain Medium Voltage Switchgear？

Maintenance of medium voltage switchgear is conventionally divided into three categories: preventive, predictive, and corrective, each with different objectives and applicable scenarios.

Preventive Maintenance (PM)

The major work of preventive maintenance involves cleaning switchgear enclosures, tightening connections, testing protective devices, and inspection mechanical interlocks. It helps your equipment perform normally throughout its operational life by assuring early detection of potential hazards.

Predictive Maintenance (PdM)

Predictive maintenance techniques will mainly rely on condition monitoring technologies to monitor equipment conditions. Using thermal imaging, contact resistance test, and partial discharge detection, issues such as insulation aging, overheating, or electrical stress could be detected with real-time status. Therefore, this empowers maintenance teams to intervene before failures occur.

Corrective Maintenance (CM)

Corrective maintenance is necessary for needed repairs or replacements after a failure or degradation in performance has occurred; also referred to as breakdown maintenance, ZHONGSHAO can deal with anything from simple component replacement to major circuit overhauls.

Preventive Maintenance Inspection Checklist

ZHONGSHAO has compiled a professional preventive maintenance inspection checklist for medium voltage switchgear to help customers record equipment status in different maintenance cycles. After each item is implemented, you can check √ in the table and note the date or findings of the record in the remarks column for easy tracing and archiving.

How to Choose Medium Voltage Switchgear?

Step 1: Confirm the Installation Environment

When making medium voltage switchgear procurement, first, confirm whether your equipment is installed indoors or outdoors, and whether there are special conditions such as dampness, dust, salt spray, high temperature or underground space. Thus, the appropriate enclosure grade and protection grade (IP) can be selected based on the on-site conditions to avoid problems such as condensation, corrosion or insufficient heat dissipation in the later stage. This is also the first step in determining the specifications of medium-voltage switchgear.

Step 2: Select the Insulation Method

Select the insulating medium based on your project space, maintenance capabilities and performance requirements, and compare the range of different medium-voltage switchgear at the same time:

• Air insulation (AIS): Simple structure, easy to maintain, suitable for scenarios with ample space.
• Gas insulation (GIS, SF₆): small in size and with good sealing performance, it is often used in urban substations or machine rooms with limited space.
• Liquid insulation (E200, FR3, mineral oil): It has good dielectric properties and strong heat dissipation capacity, and is suitable for projects with high temperature rise requirements.

Step 3: Confirm Compliance and Protection Requirements

The equipment must first comply with IEC, IEEE or local electrical standards and have the necessary arc flash protection capability.

After confirming compliance, select appropriate circuit breakers, CT/VT and relay protection devices based on the short-circuit capacity and protection scheme of the system to ensure that the rated values and safety of medium-voltage switchgear can meet your operational requirements.

Step 4: Select the Configuration and Expansion Capabilities 

Based on the project scale, determine the busbar structure, the number of circuits, whether double busbars or tie schemes are needed, as well as the future expansion space.

If the project requires remote monitoring or access to the SCADA/BMS system, an intelligent configuration that supports IEC 61850, Modbus or DNP3 should be selected.

Step 5: Confirm the Model

Based on the key parameters in the following table, determine the final selection to avoid missing important indicators during procurement. This is also the core step to complete the purchase of medium-voltage switchgear.

Applications of Medium Voltage Switchgear

Medium voltage switchgear, widely used in transmission and distribution systems, provides safety and stability in the power control and protection of medium and large commercial facilities and industrial scenarios. Typical applications generally include:

Data Centers and Critical Power Systems

It is applied to ultra-large-scale data centers, colocation rooms, and critical load environments that have extremely high demands on continuous power supply. Medium voltage switchgear can ensure the stability of power supply, achieve busbar redundancy, and support intelligent monitoring.

Industrial manufacturing and High-precision Production Facilities

The medium-voltage switchgear in semiconductor manufacturing, pharmaceutical factories, and industrial parks is used to support the work of high-load equipment by providing reliable short-circuit protection, isolation, and selectivity of the system.

Renewable Energy Projects

It is widely applied in wind power, photovoltaic power, and battery energy storage systems, used to realize the purpose of grid connection, isolation, load transfer, and safety protection. It is a key control node in the new energy power system.

Public Utilities and Grid Interconnection

It is applied in substations, distributed access points of power grids, and public power infrastructure used for enhancing the reliability of network operation and handling multi-source parallel systems. These are the core application areas in medium-voltage switchgears of public utilities.

Medical and Life Support Facilities

Medium-voltage switchgear provides continuity of power supply for critical systems within hospitals, medical centers, and continuous load facilities, backup power switching, and system redundancy.

Transportation and Infrastructure

It is applicable to large-scale infrastructure projects such as rail transit, airports and ports, and is used to ensure the stable operation of traction power supply, lighting, communication and control systems, while meeting the demands of the European medium-voltage switchgear market for high reliability and intelligence.

Low and Medium Voltage Switchgear: What is the Difference?

The low voltage and medium voltage switchgear in modern power systems is crucial to ensure that electricity distribution is safe and stable. ZHONGSHAO does offer high-quality wholesale low and medium voltage switchgea that satisfy power supply requirements in different scales and industries.