Metal Clad Switchgear

What is a Metal Clad Switchgear?

Compared to a metal-clad switchgear, you may be more familiar with an electrical switchgear, which is used to control, protect, insulate, and distribute electric energy. Metal-clad switchgear is also a kind of electrical switchgear, but the electrical switchgear is enclosed in metal enclosures. In this way, the electrical system can get better protection.

A metal-clad switchgear is usually designed for medium voltage applications, ranging from 2.4 kilovolts to 38 kilovolts. The short-circuit tolerance capacity is as high as 63 kA.

The metal-clad switchgear is composed of separate compartments, which are connected by busbars, and all the grounded metal compartments contain live components. The main feature of it is that all of its cable compartments and components (except for ventilation openings and maintenance windows), such as circuit breakers, busbars, and cable compartments, are all contained in metal enclosures and insulated and grounded independently.

Metal Clad Switchgear Construction and Functions

Components of metal-clad switchgear are separated and put in independent compartments.

Switch and breaker interrupter

In metal cald switchgears, both disconnect switches and breaker interrupters are detachable. The breaker interrupter is inserted in the front compartment, and you can just draw it out to inspect and maintain. ZhongShao Electrical Incorporated Co., Ltd. has both spring-operated or magnetic-break type circuit breakers, and can provide vacuum breaker interrupters to enhance safety.

Insulation busbar

The bus bar assembly is contained in the top compartment. In a metal-clad switchgear, all the busbars, whether the main busbar or incoming busbar, are all separately insulated and have special covers and connectors, which enhance safety. There are busbar supports that help with heat dissipation and enhance structural strength during faults.

Current transformers (CTs)

Current transformers are used to detect the magnitude of the current. They safely convert a large current from the primary system into a small current of precise proportion that can be used by secondary instruments and relays, achieving measurement, monitoring and protection of the primary circuit. Current transformers and cable connectors are stored in the rear compartment.

Potential transformers (PTs)

Potential transformers are used to convert the high voltage of a system proportionally into a standardized low voltage. They can measure, protect, synchronize and monitor voltage. They can also be detached for maintenance.

Relay

Relay is a core component of the metal-clad switchgear that has ANSI (American National Standards Institute) functions such as overcurrent, under voltage, overvoltage and tripping the circuit breaker. It can analyze parameters in real time and issue instructions to cause the circuit breaker to trip when faults such as short circuits or overloads are detected.

Automatic shutter

Automatic shutters are necessary in metal-clad switchgears, because when these removable components are disconnected, removed or in a tested position, these automatics can cover and conceal main circuit elements (such as primary stabs or stubs) to prevent personnel from coming into direct contact with the live parts.

Ground ball studs

Ground ball studs are a dedicated bolt assembly used for connecting and securing the grounding wire. When maintaining the metal slad switchgear,  electricians will install temporary grounding wires between the de-energized equipment and the ground, and ground ball studs are often used as the connection head for this type of grounding wire to securely and quickly attach to the dedicated grounding terminal or exposed conductor of the equipment.

Infrared viewing ports

Infrared viewing ports are used to check the internal condition with infrared instruments.

Advanced Technologies Applied in Metal Clad Switchgear 

With the development of technologies, the metal-clad switchgear is also being upgraded. Now many advanced technologies have been applied. ZhongShao Electrical Incorporated Co., Ltd. is a leading power system solution manufacturer that can make metal-clad switchgears with the following advanced technologies. Whether you want to add a mechanical interlock device or a monitoring device, we can customize it for you.

Mechanical interlock devices 

A mechanical interlock device is a safety system that prevents dangerous misoperations. It uses purely physical mechanical structures (such as levers, cams, baffles, lock holes, keys, etc.) to enforce the correct operation sequence.

Grounded metal barriers

Grounded metal barriers (usually a galvanized steel plate) are inserted in front of the breaker interrupter to enclose all the main circuit elements in a connected status. They separate the primary components and secondary equipment (Instruments, relays, control power supplies, etc) to prevent high voltage from invading the low voltage control system, thus protecting personal and equipment safety.

Current Sensors (Rogowski Coils)

Some advanced metal-clad switchgears use current sensors to replace traditional Current Transformers because they can offer a wider range, non-saturation, and a smaller size, improving safety and simplifying design.

Voltage Sensors

Voltage Sensors are designed to replace bulky Potential Transformers. They can measure voltage without the need for an extra compartment.

Wireless Sensors

Wireless Sensors use infrared or surface acoustic wave technology to detect abnormal temperature conditions in metal-clad switchgears and have remote access capabilities.

Condition-Based Monitoring

Condition-based monitoring can help conduct predictive maintenance, identifying issues before failure.

Metal Clad Switchgear Advantages

Metal-clad switchgears are an upgraded version of common metal switchgears, so the advantages are obvious. ZhongShao Electrical Incorporated Co., Ltd. always makes high-quality products. Our metal-clad switchgears take customizability, safety, reliability, flexibility, maintenance and scalability.

Customizability

One of the largest advantages of our metal-clad switchgear is that it can be totally customized according to your requirements. Except for the fundamental functions compiled with ANSI, there are also multiple advanced functions that you can customize, such as regional selective interlock, direction ground fault and phase overcurrent. This customization may also change the size and structure. If you have any custom requirements, feel free to contact us.

Safety

Metal-clad switchgears have a higher level of security than traditional switchgears. Since all the components and compartments are enclosed by metals,  the risk of arc flash, electrical fault propagation, and accidental contact with live electrical components is highly reduced. Its arc-resistant structure reduces the probability of arc flash occurrence, lowers the risk of fire, electrical shock, casualty that caused by the arc flash. This also allows for the maintenance of specific compartments without affecting the entire system, enabling maintenance personnel to access separate compartments when necessary.

What’s more, the metal-clad switchgear is totally grounded, and even all of its compartments and components are independently grounded. Equipped with multiple safety devices, such as grounding barriers, mechanical interlock devices, circuit breaker covers and fully insulated busbars, operators can be assured of being insulated with medium voltage sections. Such a modular, compartmentalized design highly improves the safety of the switchgears.

Besides, our metal-clad switchgears can provide a remote circuit breaker maintenance function, which means the personnel can operate at a distance of up to 50 feet away from the metal-clad switchgear through the maintenance button.

Reliability

The good protection of electrical circuits and high insulation and security enable metal-clad switchgears to work well even in a harsh electrical environment. The zone design and arc suppression function can minimize the impact of faults and ensure that other parts of the system can still operate normally, which is crucial for achieving an uninterrupted power supply.

Flexibility

The modular design of the metal-clad switchgear enables easier upgrading and extension. For example, if you want to add a new outgoing line, instead of customizing a new cabinet and renovating the existing busbars, you can add a standard cabinet unit at the reserved position or at the end, and connect it to the prefabricated busbar section.

Easy Maintenance

Switches and circuit breakers of metal-clad switchgears can be withdrawn from enclosures without the need to detach the whole switchgear, which is convenient for monitoring and maintaining their electrical and mechanical components. The metal-clad switchgears made by ZhongShao Electrical Incorporated Co., Ltd. are equipped with drawout operating levers that can be pulled out from the enclosures by pressing the button or pulling the handle, making the operation easier.

Scalability

The modular design provides flexibility for future expansion. For example, when more power outlets are needed, there is no need to customize special equipment or demolish and rebuild. Just add new compartments as needed and connect them to the existing busbar system.

Metal Clad Switchgear Application

From the above part, we can understand that the metal-clad switchgears have high protectiveness. Factually, metal-clad switchgears are especially designed for harsh environments, such as severe weather, heavy dust, moisture, corrosive substances, etc, and can withstand higher fault currents, so they are widely applied in power plants, substations, mining,  industrial facilities, commercial Buildings, large electric motors, hospitals and data centers.

Power Plant

Power plants have extremely strict requirements for the distribution equipment, and metal-clad switchgears can satisfy them, including high safety, strong fault tolerance and breaking capacity, easy maintenance and expansion, etc. In power plants, metal-clad switchgears are widely used in the generator outlet switch station, plant-use high-voltage power distribution system, start-up/backup power system, and auxiliary transformer and control center for high-voltage motor.

Transformer Substation

Metal-clad switchgears are a standard and fundamental equipment for substations. They play a role in ensuring the transmission, transformation and safe distribution of electricity in substations.

Mining

Metal-clad switchgears can withstand the extremely harsh and dangerous environment underground in mines, such as dust, humidity, intense vibration and explosion risks, so they are a reliable choice to provide safe and maintainable medium-voltage power control and protection for mining operations.

Industrial Facilities

In industrial facilities, metal-clad switchgear serves as the core control and protection center of their power systems. It can ensure continuous production, protect expensive assets, enhance energy efficiency and ensure personnel safety.

Commercial

In commercial buildings, metal-clad switchgears are always used to ensure constant power supplies for equipment like lighting, elevators, HVAC systems, etc.

Large Electric Motors

Metal-clad switchgears can start and control electric motors safely, and provide multiple protection, such as overload protection, short-circuit protection, unbalance and phase loss protection, stall protection, and ground fault protection. Besides, by using current and voltage meters as well as intelligent devices, metal-clad switchgears can monitor the operating parameters and energy consumption of the motor.

Hospitals and Data Centers

In hospitals and data centers, metal-clad switchgears are the core node of a dual-power or even multi-power supply system. When the mains power fails, it can automatically and seamlessly switch the load to the backup generator or the second mains power supply, ensuring that the lighting and equipment in critical areas such as the operating room and ICU operate without interruption. Besides, it provided intrinsic safety for the medical staff and equipment maintenance personnel who frequently entered and exited the power distribution room.

Airports and Metro Stations

In airports and metro stations, metal-clad switchgears ensure the continuous safety of aviation, uninterrupted service for passengers, the punctual operation of trains and the safety of passenger evacuation.

Metal Clad Switchgear Maintenance

A metal-clad switchgear can usually last for 15 to 30 years or even longer, and the maintenance can affect its lifespan. Metal-clad switchgear needs regular maintenance, at least once a year. The products of ZhongShao Electrical Incorporated Co., Ltd. have been inspected carefully and tested strictly. The test content includes the mechanical operation inspection, insulation and dielectric tests, function control and interlock verification, circuit breaker timing and sequence, and factory-witnessed tests can be provided. We provide comprehensive after-sales service and guidance for metal-clad switchgear maintenance, and we also offer extended warranty service. You are welcome to quote at any time.

Visual Inspections

To maintain a metal-clad switchgear, you need to inspect and clean it regularly. You can visually check for condensation, dust, dirt, rust, deformation and foreign materials and use filtered suction equipment for removal. Some leakage and looseness can also be seen.

You can also inspect through listening and smelling. For example, an abnormal crackling sound or burnt smell can imply an overload or other faults.

Mechanical Checks

These parts need to be inspected carefully when checking the mechanical: 1. Jaw alignment, contact health and close conditions of breaker interrupters. By the way, it’s easier to maintain a metal-clad switchgear compared to other switchgears (such as metal enclosed switchgears) because the breaker interrupter is convenient to detach. 2. The tightness of hardware. 3. Grounding switch function and contact health.

Electrical Testing

Electrical testing includes measuring the main circuit resistance, conducting frequency and voltage tests on the control/auxiliary circuits, and performing mechanical operation tests.

Component Focus

If the metal-clad switchgear is equipped with a vacuum circuit breaker, it should be especially inspected to verify the main contacts and proper connections.

Metal Clad Switchgear Standard

To ensure safety, multiple standards regulate the operating conditions, rated values, temperature limits, classification of insulating materials, requirements for insulation (medium) withstand voltage, testing procedures and applications of metal-clad swutchgears.

The core standard is IEEE C37.20.2. It regulates that metal-clad switchgears must apply compartment design, and they should be equipped with grounding metal partitions to isolate components such as instruments, main busbars, and incoming or outgoing lines. It also regulates the rated voltage is 4.76 kV – 38kV, the continuous current rated values of the main busbar are 1200 A, 2000 A, 3000 A and 4000 A, and necessary devices must be included in MC switchgears. 

There are also lots of other relevant standards. For example, ANSI/IEEE C37.20.7 defines types (Type 1, 2, 2B, 2C) for protection against internal arcing faults; IEC 62271-200 defines Metal-Enclosed Switchgear (MESG) and provides general requirements, design, and type test guidelines for switchgear above 1kV; IEC 61439 is a relevant standard of low-voltage switchgear.

ZhongShao Electrical Incorporated Co., Ltd. products have strict certification. Our metal-clad switchgears complied with IEEE C37.20.2. standard and has obtained the ISO9001:2001 certification, which ensures high quality. The internal arc level, PI partition level and LSC-2A service interruption continuity level are compliant with the IEC 62271-200 standard for AFL.

The Differences Between Metal Clad Switchgear and Metal Enclosed Switchgear

In industrial applications, metal-clad switchgear and metal enclosed switchgear are the two most commonly used switchgears. The difference between them is always a hot topic. In fact, metal-clad switchgear is a subset of metal enclosed switchgear. They are both used to protect the transmission and distribution of electricity, but they have lots of differences in detail.

If the demand for loading and safety is high, the metal-clad switchgear is better; otherwise, metal enclosed switchgear is more cost-effective.

How to Choose a Suitable Switchgear?

When choosing a switchgear, you need to consider the specific application, total connection load, safety, maintenance requirements and costs.

Assess Your Power System

Determine the operating voltage and amperage of your system, and decide whether you need functions like overload protection, isolation, or motor protection. Thus you can ensure the metal-clad switchgear can withstand the maximum fault current to prevent damage.

Consider Physical and Environmental Factors

Consider the temperature, humidity, altitude, and dust exposure of the installation environment, and verify the path for delivery and installation.

Safety and Standards

The metal-clad switchgears chosen must comply with local and international electrical codes (e.g., IEC), which also ensure safety.

Evaluate Manufacturer

It’s better to choose a reputable manufacturer with strong technical support and reliability that ensures the provision of after-sales support, maintenance services, and spare parts supply. ZhongShao Electrical Incorporated Co., Ltd. provides a variety of power system solutions and we provide comprehensive after-sales and maintenance services. Whether for high-pressure or low-pressure applications, our engineers can custom metal-clad switchgears according to your requirements.