Our Guide To Specialist Switchgear Systems

5th March 2022

Introduction

A specialist switchgear system is essential to a safe and reliable electrical supply. Designing and manufacturing a system that is fit for purpose requires taking into consideration factors such as the type of switchgear, interrupting device, insulation and housing.

At Birmingham Specialities, we value transparency and believe that knowledge and understanding are integral to the successful completion of a project. It is difficult to produce specifications and communicate your requirements for something that you don’t entirely understand, which is why we’ve created this guide to specialist switchgear systems. Our comprehensive introduction will equip you with everything you need to know before seeking a manufacturer.

This article will answer all of your possible questions and put you in an excellent position when approaching a manufacturing service offering quality control, design and manufacture of the product you require.

What Is A Switchgear System?

A specialist switchgear system is used to control, protect and/or isolate an electric power system. Examples of switchgear include: fuses, switches, relays, isolators, circuit breakers, potential transformers, current transformers, indicating devices and lightning arresters. They can be divided into two key components, the power conducting component and the control system.

Power-Conducting Component

The power-conducting component conducts or interrupts power flow. This means that it is made from a material that can conduct electricity, such as copper or silver, to allow a charge to flow in at least one direction. As such, it is the main component of switchgear.

Control System

The control system regulates, controls and protects the power-conducting component. Examples of a control system include circuitry and control panels. They are crucial to having a stable, accurate system, although this can vary depending on whether it is an open or closed loop system, and what kind of control it allows.

What do Switchgears do?

The three main functions of switchgear systems are to control, protect and isolate. This means they have a huge range of applications and are vital to the operation and efficiency of many electrical systems.

Control

The system measures the electrical load and can perform emergency switching, functional switching and emergency stops as needed. They can do so by energising and de-energising, meaning that they can give or deprive electrical power.

Protect

When a circuit is experiencing overload, the system interrupts. It detects overcurrents and overloads through thermal imaging; more radiation is emitted when the temperature increases, allowing early detection. The system allows the electrical current to flow through the unaffected circuits, minimising the damage caused and ensuring people, animals and equipment nearby are unharmed.

Isolate

The system isolates energised circuits and system components. They can be separated from each other by a physical barrier or by a gap. This ensures the safety of the engineer that is attending to the equipment, whether they are doing periodic maintenance or fault clearing.

Types Of Switchgear

There are three main types of switchgear, and each has different applications. Using the wrong voltage switchgear could be incredibly dangerous, which is why they should only be manufactured by a professional. If you need guidance on the kind of switchgear best-suited for your requirements, consult an industry expert. There are high voltage switchgear, medium voltage switchgear and low voltage switchgear:

High Voltage (HV) Switchgear

These power systems control voltages over 36Kv, and this high voltage means that arcing during switching is also high. Arcing is when the electrical current jumps or produces a flash. Consequently, the design and fitting of an HV switchgear should be extremely careful, to ensure safety and reliability.

Medium Voltage (MV) Switchgear

MV switchgear controls voltages between 3 and 36 Kv. All systems should be capable of carrying out the following functions in a safe and reliable manner: ON / OFF switching operation, short circuit current interruption, switching of inductive and capacitive currents.

There are many types of MV switchgear, the most common of which are: gas-insulated switchgear, metal-clad switchgear, metal-enclosed switchgear, pad-mounted switchgear, vault or subsurface switchgear and arc resistant switchgear.

Gas-Insulated Switchgear (GIS)

A GIS system houses its components in a single gas tank. The sealed enclosure is compact and easy to install. One key advantage of a GIS is that distance between interrupting components is reduced, as gas is insulating. Grounding devices and lightning arresters are implemented to prevent electric shocks and dielectric breakdowns.

Metal-Enclosed Switchgear

This system is completely enclosed, with the exception of ventilation and inspection windows, by sheet metal. It includes protective, control and metering equipment, and has both domestic and industrial applications.

Metal-Clad Switchgear

A subset of the above system, metal-clad switchgear have the same external appearance. The distinction lies in the internal components, which are individually metal-clad. This makes it a considerably more expensive system, but one which allows compartment removal without impacting the wider system.

Pad-Mounted Switchgear

This type of switchgear is ideal for use in underground distribution systems, as they can provide the ideal capacity for all of the necessary switching and isolating. They are ideal for widespread, high-speed applications as they are low profile and tamper resistant.

Vault / Subsurface Switchgear

This system is ideal for electrical distribution systems between a specific voltage that operate below ground level and in dry or wet conditions. They can be operated above ground by using relays.

Low Voltage (LV) Switchgear

These power systems control voltages up to 1Kv. LV switchgear is comprised of all of the accessories required to protect a low volume system, the most common of which is a low volume distribution board. The system will have an incomer, sub-incomer and feeders, all of which are designed to protect against short-circuiting and overloading.

Interrupting Devices

Switchgear interrupting devices interrupt electricity flow, which is crucial to their ability to control, protect and isolate. A number of devices are capable of doing so, and each is accompanied by its own advantages and disadvantages.

Air Switch

Compressed air is used to blow out the arc. Although this device has a lower interrupting rating than other possible options, it is incredibly economical.

Gas Switch

A gas switch uses a gas such as Sulfur Hexafluoride to cool and quench the arc. It is a low maintenance means of breaking the circuit, with low operating noise and no hot gas emission.

Carbon Dioxide Switch

This operates under the same principle as the above gas switch. Using carbon dioxide is better for the environment, significantly reducing greenhouse gas emissions (compared to Sulfur Hexafluoride).

Fuse

Excessive current flow is interrupted by the melting of an electrical wire or strip. It is purpose-built, meaning that it is designed to melt at a specific time or temperature.

Oil Switch

The device is submerged in oil, and due to its high dielectric strength, it provides insulation between the conductors and the earth conductors once the arc has been extinguished.

Vacuum Circuit Breaker

Arc interruption and quenching occurs within a sealed vacuum bottle and is performed quickly to reduce the arc energy. They can interrupt much higher voltages than other interrupting devices, and take up considerably less space.

Vacuum Fault Interrupter

Vacuum fault interrupters have a dual function, operating as both overcurrent protection and load-break switch. This means you do not need a separate fuse and switch.

Insulation

Switchgear insulation can degrade over time when subject to electrical or mechanical stress, elevated temperatures and environmental conditions, and can require maintenance or replacement over time. However, it is essential to adhere to health and safety codes, and aid longevity and function of the switchgear itself. Different kinds of insulation are available, each with their own advantages.

Air

Air has low dielectric strength and so requires larger, more durable equipment to withstand the electrical arc. However, it is also inexpensive and the most common insulator.

Gas

Sulfur Hexafluoride is most commonly used to insulate. The electric elements are placed within a sealed tank of pressurised gas.

Fluid Mineral Oil

Various fluids can be used for electrical insulation, but it is important that they are fire-resistant. Possible fluids include: mineral oil, which has reliable insulating properties, E200 fluid, which is fire-resistant and biodegradable, and Envirotemp FR3 fluid, which is nontoxic and biodegradable.

Housing

Switchgear system housings should be purpose-built, allowing both security and functionality. Most manufacturers offer bespoke housings so that it is best suited to the requirements of your system. This can include temperature resistance, humidity control and blast resistance, as required for sensitive equipment. Low voltage systems can be inside, while higher voltage levels will typically be outdoors. The housing of your system will influence its mode of operation: they can be manually operated, or use a motor drive allowing remote control.

At Birmingham Specialties, we have the capacity and capability to manufacture switchgear housings of varying sizes and for a vast range of purposes, which has allowed us to provide our services to some of the world’s largest electrical engineering firms.

Maintenance

Switchgear systems are subject to difficult conditions, which can lead to accelerated device ageing, regardless of your choice of interrupting device, insulation or housing. Some such conditions include temperature, vibration, dust, corrosive atmosphere, per cent load, humidity, current harmonics and salt environment. The only way to prevent these conditions from posing a danger is by carrying out maintenance services. There is a huge range of proactive and reactive maintenance types, and the most common for switchgear systems are periodic and conditional.

Periodic Maintenance

Periodic maintenance is carried out at predetermined intervals, as advised by the manufacturer. The purpose of this is to maintain your systems or subassemblies, to ensure that it is operating in optimum conditions and that it will meet its target service life.

Conditional Maintenance

Conditional maintenance is carried out when a predefined threshold has been reached and can be done without shutting down the system. This means that it is based on the actual condition of the switchgear, and so it is only done when absolutely necessary.