Switch disconnectors - How to safely control the electrical network?

Switch disconnectors are commonly used critical components of electrical systems, allowing the disconnection of electrical equipment for maintenance or repair. In the article we present the construction and operation of switch disconnectors, their basic functional features, and discuss how to find the right product for your application.

  • Switch disconnectors – principle of operation
  • How to choose the switch disconnector?
  • Switch disconnector – what to look for?

In an electrical installation, switch disconnectors are electromechanical elements that are used for breaking the circuit. Installed in a distribution board, they often function as the main switch. Undoubtedly, it is one of the basic elements of current flow control systems, commonly used in distribution networks and switchgears in construction, industrial plants, commercial facilities, photovoltaic installations, and in machine control. As you can see, the range of applications is wide and varied, but the common point is the need to keep networks, people, and machines safe. Given that the requirements for system components vary depending on the application, it is worth knowing what the market has to offer and which product features to pay attention to.

 

Switch disconnectors – principle of operation

Switch disconnectors are used for making and breaking currents in electrical installations under rated operating conditions. In the conduction mode, the task of the disconnector is to supply current to the electrical installation or one of its components. The isolation of the system is achieved by setting the element to a disconnected state. The absence of current flow is associated with the physical opening of the contact and thus isolation of the circuit from the supply. This makes it possible to safely carry out repairs and maintenance on the electrical system or, in industrial conditions, to install a new machine. According to the standard, the design of the switch disconnector must provide sufficient isolation gap between the contacts to fully cut off the supply voltage. Switch disconnectors are usually also equipped with a status indicator, which can simultaneously serve as a knob and a lever to control the operation of the component.

The main difference between switch disconnectors and circuit breakers is that the latter disconnect the circuit only after a certain current is exceeded, and this is primarily to protect electrical equipment against short circuits and overloads. On the other hand, switch disconnectors are mainly used to cut off the supply; however, fuse switch disconnectors in the form of a fuse placed in the housing of the device are also available. It blows when the load is too high, which can happen, for example, as a result of a short circuit in the system, providing additional protection for devices connected to the installation.

How to choose the switch disconnector?

When choosing a disconnector, the first thing that catches your eye is the fact that there is a multitude of products and suppliers on the market, including leading companies and smaller manufacturers. The market offers a wide range of available versions, mounting options, and operating parameters. This is due to the fact that manufacturers are constantly putting a lot of effort into technology development, improving performance and reliability parameters and using ever better materials. All these activities are part of several larger trends observed in the field of electrical circuits, such as miniaturisation, improved design, ease of assembly, and use. At the same time, the environmental resistance and durability of components are increasing, thus expanding the area of application.

It is worth taking a moment to select the right disconnector for the intended application. They are an important part of power systems, affecting safety, so it pays to choose high-quality products. Do not be tempted to compromise between quality and price, as a faulty or carelessly made disconnector may lead to a dangerous situation or malfunction in the installation.

When choosing the switch disconnector the expected operating conditions of the circuit must of course be taken into account. One of the main parameters of disconnectors is the rated current, that is the maximum current an appliance should ever draw. The market offers general-purpose components designed for currents of 25 or 32 A. There are also products that can handle significant currents and voltages and withstand an amperage of several hundred amperes. Additional parameters given by the manufacturers include the rated short circuit making current and the rated short time withstand current. Detailed information is usually available in the manufacturer documentation.

Depending on electrical installation type switch disconnectors with a specific number of poles are selected. For single-phase installation, 1- or 2-pole disconnectors are used, capable of cutting off a selected section or the entire electrical installation, respectively. For three-phase current, use 3-pole or 4-pole disconnectors which, like the previous group, can cut off the supply from all of a selected section or the installation.

Functional features are a separate class of switch disconnector parameters. These devices are offered in a variety of housings, dimensions, connection, mounting and control types. Consumers benefit from this by being able to optimally select the device in terms of dimensions, easy installation, and maintenance. The most common models are those mounted on a DIN rail or on a panel. In line with the current trends in construction and industry, the models with extensive communication capabilities, allowing efficient monitoring and control, are available on the market.

Switch disconnector – what to look for??

Next to switches and disconnectors, switch disconnectors are the basic elements used to control current in an electrical installation. In most cases, they are essential to ensure the safety of people and machines, so it is worth taking them into account in the design and using tried-and-tested, tailor-made solutions. Once you have chosen the right technical parameters, it is also a good idea to make sure that the products meet the requirements of the IEC/EN 60947-1 standard. This ensures that a given element of the switchgear complies with safety standards. It is worth mentioning, for example, the requirement that switch disconnectors should be designed in such a way that the user cannot even accidentally touch conductive parts. Failure to comply with these standards may affect the safety of those working on the installation.

If the switches are to be used in harsh environments such as industry or outdoor applications, it is worth choosing products with additional safety certification for electrical products. In such cases, the IP protection code is of great importance.

Text prepared by Transfer Multisort Elektronik Sp. z o.o.

https://www.tme.eu/en/news/library-articles/page/44881/switch-disconnectors/