Why do we need switch disconnectors?

Schneider Electric Compact INS / INV Product Brief Overview

What are switch disconnectors for? This switching device is primarily intended for switching rated currents in manual mode. The main difference between switch-disconnectors and circuit breakers is that they do not protect the circuits from emergency operation - overload and short circuit. What are the functions of these switching devices?

In this article, we briefly characterize the switch-disconnectors on the example of electric devices of the Compact INS / INV series of the well-known manufacturer Schneider Electric.

The main advantages of this type of circuit breaker are its simplicity of design, wide range of applications, compliance with international standards, as well as the possibility of expanding functionality by installing various additional devices. At the same time, a huge advantage is that the complete safety of personnel is ensured when operating these electrical devices.

Switching devices of the considered series can have several options:

• Compact INS - a switching device in which a guaranteed contact break is created. When disconnecting this switch-disconnector, it is not possible to visually see the contact break. Guaranteed separation is such a feature of the design of a mechanical device in which the position of the control handle corresponds to the actual position of the contacts of the switching device;

• Compact INV - switch-disconnector, which creates a visible gap during shutdown. The case of this unit has a transparent screen through which you can clearly see the gap of all contacts. In addition, the electric apparatus has the function of guaranteed disconnection, which, together with a visible gap, provides double safety for personnel operating an electric panel with these electric devices;

• Compact INS and Compact INV emergency (emergency) shutdown - according to their characteristics they are no different from the two previous switch-disconnectors. The only difference in the special color scheme: the yellow color of the front of the case and the red handle - for ease of detection by maintenance personnel in case of emergency load disconnection.

Where are switch disconnectors used?

Due to its versatility and a very wide range of rated currents - from 40 A to 2500 A, the Compact INS / INV series switch-disconnectors are widely used everywhere in modern distribution cabinets for various purposes ranging from distribution cabinets in domestic premisesending with the main DC distribution cabinets at manufacturing enterprises and in electrical installations for various purposes.

In switch cabinets, both AC and DC, switch-disconnectors can perform various functions.

For example, in an AC distribution board, powered by two independent sources, switch-disconnectors are installed:

• on each of the supply inputs for the implementation of a visible gap, as well as manual disconnection of the load currents;

• on the tire section for the possibility of separating a specific section of the section for ease of repair and maintenance;

• for switching rated currents of individual consumers or a group of consumers;

• for the implementation of the input reserve from another power source for one consumer or as a sectional switch-disconnector for the ability to turn on the power of a group of consumers from another independent bus section.

In the circuits of the operating current of the electrical equipment of the substations, switch-disconnectors are installed between the elements of the equipment for the convenience of separating a particular section from the ring of the operational current when searching for damage.

In cabinets for ventilation, heating equipment, power supply of various auxiliary equipment devices, switch-disconnectors are used to power up various devices. You can use them manage various powerful power consumers.

Additional functions of switch-disconnectors

Consider several additional functions of switch-disconnectors, which are implemented by connecting additional devices.

1. Monoblock pole expander - designed to provide ease of connection of a switch-disconnector. By choosing a suitable pole expander, you can connect this switching device to any busbars, conductors, contact plates, terminals. It is also possible to expand the number of terminals of each phase for the convenience of connecting several consumers without the need to install other elements for branching.

2. Voltage indicator - allows you to control the disconnected position of the switch-disconnector, not only by the position of the contacts, but also visually by the absence of voltage on the indicator, which, of course, is a plus from the point of view of electrical safety when servicing the electrical panel.

To increase the safety of personnel during operation of switch-disconnectors, it is also possible to install insulating pole separators, terminal plugs, as well as screw covers. Also, after disconnecting this switching device, it is possible to realize the locking of the control handle by installing a padlock, which allows you to fulfill the requirement of safety rules - to prevent erroneous supply of voltage.

3. Remote rotary handle - simplifies the process of switching, since using the external handle you can switch with a switch-disconnector without opening the switchboard door. For the switching device having the function of emergency shutdown - the remote handle allows personnel to work as quickly as possible.

4. Ammeter block - allows you to measure the load current in phases, which flows through the switch-disconnector.

5. Current transformer block - designed to connect various measuring instruments, both digital and analog. The current transformer unit is compact and can significantly save space in the distribution panel, as well as simplify the process of mounting and connecting devices and measuring circuits in the distribution panel as much as possible.

6. Additional (auxiliary) contacts - allow you to connect additional devices to the switch-disconnector and implement various functions. For example, you can connect alarm devices, LEDs to indicate the current position of the switching device, use additional contacts to implement the logic of the protective and automatic devices, and electrical interlocks.

Separately, mention should be made of auxiliary contacts of the leading action. This contact closes before the operation to disconnect the switch-disconnector is completed. If you connect a circuit breaker with remote control to these contacts, then when you disconnect the switch-disconnector, the circuit breaker will disconnect the load before it is disconnected, that is, ahead of schedule.

In conclusion, let’s summarize why switch disconnectors are needed, listing their main functions:

• the implementation of its main function - switching rated currents in manual mode, emergency load shedding, creating an additional open circuit;

• simplification of the installation and connection process in the electrical panel as a whole due to the use of various auxiliary elements;

• implementation of additional functions in distribution panels, thanks to which it is possible to significantly reduce the size of the electrical panel;

• ensuring maximum personnel safety during operation and maintenance of electrical panels;

• convenience of performing operational switching.