To ensure safety during a power outage, special products are used - load switches. They can disconnect the circuit remotely, manually or automatically. There are different types of switches suitable for a certain voltage and types of work.
The purpose of the load switch
The load switch is a switching device that is equipped with an arcing chamber and a drive for control. The electric drive can be muscular, triggered by a tensioned spring, or with a remote shutdown solenoid. The main purpose of the device is mechanical opening or closing of a circuit in a section that is under load. It is designed to turn off emergency currents, which is why installation is permissible only if there is protection against overload and short circuit.
Any load switch consists of the following parts: spring mechanism, power contacts, grounding knives, disconnector with poles. The poles are placed in a frame. The main movable contact is 2 steel plates. A special copper contact is used to extinguish the arc. The mechanism turns on and off with tensioned springs. A detailed description of the design will be considered on the example of the BHP 10/400 model. It includes:
- frame;
- reference insulator;
- working, grounding knives;
- holder with contacts;
- blanking chamber;
- traction insulating and locking device;
- grounding shaft and working knives;
- lever arm;
- springs;
- internal linings.
When turned on, the movable contacts are located in the chamber. Below there are other contacts that perform blanking. When disconnected, the main contacts are eroded, after which the interrupter contacts. The arc passes into the chamber, where under the influence of high temperatures gas from plexiglass is released. In this gas, the arc is extinguished in a few milliseconds.
Specifications:
- fixing method;
- rated current;
- additional options;
- equipment;
- design;
- Rated voltage.
The main area of use is networks of voltage class 6 kV and 10 kV. Such devices are used in power transformers, hoisting machines, laundries, in public catering facilities, in car washes and other important facilities operating under high voltage. Manufactures use similar devices in their plants and factories, but more expensive and with more functionality.
Types of devices
Switches are divided by the method of extinguishing the arc. There are the following types:
- Vacuum They operate on vacuum properties in which the arc does not propagate.
- Autogas. The arc is extinguished by the action of gases that are released at high temperatures in the chamber.
- Autopneumatic. The air is compressed, which causes the extinction of the arc.
- Electromagnetic The direction of the arc changes under the influence of an electromagnetic field.
- Electric gas. Extinguishing occurs in an electrotechnical gas environment consisting of sulfur hexafluoride.
By the number of poles can be distinguished:
- unipolar;
- bipolar;
- three-pole devices.
By design, they distinguish:
- thermal;
- semiconductor;
- electromagnetic;
- combined.
According to the installation method, the switches are classified as stationary and withdrawable. There are devices for indoor and outdoor installations. The devices can be mounted on a DIN rail, wall or panel.
Marking of circuit breakers
Each electromechanical device has its own marking, and a circuit breaker is no exception. The marking consists of letters and numbers that indicate the location of the drive, voltage, current and other characteristics.
For example, the designation of the 10 kV load switch VNRp 10 / 400-10zp stands for:
- In - switch;
- N is the load;
- P - manual drive;
- P - built-in fuse;
- 10 - voltage 10 V;
- 400 - current 400 A;
- 10 - through current;
- Z - the presence of grounding knives;
- P - the location of the knives behind the fuse.
Other models are recorded in the same way.
Advantages and disadvantages
The main positive qualities of load breakers include:
- ease of manufacture and operation;
- the cost of the circuit breaker is lower than other similar products;
- convenience of turning currents on and off;
- overcurrent protection;
- there is a visible gap between the contacts;
- safety.
The disadvantages of load breakers include the ability to switch rated power. Work with emergency currents is not carried out. Also, autogas circuit breakers have a small service life.
Differences from the circuit breaker
At home, other devices are often used - automatic differential switches. They are installed on various household appliances to protect against power surges. They can disconnect the room if necessary, protect current collectors and wiring from the aggressive effects of high currents. Circuit breakers are not suitable for frequent shutdowns and shutdowns. This can lead to rapid wear of the module and burnout of the working resource, after which the device will have to be changed. For such purposes, it is recommended to use modular load switches. Input switches provide high security switchboards, uninterrupted supply of electricity, ease of opening the circuit. The best option is to use the load switch and the machine at the same time. Then the security of the power grid increases.
The main difference from the machine is the inability to work in automatic mode. Switching requires external intervention - manual or remote. The machine trips when the current limit is reached. Also, devices may vary in marking and appearance.
Connection Rules
On power lines, the device is installed in front of the transformer. In residential buildings, the switch is placed in a distribution panel or other place for each apartment separately. In the apartment itself, the switches are installed in front of the meter, but they can be mounted after the meter. It is imperative to set the switch according to the scheme in front of other protective devices (plugs, automatic machines).
In factories, factories and other industrial premises, the switch is placed next to the machines, which may require an emergency shutdown.
