Load breaker: purpose, device, features of selection and installation

In order to repair a part of the power supply network under load or to replace equipment, it is necessary to interrupt the current supply to the system. The load switch will help to do this. It will correctly disconnect the current-carrying circuit and, thanks to the presence of a camera, it will extinguish the electric arc that occurs when the contacts open.

In the article we presented, the varieties and the principle of the operation of devices ensuring the safety of equipment and the safety of subsequent work are described in detail. The technical characteristics of the models demanded in everyday life are given. Recommendations on the selection and operation of a protective device are given.

Detailed description of the device

The load switch is a progressive switching device equipped with an arcing chamber and a drive for automatic or mechanical control.

Intended for mechanical opening / closing of a group of contacts in a section of an alternating current electrical circuit under load. Suitable for switching low and high voltage circuits with a workload.

Breaking devices have an extended handle. The range of operating temperatures ranges from –40 - +50 ° С. Notches on the contact terminals reduce heat loss and increase the mechanical stability of the connection

In case of short circuit it is not used, as it is designed to extinguish a low-power arc and relieve the rated load.

In production halls and in enterprises occupying a large area, autogas load breakers are usually installed. These items are easy to operate and easily repaired by low-skilled personnel.

It belongs to the class of high-voltage devices and, as a rule, is located in electrical installations operating under a voltage of 6-10 kilovolts, not equipped with an automatic system that protects the network from short circuits.

The device is equipped with reinforced contacts having a prolonged service life, significantly exceeding the operational period of contact connections in simple machines. This provides the ability to completely de-energize the line under load and carry out all the necessary measures.

Separate advanced switch-disconnector modules are equipped with special viewing windows. Through it, you can visually verify in what state - open or closed - at a particular moment are the contacts of the switch

The device for disconnecting the load consists of a durable welded frame equipped with a special shaft. There are 6 support insulators on it.

Contact knives are pivotally attached to the three located in the lower part, and the main and arcing contacts are held on the remaining elements located above. Insulating rods correctly transmit movement from the gross linkage elements directly to the contact blades.

The unit is equipped with breaking springs welded to the ends of the shaft. They allow you to deactivate the switch with a certain speed after the mechanism of free uncoupling of the wire is released

The contacts responsible for the interruption are opened in special arcing chambers made of phenolic. This material has high mechanical and corrosion resistance, demonstrates extreme strength and has unprecedented high electrical insulating characteristics.

The inner liners in the chambers are made of glass-filled polyamite, characterized by a dense structure and impact resistance. The arched shape of the chambers and inserts allows the movable arcing contacts to enter inside easily and without voltage.

Devices for switching off the load in electric networks are used to interrupt / resume the supply of voltage at substations responsible for the distribution of electricity in urban and rural areas

When the device is activated, the arcing contacts are closed first, and after them the knives close the main contacts. At the moment of disconnection, everything happens the other way around: first the main contacts open and only after them the arcing contacts.

The installation of a portable grounding device for disconnecting the voltage will ensure the safety of the network and allow without any risk to carry out any scheduled or repair work with the electrical system and equipment

In inactive mode, the movable arcing contact creates a clearly visible air gap with an arcing chamber, exactly the same as in a traditional disconnector. Immediately at the moment of shutdown, an arc is formed between the arcing contacts.

Under the influence of a high arc temperature, a glass-filled polyamide liner emits specific gases. This stream, which appeared in the chamber, extinguishes the arc, providing further safety for working with the current circuit and electrical equipment.

Elements responsible for switching off / on the load differ from each other in the following technical characteristics:

• mounting method;
• rated current level;
• basic equipment;
• the presence and number of additional functions;
• design features of the module;
• Rated voltage.

Most household switches, unlike industrial appliances, are manually controlled and turn off the current flow of not more than 100 amperes. To prevent the contacts from overheating during operation and potential overload, the product is purchased so that its rated current indicator necessarily exceeds the total current flow of consumer loads.

The device designed to disconnect the load has a letter marking - VN and a wider control handle.These positions serve as a guide for the consumer and do not allow him to confuse the unit with another externally similar device - automatic

In contrast to the classic circuit breaker, the load deactivator is equipped with reinforced contacts that can withstand continuous operation.

The increased reliability of the module is provided by such positions as:

• automatic blocking of the control handle from unauthorized switching on;
• the presence of viewing windows to visually verify the severance of contacts and giving the ability to control the situation at all stages of work;
• double rupture of chain contacts, providing a complete power outage and guaranteeing the safety of all ongoing repair and maintenance activities.

All these parameters make the voltage switches very useful for use and encourage the consumer to buy such devices and implement them in an electrical system to increase reliability and ensure operational safety.

Classification of shutdown modules

Products responsible for deactivating the load in the power grid are produced in several different versions. Classification of devices is carried out according to the method of extinguishing the arc that occurs when the load is deactivated, and according to the type of arcing chamber.

An autogas-type load breaker is most often mounted in switchgears serving boxes and at transformer substations. The activating drive in the module is manual and electric

Manufacturers working in the market of electrical equipment produce circuit breakers of the following types:

• autogas - the walls of the chamber, heating up under the influence of an electric arc, emit a special gas, which absorbs it;
• vacuum - at vacuum circuit breakers the properties of the medium in which the electric arc does not propagate are used;
• electromagnetic – electromagnetic relays act on the arc by an electromagnetic field and in this way change its direction;
• autopneumatic - extinguish the electric arc by compressing the air in the chamber with a powerful spring element;
• gas-insulated - cavity of the absorption chamber SF6 circuit breakers filled with electrical gas, consisting of sulfur hexafluoride. This colorless heavy element is six times heavier than air and very quickly extinguishes the electric arc that occurred when the contact was disconnected.

Auto-gas devices are most widely distributed today and are in maximum demand. However, they literally "step on their heels" vacuum units, recognized by experts as the most promising, progressive, efficient and reliable voltage switches.

In vacuum circuit breakers, quench chambers are provided with additional reliable insulation. Due to this, their service life and resistance to operational wear are significantly higher than for autogas analogues

Direct control of the devices is carried out using a lever-type manual drive equipped with a built-in electromagnet, allowing remote shutdown.

In addition to the parameters described above, the load switches differ from each other in the number of contact poles. Today, the market offers one-, two- and three-pole modules designed to correctly disconnect the load in the current-supplying system.

Another important feature is the design of the actuator.

This node can be:

• electromagnetic;
• thermal;
• semiconductor;
• combined.

The last feature concerns the principle of installing the module. It can be retractable, stationary or motionless. The choice is made depending on the location of the power grid and external weather conditions at the location.

Product Specifications

Devices performing load off by opening an electric circuit have various technical characteristics. All of them are important and become decisive when choosing a suitable unit for the acquisition and its subsequent installation.

Index voltage rating reflects the operating voltage of an electrical device for which it was originally designed by the manufacturer.

Maximum value of operating voltage shows the extremely possible permissible high voltage at which the circuit breaker is able to function in normal mode without affecting its performance. Usually this figure exceeds the size of the rated voltage by 5-20%.

The flow of electric current, through which the level of heating of the insulation coating and parts of the current lead does not interfere with the normal operation of the system and can be maintained by all elements for an unlimited time, is called rated current. Its value must be taken into account when choosing and buying a load switch.

Value through current tolerance demonstrates how much current flowing through the network in the short circuit mode can withstand the load switch installed in the system.

Electrodynamic resistance current reflects the magnitude of the short circuit current, which, acting on the device for the first few periods, does not have any negative effect on it and does not damage it mechanically.

Thermal current determines the limit current level, whose heating effect for a certain period of time does not disable the load switch.

The technical design of the drive and the physical parameters of the devices that determine the overall size and weight of the device are also very important. Focusing on them, you can understand where it will be more convenient to place the devices so that they work correctly and clearly carry out the tasks.

Among the unconditional positive qualities of the devices responsible for disconnecting the load are the following items:

• simplicity and affordability in manufacturing;
• elementary way of exploitation;
• very low cost of the finished product compared to other types of switches;
• the possibility of comfortable activation / deactivation of rated currents of loads;
• a gap between the contacts visible to the eye, ensuring the complete safety of any work on outgoing lines (installation of an additional disconnector is not required);
• inexpensive protection against overcurrent by means of fuses, usually filled with quartz sand (type FCT, PC, PT).

Of the minuses of all types of circuit breakers, the ability to commute only rated powers is most often mentioned, while not working with emergency currents.

Despite the cheapness in cost and maintenance, auto-gas modules are considered obsolete and, during scheduled maintenance or during the reconstruction of networks and substations, they are purposefully replaced with more modern vacuum elements

Auto-gas modules are usually blamed for their limited working life, due to the gradual burnout of internal parts that generate gas in the arcing chamber.

However, this point is completely resolved, and by small means, since gas generation elements and paired contacts designed for arc absorption are very inexpensive and easily replaced, not only by professionals, but also by low-skilled workers.

What to consider when choosing?

When planning to purchase a load break switch, it should be remembered that the device is not primarily intended to protect electrical appliances, but to protect the wiring from overheating, burning and overvoltage.

In order for the purchase to be correct, and the device copes with the tasks, it is necessary to first find out the cross-section of the cable included in the apartment or house shield and the current level for which it is designed.

Vacuum modules are gaining in popularity. They have small external dimensions and due to this they become convenient for installation in various types of junction boxes

When this information is received, it is compared with the factory characteristics of the load switch. The response current of the device should be slightly less than the maximum permissible current for the wire.

Vacuum circuit breakers are a progressive view of related electrical components. It significantly increases the level of basic security of the system, does not create combustion products and does not emit them into the atmosphere

If the cable capacity is much higher than the load current, consider buying an automatic module under load.

To determine the necessary parameters of the device, first summarize the power of all electrical appliances available in the living room. From 5 to 15% of the stock is added to the resulting amount and the total total current of consumption is determined by the Ohm's law formula. Then they buy an automaton that has a trip current slightly larger than the calculated one.

Scope of switches in life

Usually in private houses and apartments use circuit breakers. With their help, if necessary, de-energize the living quarters and carry out all the necessary installation work related to the scheduled maintenance or repair of electrical networks.

However, these devices are by no means a panacea. Machines are primarily used to protect current collectors and electrical wiring from the aggressive effects of overcurrents. Open circuit refers to the secondary tasks that these devices perform.

Companies involved in the manufacture of electrical system elements always indicate in the accompanying documentation that the machine does not provide for frequent switching. The maximum shutdown mode should not exceed 6 times per hour

Regular power outages with a machine are not a good idea. Especially if the load is not removed from the outlet. The module in this case wears out much faster and selects its working resource in a shorter time than it was declared by the factory characteristics.

If the load shedding module does not work correctly or a defect is detected in the device itself, do not disassemble the device and try to repair it. It is wiser to purchase a new device and mount it in place of the old (faulty)

Inside the case, the contacts gradually fade and blacken, and the product itself loses its nominal throughput, ceases to fulfill its tasks and then fails. Owners in this situation have to urgently change the device.

If you ignore this moment, the next short circuit will ruin the wiring, provoke ignition of the machine and, possibly, even lead to more serious consequences.

In group shields, a load shedding device is often used as an input switch. It is through it that the power cable coming from the substation or other panel is connected to the distributor

That is why experts recommend not using ordinary machines, but progressive and reliable load breakers for frequent shutdowns.

These elements will increase the safety of electrical panels, provide high-quality, uninterrupted power supply of electricity to any living room and will allow, if necessary, conveniently and quickly open the circuit, carry out repair and installation activities of any complexity and reconnect the housing to the common power supply system.

Installation of a device for deactivating loads at the entrance to switchboard allows you to remove voltage from the shield itself and correctly replace failed circuit breakers.

In the presence of such an apparatus, it is very easy to disconnect any room from the centralized power supply network for the purpose of scheduled maintenance or the performance of necessary repair work. The unit will provide complete safety to the master and will quickly fix all detected problems.

Conclusions and useful video on the topic

More about load breakers is in the videos below, where experts share their work experience and installation nuances.

Features of installation of the switch of loads. Step-by-step instructions from the wizard.

A detailed and understandable description, the rules for correct use and the direct purpose of the device from a professional electrician.

Hyundai Modular Load Switch Overview Using this device, you can inexpensively solve the issue of switching an electrical circuit.

Features of the operation of the VN32-100 load switch and the practice of using this device as a switch in electric circuits of alternating 50-60 Hz current with a rated mains voltage of 230-400V.

A practical and reliable switch of loads helps to increase the level of operational safety of the electrical network and helps to timely open the current circuit in the right place and eliminate the breakdown or replace failed equipment.

The presence of the switch ensures the safety of the house or apartment wiring, protects it from premature wear and significantly increases its service life.

Do you want to talk about how you selected a protective device for the electric network in your own house / apartment? Do you have information that will be useful to site visitors? Please write comments in the block below, ask questions, share information and photos on the topic of the article.