AVR - what is it? Automatic Transfer Entry Assignment

Sources of electricity supply do not have absolute reliability and are sometimes switched off, which leads to a negative impact on consumption objects. For critical devices, this is unacceptable, so they are provided by power from two or more additional sources. When they are connected, ATS devices are used. What is it, explains the deciphering of the abbreviation - "automatic input of the reserve." It is a way of creating uninterrupted power supply to a consumer with two or more supply inputs. This is achieved by automatically connecting the backup input when the primary is lost.

Both power supplies can be connected at the same time. Disadvantages of the method are high short-circuit currents, high losses and complexity of network protection. The input of a reserve is usually made by means of a switching device that disconnects the main power source. The capacity of the reserve must correspond to the loads. If it is not enough, only the most important consumers are connected.

Requirements for ATS

• Fast input of a reserve after operation of the relay of a voltage.
• Turn on in any cases with power failure, except for short circuits.
• The lack of response to the landing of voltage when starting powerful loads in the consumer.
• One-time operation.

Classification

The devices are divided according to the principle of operation.

• One-sided. The circuit contains two sections: power and backup. The latter is connected when the main voltage is lost.
• Two-sided. Any of the lines can be either working or standby.
• Rebuildable ATS. When the main power is restored, the previous circuit is automatically put into operation, and the standby circuit is switched off.
• Without automatic recovery. Setting the mode of operation with the main power source is done manually.

The principle of ATS

In low-voltage networks, it is convenient to use monitoring voltages in protection circuits for special relays (ATS circuits, etc.). ATS is preferable here, because not all equipment can withstand frequent power supply switching. How does the ATS look like? What is it and how does it work? This device can be clearly seen in any simple scheme.

• The EL-11 relay monitors the three-phase voltage, monitors the phase skew, their breakage and alternation.
• Electromagnetic relays with powerful contacts are used to connect loads. In normal mode, the coil of the magnetic starter of the main input is fed from it and, with its contacts, the CM1 connects the supply of power to the load.
• When the voltage in the main circuit disappears, the KM relay 1 is turned off and the power is supplied to the CM 2 relay coil that connects the redundant input.

This ATS scheme can be used in private houses, industrial and administrative buildings, where the switched load reaches tens of kilowatts. The disadvantage of the circuit is the difficulty of choosing a relay for large currents. For switching low-power consumers, it is still suitable, but for larger loads it is better to take an AVR starter or a triac.

Indispensable sources of additional power are gasoline or diesel generators. The latter are widely used due to the economy and greater capacity. The market offers a wide range of diesel-generator sets (DGU), which contain protection systems against large overloads.

Work of ATS

How does the ATS function? What is this in terms of reliability in the supply of electricity to consumers? Devices are divided into 3 categories. Electricity supply of housing is the lowest. With frequent failures in the supply network, it is better to install a reserve in the house, since the durability of household appliances depends on this, as well as the comfortable living conditions. In the apartments are installed battery chargers, which are mainly used for electronic equipment. Generators are most common as stand-by power sources for private houses.

The gasoline generator in the simplest version is connected to the electricity supply of the house through the changeover switch. This prevents a short circuit when the reserve is entered erroneously, when the automatic power supplies to the house are not switched off. The switch is selected with three positions, where the middle one completely cuts off electricity.

The ATS can be installed manually in automatic mode if the generator is provided with an automatic starting device and controlled from the cabinet by means of contactors that also switch the inputs. The automation operates on microprocessor control, for example, on the Easy Control relay controllers. To introduce reserve AVR apply voltage sensors. As soon as the power is turned off, the generator motor starts immediately. It takes some time to reach the operating mode, after which the ATS switches the load to the reserve. Such delays are permissible for domestic needs.

The block of automatic start of the generator (BAZG)

AVR is a private house system that ensures the startup and management of a backup generator in case of a power failure. The latter is equipped with a special block BASH, which is an inexpensive solution for failures in the supply of electricity in the main network. It makes five attempts to start for 5 seconds in each interval after the voltage on the main input has disappeared. In addition, he controls the air dam, closing it at the time of launch.

If the main input voltage reappears, the device switches the load back and stops the generator motor. When the generator is idle, the fuel supply is blocked by a solenoid valve.

Features of ATS private house operation

The most common method is with two inputs, where the first one takes precedence. When connected to a network, household loads mostly work in one phase. When it disappears, it is not always convenient to connect the generator. It is enough to connect another line as a backup line. With three-phase input, the power is controlled by a relay at each phase. When the voltage falls outside the normal limits, the phase contactor is switched off and the house is powered by the two remaining phases. If another line comes out of operation, the entire load is redistributed to one phase.

For a small cottage or a summer cottage, a DGU with a power of no more than 10 kW is used for a board operating at 25 kW. This generator is enough to provide the house with the necessary minimum of electricity for a short time. In the event of an emergency, the voltage monitoring relay switches the consumer's bus to standby power and sends a signal to start the DGU. When the main power is restored, the relay switches to it, after which the generator stops.

Extending the functions of the ATS

For the control of circuit breakers , programmable logic controllers (PLCs) are used for the selected algorithms. They already have an ATS program, which only needs to be set up to implement a particular mode of operation. Using a PLC, for example, the AC500 controller, makes it possible to simplify the electrical circuits, although at first glance the device seems complicated. The ATS control can be located on the door of the switchboard in the form of a set of switches, buttons and display.

The standard solution already provides software. It is installed in the PLC.

Conclusion

Failures in electricity supply can lead to various negative phenomena among consumers. Most users have only a vague idea of the ATS. What is it, many do not know and accept for the device products that are intended for other purposes. In connection with the high costs of electrical equipment, it is important to select the automatic input of the reserve input correctly. It will require expert advice. AVR allows to increase the efficiency of household appliances and objects, for which a constant power supply is important.