Even a modern power supply system is not always completely reliable. In cases of emergency situations, consumers may remain without energy, who a long power outage can lead to large material losses, and even a threat people's lives. Therefore, both in everyday life and at work, it makes sense to organize power from two sources of electricity, with the transfer of power from one. Such a system is called automatic transfer of reserve, abbreviated as ATS. Its work consists in fully automatic connection of electrical circuits of consumers from a backup power source in case of disconnection of the main one. In this article, we will take a closer look at the purpose and principle of operation of various types of ATS.
Content:
- Appointment of ATS
- How automatic backup power input works
- System Requirements
- ATS classification and options for implementation
- Features of working with household generators
- ATS on accumulators
- Logic controller application
- Organization of automatic transfer switch in high-voltage circuits
Appointment of ATS
The purpose of this system in electrical engineering is similar to the organization of an uninterruptible power supply. The main task of automatic input of backup power is to quickly restore power supply without human participation in this process. At large substations, there are always two inputs into two, separated by a sectional switch, switchgear sections, operating autonomously from each other. According to the PUE (rules for electrical installations), automatic connection of backup power and supply for 2 inputs is a mandatory measure for providing electricity to consumers of the first categories.
A simple example of the need for this system can be given regarding the lighting of some important protected area. That is, when the main input is turned off, the system itself will turn on the power from the backup source, while this important section will remain clarified. The maximum that can occur is a short cessation of nutrition, which is even difficult to trace visually. It depends on the speed of operation of the automatic transfer switch, the time for switching on the reserve should be about 0.3–0.8 seconds.
How automatic backup power input works
The principle of operation of the ATS is based on monitoring the voltage in the circuit. This can be done using any voltage relay or digital logic protection blocks. However, the principle of operation remains unchanged early on. Let's consider it on the simplest example.
This is a one-line diagram showing that voltage monitoring is in progress. contactor KM. Both QS1 and QS2 must be turned on, while the KM coil will receive power and will be drawn in, and accordingly, its NO contact in the main input circuit is also closed and an NC contact in the backup circuit input is open. Thus, the power supply to the consumer is carried out from the main network and the corresponding lamps are lit. In the event of a power failure on the L12 line and a decrease in voltage to the value when the KM contactor turns off, an opening contact will open in the main line and at the same time, the contact in the backup power supply circuit of the L22 line will go into a closed state, thereby supplying voltage to the consumer from the backup source. The opposite situation will occur when the main power supply is restored via the L12 line.
The video below clearly shows the principle of operation of the ATS in 6 kV networks:
System Requirements
The main requirements for ATS systems are:
- High-speed performance.
- Reliability of inclusion.
- Supply voltage only if there is no short circuit, that is, there must be a short circuit blocking.
- One-shot operation.
- Possibility of setting the threshold for switching on the backup power supply so that it does not work, for example, in case of voltage dips during the start of powerful electric motors.
- Tripping only if there is electricity at the backup input.
Naturally, the simplest contactor circuit will not be able to fulfill all the requirements for the ATS system. For this, in modern electronics, logical systems are used that give a signal to turn on a backup power source only if all rules and interlocks are observed. Also, for additional reliability, a mechanical interlock is even used.
ATS classification and options for implementation
Backup power is provided and its automatic input can be from a separate generator, storage battery or a separate line.
In turn, all ATS systems, according to their action, are divided into:
- One-sided. One section or input is working (main), and the second is backup. In the event of a failure of the operating voltage, the reserve is switched on.
- Double-sided. When there are two separately powered sections and, accordingly, two lines are working, and when one of them is disconnected, the other is backup.
Also, the ATS can be with and without power restoration according to the normal scheme. In the second case, the inoperative network is completely repaid, and even if the power is restored again, the circuit will not work as before on two lines.
Features of working with household generators
In order to organize automatic input of a reserve in the house, you can use a generator as a source of backup power. It will make it possible to provide a whole house with voltage for a long time, its load depends on the power of the generator itself. Here is the connection diagram:
The introduction of the generator instead of the mains voltage can be used in single-phase and three-phase networks, depending on its model. However, in order for this process to be fully automated, it is necessary that the generator be equipped with a starter, and you will also need a special unit, consisting of a set of switching devices that turn on the starter only for the time of starting and turn off when the mains voltage is restored, it looks like like this:
Such a block for a generator is compatible with any type of engine and has three positions: "Stop", "On," Start. True, in winter, the internal combustion engine needs to warm up, but this unit can be programmed taking this feature into account. It is attached to din reiku in the switchboard.
The video clearly explains the scheme by which you can make an automatic input of a reserve for the generator with your own hands:
ATS on accumulators
With the development of converters that transform direct current into alternating current, it becomes possible to use, for example, a car battery as a backup power source. In addition to the battery, you will need to purchase a modern car inverter that converts 12 Volts DC to 220 Volts AC.
True, this source can hardly be used for a power load, but it can easily provide a lighting circuit with a stable voltage for the duration of a short outage on the line. In this case, the duration of operation will depend on the power of consumers and the capacity of the batteries.
To increase the capacity, several batteries can be connected in parallel. The connection diagram of the ATS system itself can be implemented using starter.
The starter is included in the main circuit, and in case of problems in the network, its moving part disappears, thereby an opening block contact, inserted into the battery circuit, starts the automatic power supply. This method is less expensive than the generator method, but it is not capable of delivering current for a long time for powerful household appliances.
Logic controller application
For two three-phase power supply networks, ready-made ATS units are used with the use of logical digital controller that can take into account the many parameters required to create ideal system. It has all the necessary markings and instructions for operation and connection.
True, before connecting the module and purchasing it, you need to think about whether there is a backup power source with a more reliable power supply. Since it makes no sense to connect it to the same three-phase network system, that is, powered from one 6 / 0.4 kV transformer.
Organization of automatic transfer switch in high-voltage circuits
In order to carry out the organization of automatic redundancy in circuits with a voltage of more than 1000 Volts, as an element that measures and controlling the network energy, there is a special voltage transformer, on the secondary winding of which in normal operation 100 Volt. To communicate it with the ATS system, an undervoltage relay is used or phase control relay. It reacts not only to a decrease in the value of the mains voltage, but also to the disappearance of at least one phase, for example, when an overhead line is broken. Here it is already necessary to fulfill all the requirements regarding the correct input of the automatic transfer switch, and sometimes even with system with recovery, a time delay is set to return to the original initial configuration.
It is also important to note that in high-voltage networks, the automatic transfer switch circuit is implemented on old-style electromechanical relays or modern multifunctional microprocessor-based protection terminals that perform several functions, including AVR.
Finally, we recommend watching a useful video on the topic of the article:
Now you know what automatic input of a reserve is, what are the ATS schemes and what is the principle of operation of this power supply system. We hope the information and video tutorials provided were useful to you!
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