Why do I need automatic re-inclusion of power lines
Modern electric networks must be reliable and uninterruptedly supply electricity to consumers. Often, the generation of electrical energy is geographically located hundreds of kilometers from consumers. A large extended infrastructure requires special operating conditions. Since the operational monitoring of long power lines is difficult, the airways are equipped with special protective devices. In real time, they will protect electrical networks in case of abnormal operating conditions and in the event of an accident or threat they can prevent it by timely disconnecting the problem area. In this article we will consider the principle of operation and the purpose of automatic re-inclusion of power lines.
Appointment
Conditionally, faults on power lines can be divided into two types:
- short-term;
- long.
The first type includes a temporary breakdown of the air gap at the insulator or line when crossing by extraneous, small animals, birds, tree branches, etc. The second type of malfunction is the destruction of insulators, breakage, destruction of the support.
In any case, the automation will de-energize the circuit. Then, to ensure the resumption of power supply, it is necessary to quickly determine what type of emergency shutdown occurred. Therefore, the voltage is re-applied: automatically in several stages or manually by the operational personnel according to the specified algorithm. This is the automatic reconnection (AR) of power lines.
Principle of operation
At power line substations, power switching switches operate, which are controlled by an automation system or a dispatcher. After emergency shutdown testing, the automatic reclosure system starts to operate, but not immediately after shutdown, but after a certain time, sufficient for self-elimination of short circuit in the power supply section.
With a short-term type of emergency shutdown for each type of power transmission line, depending on the voltage, length and other factors, its time is calculated for a repeated emergency shutdown. After the countdown, the automation supplies power to the switch solenoid for re-supplying power.
In the case of a successful start, when the cause of the malfunction has self-destructed, the power line is put into operation. In the event that, after applying the voltage, the malfunction did not disappear anywhere, the line is de-energized. The automatic reclosure system with a delay of more than 15 seconds, makes a second restart.
As practice and inexorable statistics showed, by repeated automatic reclosure of power lines 65% of short-term malfunctions are eliminated. Otherwise, when the malfunction is continuous in nature, the protection switches off the circuit breaker. In this case, the intervention of operational personnel is required to visually assess the status of power lines and repair.The troubleshooting is carried out by the visiting team and the voltage is supplied to the repaired network section after numerous checks.
Requirements for AR
So, the basic requirements for automatic restart:
- speed on and off;
- resistance to short circuit currents;
- sustainability and prevention arcs and transients during switching;
- readiness for repeated automatic switching on when shutdown by protections;
- a sufficient supply of energy to re-enable reclosure cycles;
- blocking of automatic reclosure after operation of certain types of protection;
- blocking of automatic or remote power supply when the automatic reclosure is in the manual position.
We also recommend watching a video on which this issue is considered in more detail (classification of automatic reclosure devices, scope and system operation scheme is provided):
Now you know what automatic re-inclusion of power lines is, what is the purpose of this system and the principle of operation. We hope the information provided was useful and interesting for you!
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