Modern electrical networks must be reliable and supply consumers with electricity without interruption. Often, power generation is geographically located hundreds of kilometers from its consumers and such an extended infrastructure requires special operating conditions. Since the operational supervision of extended power lines is difficult, airways are equipped with special protective devices. They will monitor the state of electrical networks in real time and in the event of an accident or threat, they will be able to prevent it by timely shutting down the problem area. In this article we will look at the principle of operation and purpose of automatic reclosing of power lines.
Content:
- Appointment
- Principle of operation
- Requirements for automatic reclosure
Appointment
Conditionally, faults on power lines can be divided into two types:
- short-term;
- long lasting.
The first type includes a temporary breakdown of an air gap on an insulator or a line when it is crossed by strangers, small animals, birds, tree branches, etc.
In any case, the automation will de-energize the circuit. After that, to ensure uninterrupted power supply, it is necessary to quickly determine what type of emergency shutdown occurred. Therefore, the voltage is reapplied: automatically in several stages or manually by operating personnel according to a given algorithm. This is the automatic reclosing (AR) of power lines.
Principle of operation
Power switching switches operate at power transmission line substations, which are controlled by an automation system or a dispatcher. After emergency operation of the line disconnection, the automatic reclosure system is activated, but not immediately after shutdown, and after a certain time, sufficient for self-elimination of short circuit at the site electrical network.
With a short-term type of emergency shutdown, for each type of power transmission line, depending on voltage, length and other factors, its own time is calculated for repeated emergency switching on. After the countdown, the automation supplies power to the circuit breaker solenoid for re-energizing.
In the case of a successful switch-on, when the cause of the malfunction has self-destructed, the power transmission line is put into operation. In the event that, after energizing, the malfunction has not disappeared anywhere, the line is de-energized. The automatic reclosure system, with a delay of more than 15 seconds, performs a second reclosing.
As practice and inexorable statistics have shown, re-reclosing of power lines eliminates 65% of short-term malfunctions. Otherwise, when the malfunction is prolonged in nature, the protection switches off the breaker. In this case, the intervention of operating personnel is required to visually assess the condition of the power transmission line and repair. The elimination of the malfunction is carried out by the mobile team and the voltage supply to the repaired section of the network is carried out after numerous checks.
Requirements for automatic reclosure
So, the basic requirements for automatic reclosing are:
- speed of switching on and off;
- resistance to short-circuit currents;
- stability and prevention of arcing and transient processes during switching;
- readiness for repeated automatic switching on when disconnected by protections;
- sufficient energy reserve for repeated reclosing of automatic reclosing cycles;
- blocking of automatic reclosing after activation of certain types of protection;
- blocking of automatic or remote power supply when transferring the automatic reclosure to the manual position.
We also recommend watching a video that discusses this issue in more detail (a classification of automatic reclosing devices, scope and system operation diagram are provided):
Now you know what automatic reclosing 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!
You probably don't know:
- Causes of electricity losses in networks
- What is an air circuit breaker for?
- What is relay protection
