Load break switch is a high-voltage switching device designed for switching currents of a three-phase electrical network in nominal mode. The switching of currents by this piece of equipment, depending on the type, can be carried out remotely, including automatically or manually, from the place. This type of device is quite popular and is used in high voltage electrical networks. Next, we will consider the device, the principle of operation and the purpose of the load break switches.
Content:
- Appointment
- Application
- Design
- Operating principle
Appointment
The purpose of HV is the switching of operating currents in electrical installations, that is, capacities that do not exceed the permissible (nominal) values for a particular section of the electrical network. This device is not designed to trip emergency currents, so it can only be installed if there is short circuit protection in the circuit. and overload, which is realized by fuses (PC, PKT, PT) or a protective device installed on the side of the power supply or on the group consumers.
At the same time, the HV has a breaking capacity that corresponds to the electrodynamic resistance in case of short circuits, which makes it possible to use this electrical apparatus for supplying voltage to a section of an electrical network, regardless of its current state, for example, for a trial inclusion.
Thus, subject to the presence in the overcurrent protection circuit, the considered piece of equipment can be used as a full-fledged high-voltage protective device (oil, vacuum or SF6). And in the presence of a motor drive, it can participate in the operation of various automatic devices (AVR, APV, AChR, CHAPV), as well as controlled remotely by the automated system of the dispatching technological management.
Application
The area of application of the switch-disconnector is mainly networks of voltage class 6 and 10 kV. The use of these switching devices is primarily due to savings: HV is much cheaper full-fledged high-voltage protective devices, and also require significantly less maintenance and repair.
Where are these pieces of equipment used? VN are an alternative separators and short-circuits - they are used for switching currents of the high voltage side of power transformers. But only if there is a transformer in the connection circuit, as mentioned above, fuses or protective elements of equipment on another the end of the line from the side of the adjacent supply substation or line switches from which the switchgear supplying this transformer.
Load break switches are used in other low-power networks as an independent switching device. On long and branched overhead lines, devices are used for the convenience of disconnecting sections of the lines without the need to completely de-energize it. At the same time, a switch is installed at the supply substation to protect the entire line from damage.
Design
Let us consider what a load switch consists of using the example of a switching device of the type BNR-10/400
- Base (frame).
- Support insulator.
- Holders with contacts.
- Movable working knife.
- Arc extinguishing chamber.
- Fixed top contact.
- Insulating rod.
- Lever arm.
- Flexible communication.
- Grounding knife.
- Grounding shaft.
- Lock rod.
- Springs.
- Rubber gaskets.
- Shaft of working knives.
Operating principle
Let us briefly consider how load break switches work using the example of the aforementioned VNR-10/400, provided in the photo:
Structurally, this switching device is similar to a disconnector. The main difference between the disconnector and the HV is that the latter has an arcing device and a drive, which ensures faster execution of operations.
The principle of operation of the load break switch is as follows. When switched on, the moving contacts are in the arcing chamber. Additional arcing contacts are located in the lower part of the arcing device. During the tripping operation, the main contacts open first, and then the arcing contacts. The electric arc formed in the process of breaking the contacts enters the arc extinguishing chamber, where he heats plexiglass to a high temperature, which in turn releases a large amount gases. These gases burst out of the arcing chamber in a powerful stream, thereby extinguishing the arisen electric arc in a few milliseconds.
How is HV depicted in single-line diagrams? Below is the legend in the diagram:
On the left in the diagram, HV is shown, on the right - a switching device, which is structurally equipped with fuses (FNP).
So we examined the device, purpose and principle of operation of the load break switch. We hope the provided material was useful and interesting for you!
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