Isolating switch: "safety switch" in the power system, accurately isolating circuit hidden dangers

In the huge and complex power system, the isolating switch is like a loyal guard, shouldering an indispensable mission. Its main function is to isolate the power line under no-load current or very small load current. When the power system needs to carry out equipment maintenance, line switching or fault isolation, the isolating switch can accurately cut off the circuit, so that the power outage area and the live area are clearly separated, providing a safe environment for subsequent operations. For example, in a substation, when a transformer is regularly maintained and repaired, the isolating switch can reliably disconnect the connection line between the transformer and the power grid, effectively preventing the risk of mis-powering or live operation that may occur during the maintenance process, and ensuring the personal safety of the maintenance personnel and the integrity of the power equipment. It is precisely because of the ability of the isolating switch to accurately isolate circuit hidden dangers that it has become one of the key links in the safe and stable operation of the power system, like a solid line of defense, firmly guarding the normal operation of the power network.

1. Structural composition and working principle of disconnectors

Contacts and conductive parts

The contacts and conductive parts of disconnectors are the key paths for current conduction. Contacts are usually made of special metal materials with good conductivity and wear resistance to ensure stable current transmission during long-term opening and closing operations, reduce contact resistance and heat generation. The conductive part connects the contacts to the power line. Its structural design must meet the current capacity requirements and have sufficient mechanical strength to withstand various forces during the opening and closing process. For example, in high-voltage disconnectors, the contacts are made of copper-tungsten alloy material. This material can withstand the high temperature generated by the arc while ensuring good conductivity, effectively preventing the burning and adhesion of the contacts.

Insulation part

The insulation part is the core element for disconnectors to achieve electrical isolation. It is composed of insulators and other components. Insulators are generally made of ceramic or composite insulating materials, have extremely high insulation resistance and withstand voltage, and can effectively prevent current from being conducted on unexpected paths. In disconnectors of different voltage levels, the number, shape and size of insulators will vary to meet the corresponding insulation requirements. For example, in ultra-high voltage disconnectors, multiple strings of insulators are connected in series to enhance insulation performance, ensuring that in high voltage environments, disconnectors can reliably isolate live parts from grounded parts or other live equipment to prevent flashover and breakdown accidents.

Operating mechanism

The operating mechanism is responsible for controlling the opening and closing of the disconnector. Common operating mechanisms include manual operating mechanisms, electric operating mechanisms, and pneumatic operating mechanisms. The manual operating mechanism has a simple structure and is suitable for some small disconnectors or disconnectors with low operating frequency requirements. The switch is opened and closed by manual manual operation handles. The electric operating mechanism uses the power of the motor to drive the action of the disconnector. It has the advantages of convenient operation and remote control. It is widely used in places such as substations that require frequent operation and have high automation requirements. The pneumatic operating mechanism uses compressed air as a power source. It has fast action and strong power. It is often used in some special environments or occasions with strict requirements on operating speed. The reliability and accuracy of the operating mechanism directly affect the normal operation of the disconnector. It must be able to accurately complete the opening and closing of the switch according to instructions and maintain stable performance under various working conditions.

2. Application of isolating switches in different power scenarios

Application in substations

Substations are the hubs of the power system, which concentrate a large number of power equipment and complex electrical connections. Isolating switches play a vital role in substations. They are distributed in various areas of substations and are used to isolate busbars, incoming and outgoing lines, transformers and other equipment of different voltage levels. In the daily operation of substations, when equipment switching operations are required, isolating switches work in conjunction with equipment such as circuit breakers. For example, when switching a transmission line from operation to maintenance, the circuit breaker first cuts off the line current, and then the isolating switch isolates the line from the live busbar, ensuring that the maintenance area is completely de-energized, creating safety conditions for subsequent maintenance work. At the same time, isolating switches can also conveniently isolate and connect old and new equipment when the substation is expanded or renovated, ensuring the flexible operation and upgrading of the substation.

Application in transmission lines

Isolating switches also play an irreplaceable role in transmission lines. They are usually installed on the towers of transmission lines to isolate different line sections or branch lines. In the maintenance and repair of transmission lines, the isolating switch can quickly isolate the faulty line section from the normal operating line, reduce the scope of power outage, and reduce the impact on users. For example, when a section of the transmission line fails, the faulty section can be isolated by operating the isolating switch on the tower along the line, so that other unaffected line sections can continue to be powered on, and then the maintenance personnel can inspect and repair the faulty line in a safe environment. In addition, in some special cases, such as when the transmission line needs to be shut down for maintenance or expansion and connection of the line, the isolating switch can also accurately complete the isolation and connection operations of the line to ensure the stable operation of the transmission line and the smooth progress of maintenance work.

3. Key points for the operation and maintenance of the isolating switch

Operation specifications and precautions

The operation of the isolating switch must strictly follow the relevant operating procedures and safety specifications. Before operation, the operator needs to conduct a comprehensive inspection of the status of the isolating switch, including whether there is any abnormality in the appearance, whether the connection parts are firm, and whether the insulation performance is good. During the operation, pay attention to the operation sequence. It is strictly forbidden to pull and close the isolating switch with load, otherwise a strong arc will be generated, which may cause equipment damage or even cause serious power accidents. For example, when performing a power outage, the circuit breaker should be disconnected first, and after confirming that there is no current in the line, the disconnector should be slowly operated to open the gate; when performing a power supply operation, the disconnector should be closed first, and then the circuit breaker. At the same time, the operator should wear appropriate protective equipment and set up warning signs at the operation site to prevent unrelated personnel from approaching. For disconnectors with electric or pneumatic operating mechanisms, it is also necessary to regularly check the supply of operating power or gas source to ensure that the operating mechanism can work normally.

Maintenance and troubleshooting

In order to ensure the long-term and reliable operation of the disconnector, regular maintenance work is essential. The maintenance content includes cleaning and polishing the contacts, removing the oxide layer and dirt on the contact surface to ensure good contact performance; checking whether the surface of the insulator is damaged, dirty or has discharge marks, and cleaning or replacing it in time if necessary; lubricating and debugging the operating mechanism to ensure its flexible and reliable operation. In addition, it is also necessary to regularly test the electrical performance of the disconnector, such as insulation resistance test, contact resistance test, etc., so as to detect potential fault hazards in time. In terms of troubleshooting, when the disconnector is abnormal, such as operation failure, severe heating or discharge, the maintenance personnel need to conduct detailed inspection and analysis according to the fault phenomenon. For example, if the disconnector is hot, it may be caused by poor contact of the contacts and excessive contact resistance. At this time, it is necessary to check the connection of the contacts and handle them accordingly; if operation failure occurs, it may be caused by operating mechanism failure, control circuit failure or mechanical jamming. It is necessary to check the relevant components one by one, find out the fault point and repair it.

As the "safety switch" in the power system, the disconnector plays a vital role in ensuring the safe and stable operation of the power system with its unique structure and function. Whether in the busy operation of the substation or in the remote maintenance of the transmission line, it silently sticks to its post, accurately isolates the hidden dangers of the circuit, and escorts the reliable supply of electricity. With the continuous development of power technology, the disconnector is also continuously innovating and improving. In the future, it will continue to play an indispensable role in the power system and contribute to the construction of a more intelligent, efficient and safe power network.