Common Faults Of Vertical Fuse Disconnectors

Isolating switch, also known as isolating knife switch, is a kind of high-voltage switch. It plays an important role in isolating power supply, changing system operation mode, switching small load current, and switching operation in the operation of power system. There are many vertical fuse switch disconnector in the operation of power system, and its quality, operation and maintenance will directly affect the safe operation of power system. Due to the influence of factors such as air pollution, manufacturing process, maintenance and management, isolating switch has serious rust, transmission difficulty, poor contact, porcelain bottle breakage, poor sealing and other problems in operation, which has caused serious damage to power safety production. Therefore, ensuring the good operation state of isolating switch, carrying out reasonable maintenance and management work, improving the technical transformation measures for the reliable operation of isolating switch, and avoiding the operation of equipment with defects as much as possible have become important guarantees for the safe operation of isolating switch.

1. Common faults in operation of nhrt40 vertical fuse switch disconnector
1. Heating of isolating switch
The contact material and manufacturing process of isolating switch are poor. In China, galvanized steel pins are generally used with brass sleeves. Most of these parts will rust when they are wet with rainwater, and in severe cases, they will rust and cannot produce relative movement. If the main contact is not tin-plated or silver-plated, the contact is silver-plated but the coating is too thin and copper is exposed, and the contact is poorly contacted due to rust, resulting in severe heat and even burning of the contact fingers. The current is too large and exceeds the rated current. Rust or improper adjustment of the outlet seat causes poor contact, and loose conductive belts, terminal clamps and bolt connections cause poor contact, which leads to heating of the outlet seat and lead terminal board. The rated current of the disconnector refers to the maximum working current allowed to pass through the disconnector for a long time. When the disconnector passes the rated current for a long time, the heat generated by its various parts should not exceed the specified temperature rise standard. If the rated current is exceeded, the heat generated by the conductive part of the disconnector will exceed the specified temperature rise standard. The contact pressure of the contact is not enough, the disconnector is overloaded, and the circuit of the conductive part of the disconnector is heated.
2. Broken porcelain bottle
Improper control of the insulator during the firing process may cause problems such as porcelain parts being raw, uneven density and poor cement glueing. Lax inspection methods also leave hidden dangers for operation. Defective and hidden insulators are not detected. After being assembled into products, they pose a great threat to safe operation. Improper operation and excessive force by operators when opening and closing the disconnector can easily cause damage to the porcelain bottle. Stress is generated by the expansion of cement adhesive, stress caused by temperature difference, stress caused by excessive tension of the wire during installation, stress caused by long lead distance and large gravity, stress caused by operation, poor quality of porcelain column and insufficient bending strength. In addition to supporting insulators, rotating insulator fracture failures also occur from time to time. Rotating insulators are mainly affected by torque during operation.
3. Isolating knife switch refuses to open
Isolating knife switch refuses to open failure is caused by the jamming of the transmission part of the mechanism, rusting of the rotating shaft, excessive friction between the moving and static contacts, or reduced pressure of the operating mechanism. After years of operation, the failure rate of the isolating knife switch of the GW4 series is relatively high. It manifests as failure of operation and is easy to cut off the shaft pin of the middle phase arm. If the switch refuses to move or the switch is not in place, it often occurs during the switching operation, affecting the safe operation of the system. Parts will also be damaged, and the speed change gear may break and the connecting rod may be twisted.
4. The isolating switch stops midway
During the operation of the isolating knife switch, the operating circuit is opened too early, causing poor contact in the circuit. If the distance between the contacts is small, the arc discharge will last for a long time.
5. Closing (or opening) is not in place
During the operation of the isolating knife switch, the knife switch cannot be fully closed, the contact is poor, the switch is operated, the switch does not move, and the self-holding circuit is energized for a long time until the switch is manually opened to control the power supply knife of the closing (or opening) switch. The self-holding circuit can be disconnected, otherwise it will burn out the closing (or opening) coil or the relay self-holding coil or the combination device to protect the thinner internal self-holding circuit connection line.
6. Sealing failure
The sealing problem of the mechanism is manifested as the sealing of the mechanism box is not tight and water enters, resulting in failure of the operating circuit of the electrical components, such as refusal to open or refusal to close. During the switching operation, the operation progress of the system is affected, and even safety problems are caused. Because the sealing strip of the mechanism box of the isolating switch is not tightly sealed or the mechanism is rusted due to long-term operation outside, water enters, causing serious rust on the operating part of the mechanism, the system is not sensitive, and the resistance of the on-duty personnel to turn the mechanism during normal operation is relatively increased, causing delays in power transmission and other faults.
2. Fault handling methods for high-voltage isolating switches:
Fault handling and accident repair should follow the principle of "first pass and then restore". In accident handling, it is allowed not to write an operation ticket, but all operations should be strictly supervised except for direct endangerment to personal and equipment safety. In particular, the switch position and parts that are not easy to see clearly should be personally checked by the supervisor. If there is spare equipment, first consider putting it into standby, adopt a correct and feasible plan, quickly and decisively handle and repair the accident, and try to deliver power first as quickly as possible. And promptly notify the relevant departments to repair or replace the faulty equipment and restore normal operation.
2.1 Handling of heating faults
During maintenance, select contacts with high strength and good conductivity, the contact finger spring pressure should be adjusted appropriately, the fixing bolts of the knife switch should all be made of stainless steel, adjust the contact insertion depth and clean the contact surface to make the contact surface good. After a long period of operation, the equipment tends to age, the contact clamping spring is loose and deformed, and the clamping force is insufficient, resulting in some contact fingers not contacting the moving contact, reducing the contact surface between the contact fingers and the moving contact, and there is dirt on the moving and static contacts, which is easy to oxidize, the contact resistance is too large, and there are obvious burn pits on the contact fingers. When the busbar is powered off, the disconnector is powered off for maintenance. The wiring of a half circuit breaker can be operated in an open loop. After on-site inspection, if the live working safety distance is met, the busbar side lead-down joint can be removed with power on, and then processed.
2.2 Handling of porcelain bottle breakage faults
Ensure that the overall design structure of the selected disconnector is scientific and reasonable, and select products from porcelain bottle manufacturers with strong strength, excellent quality and reliable reputation. The on-duty personnel should strengthen the careful inspection of the bonding surface of the porcelain bottle at ordinary times. You should master the essentials of operation and scientific methods. For example, when the operation is very difficult during the switching operation, you should not blindly use force to operate it, and appropriately install anti-fouling support porcelain columns.
2.3 Handling of the disconnecting knife switch refusing to open
Due to mechanical failures such as shaft pin falling off, wedge bolt withdrawal, cast iron breakage, or electrical circuit failure, the knife rod and the operating mechanism may be disconnected, causing the disconnector to refuse to close. At this time, an insulating rod should be used for operation, and the shaft of each phase disconnector should be turned with a wrench. Refuse to trip. When the disconnector cannot be pulled open, if the operating mechanism is frozen, you can gently shake it to find the location of the obstacle. If the obstacle occurs in the contact part of the disconnector, it should not be forcibly pulled open, and the only way to deal with it is to change the operation mode of the equipment.
2.4 Handling of the disconnector operation midway stop failure
During the electric operation of the disconnector, if the distance between the contacts is small, arc discharge will be long, mostly due to the premature opening of the operating circuit and poor contact in the circuit. When pulling the isolating switch, if there is a stop in the middle, it should be quickly opened manually; when closing the switch, if there is a stop in the middle and time is urgent and it must be operated, the isolating switch should be quickly closed manually; if time permits, the isolating switch should be quickly opened, and the fault should be eliminated before operation.
2.5 Fault handling of isolating switch not closing in place
If the isolating switch cannot be fully closed in place during operation and the contact is poor, it will heat up during operation and endanger the safe operation of the power grid and equipment. When the isolating switch is not closed in place and the three phases are out of sync, most of them are caused by rust, jamming, and maintenance and debugging. The reclosing should be opened and closed repeatedly several times. The operation should be in accordance with the essentials and the force should be appropriate. If it cannot be fully closed and the three phases cannot be fully synchronized, the operator should wear insulating gloves and use insulating rods to push the three-phase contacts of the knife switch into place. For 220KV isolating switches, insulating rods can be used to push them in, and power outages should be applied if necessary. Report to superiors and arrange planned power outages for maintenance.
2.6 Sealing Failure Handling
Install sealing strips on the mechanism box of the isolating switch, select a mechanism box with good sealing, and there should also be a moisture-proof heater in the mechanism box, which should be turned on when the humidity reaches a certain level. Use high-quality stainless steel products for the mechanism box to make the mechanism box seal more perfect, and strengthen operation and maintenance.
In short, in actual production and operation, we must effectively strengthen leadership, improve work style, and do a good job in "preventing errors" in accordance with the requirements of "strict, detailed, and practical". Strengthen the daily maintenance of the isolating switch, understand the structure, working principle and performance of the isolating switch, anticipate the potential faults that may occur during the operation of the equipment, and use scientific means to strengthen the operation monitoring of the equipment to ensure the safe, stable and reliable operation of the equipment and the power grid.