What Is a Disconnect Switch?

Isolating switch ^[1] (Isolating switch) is a switching device mainly used for "isolating power, switching operation, to connect and cut off small current circuits", without arc extinguishing function. When the disconnector is in the sub-position, there is an insulation distance between the contacts that meets the required requirements and a clear disconnection mark; in the closed position, it can carry the current under normal circuit conditions and the abnormal conditions (such as short circuits) within a specified time. Switching device for current. Generally used as a high-voltage disconnector, that is, a disconnector with a rated voltage above 1kV. Its own working principle and structure are relatively simple, but due to the large amount of use and high reliability requirements, it is necessary to design, build and The impact of safe operation is large. The main feature of the disconnector is that it has no arc extinguishing capability, and can only open and close the circuit without load current. The entry introduces the functions, characteristics, types, applications, error prevention improvements, maintenance, common problems, etc. of the isolating switch.

1. After opening the gate, establish a reliable insulation gap, and separate the equipment or line that needs to be repaired from the power supply with an obvious disconnection point to ensure the safety of the maintenance personnel and equipment ^[2]

1. When servicing electrical equipment, provide an electrical interval and a clearly visible disconnection point to protect the personal safety of the maintenance personnel ^[3]

According to its installation

Can be divided into outdoor isolation switch and indoor high-voltage isolation switch ^[4]

The control wiring of the disconnect switch and the corresponding circuit breaker can be locked to effectively prevent the switch from being pulled and closed with load. However, in the operation of the bus-side isolating switch and the line-side isolating switch, due to human reasons, the operating order may be reversed. This is not allowed by the operating principle of switches and knife gates, and it is also one of the causes of accidents in the power system. In order to prevent the operation sequence of the disconnectors from being reversed, the control wiring of the original disconnectors has been improved for factories and stations that do not use program locks to prevent mistakes, which can prevent misoperations and reduce unnecessary accidents ^[8]

1) Clean the dust on the surface of the porcelain, check whether the surface of the porcelain is glazed or damaged, whether there are cracks and flashover marks, and whether the iron and porcelain joints of the insulator are firm. If damaged, it should be replaced ^[9]

1. What are the common faults ^[10]

Application classification load classification load classification ^[2]

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Isolation switch application classification

Industrial applications

In order to meet the needs of industrial production such as petroleum mining, petrochemicals, metallurgy, building materials, lifting, mining, textile, papermaking, tobacco, sugar manufacturing, food production, water treatment, light industry, electricity, coal mining and other industries Reliability, control accuracy, and other requirements are high and even severe. Once the machine is shut down, it can cause serious property damage or death. Schneider Electric inverter ATV71 / 61 is suitable for industrial applications.

Construction application (civilian)

In order to meet the needs of people's daily life, such as comfortable air-conditioning, such as HVAC in shopping malls, hospitals, office buildings, office buildings, conference centers, airports, hospitals and other places, there are no special requirements for products, and downtime generally brings inconvenience. No major property loss or personal injury Schneider Electric inverter ATV21 is suitable for civil engineering applications Schneider Electric soft starter ATS48 / ATS22 is suitable for civil engineering applications

Isolation switch load classification

Divided according to load speed regulation characteristics (load torque-speed)

Fan load (or quadratic load) Constant torque load Constant power load is suitable for inverter

Difficulty of starting according to load

Standard load (Class 10 standard application) Heavy load (Class 20 heavy load application) Suitable for soft starters

No-load start Light-load start

Common load torque characteristics: load torque-speed relationship

Constant torque load

Potentiality, the direction is always the same, regardless of the direction of movement, such as the relationship of the weight function of lifting: TL = f (n) = C Resistance, the direction is always opposite to the direction of movement, such as the function of the conveyor belt: TL = f (N) = ± C

Potential constant torque resistance constant torque

Fan load

The torque is proportional to the quadratic function of the speed: TL = f (n) = T0 + kn2 Typical load: centrifugal pump, fan

Fan load

Constant power load