Introduction to electrical equipment - LS Electricity

According to the requirements of safe, high-quality, reliable and economical operation of the production, transforming, transportation, distribution and use of electric energy in power plants and substations, the following electrical equipment is mainly included.

Introduction to electrical equipment - LS Electricity

Introduction to electrical equipment - LS Electricity

1. Primary equipment

Electrical equipment directly involved in the production, transportation and distribution of electrical energy is called primary equipment, which generally includes the following 5 categories.

(1) Energy conversion equipment

Generators, transformers, motors, etc. belong to this category. The generator and main transformer are the heart of the power station, referred to as the main engine and main transformer.

(2) Switchgear

This type of appliance is used to make and break electrical circuits. When the current passes through the circuit and a large short-circuit current is specially passed, it is not simple to break the circuit, and the arc extinguishing ability is required. According to the effect and structural characteristics, switching appliances are divided into the following types.

1) Circuit breaker. Not only can the normal load current be switched on and off, but also the short-circuit current can be switched on and off. It is the most important, the most chaotic structure, the most perfect function of the switchgear.

2) Fuse. It cannot turn on and off the load current, it is set in the circuit and is dedicated to breaking the faulty short-circuit current and cutting off the faulty circuit.

3) Load switch. Load-on and on-off circuits are allowed, but their arc extinguishing capacity is limited and not enough to interrupt short-circuit currents. Connecting a load switch and a fuse in series in a circuit is roughly equivalent to the function of a circuit breaker.

4) Barrier switch. It is mainly used to block the power supply during equipment or circuit maintenance, resulting in a visible and satisfactory air distance.

Circuit breakers and fuses can interrupt a certain short-circuit current to cut off faulty circuits when their circuits fail, so they are called maintenance appliances. Circuit breakers and load switches can turn on and off a certain load current, which is called operating appliances. The barrier switch cannot interrupt the load current because it does not have arc extinguishing ability. If the blocking switch is cut wrongly under the load current, it is called a load pull, which will cause an arc short circuit, which is a serious misoperation, and should be prevented as much as possible.

(3) Current-carrying conductors

This kind of equipment has busbars, insulators and cables, etc., which are used for the connection between electrical equipment or equipment, and transmit power through strong current. The busbar is a bare conductor and needs to be supported and insulated with insulators. The cable is an insulated conductor and has a sealed envelope to maintain the insulation, and a mounted or plastic sheath on the outside to maintain the envelope.

(4) Transformer

The transformer is divided into voltage transformer and current transformer, etc., which convert the high voltage or large current on the primary side into the low voltage or small current on the secondary side according to the transformation ratio, so as to supply the measurement surface and relay of the secondary circuit.

(5) Reactors and lightning arresters

Reactors are mainly used to restrain short-circuit currents in circuits, and lightning arresters are used to restrain overvoltages in electrical equipment.

2. Secondary equipment

Auxiliary electrical equipment that monitors, controls and maintains the working conditions of electrical primary equipment is called secondary equipment. For example, all kinds of electrical appearances, relays, automatic control equipment, signal and control cables, etc. The secondary equipment does not directly participate in the production and distribution process of electric energy, but it plays a very important role in ensuring the normal and orderly work of the main equipment and the economic benefits of its operation.

The primary equipment is mainly used for high-voltage and high-current circuits, while the secondary equipment is used for low-voltage and low-current circuits. However, the small-capacity electrical equipment in the primary equipment is also mostly low-voltage. Some equipment categories are both primary and secondary, such as fuses, load switches, busbars, cables, etc., with the same name and nearby principle, but the physical structure is very different. Some low-voltage equipment and high-voltage equipment belong to the same category, and the effect in the circuit is basically the same, but the name is different, such as the low-voltage circuit breaker is called automatic switch, and the barrier switch is also called the knife switch. As for the common low-voltage rubber cover switches, steel shell switches, conversion switches, contactors, etc., they all belong to the category of load switches, and only some switches have added some functions. For example, some transfer switches can switch power supplies, contactors can be used for remote and automatic control, etc.

Introduction to electrical equipment - LS Electricity

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