High voltage switchgear refers to the electrical equipment of the cabinet that plays the role of on-off, control or protection in the power generation, transmission, distribution, and power conversion and consumption of the power system. The internal components of the switchgear are mainly composed of circuit breakers, isolating switches, load switches, operating mechanisms, mutual inductors, and various protection devices.
1. Functional classification of high voltage switchgear
(1) Incoming cabinet: also called receiving cabinet, it is the equipment used to receive electric energy from the power grid (from the incoming line to the busbar). Generally, it is equipped with circuit breakers, current transformers, isolating switches, lightning arresters and other components.
(2) Outgoing cabinet: also called feeder cabinet, power distribution cabinet or collection cabinet, it is the equipment used to distribute electric energy (from bus to each outlet). Circuit breakers, current transformers, isolating switches, lightning arresters, etc. are also generally installed. Components.
(3) Busbar connection cabinet: also called busbar section cabinet, it is used to connect the network segment busbar equipment (from busbar to busbar). Busbar connection is often used in single busbar section and double busbar system to satisfy The user chooses the requirements of different operating modes or guarantees the selective removal of the load in the event of a fault.
(4) Voltage transformer cabinet: also known as TV cabinet, it is usually installed directly on the bus bar to detect the bus voltage and realize the protection function. The internal main installation of voltage transformer, isolation switch, high voltage fuse, harmonic elimination device, lightning arrester Wait.
(5) Isolation cabinet: It is used to isolate two sections of busbars or to isolate power receiving equipment and power supply equipment. It can provide operators with a visible endpoint to facilitate maintenance and repair operations. Since the isolation cabinet does not have the ability to break and connect the load current, the handcart of the isolation cabinet cannot be pushed or pulled when the circuit breaker is closed. In general applications, it is necessary to set up auxiliary contacts of the circuit breaker and the isolation handcart. The interlocking prevents misoperation of operators.
(6) Metering cabinet: It is mainly used as an equipment device for measuring electrical energy, and is generally installed with isolation switches, high voltage fuses, voltage transformers, current transformers, and electric energy meters.
(7) SVG reactive power compensation cabinet: The so-called reactive power compensation cabinet is an ordinary low voltage cabinet used to prevent capacitors, reactors, primary and secondary circuits, and its main function is to make reactive power compensation. Convert electrical energy into another form of energy. This energy is a prerequisite for electrical equipment to perform work, and this energy is periodically converted with electrical energy in the grid. This part of power is called reactive power. The purpose of reactive power compensation is to use an external current source to compensate for the reactive power consumed during load operation, and the equipment that provides this current source becomes a reactive power compensation device.
(8) Grounding transformer switch cabinet: Connect a grounding (stationary) transformer to the lower end of the grounding transformer switch cabinet, and then connect to the arc suppression coil. Cooperate with the small current line selection grounding device and the arc suppression coil to automatically track the grounding compensation device controller. When grounding occurs, the faulty line will be tripped to protect the safety of the system through compensation and line selection judgment. According to the requirements of the power grid, this system cannot operate the outlet switch. The grounding transformer can also be used as a station transformer to supply power to the 400V low voltage bus, as a common power source for the power station.
2. Tuning mode of high voltage switchgear
All equipment in the high voltage power distribution room shall be under the jurisdiction of the local public power grid dispatching management department, in accordance with the signed dispatch agreement, and the specific implementation shall be carried out in accordance with the following rules:
(1) Provincial dispatching and dispatching equipment: equipment that can change its operation mode only after the approval of provincial dispatching, such as photovoltaic units and SVG reactive power compensation cabinets.
(2) Local dispatching equipment: Only after the approval of the local dispatching, can the operation mode be changed, such as the incoming switchgear.
(3) Provincial dispatch authorization and local dispatch management equipment: Provincial dispatch is authorized to prefecture level dispatch, which is directly managed by prefectural dispatch, such as SVG reactive power compensation devices and photovoltaic units.
(4) Self dispatching equipment: The equipment that is self dispatched by the photovoltaic power station, if it conforms to the operating regulations, can change its operation mode by itself without going through the provincial or prefecture level dispatch, such as the outlet switch cabinet (collecting cabinet).
3. Specification requirements for operation and maintenance of high voltage switchgear
The high voltage switchgear should be inspected daily to check the equipment operating parameters in time to ensure the safe and stable operation of the equipment. The main inspection contents are as follows:
(1) Whether the ventilation, lighting and safety fire protection devices of the high voltage power distribution room are normal.
(2) The door of the high voltage switch cabinet is tight and free from damage, and the cabinet is clean and dust free.
(3) All switch cabinets in the station should be marked with double names of equipment.
(4) Whether the indications of the meter, signal, indicator light, etc. are correct, and whether the position of the relay protection connection piece is correct.
(5) Whether the setting value and time of the protection device are correct.
(6) Whether the bus bar and each contact are overheated.
(7) Whether the electrical components in the switch cabinet have abnormal smells and noises during operation.
(8) Whether the relay and DC equipment are operating well.
(9) Whether the connection wire of the grounding and zero connection device is loose or disconnected.
(10) Whether the mechanical interlocking of the circuit breaker and the isolating switch is flexible and reliable. If an electromagnetic interlocking device is adopted, it must be energized to check whether the electromagnetic lock action is flexible and whether the opening and closing is accurate.