The main parts of the switchgear include: vacuum circuit breakers, current transformers, on-site installation of microcomputer protection devices, operating circuit accessories (handles, indicator lights, pressure plates, etc.), various position auxiliary switches. Among them, the circuit breaker and the current transformer are installed inside the switch cabinet, and the microcomputer protection, accessories, and watt-hour meter are installed in the relay room (using the previous name, in fact, there is no relay), the terminal block and various power supply air The switch is installed inside the relay chamber, and the terminal block is connected to the circuit breaker mechanism through a control cable or a dedicated socket. Â
To understand the secondary wiring of the switchgear, we need to find two drawings: the protection schematic diagram and wiring diagram provided by the microcomputer comprehensive protection manufacturer; the secondary schematic diagram, wiring diagram, terminal diagram, and circuit breaker mechanism principle provided by the switchgear manufacturer Figure.
The manufacturer's paper is the original basis for the design of the switchgear manufacturer, and it is also the basis for us to review the drawings of the switchgear manufacturer. The schematic diagram of the switchgear factory is generally modified according to the schematic diagram of the microcomputer protection, and then the input of the current, voltage and signal quantity and the output of the control quantity are schematically shown. Â
Second, the secondary wiring of the central switchgear Â
The KYN28A central cabinet is the most used 10kV switchgear type in urban substations. It consists of two parts: the cabinet and the extractable parts (center-mounted handcart). The cabinet is divided into a handcart room, a main bus room, and a cable room. Relay instrument room. As shown below.
The panel of the relay room is equipped with a microcomputer protection device, an operating handle, a protection outlet pressure plate, an indicator light (a red light in place, a green light in a position, and a yellow light in the energy storage); and a terminal block and a microcomputer protection control circuit are installed in the relay room. DC power switch, microcomputer protection working DC power supply, energy storage motor working power switch (DC or AC).
2.2 handcart (circuit breaker) room
The most commonly used circuit breaker in the center cabinet is the VS1 vacuum circuit breaker. The wiring in the circuit breaker mechanism is connected to the terminal block of the relay room through a dedicated socket. One section of the plug is fixedly connected to the circuit breaker mechanism, and the other section is a special plug. The matching socket is installed at the upper right of the circuit breaker chamber, and the outlet wire of the socket is connected to the terminal block of the relay room. In order to understand the secondary circuit, we need to have a certain understanding of the operation process.
The center-mounted cabinet circuit breaker has three positions: disconnection, test, and operation (it is worth noting that the circuit breaker handcart and the circuit breaker are two concepts, and the circuit breaker handcar is actually the circuit breaker and its seat). In normal operation, the circuit breaker handcart is in the running position, the circuit breaker is in the closing position, the secondary line plug is connected with the socket; after the manual trip, the circuit breaker is in the open state, the handcart is in the running position; the special rocker will be used to open the circuit. The handcart is shaken out to the test position, and the secondary plug can be unplugged (the handcart cannot be pulled out when it is in the running position); continue to shake, the handcart exits the circuit breaker room and is in the disconnected position.
Disconnected position: The circuit breaker is not connected to the primary equipment (busbar), the operating power is lost (the secondary plug has been unplugged), and the circuit breaker is in the open position;
Test position: The secondary plug can be plugged into the socket to obtain power. The circuit breaker can be closed and opened, and the corresponding indicator light is on; the circuit breaker is not connected to the primary equipment, and various operations can be performed, but it does not have any influence on the load side, so it is called the test position.
Operating position: The circuit breaker is connected to the primary equipment. After closing, the power is transmitted from the busbar to the transmission line via the circuit breaker.
The center cabinet does not have the concept of a disconnector in the traditional sense. When the handcart is in the test position, it is equivalent to the traditional disconnector disconnection, that is, the circuit breaker has a significant disconnection point from the main circuit (primary bus).
The 95X series microcomputer protection device is a microcomputer protection device designed by our company for the center cabinet, which has a small size. Full-featured features. Three-stage overcurrent can be achieved. Overpressure. Conventional relay protection functions such as undervoltage, three-phase reclosing, and inverse time limit.
2.32 voltage loop
   It can be seen from the above figure that the PT analog quantities that need to be connected are A, B, C, and phase voltages. Of course, if necessary, you can access the zero-sequence voltage for zero-sequence voltage protection. It can be seen from the figure that this connection is a star/star connection. If it is a V/v connection, D9 and D12 can be shorted.
2.33 operating circuit
   As can be seen from the above figure. The overall operation of the 95X is relatively simple. Intuitive. It is more convenient than traditional integrated operation and use. Easy to understand. It's easier to get started. The devices in the red box are not part of the 95X, they are supplied by the switchgear cabinet and are mounted on the relay room panel. And connected to the breaker position.
2.34 opening amount loop
   The above is the remote signaling (switching) circuit of the device. Unlike the protection device of the 110kV voltage class device, the protection, measurement and control of the 35/10kV device is an integrated design, that is, integrated in one device. Remove the breaker position. Other openings may be defined by themselves. At the same time, an alarm input signal is also provided. Signals for non-power trips can be turned on.
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