Switchgear those who do not know the knowledge
Switchgear is a complete set of power distribution devices assembled by a device and a secondary device according to a certain scheme, which is mainly used for controlling and protecting circuits and devices. Switchgear according to the voltage level can be divided into high voltage switchgear (fixed and handcart type) and low voltage switchgear (fixed and drawer).
The structure of high-voltage switchgear is generally similar, mainly divided into bus room, circuit breaker room, secondary control room (instrumentation room), feeder room, the rooms generally have steel isolation.
Internal components include:
bus (bus), circuit breakers, conventional relays, integrated relay protection , measuring instruments, isolation knife, light, ground knife and so on.
Divided from the application point of view
1, into the line counters: also known as cabinet, is used to receive power from the grid equipment (from the line to the bus), the general installation of circuit breakers, CT, PT, isolation knife and other components.
2, outlet cabinet: also known as feeding cabinet or distribution cabinet, is used to distribute power equipment (from the bus to each outlet), generally also installed circuit breakers, CT, PT, isolation knife and other components.
3, bus cabinets: also known as bus disconnecting cabinet, is used to connect the two bus devices (from the bus to the bus), in a single busbar section, double busbar system often need to use the bus to meet the user to choose different Operating requirements or to ensure that there is a selective fault removal load.
4, PT cabinet: also called voltage transformer cabinet, usually installed directly to the bus to detect bus voltage and achieve protection. The main installation voltage transformer PT, isolation knife, fuse and arrester.
5, isolation cabinet: is used to isolate the bus at both ends used or isolated power equipment and power equipment used, 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 turn on the load current, it is not possible to push and pull the handcart of the isolation cabinet when the circuit breaker with which it is closed is closed. In general applications, you need to set the circuit breaker auxiliary contacts and isolation handcart interlock to prevent misoperation of operating personnel.
6, measuring cabinet: mainly used for measuring electrical energy (kWh), there are high pressure, low pressure of the points, the general installation of isolating switches, fuses, CT, PT, active watt-hour meters , Reactive power meter, relays, and some other secondary equipment (such as load monitors, etc.).
7, SVG: Static and reactive power generator, the English description is: Static Var Generator, referred to as SVG. Also known as high voltage dynamic reactive power compensation device, or static synchronous compensator. Refers to by the commutation of the power semiconductor bridge converter for dynamic reactive power compensation device. SVG is currently the best solution in the field of reactive power control. SVG has an unparalleled advantage over the traditional tune-up cameras, capacitor reactors and traditional SVC, which is mainly represented by thyristor control reactor TCR.
8, inflatable switchgear: also known as enclosed combination of electrical cabinet, which is the circuit breakers, disconnectors, earthing switches, CT, PT, arrester, bus and other closed combination of metal housing, and then to the insulation performance and arc performance Good gas (usually sulfur hexafluoride SF6) as a phase and ground insulation measures for high voltage and high capacity level of the grid, as the distribution and control.
From the perspective of components
1, circuit breaker: under normal operating conditions, the circuit breaker is closed (except for special applications), connected to the circuit. When automatic control or protection control operation, the circuit breaker in the comprehensive protection device under the control of the circuit breaking or on operation. The circuit breaker can not only cut off the normal load current, but also can withstand the short-circuit current (several times or even several times the normal operating current) for a certain period of time, and can break the short-circuit current and cut off the fault lines and equipment. Therefore, the main function of the circuit breaker is to break and connect the circuit (including breaking and connecting the normal current and breaking the short circuit current). Because of breaking and connecting the circuit in the process, the circuit breaker of the moving contact and the static contact between the inevitable to produce arc. In order to protect the contacts and reduce the loss of contact materials and reliable breaking circuit, measures must be taken to extinguish the arc as soon as possible. One of them is to use different interrupting mediums to fill the circuit breaker's moving and static contacts. According to interrupter medium different circuit breakers can be divided into: oil circuit breakers (oil, less oil), sulfur hexafluoride (SF6) circuit breakers, vacuum circuit breakers, air circuit breakers. The main equipment we have in our high and low voltage switchgear is the circuit breaker. As the circuit breaker, the static contact is generally surrounded by a container filled with interrupter medium, so the circuit breaker points, the state can not be directly judged, usually through the circuit breaker auxiliary devices (such as sub-place pointer Etc.) to determine.
2, Microcomputer protection device: Microcomputer protection is composed of high integration, the bus is not chip microcontroller, high-precision current and voltage transformers, high dielectric strength outlet intermediate relay, high reliability switching power supply module and other components. Mainly as a computer protection device 110KV and below the voltage level of power plants, substations, distribution stations, etc., can also be used as part of the voltage level between 70V-220V voltage and current protection and monitoring.
3, isolation knife: isolation knife (or isolation switch) due to obvious fracture can be identified on or off, mainly used to isolate high-voltage power supply, in order to ensure the safety of wiring and equipment maintenance, can break the current is small Usually only a few amps). Because there is no special arc extinguishing device, so it can not be used to break the fault current and normal operating current, does not allow the load with the breaking operation.
4, Fuse: Fuse is a simple circuit protection appliances, the principle is that when the current flowing through the fuse reaches or exceeds the value of a certain period of time, the melt itself, cut off the circuit. Its action principle is simple, easy to install, generally not used alone, mainly used with other electrical appliances.
5, load switch: Load switch has a simple arc device, the arc medium generally use air, you can connect and disconnect certain current and over current, but can not break the short circuit current, can not be used to cut off the short circuit fault. So it is absolutely not allowed to simply use the load switch to replace the circuit breaker; if you want to use the load switch, must be used in conjunction with the previously mentioned high-voltage fuses (in fact often use fuses and load switches in series for simple overload protection , In order to reduce the project cost). Load switch similar to the isolation knife, there is a clear gap between the disconnect, you can easily determine the circuit is turned on or off.
6, PT (TV) / CT (AV) Transformer: Transformer is actually a special transformer, mainly used to electrically isolate the primary circuit and control loop, thereby expanding the secondary equipment (instruments, comprehensive insurance, etc.) The use of. The use of PT / CT can avoid the high voltage / high current of the primary circuit directly entering the secondary control equipment (such as meter, comprehensive protection device, etc.), and also can prevent the primary circuit from running due to the control equipment failure.
7, handcart: handcart is part of high voltage switchgear, respectively, to install high voltage circuit breakers and other components. Their function is basically the same as that of the fixed switchgear. The main difference is the convenience of maintenance and overhaul (the handcart can be pushed in and out by the mechanical operating mechanism rocker). The handcart generally has three working positions (during normal operation), tests (during commissioning and on-site tests), and exits (during maintenance and overhauls).
8, ground knife: ground knife (also known as grounding switch) Main: First, used in line and equipment maintenance, in order to ensure the safety of personnel for grounding; Second, it can be used to artificially cause the system ground short circuit, to control The purpose of protection. The first one is well understood and not introduced. The second role is this: Grounding knife is usually connected to the high-voltage side of the step-down transformer, when the receiving end fails or transformer internal failure, ground knife switch should be automatically closed, resulting in short circuit to ground, forcing the power supply side The top) circuit breaker rapid action, cut off the fault, so that this is a personal short circuit to ground fault, the purpose is to ensure that the power supply circuit breakers can quickly move.
9, instrumentation: Multi-function instrument is developed for low-voltage power monitoring telemetry, remote communications, remote control in one multi-function digital three-phase intelligent measurement and control instruments. It uses high-end configuration, high-performance 32-bit embedded microprocessors, high-precision AD sampling, direct or indirect measurement of three-phase power grid voltage, current, power, power factor and frequency, but also with industrial equipment connected to form control system. Can be widely used in substation automation , distribution automation, residential power monitoring, industrial automation , intelligent building, smart power distribution panels, dashboards, switchboards as the power parameter measurement and control components. Instrument can have RS-485 or TTL communication interface, using Modbus-RTU protocol. According to different requirements, through the instrument panel keys, variable ratio, alarm, communication and other parameters to set and control.
10, the temperature on-line monitor: handcart type switchgear commonly used in the power supply system, in the high-voltage circuit breaker handcart structure, static contact, moving contact is a basic component in the moving contact with the static contact contact When there is a contact resistance between them, if the contact resistance is too large, the temperature rise will exceed the specified value, thus accelerating the dynamic and static contacts at the contact oxidation, the oxidation result in turn increases the contact resistance, thus contributing to increased fever , The temperature increases, and even arc burn. Contact temperature on-line monitor is developed to avoid such accidents.
11, intelligent ring counter monitoring: ring counter in the long run, due to a variety of objective causes ring counter in the process of installation and put into operation after the cable lap at the fault, the gas chamber failure, operating mechanism failure, Arrester failure, etc., thus bringing about a hidden danger to the reliable operation of the power grid.
Common switchgear production equipment, including:
12, sheet metal three pieces: CNC punch, shears, bending machines. These three are the basic tools for sheet metal production, mainly used to make switch cabinet cabinet. Sheet metal processing accuracy of high-pressure handcart-type switchgear, low-voltage drawer-type switchgear greater impact, manifested in the hand truck shake and shake out, drawer interchangeability.
13, spray equipment: switch cabinet cabinet surface electrostatic spray processing. Electrostatic spray is the use of electrostatic adsorption method to make the powder coating adsorbed on the metal surface after high temperature curing the surface of the protective film formed a full set of processes. Electrostatic spray without thinner, the construction of the environment pollution-free, non-toxic to the human body; coating appearance of excellent quality, adhesion and mechanical strength; spraying construction curing time is short. Spray equipment mainly pickling, degreasing, phosphating, electrostatic spraying, curing and other processes, respectively, using different equipment, the current use of more spray production lines.
14, busbar processing equipment: busbar processing equipment is mainly used for switchgear cabinet and copper busbar cutting, punching, bending operation, the use of multi-station bus processing machine more.
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