Switchgear: It is a complete set of power distribution equipment assembled from primary and secondary equipment according to a certain line scheme, which is used to implement control and protection for lines and equipment, divided into fixed and trolley type, and can be divided into high-voltage switchgear (fixed and trolley type) and low-voltage switchgear (fixed and drawer type) according to the voltage level of incoming and outgoing lines. The structure of switchgear cabinet is similar, mainly divided into busbar room, circuit breaker room, secondary control room (instrument room), feeder room, and each room is generally separated by steel plates.
Internal components include: busbar (busbar), circuit breaker, conventional relay, comprehensive relay protection device, metering instrument, isolation knife, indicator, grounding knife, etc.
Divided from the application point of view
Also called the receiving cabinet, it is used to receive electrical energy from the grid (from the incoming line to the busbar), generally installed with circuit breakers, CT, PT, isolation knife and other components.
Also called feeder cabinet or distribution cabinet, is used to distribute electrical energy equipment (from the busbar to each outlet), generally also installed with circuit breakers, CT, PT, isolation knife and other components.
Busbar contact cabinet
Also called busbar breakout cabinet, is used to connect two sections of busbar equipment (from busbar to busbar), in the single busbar segmentation, double busbar system is often used busbar liaison, to meet the user to choose different operating requirements or to ensure that the fault situation has the option to remove the load.
Voltage transformer cabinet, generally installed directly on the busbar to detect the busbar voltage and achieve the protection function. Mainly installed inside the voltage transformer PT, isolation knife, fuse and lightning arrester, etc.
It is used to isolate the two ends of the busbar or isolate the powered equipment and power supply equipment, which can provide a visible end point for the operating personnel to facilitate maintenance and overhaul operations. Since the isolation cabinet does not have the ability to break and connect the load current, it is not possible to push or pull the trolley of the isolation cabinet when its mating circuit breaker is closed. In general applications, it is necessary to set the interlock of the auxiliary contact of the circuit breaker and the isolation trolley to prevent the misoperation of the operating personnel.
Also called compensation cabinet, is used to improve the power factor of the power grid, or reactive power compensation, the main components are connected in parallel with groups of capacitors, throwing control circuit and fuses and other protection appliances. Generally installed in parallel with the incoming cabinet, one or more capacitor cabinets can run in parallel. After the capacitor cabinet is disconnected from the grid, the capacitor bank needs a period of time to complete the discharge process, so you can not directly touch the components inside the cabinet, especially the capacitor bank; within a certain period of time after the power failure (depending on the capacity of the capacitor bank, such as: 1 minute), it is not allowed to re-close, so as not to produce overvoltage damage to the capacitor. When doing the automatic control function, we should also pay attention to the reasonable distribution of the number of times to cut each capacitor group, so as to avoid the situation that one group of capacitors is damaged while the other groups are rarely cut.
It is mainly used for measuring electric energy (kilowatt-hour), and there are high-voltage and low-voltage, generally installed with isolation switch, fuse, CT, PT, active meter (traditional meter or digital meter), reactive meter, relay, and some other auxiliary secondary equipment (such as load monitor, etc.).
It is also called closed combination electrical cabinet, which is a combination of circuit breaker, isolation switch, grounding switch, CT, PT, lightning arrester, busbar, etc. enclosed in a metal shell, and then insulated with good insulation and arc extinguishing performance of gas (generally with sulfur hexafluoride SF6) as the insulation measures between phases and to ground, suitable for high voltage and high capacity level of the power grid, used as subject to distribution and control.
Under normal operating conditions, the circuit breaker is in the closed state (except for special applications) and connects the circuit. When automatic control or protection control operation is carried out, the circuit breaker can be used to break or turn on the circuit under the control of the integrated protection device. The circuit breaker can not only pass normal load current, but also withstand short-circuit current for a certain period of time (several times or even dozens of times the normal operating current), and can break the short-circuit current and remove faulty lines and equipment. Therefore, the main function of the circuit breaker is to break and turn on the circuit (including breaking and turning on the normal current, breaking short-circuit current).
As in the process of breaking and turning on the circuit, the arc between the dynamic and static contacts of the circuit breaker is inevitable. In order to protect the contacts, reduce the loss of contact materials and reliable circuit breaking, measures must be taken to extinguish the arc as soon as possible, one of which is the use of different arc extinguishing media filled to the dynamic and static contacts between the circuit breaker. According to the different arc extinguishing medium circuit breakers can be divided into: oil circuit breakers (more oil, less oil), sulfur hexafluoride (SF6) circuit breakers, vacuum circuit breakers, air circuit breakers, etc.. The main primary equipment in the high-voltage switchgear that we often come into contact with in engineering is the circuit breaker.
As the dynamic and static contacts of the circuit breaker are generally wrapped in a container filled with arc-extinguishing medium, so the breaking and closing state of the circuit breaker can not be directly judged, generally through the auxiliary devices of the circuit breaker (such as splitting and closing position pointer, etc.) to discern.
Isolation knife gate
Isolation knife gate (or isolation switch) because of the obvious break can be identified to connect or break, is mainly used to isolate the high-voltage power supply to ensure the safety of the line and equipment maintenance, can break the current is very small (generally only a few amperes). Because there is no special interrupting device, so it can not be used to break the fault current and normal operating current, not allowed to carry a load for breaking operation.
Fuse is a simple circuit protection apparatus, the principle is that when the current flowing through the fuse reaches or exceeds the fixed value for a certain period of time, the melt itself melted, cut off the circuit. Its action principle is simple, easy to install, generally not used alone, mainly used with other appliances.
Main action characteristics.
First, the current to reach a certain value, the value in the fuse factory has been done before, can not be changed;
Second, the current to reach a certain value after a certain time, the time is also the manufacturer well, can not be changed, but many types, including delayed action, fast action, super fast action, etc.;
Third, the action of the body damage, can not be reused, must be replaced;
Whether the fuse is fused can be discerned by the fuse indicator, but also by the appearance of the fuse body; commonly used fuses, fuses belong to the range of this type of electrical appliances.