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Electrical switchgear is a complete set of equipment composed of circuit breakers and isolation switches. It is the core component of the power system, so it is responsible for the control, protection and isolation of circuits and equipment, and is also used to regulate power flow, quickly cut off the faulty part in case of failure, and maintain the normal operation of the circuit.
It is the “security guard” and “dispatch center” of the power system: it can ensure the orderly distribution of electricity and coordinate the energy transmission from power generation to power consumption.At the same time, when a fault occurs, it can immediately cut off the hidden danger, which can not only protect household electrical appliances from damage, but also prevent the entire power system from being damaged and causing large-scale power outages, which is why it is important.
High Voltage (HV) switchgear consists of a set of integrated electrical circuit breakers, fuses and disconnecting switches. It is mainly used to protect, control and isolate electrical equipment. Its primary functions are to cut off the power supply of equipment to facilitate subsequent maintenance work and quickly clear faults in the downstream circuit.
Why the high Voltage (HV) switchgear so important is because it has multiple functions.
Power Control:It controls the flow of high voltage electricity,witch can open or close circuits as required, allowing for the distribution of power to different parts of the electrical network.
Protection:The operator controls the current, switches the circuit, connects or disconnects the equipment, and manages the distribution as needed.
Isolation: During maintenance or when a fault occurs, the high-voltage switchgear provides isolation.The isolation device in the switchgear can ensure that the working part is completely disconnected after the circuit is cut off, which protects the safety of maintenance personnel.
Circuit Breakers: These are the most critical components, commonly used in high voltage applications. They use sulfur hexafluoride gas with excellent dielectric properties as an insulating and arc extinguishing medium, so that they can quickly cut off the circuit.
Disconnectors: Also known as isolators, they are used to isolate a part of the circuit for maintenance or repair. They provide a visible break in the circuit, ensuring that the equipment is safely de – energized.
Surge Arrestors: High voltage systems are prone to voltage surges caused by lightning strikes or sudden changes in load. Surge arrestors in the HV switchgear divert these high voltage surges to the ground, protecting the equipment from damage.
Current Transformers (CTs) and Voltage Transformers (VTs): CTs are used to measure high current values by stepping down the current to a measurable level. VTs, on the other hand, step down high voltage values for measurement and protection purposes. These measurements are used for monitoring the performance of the high voltage system and for protection relaying.
Medium voltage switchgear is electrical equipment with a voltage range of 1kV to 35kV. Composed of circuit breakers and other components, it connects high and low voltage power grids, controls power distribution, protects circuits, and is used in industries, distribution networks and other scenarios.
Power Distribution: MV switchgear distributes power from the substation to various load centers within a facility.
Protection:It provides protection against faults. It uses circuit breakers and protective relays to detect and interrupt abnormal currents. But the design and rating of these components are more suit for the medium voltage range.
Control: It controls the electrical equipment witch connected to the medium voltage system, including starting and stopping motors, and managing other electrical loads.
Circuit Breakers: MV switchgear may use vacuum circuit breakers or SF₆ circuit breakers, depending on the application requirements. Vacuum circuit breakers are popular in medium voltage applications due to their fast – acting nature and long – life expectancy. They use a vacuum environment to extinguish the arc when interrupting the circuit.
Load Break Switches: These switches are used to break the load current under normal operating conditions. They are often used in combination with fuses for protection. Load break switches can be manually or remotely operated.
Disconnect Switches: They are used to isolate parts of the MV system for maintenance or repair. Disconnect switches provide a visible break in the circuit, ensuring the safety of workers.
Control and Protection Relays: These relays are responsible for monitoring the electrical parameters of the medium voltage system. They can detect overcurrents, undervoltages, and other abnormal conditions and send signals to the circuit breakers to trip if necessary.
Low voltage switchgear is electrical equipment with voltage AC ≤ 1000V, DC ≤ 1500V, including circuit breakers and other components. It is used for terminal power distribution, circuit protection, and applicable in buildings, factories, etc.
Power Distribution: Distribute electrical energy to various branches and control, protect circuits.
Protection: It protects the circuit from overload and short circuit. During operation, if the circuit breaker and fuse in the switch detect abnormal current, they will cut off the circuit to prevent damage to electrical appliances.
Control: LV switchgear can control the electrical loads.
Circuit Breakers: These are essential components in LV switchgear, including Miniature circuit breakers (MCBs) and while molded – case circuit breakers (MCCBs). MCBs are designed to protect against overloads and short – circuits in low – current circuits, while MCCBs can handle higher currents.
Contactors: Contactors are used to control the operation of electrical motors and other high – current loads. They can be remotely controlled, allowing for the automation of electrical systems.
Relays: Relays are used to control and protect electrical circuits. They can be used to sense abnormal conditions such as overcurrents, undervoltages, and overheating and trigger the appropriate action.
Fuses: Fuse is a simple and effective protection device. When the current through it exceeds a certain value, the device’s fine wire will melt, thus disconnecting the circuit and protecting the equipment, which is its purpose.
Bus Bars: Bus bars are used to distribute power within the LV switchgear,which are made of copper or aluminum and can carry high currents.
Voltage Rating:This is the most basic factor. Choosing the wrong voltage rating can cause equipment failure and safety hazards, so we need to determine the rated voltage of the power system first.
Current Carrying Capacity: We need to accurately assess the current-carrying capacity of the system, as this relates to the maximum current that the switching equipment should be able to handle under normal and fault conditions.
Protection Features: The comprehensive protection function of the switch cabinet can better avoid and protect overcurrent, short circuit and ground fault.
Reliability: Consider the reputation of the manufacturer. Reliable switching equipment can reduce the likelihood of unexpected failures and downtime.
Maintenance Requirements: Different types of switch cabinets have different maintenance requirements. We should choose switch equipment that is easy to maintain and has ready-made spare parts.
Cost – Effectiveness: Although cost should not be the only determining factor, we need to comprehensively consider the overall cost-effectiveness of the switching equipment.
Environmental conditions: Considering the environmental conditions in which the machine is used can help us choose a switch cabinet that is more suitable (we need to consider factors such as temperature and humidity).
Understanding the differences between high-voltage, medium-voltage, and low-voltage switchgear is crucial for designing reliable and efficient electrical systems. By carefully evaluating voltage requirements, application scale, and the priority of core functions, enterprises can more accurately select the appropriate switchgear solution to ensure the safety, efficiency, and long-term stable operation of the electrical system. At Chuanli, we are committed to providing high-quality switchgear solutions tailored to meet these needs, empowering our clients with safety, performance, and reliability they can trust.
