High and low voltage electrical switchgear plays a crucial role in power systems. It controls and protects the normal operation of the power system, ensuring stable current and voltage, thus providing reliable power support for people's production and daily life. It can control the magnitude of current and voltage and protect the power system from damage caused by abnormal currents and voltages. These switchgear typically consist of components such as high-voltage switches, transformers, circuit breakers, contactors, relays, and cables. They are widely used in various industries, including power, metallurgy, petrochemicals, and construction. In these industries, the role of high and low voltage electrical switchgear is to control and protect the normal operation of the power system, ensuring stable current and voltage, and improving production efficiency and quality of life.
In short, high and low voltage electrical switchgear is one of the most important pieces of equipment in a power system. Its design and manufacture must strictly adhere to relevant standards and specifications and undergo rigorous testing and verification. In future development, high and low voltage electrical switchgear will become more intelligent and digital, providing better guarantees for the reliability and safety of power systems. This article will share some basic knowledge about high and low voltage switchgear, hoping to help electrical personnel gain a deeper understanding of high and low voltage electrical complete sets of switchgear.
I. High-Voltage Switchgear (typically referring to 3.6kV - 40.5kV voltage levels)
High-voltage switchgear is mainly used in power plants, substations, industrial and mining enterprises, etc., responsible for receiving and distributing electrical energy and controlling high-voltage motors.
Main Types:
◆Classified by Insulation Medium:
Air-Insulated Switchgear (AIS): Busbars, circuit breakers, and other main components are exposed to air, relying on air and insulators for insulation. Simple structure, low cost, and most widely used, but requires a large footprint.
Gas-Insulated Switchgear (C-GIS/GIS): Busbars, circuit breakers, disconnectors, etc., are sealed in a stainless steel housing (gas box) filled with insulating gases such as SF6 (sulfur hexafluoride). Small size, unaffected by the environment, high reliability, often used in space-constrained or harsh environments.
Solid-Insulated Switchgear (SIS): Main live parts are encased in solid materials such as epoxy resin. Size between AIS and C-GIS, no SF6 gas, more environmentally friendly.
◆Classification by Structural Form (Common in AIS):
Armored Removable Metal-Enclosed Switchgear (KYN Type):
Structure: The enclosure is divided into multiple compartments by metal partitions (e.g., busbar compartment, circuit breaker compartment, cable compartment, relay instrument compartment). The core circuit breaker is mounted on a removable trolley.
Advantages: High safety (complete "five-proof" functions), convenient maintenance (the trolley can be moved to the "test position" or "isolation position" for testing or maintenance without shutting down the busbar). It is currently the mainstream model.
Metal-Enclosed Box-Type Switchgear (XGN Type):
Structure: Fixed installation; circuit breakers, disconnect switches, and other components are fixedly installed, typically using a combination of pneumatic load switches and fuses.
Advantages: Simple structure, low cost, small footprint. Commonly used in ring network power supply systems, hence often called a ring network cabinet.
Interval-Type Metal-Enclosed Switchgear (JYN Type):Similar to the armored type, but with a slightly lower protection level; now rarely used.
Core Functions:
Control Function: Connects or disconnects high-voltage circuits by operating circuit breakers or load switches as needed.
Protection Function: Core function. Works in conjunction with relay protection devices (such as microprocessor-based integrated protection systems) and circuit breakers to quickly disconnect faulty parts in the event of short circuits, overloads, grounding faults, etc., ensuring the normal operation of non-faulty lines and equipment.
Isolation Function: Establishes a clearly visible disconnection point through the working position of disconnect switches or handcarts, reliably isolating the equipment under maintenance from live parts and ensuring the safety of maintenance personnel.
Measurement and Monitoring Function: Monitors line parameters such as voltage, current, power, and energy in real time through voltage transformers (PTs), current transformers (CTs), instruments, and intelligent devices installed in the cabinet, and uploads the data to the monitoring system.
Energy Distribution Function: Safely and reliably distributes electrical energy from the upstream power source to multiple downstream power circuits or transformers through busbars and outgoing circuits.
II. Low-Voltage Switchgear (usually referring to AC 1000V and below voltage levels)
Low-voltage switchgear is located at the end of the power system, directly supplying power to electrical equipment, and is the core of the power distribution network.
Main Types:
◆Fixed Low-Voltage Switchgear (e.g., GGD type):
Structure: All electrical components (circuit breakers, fuses, contactors, etc.) are fixedly installed, resulting in a simple structure and low cost.
Disadvantages: Power outage is required for maintenance or component replacement. Mostly used in locations with low load requirements.
◆Drawer-Type Low-Voltage Switchgear (e.g., GCS, GCK, MNS types):
Structure: The main functional units (such as outgoing circuits) are installed in removable drawers. The drawers have multiple positions: working, testing, and disconnected.
Advantages:
High power supply reliability: In case of a circuit failure, the faulty drawer can be quickly removed and replaced with a spare drawer to restore power.
Convenient maintenance: After the drawer is removed, it provides safe isolation, facilitating maintenance and testing.
Compact and versatile: Standardized design allows for interchangeable drawers. It is currently the most widely used type in the industrial field.
◆Power Distribution (Control) Boxes/Cabinets (e.g., XL-21 type):
A relatively small low-voltage cabinet, mainly used for power distribution, control, protection, and monitoring of power equipment such as motors. It typically contains circuit breakers, contactors, thermal relays, frequency converters, etc.
◆Reactive Power Compensation Cabinets (Capacitor Cabinets):
Specifically designed to improve the system power factor. They mainly house capacitors, reactors, switching switches (contactors or thyristors), and controllers. By automatically switching capacitor banks, they reduce reactive power losses in the power grid and improve power quality.
Core Functions:
Power Distribution and Control: Distributes low-voltage electrical energy from transformers to various electrical devices, lighting circuits, sockets, etc. It also controls the starting, stopping, and speed regulation of motors and other equipment.
Protection Function: Provides overload, short circuit, undervoltage, and leakage current (via residual current devices) protection for lines and electrical equipment through low-voltage circuit breakers, fuses, and thermal relays.
Energy Metering: Installs energy meters to measure the energy consumption of electrical units.
Reactive Power Compensation: Improves the system power factor, reducing grid losses and electricity costs.
Monitoring and Intelligentization: Modern low-voltage switchgear is generally equipped with intelligent instruments and communication modules, enabling real-time monitoring of electrical parameters and power quality. It can be integrated into energy management systems (EMS) or building automation systems (BAS) to achieve remote monitoring and intelligent management.
Summary
| Characteristics | High-voltage switchgear | Low-voltage switchgear |
|---|---|---|
| Voltage Level | High voltage (3.6kV - 40.5kV) | Low (≤ 1000V AC) |
| Core Focus | Insulation, arc extinguishing, system stability | Protection selectivity, control flexibility, power management |
| Main Components | High-voltage circuit breakers, disconnectors, PTs, CTs, surge arresters | Low-voltage circuit breakers, contactors, fuses, smart meters |
| Structural Features | Emphasis on "five-proof" interlocking, available in withdrawable and fixed types | Emphasis on modularity, available in drawer-type and fixed-type |
| Core Function | Power distribution, system-level protection, safety isolation | Terminal power distribution, equipment control, detailed protection, power quality management |
Whether it is a high-voltage switchgear or a low-voltage switchgear, its design and manufacturing must strictly adhere to rigorous standards to ensure safety, reliability, maintainability, and intelligence, which together form a solid foundation for ensuring the safe and efficient operation of the power system throughout the entire process from power transmission to power consumption.
With years of professional experience and technological innovation, Shaanxi Huadian is committed to providing safe, intelligent, and efficient high and low voltage switchgear and integrated solutions for every stage of power generation, transmission, and consumption. For inquiries, please contact:pannie@hdswitchgear.com.
