Power grid system
Fuses are one of the simplest, lowest-cost, and fastest-acting protective components in power systems. They are widely used in power generation, transmission, transformation, distribution, and consumption. Their core function is to protect power equipment (such as transformers, cables, capacitors, and motors) and systems by melting their fuses in the event of an overcurrent (overload or short circuit), thus severing the fault circuit and preventing further escalation of the fault.
1. Power Generation Link: Auxiliary Equipment Protection
In the power generation link (e.g., thermal power plants, hydropower stations), the core equipment (generators, main transformers) relies on relay protection and circuit breakers as primary protection. Fuses are mainly used for the protection of low-voltage auxiliary circuits and small equipment:
Generator auxiliary systems: Low-voltage fuses (e.g., RT18 series) are configured in the control circuits of generator cooling fans and lubricating oil pumps to prevent motor overload or control circuit short circuits.
Power plant lighting and control circuits: Miniature fuses (e.g., 5×20mm glass tube fuses) are used on the power supply side of small lighting distribution boxes and PLC control circuits to achieve "precision protection".
Excitation systems: Fast-acting fuses are configured in the low-voltage side branches of excitation circuits to protect rectifier components (e.g., thyristors) from overcurrent damage.
2. Power Transmission Link: Backup Protection for High-Voltage Lines
The power transmission link (e.g., 110kV, 220kV high-voltage lines) is centered on "relay protection + high-voltage circuit breakers". However, in short-distance high-voltage lines in remote areas, fuses can serve as more cost-effective backup protection:
High-voltage current-limiting fuses (HRC): Connected in series on the branches of high-voltage lines. When a short circuit occurs in the line and the circuit breaker fails to operate, the fuse blows quickly to isolate the faulty branch and avoid affecting the power transmission of the main line.
Features: Must have extremely high rated voltage (matching the line voltage, e.g., 110kV, 220kV) and breaking capacity (≥50kA), and be able to withstand line inrush current.
3. Power Transformation Link: Primary/Backup Protection for Core Equipment
Substations are the "hubs" of the power system, concentrating key equipment such as transformers, capacitor banks, and mutual inductors. Fuses are one of the core protection components for these devices.
4. Power Distribution Link: Protection for Terminal Distribution Networks
The power distribution link (e.g., community distribution rooms, factory distribution rooms) directly faces users. Fuses are the "last line of defense" for low-voltage distribution networks and are most widely used:
Low-voltage distribution cabinets (GGD cabinets):
Main incoming line side: Equipped with main low-voltage fuses or knife switches with fuses, serving as the primary protection for the distribution panel.
Outgoing branches: Each outgoing line (e.g., lighting, sockets, motors) is individually equipped with a fuse to achieve "fault isolation of branches"—when a short circuit/overload occurs in one line, only the fuse of that branch blows without affecting other users.
Distribution boxes/switch boxes:
Household distribution boxes: Use miniature circuit breakers (MCBs, with built-in fuse characteristics) or small fuses to protect household circuits (e.g., overload of air conditioners, water heaters).
Temporary construction site distribution boxes: Equipped with waterproof low-voltage fuses to adapt to harsh outdoor environments and protect construction machinery (e.g., welding machines, water pumps).
Cable lines: Fuses are connected in series at the cable ends or intermediate joints to prevent the expansion of short-circuit faults caused by cable insulation damage.
5. Power Consumption Link: Protection for Terminal Equipment
In the power consumption link (enterprise production equipment, residential household appliances), fuses are used for direct protection of small electrical equipment:
Industrial motors: Low-voltage fuses are configured in the control circuits of small asynchronous motors (≤5kW) as protection against motor overload and control circuit short circuits (used in conjunction with thermal relays).
Household appliances: Glass tube fuses are built into the power plugs of old small appliances such as washing machines and electric fans to prevent burnout caused by motor stalling or internal short circuits.
Electronic equipment: Chip fuses or miniature glass tube fuses are used on the power boards of electronic devices such as computer power supplies, routers, and chargers to protect internal components like chips and capacitors from overcurrent impact.