In China's economic and social development, the use of electrical energy is becoming increasingly common. Electrification is indispensable for intelligent industrial production, agriculture, national defense, and technological progress. To ensure safe and reliable application of electrical energy, power circuits must be equipped with various electrical devices (commonly called "electrical apparatus"), classified as high-voltage or low-voltage based on operating voltage levels:
High-voltage apparatus: Used in circuits above 5kV.
Low-voltage apparatus: For 50/60Hz AC circuits (rated voltage ≤1200V) or DC circuits (≤1500V), performing protection, control, regulation, conversion, and conduction functions.
Classification by Purpose and Function
1. Power distribution equipment (e.g., knife switches, transfer switches, air circuit breakers):
● Key requirements: High current-breaking capacity, effective overcurrent protection, fault response reliability, and thermal/dynamic stability.
2. Control equipment (e.g., AC contactors, drives, control relays):
● Key requirements: Moderate switching capacity, high operating frequency, and long mechanical/electrical lifespan.
DC Circuit Breakers
1. Functions:
● Load protection (long-delay), short-circuit protection (instantaneous)
● Used in solar power systems to isolate DC fault currents, protecting photovoltaic modules from reverse currents and inverter faults.
2. Features:
● Rapid closing/breaking, compact design, and user-friendly operation.
Classification by Operation Method
1. Automatic devices (e.g., control switches, contactors): Operate based on system parameters without manual intervention.
2. Manual devices: Require direct human operation.