Abstract: This paper compares commonly used low-voltage power distribution switchgear and then, based on the characteristics of wind power generation systems, conducts a preliminary discussion on solutions for their power distribution systems. 1 Introduction With the increasing scarcity of conventional resources on Earth, the world advocates resource conservation. Wind energy, an environmentally friendly and clean renewable energy source, plays an important role in this era of energy shortage. The Chinese government has also proposed building a conservation-oriented and environmentally friendly society, providing significant development opportunities for the wind power generation industry. China has vast wind energy reserves, widely distributed, with onshore wind energy reserves alone reaching approximately 253 million kilowatts. Although China lags far behind other countries in the development level of its wind power industry, the Chinese government has strongly supported and actively promoted the development of the wind power industry in recent years. It is believed that in the near future, wind power generation in China will become one of its main sources of electricity. 2. Characteristics of Wind Power Generation Distribution Systems Compared to conventional thermal and hydroelectric power plants, wind power plants have fewer supporting facilities and fewer electrical devices. Therefore, dedicated power distribution systems are rarely provided for wind power plants, especially inside the wind turbine towers. Power is typically supplied by the 690V busbar inside the tower, stepped down by a transformer, and used for lighting, monitoring equipment, and other electrical appliances. Due to the harsh weather conditions, flame-retardant components with a wide temperature range are required. Considering the characteristics of its source, the quality of the power distribution depends on the quality of the 690V busbar and the performance of related distribution components. Compared to conventional power plants with dedicated power distribution systems, wind power generation distribution systems face higher requirements. 3. Solutions for Wind Power Generation Distribution Systems 3.1 Distribution System Principles Inside the wind turbine tower, only the 690V busbar is continuously energized, becoming the tower's power supply. Typically, the voltage is stepped down by a 690V:400V transformer before being directly supplied to the electrical equipment. The schematic diagram of the power distribution system is as follows: As shown in the figure, the power switch equipment of the entire 400V voltage level (three-phase four-wire system) plays a crucial role in the safety and reliability of the downstream power system. Selecting a switch protection device with excellent performance and matching parameters is particularly important for the safe and stable operation of the entire system. 3.2 Selection of switch equipment for power distribution system Common power distribution protection products include: miniature circuit breakers, load switches, disconnect switches, residual current operated devices, etc. Their functional characteristics are briefly described as follows: (1) Miniature circuit breakers have overcurrent protection, the ability to break loads, and a certain short-circuit breaking capacity. They have the function of isolating loads and have different tripping characteristics according to the load characteristics. (2) Load switches do not have protection functions but have the ability to break loads and the function of isolating loads. (3) Disconnect switches do not have protection functions but do not have the ability to break loads and the function of isolating loads. (4) Residual current operated devices The residual current operated device is commonly known as a "leakage switch". It has all the functions of a miniature circuit breaker and also adds leakage protection. The residual current operated device (RCD) is briefly described below for its leakage current protection function:  Working Principle: The RCD mainly consists of several parts, including a detection element (zero-sequence current transformer), intermediate components (including amplifiers, comparators, trip units, etc.), an actuator (main switch), and a testing element. All power input lines pass through the zero-sequence current transformer before supplying the load. When the protected circuit is operating normally and no leakage or electric shock occurs, according to Kirchhoff's laws, the phasor sum of the currents on the primary side of the zero-sequence current transformer is equal to zero. Therefore, the vector sum of the magnetic flux in the core of the zero-sequence current transformer is also zero. Consequently, no induced electromotive force is generated on the secondary side of the zero-sequence current transformer, and the RCD considers the protected circuit to be operating normally, the actuator does not operate, and the system operates stably. When leakage occurs in the protected circuit or someone is electrocuted, due to the presence of leakage current, the phasor sum of the currents on the primary side of the zero-sequence current transformer is no longer equal to zero, resulting in leakage current. This leakage current generates an alternating magnetic flux in the iron core, leading to an induced electromotive force on the secondary side. The signal is processed and compared through intermediate links. When it reaches a predetermined value, it energizes the shunt trip coil of the main switch, driving the main switch to trip automatically, cutting off the faulty circuit, thus achieving protection. Residual Current Operated Protective Devices (RCDs) are classified into two types according to their tripping method: electronic and electromagnetic. ① Electromagnetic Tripping Residual Current Operated Protective Devices (RCDs) use an electromagnetic trip unit as the intermediate mechanism. When leakage current occurs, the mechanism trips to disconnect the power supply. The disadvantages of this type of protector are: high cost and complex manufacturing process. The advantages are: strong anti-interference capability and strong impact resistance (overcurrent and overvoltage impact); no auxiliary power supply required; leakage characteristics remain unchanged after zero voltage and phase loss. ② Electronic Residual Current Operated Protective Devices (RCDs) use a transistor amplifier as the intermediate mechanism. When leakage occurs, the amplifier amplifies the signal and transmits it to a relay, which controls the switch to disconnect the power supply. The advantages of this type of protector are: high sensitivity (up to 5mA); small setting error; simple manufacturing process and low cost. The disadvantages are: transistors have weak impact resistance and poor resistance to environmental interference; they require an auxiliary power supply (electronic amplifiers generally require a DC power supply of tens of volts), making leakage characteristics susceptible to fluctuations in the operating voltage; and the protector will lose its protection function when a phase is lost in the main circuit.  Use of Residual Current Operated Protective Devices (RCDs): ① According to the working principle of RCDs, the power lines of electrical equipment must all pass through the primary coil of the zero-sequence current transformer of the RCD; otherwise, the vector sum of the currents passing through the primary coil of the zero-sequence current transformer will not be zero, causing the RCD to malfunction. ② For three-phase four-wire power distribution systems, if a four-pole RCD is selected, it must be connected to the input terminal of the protector regardless of whether the neutral line is used. The neutral line passing through the RCD must not be used as a protective line, and must not be repeatedly grounded or connected to exposed conductive parts of the equipment. ③ RCDs with different operating characteristics should be selected according to the different functions of the protected object. For main lines, medium-sensitivity, time-delay type residual current operated (RCD) devices should be selected; for the ends of electrical loads, high-sensitivity, fast-acting RCD devices should be selected. Based on the analysis of the performance and characteristics of each device, considering the characteristics of wind power generation system distribution, RCD devices are the most suitable choice as the main switch of the distribution system. 3.3 ABB Residual Current Operated (RCD) Devices ABB has successfully launched modular residual current devices since 1968, with nearly 40 years of history. It now offers RCD products tailored to the characteristics of different electrical equipment. Their electrical performance characteristics include: providing comprehensive protection against overload, short circuit, grounding, and leakage faults in the system. Furthermore, RCD devices with different operating characteristics are available for use with different load types. Its hardware housing features include: flame-retardant and easily decomposable housing material; in the event of a fire, the housing will burn but will not affect the normal operation of its actuators; the housing also possesses properties similar to tempered glass, meaning that after impact, it will not deform and affect the normal operation of the actuators, but will simply detach into small pieces. It has good temperature characteristics: operating temperature -25℃ to +55℃, storage temperature -40℃ to +55℃. Considering the various performance characteristics of ABB's residual current operated protective devices, they are suitable for use in wind power distribution systems. Due to the diverse load types, including both three-phase and single-phase loads, three-pole and four-pole residual current operated protective devices are required. Since the main components of a wind power system are all inside the tower, it is impossible to have dedicated personnel on duty for extended periods; therefore, the reliability of the devices is particularly important. Even in the event of an anomaly, it is crucial to minimize the subsequent impact of the accident; for example, it is important that the actuators can still operate normally after the component housing is damaged. This feature of ABB products provides a certain degree of assurance for handling anomalies. Furthermore, due to the harsh operating environment of wind power generation systems, devices require a wide operating temperature range. Therefore, the environmental adaptability of ABB's devices is particularly important. 4. Conclusion This article only provides a brief introduction to the application of residual current operated protective devices (RCDs) in wind power generation distribution systems. With the increasing market penetration of ABB low-voltage products, related product solutions will gain wider acceptance among users.