In power grids, circuit breakers are crucial components of switches at all voltage levels. Their sensitivity and reliability in opening and closing determine the safe and economical operation of electrical equipment at all levels. I. Basic Information on Circuit Breaker Operating Mechanisms Circuit breakers achieve their preset objectives by changing the direction and point of force through the transmission components of their operating mechanisms. The energy source is generally either electricity or human power. Besides human-powered mechanisms, electromagnetic, pneumatic, spring, and hydraulic mechanisms all rely on the work done by electricity, using the instantaneous release of energy to achieve the circuit breaker's action. Looking at the new equipment used in rural power grid upgrades, although components have been improved, there haven't been any major breakthroughs. Problems such as too many operating links and lubrication issues lead to inefficiencies in the mechanisms, and wear and damage to components can also occur, resulting in a high failure rate. Based on recent practical experience and field operation, operational mechanism failures account for the largest share of circuit breaker failures, approximately 80%, and among these, operating mechanism failures make up the vast majority. The main reason for this is that the operating mechanism is in a static operating state, and the working status of its various active links cannot be monitored, making it impossible to detect potential problems in a timely manner. This is especially true for outdoor equipment, which is more prone to failure due to environmental conditions. Therefore, optimizing the structure of the operating mechanism, using new materials and processes for components, and improving processing precision are long-term tasks to eliminate existing defects. II. Basic Requirements for Operating Mechanisms Since the effective and reliable operation of a circuit breaker largely depends on the performance and quality of the operating mechanism, the operating mechanism should meet the required properties and reliability, depending on the type of circuit breaker. The main points are as follows: 1. The operating mechanism should have sufficient closing capacity. In actual operation, the energy of the operating mechanism will not remain at the rated value but will vary within a certain range. According to the original departmental regulations, the lower limit is 80%-85% of the rated value, and the upper limit is 110% of the rated value. That is to say, at the lower limit, the operating mechanism should be able to close and short-circuit currents, while at the upper limit, it should not damage related components due to excessive operating force. 2. It should have a closing retention function. When the operation command duration and operation function coordination are short, a closing retention mechanism should be provided to ensure that the circuit breaker remains in the closed position after the closing command and operation function disappear. 3. It should have a short opening time. The opening time should be independent of the operator's speed and the length of time the command is issued. At a minimum, the opening speed should not allow arc reignition, i.e., the opening time should be shortened as much as possible to reduce the duration of short-circuit faults, thereby improving the stability of the power system and minimizing the fault range. 4. It should have an anti-jump device. To prevent the circuit breaker from repeatedly opening and closing after closing, mechanical or electrical methods should be used to prevent the circuit breaker from arbitrarily opening and closing after opening, thus reducing unnecessary actions. 5. A linkage device is necessary in the operating mechanism to ensure the reliability of the circuit breaker. This ensures that the circuit breaker is not affected by malfunctions of the operating mechanism when it is in a certain state. Generally, the operating mechanism should have interlocks for the open position; low-pressure and high-pressure interlocks; and position interlocks in the spring mechanism. III. Advantages and Disadvantages of Various Operating Mechanisms 1. Manual Operating Mechanism: The opening and closing speed depends on the amount of manpower and the operator's skill level. In other words, reliability varies from person to person. If there is a latent fault in the system, excessive electric force or too slow closing speed may cause the circuit breaker contacts to melt or even explode, which is very unsafe. 2. Electric Energy Storage Spring Mechanism: Advantages: Fast opening and closing speed, low motor power, can be used with both AC and DC. Disadvantages: Complex structure, many parts, high precision requirements. Suitable for operating medium-voltage circuit breakers, especially suitable for small-capacity power distribution systems. 3. Pneumatic Operating Mechanism: Advantages: Fast action, stable operation, low DC power, can still operate several times even after a short power outage. Disadvantages: Higher price, stricter manufacturing requirements. Applicable to both high-voltage and medium-voltage circuit breakers. 4. Electromagnetic operating mechanism advantages: simple structure, reliable operation, and low manufacturing cost. Disadvantages: high power consumption of the closing coil, easy damage to components, bulky structure, and long closing time. IV. Principles for Selecting Operating Mechanisms for Circuit Breakers Comparing the above types of operating mechanisms, their performance varies, but considering operational reliability requirements, electric energy storage operating mechanisms are the future direction. Applicable to medium-voltage circuit breakers, especially suitable for circuit breakers in small-capacity power distribution systems. Pneumatic mechanisms are suitable for medium-voltage, high-voltage, and ultra-high-voltage operating circuit breakers. Pneumatic operating mechanisms are being phased out. For renovated substations, the selection scheme should be proposed based on the existing AC/DC power supply capacity and the requirements for the characteristics and reliability of the circuit breaker. For newly built substations, the selection should be made after comprehensively considering the design requirements, the importance of the circuit breaker's actual function, the requirements for its characteristics, and various other factors. In summary, when selecting an operating mechanism, it is advisable to choose a similar circuit breaker from within the same voltage level available in the unit. Furthermore, products with optimized mechanisms, flexible and reliable operation, and promising future development prospects should be selected as circuit breaker accessories. Since there are various energy sources for the operating mechanism, the reliability of the energy source directly affects the safe operation of the power grid after the circuit breaker is operated. Therefore, a power source with sufficient capacity and high reliability should be selected first.