1. Problem Statement The concept of electrical life of high-voltage AC circuit breakers in China was first raised by power system users. In the 1960s, oil circuit breakers in the power grid required major overhaul after breaking three short-circuit faults. Due to poor type testing conditions and insufficient testing equipment at the time, some high-voltage circuit breakers could only undergo short-circuit breaking tests using the extension method. This meant that passing the rated recovery voltage, small current test, rated short-circuit breaking current, and low voltage test was considered equivalent to passing the rated short-circuit breaking current test at the rated recovery voltage. This method made it difficult to guarantee that the product could reach its rated breaking capacity. Furthermore, users did not record the short-circuit fault capacity during circuit breaker operation. Therefore, for safety reasons, it was stipulated that after breaking three faults, the circuit breaker was considered unsafe to operate and required major overhaul. This regulation wasted a significant amount of manpower, material resources, and financial resources. This situation persisted until the late 1970s, when China's circuit breaker short-circuit breaking type testing equipment had reached a considerable scale, and the power grid could begin recording short-circuit fault currents. Meanwhile, the Ministry of Electric Power required the development of short-circuit fault recorders and demanded that manufacturers provide methods for calculating the number of fault current interruptions of circuit breakers under maintenance-free conditions and the conversion between different interruption currents, or provide curves of the allowable number of interruptions under different fault interruption currents, i.e., the electrical life of the circuit breaker, so that the power sector could formulate and revise operating and maintenance procedures for high-voltage circuit breakers. 2. Electrical Life and Continuous Breaking Capacity Without Maintenance Electrical life and continuous breaking capacity without maintenance refer to the same event, but their concepts are not the same. Continuous breaking capacity refers to the number of consecutive interruptions or the cumulative interruption current value under conditions where intermediate maintenance is not allowed. Electrical life does not necessarily have such strict limitations. However, the electrical life and continuous breaking capacity of GIS circuit breakers and vacuum circuit breakers have the same meaning because these products do not allow intermediate maintenance or do not require maintenance within a specified period. The electrical life of air circuit breakers and oil circuit breakers can be much longer than their continuous breaking capacity because maintenance can restore these circuit breakers to their original condition. With the advancement of high-voltage circuit breaker technology, vacuum circuit breakers and SF6 circuit breakers are increasingly widely used. Although type tests can only perform continuous breaking tests, they are actually electrical life tests. To simplify language and consider common practice, the new standard refers to them all as electrical life tests. 3. Evolution of Electrical Life Tests In January 1982, the secretariat of Subcommittee 17A of the International Electrotechnical Commission (IEC) discussed three methods for characterizing electrical endurance tests: ① The United States recommended that samples be tested only at 100% of the rated short-circuit breaking current, with the electrical life, i.e., the cumulative breaking current value, at levels of 400%, 800%, 1200%, etc., i.e., 4 times, 8 times, 12 times, etc. ② Italy recommended that, considering the random combinations of various current values ​​encountered by the circuit breaker during breaking, the electrical life test should be conducted according to the scheme in Table 1. The calculation is converted to the number of breaking cycles. For example, 6 breaking cycles at 100% rated short-circuit breaking current, 10 breaking cycles at 60% rated current, 20 breaking cycles at 30% rated current, 60 breaking cycles at 10% rated current, and so on. ③ Switzerland and France recommend that the electrical life test of circuit breakers with voltage levels of 52 kV and above should be conducted according to the scheme in Table 2. Circuit breakers below 52 kV can be exempted from near-zone faults, and other items should be tested according to Table 2. The cumulative test current value is also graded according to 400%, 800%, 1200%... Table 1 shows the three electrical life test schemes proposed by Italy. These schemes all basically use 4, 8, 12… times the rated short-circuit breaking current as constant values ​​for electrical life testing. Specifically: one scheme uses only the rated short-circuit breaking current for testing; another uses methods 1, 2, 3, and 4 in a certain proportion; and the third arranges all the breaking tests that the circuit breaker should undergo in a certain order. In essence, this does not increase the workload of type testing; it simply considers whether maintenance is allowed after the cumulative breaking current reaches 4, 8, 12, or 16 times the rated short-circuit breaking current, and then retests without maintenance, to determine the product's electrical life. The starting point of this method is that contact burn-out is directly proportional to the breaking current, not a square relationship. At the IEC 17A subcommittee annual meeting in June 1982, none of the above three schemes were accepted. That is to say, electrical life testing was not included in the IEC 56:1987 standard "High Voltage AC Circuit Breakers" until 1987. Table 2. Recommended Electrical Life Test Schemes from Switzerland and France. These electrical life test data are highly valuable for operational departments. Many manufacturers, both domestically and internationally, are conducting a series of tests to determine the electrical life of their products in order to enhance their competitiveness. For example, the French company MG advertises its FA4-525 kV SF6 circuit breaker with a continuous breaking capacity of 500 cycles (various currents and operating sequences), accumulating a breaking current of 2000 kA. This is estimated to be the test requirement for this type of circuit breaker to operate continuously for 25 years without maintenance. The Swiss company ABB's ELK SP 32 (550 kV) SF6 circuit breaker can break 63 kA 20 times and 4 kA 5000 times. The French company Alstom provides the permissible breaking number curves for its HVX (12 kV) vacuum circuit breaker: 50 consecutive breaks at 100% rated short-circuit breaking current, 124 consecutive breaks at 50% rated short-circuit breaking current, and 1100 consecutive breaks at 10% rated short-circuit breaking current, etc. In accordance with user requirements, in 1985, the former Ministry of Machinery Industry, in formulating JB 3855—1985 "General Technical Conditions for 10 kV Indoor High-Voltage Vacuum Circuit Breakers" and JB/DQ 2184—1985 "General Technical Conditions for Vacuum Interruptors for 3 kV~35 kV Vacuum Circuit Breakers," specified the number of times the rated short-circuit breaking current could be interrupted: 16 or 30 times for products with a rated short-circuit breaking current of 20 kA or less; and 8, 12, or 20 times for products with a rated short-circuit breaking current of 25 kA or more. The former Ministry of Energy standard DL/T 403—1991 "Technical Conditions for Ordering 10 kV~35 kV Indoor Vacuum Circuit Breakers" specified the number of times the rated short-circuit breaking current could be interrupted: 30, 50, 75, or 100 times for products with a rated short-circuit breaking current of 25 kA or less; and an additional 20 times for products with a rated short-circuit breaking current of 25 kA or more. These standards all use the number of repetitions of the same rated short-circuit breaking current as the test standard for electrical life. As user demands for electrical life testing increased, the IEC established a working group to conduct an electrical life survey of circuit breakers in operation worldwide. The survey results showed that in actual operation, few circuit breakers actually interrupted their rated short-circuit breaking current; the majority of interrupted currents were only 10%–30% of the rated breaking current. Furthermore, ultra-high voltage circuit breakers almost never experienced interrupting their rated short-circuit breaking current during operation. Therefore, in a standard revision published in the mid-1990s, the IEC introduced the concept of electrical life for Class E2 circuit breakers: "During their expected service life, the breaking parts in the main circuit require no maintenance, and other parts require very little maintenance (for circuit breakers with extended electrical life)." The current magnitude, operating sequence, and number of operating tests for Class E2 circuit breakers with voltage levels of 52 kV and below were proposed based on probability statistics from the survey results, as shown in Table 3. Table 3 shows the electrical life test scheme for E2-class circuit breakers with voltage levels of 52 kV and below. As can be seen from Table 3, the test passes if the circuit breaker can withstand 130 interruptions at 10% of the rated short-circuit breaking current, 130 interruptions at 30% of the rated short-circuit breaking current, 8 interruptions at 60% of the rated short-circuit breaking current, and 6 interruptions at 100% of the rated short-circuit breaking current, totaling 274 interruptions. This means the breaking life meets the requirements, and maintenance-free operation is achieved in terms of breaking capacity. The China IEC Committee once suggested to the IEC working group that the electrical life test adopt the provisions of the Chinese industry standard, but the reply was that "the relationship between current and wear is not as simple as it appears and cannot be effectively converted," and therefore it was not adopted. The working group's proposed scheme was officially included in the IEC 62271-100 "High Voltage AC Circuit Breakers" standard in 2001. In 2002, the revision of my country's national standard GB 1984—2003 "High Voltage AC Circuit Breakers" also adopted this provision. It does not distinguish between product types, does not consider the length of electrical life, does not study the actual operating conditions of products, and does not distinguish between quality grades, which is no longer the original intention of proposing electrical life. 4 Discussion on electrical life test methods 4.1 Significance to circuit breaker manufacturers (1) The various arc-extinguishing media used in circuit breakers, such as oil, air, vacuum, and sulfur hexafluoride, have different performance in terms of contact burn-out during the arc-extinguishing process, and the same medium also has different performance in terms of contact burn-out due to different circuit breaker design structures. Therefore, the electrical life of circuit breakers should be differentiated by length, and a single electrical life test standard should not be used to assess all types of circuit breakers. The E2 level electrical life test standard is easy for vacuum circuit breakers to meet, difficult for sulfur hexafluoride circuit breakers to pass, and oil circuit breakers can only reach the E1 level. In addition, the electrical life of some vacuum circuit breakers can greatly exceed this requirement, while some can only barely meet it. The quality of products cannot be reflected, which limits the improvement of technical and manufacturing levels. (2) Comparison of electrical life type test costs. For a 12 kV, 31.5 kA circuit breaker, the new standard electrical life test cost is 3.17 times that of the electrical life test cost of 20 rated short-circuit breaking currents; while for a 20 kA circuit breaker, the new standard test cost is 2.83 times that of the electrical life test cost of 30 cycles. If roughly calculated according to the cumulative current ∑I2 relationship, the breaking capacity of 274 cycles under the new standard is equivalent to the breaking capacity of 21.88 cycles under the rated short-circuit breaking current, which requires twice the test cost, which is very uneconomical. Especially in China, there are hundreds or thousands of circuit breaker manufacturers, and the cumulative increase in manpower and financial resources is huge. 4.2 Significance to users (1) Users can select circuit breakers with different electrical life lengths according to the application of the circuit breaker to ensure safe and reliable operation. (2) To promote condition-based maintenance of circuit breakers, the instruments currently developed measure the waveform of the current during interruption and accumulate it using a certain weighted method (∑Iα or ∑Iαt). When the accumulated interruption current of the circuit breaker reaches the interruption threshold of the circuit breaker, an alarm is triggered. This requires the conversion relationship between different interruption current magnitudes. Some instrument manufacturers believe that contact burn-out is proportional to the square of the current (some manufacturers set α to 1.5~2.0) and incorporate it into the instrument software, which is very useful for users. Others believe that because the process of contact burn-out by electric arc is extremely complex, it is difficult to achieve the correct conversion between different interruption currents. Although many manufacturers have provided some conversion formulas or electrical life curves, they still reject this approach. To avoid this contradiction, based on actual probability, the "274-times test method" is proposed. However, such statistics change over time and with advancements in product technology, and do not truly reflect the actual operating conditions of specific installation points. In use, the actual breaking current is random. If the actual breaking current does not conform to the magnitude, sequence, and number of the 274 breaking current tests, how should this be handled, and how should the end of the electrical life be determined? To determine if the electrical life has ended, it is still necessary to find a way to determine the conversion relationship between the various breaking currents from the 274 tests, which brings us back to the problem we wanted to avoid. Without resolving the conversion relationship, the power sector cannot implement condition-based maintenance. 4.3 The Focus of Electrical Life Testing Issues We believe that the proposals submitted by various countries to IEC 17A are all quite practical, especially the US proposal, which is very close to China's. Since using different electrical life tests to classify products can reflect different quality and levels of products, allowing users to choose the products they need, implementing a premium price for high-quality products, is the most reasonable approach. The problem lies in the conversion between different breaking currents. Some believe that breaking the rated short-circuit current once is equivalent to breaking the 10% rated short-circuit current 10 times, while others believe it is equivalent to 100 times. Therefore, it was believed that the electrical life test cycles in China's industry standards were too high, much higher than the requirements of the new IEC standards. As a result, the GB 1984-2003 standard, "High Voltage AC Circuit Breakers," adopted this suggestion. Actual comparative tests also showed that electrical life testing according to IEC standards was easier to pass than electrical life testing based on 30 cycles of rated short-circuit breaking current. The appropriate number of electrical life test cycles in China's standards is still under discussion; the key is to develop a conversion method, even if it's not perfectly precise, as long as it's practical and useful to users. As for the IEC standard's provisions, from the current perspective, there are still significant irrationalities. The China High Voltage Switchgear IEC Working Group should continue its efforts and, in conjunction with other countries, propose to the IEC TC17A committee that the electrical life test should adopt the test scheme of the China Electric Power Industry Standards Committee, until the proposal is adopted. 5. Conclusion In summary, the provisions for circuit breaker electrical life testing in China's industry standards are reasonable and feasible, and have been implemented for nearly 20 years, promoting the technological progress of vacuum circuit breakers and SF6 circuit breakers in China. Therefore, they should be retained. Given the new regulations in IEC international standards, my country's national standards should also be adopted to align with international standards and facilitate product exports. To ensure that national standards are both suitable for China's national conditions and feasible, it is recommended that the provisions for E2-class circuit breakers in GB 1984—2003 "High Voltage AC Circuit Breakers" be revised according to the requirements for E2-class circuit breakers in DL/T 402—1999 "Technical Conditions for Ordering AC High Voltage Circuit Breakers." Specifically, the requirements for E2-class circuit breakers in IEC 62271-100 "High Voltage AC Circuit Breakers" and the provisions for electrical life testing of E2-class circuit breakers in the power industry standard DL/T 403—2000 "Technical Conditions for Ordering 12 kV～40.5 kV High Voltage Vacuum Circuit Breakers" should be adopted in parallel.