At present, DC feed-through networks in substations mostly use tree structures. From the battery to the station, electrical equipment is generally distributed through three levels. Most DC circuit breakers are used as protection appliances for each level of distribution. Due to the mismatch of the protective action characteristics of the DC circuit breakers at the upper and lower levels, when the DC system is running, when the power equipment at the lower level has a short-circuit fault, it often causes an overpass trip of the DC circuit breaker at the upper level, causing a power outage accident on other power feeding lines. In turn, it caused accidents in substation equipment such as high voltage switches, Transformers, and capacitors. In order to prevent the hidden dangers caused by the mismatching of DC circuit breakers and other DC protection appliances, the State Electric Grid Company has stipulated that the newly installed and operating DC protection appliances must be tested for the safety second characteristics to ensure that the performance is consistent with the design. To ensure the correctness of the DC loop differential match. Article 12, paragraph 8 of the Code for the Operation of DC Power Supply Systems promulgated in 2005 stipulates that "DC fuses and air circuit breakers shall adopt products of qualified quality, and their melting bodies or values shall be arranged and adjusted according to relevant regulations, and shall be checked periodically. Prevent the expansion of accidents due to their incorrect actions; " Article 27 of the Regulations on Technical Supervision of DC Power Supply Systems stipulates: "... The characteristics and action current checks shall be conducted before the use of the automatic air circuit breakers. "; Article 11 of the "Measures for the Prevention of Accidents in DC Power Systems" stipulates: "... Safety characteristics and action current sampling should be performed before use ...".
The safety second characteristics of DC protection appliances are generally tested in national laboratories or test stations. The equipment covers a large area and needs to be equipped with a special charging device and a large current load box. The operation is complex; Some operating units use substation batteries to test the stage difference of DC protection appliances, but they can not accurately test their current-action time characteristics. As a result, after the DC system is put into operation, the on-site maintenance and repair personnel can not check whether the safety and second characteristics of DC protection appliances meet the requirements because they do not have the corresponding testing methods and tools.
According to the reality of the DC protection electrical appliance An-second characteristic test, the company has introduced a DC circuit breaker An-second characteristic test system that is suitable for the use of substation site, easy to carry, and high degree of automation. It can provide DC protection electrical movement characteristics for the operation and maintenance department. Test means, In order to improve the reliability of the DC system operation and ensure the safe and reliable operation of the power grid, the operation characteristics of the DC protection appliances and the difference of grades are verified.
