Design of Current Selective Protection in Intelligent Molded Case Circuit Breaker

Abstract:

Synthetically applied the technology of Full Current Selective Protection and Zone-Selective interlocking mainly, this paper comes up with a new Intelligent Molded Case Circuit Breaker system. Use the accurate calculation method, to achieve a good function of three kinds of current protection. By means of coordinate communication, the system implements selective trip and protection function, and improve the reliability and safety of the distribution system. Self-diagnostic function works when the system goes wrong, which extend the service life of this circuit breaker system.

• Periodical: Advanced Materials Research (Volume 544)
• Pages: 77-81
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.544.77
• Online since: June 2012
• Authors: Ya Jun Zhou, Wen Bo Chen, Zhe Chen
• Keywords: Circuit Breaker System, Communication, Self-Diagnosis, Zone-Selective Interlocking

References

[1] Where K is overloading multiples of the certain point, Ie is rated current of the object monitored and protected by breaker, and tD is action time that corresponding the current of the certain point[6] B.Stephen, S.M. Strachan, S.D.J.McArthur, etc. Design of Trip Current Monitoring System for Circuit Breaker Condition Assessment. J.IET Gener. Transm. Distrib, 2007, 1(1)89-95. . Discretization calculation formula of equation (1) is:

DOI: 10.1049/iet-gtd:20060074

[2] Where ik is sample current of point K, N is the sample point number in one period, and Δt is one sampling period. Usually action threshold judgment value is the point where the current is biggest, and the time is shortest in inverse time feature curve. Short delay protection of Short-Circuit. Short delay protection of Short-Circuit is basic requirements in monitored and protected circuit, as well as intelligent electrical of low and medium voltage. It abides by definite time protection and inverse time protection features. When the current exceeds the time limit of the largest current value, it can point off circuit breaker immediately and cut off fault source to avoid failure expanded. Judge whether the calculated current RMS is more than the short time delay current RMS protection value is the commonly way. [7] Zeng Zhe. The Intelligent Circuit Breaker Designed and Implemented Based on Modbus Bus Demo Platform. Chang Sha: Hu Nan University, 2010. Use 8Ir, as the boundary, when the instantaneous short delay current ＜8Ir , short delay protection act in accordance with inverse time lag. It meets the formula as: