Study on the possibility of designing protection system for fast and slow rising voltage surge in ring main unit (RMU) 11 kV / Abdul Fattah Mohd Mokhtar

Ring main unit (RMU) is one of the important equipment that is used in electrical ring network, which function as switching device for a network. The RMU normally employs circuit breaker with fuse or relay protection circuit. This project addresses the possibility of designing a protection system for both fast and slow rising voltage surge in the RMU by combining fuse, relay and circuit breaker into one RMU. When the performance of this equipment is increase, it will defense better against the instant or gradual destruction of electrical equipment at the load. This design of the new protection design has been simulated in MATLAB Simulink and PSpice softwares. Based on simulation results, recommendations regarding new protection design will be made. All protective devices are first simulated separately and then combined into one integrated system. The newly protection system has been examined and recommendation for future development is given. Through the simulations made, it was found out that the parameters that operate the fuse, relay, and circuit breaker are time, overcurrent, and overvoltage, respectively. The fuse has been successfully modeled and functions as per expected. On the other hand, it has been found that circuit breaker does not operate solely on overvoltage. Other factors such as recovery voltage, capacitive current and resistive must also be taken into account.