Keywords: 
• module selection /
• computer-based five-preclusion interlocks system /
• key-replacement interlock system /
• distribution networks

Abstract: There are two types of five-preclusion interlocks in power system at home and abroad. Almost all other countries except China are using key-transfer type of five-preclusion interlocks. Being fully understanded the actual situation of the two five-preclusion interlocks and model selection has been our focus. In this investigation we listed essential shortcomings of microcomputer based on five-preclusion interlocks, introduced the working principle of two kinds of five-preclusion interlocks, pointed out that the key-transfer type five-preclusion interlocks have the characteristics of simple structure, clear logic, non-electronic components, completely maintenance free, which have been using in all domestic nuclear power plants, all pumped storage power stations and representing the trend and development direction of five-preclusion interlocks technology. We also listed examples of installation key-replacement type five-preclusion interlocks. The results show that the key transfer five-preclusion interlocks is obviously better than computer-based five-preclusion interlocks for power distribution network and power plant.This work provides some guidance for selection of any five-preclusion interlocks.