Abstract: In this paper, according to“25 Requirements for Prevention of Major Power Production Accidents” and “Guidance on Improving Thermal Control Protection and Automatic Device Reliability for China Datang Corporation”, key protections and interaction signals shall be determined through“two out of three” or“ two out of two” logics to improve their reliabilities. However, it is difficult for the process variables to meet the requirements by adding measurement spots on site. As a result, some correlated process variables are attempted as the signals for verification. Through the internal relationship between these signals, appropriate alarm value set for reference is added to the logics. Without any extra measuring spots or equipment, the reliabilities of protection and interaction are improved. This method is proved to be a convenient way to improve the protection reliabilities for the sites where no more measuring spots can be added.

Key words: thermal generation unit, thermal control protection, protection linkage, correlated variable verification, reliability, interaction signal, judgment logic