涉外合同中要求因火电厂机组能够小岛运行，这对机组的可靠性提出了更高的要求。针对印度Sagardighi电厂300 MW机组调试过程中因逻辑缺陷造成的问题，包括小岛运行中再热器超压、低压旁路阀频繁开启关闭、低压旁路喷水调节阀频繁动作、调节品质差、高压旁路喷水隔离阀在关闭之后又重新开启等，提出一套新的旁路系统逻辑。实践表明，采用改进后的旁路系统逻辑使上述问题出现的概率显著减少。

It is required that power plant units can run in island operation in the contract with a foreign element, which is a strict requirement for the safety of units. During the commissioning process of India Sagardighi 300MW power plant unit, there were many problems due to the existing logic limitations, such as reheater overpressure in island operation, frequent action of spray water adjusting valve in low pressure (LP) bypass, poor regulating quality, spray water isolating valve in high pressure (HP) bypass opening without command, superheating in turbine with reheater overpressure, and turbine trip with high HP exhaust temperature. In order to solve these problems, a new logic for bypass system is put forward. The practice shows that the application of the bypass systems logic can significantly reduce the probability of problems in island operation.