The implementation of mal-operation proof operation within or between bays has become an important function of the substation automation system. A mal-operation proof method is described that consists in writing proofing rules at the workstation

equipping relay and control units with a script virtual machine

and downloading proofing rules to units. The design of a script language and its virtual machine is explained in detail. The compiling and security test of the proofing rules are realized by the back-end system.