An Integrated PMU and Protection Scheme for Power Systems

This paper presents the design and development of a novel scheme for the integrated control and protection of power transmission systems. The scheme integrates local and wide area control and protection systems by implementing the WAMS function and substation protections into one system. This integrated system developed coordinates stability and emergency control, system oscillation detection and protection. Combining the functions of the PMU and the integrated protective IEDs into a central unit, the system mainly consists of three major components: (1) An interface unit (IU) responsible for measurement and control interfaces to apparatus through various types of transducers, such as the conventional CTs and VTs, optical combined sensors and electronic combined sensors. The analogue and digital signals measured are converted into optical format and sent to the central Integrated Phasor measurement and protection unit (IPP) through the redundant optical network. The unit also receives and executes control signals from the IPP through the control circuit. (2) An optical communication network interfaces not only to the IUs and the IPP, but also to a number of other equipment, such as communication gateway, human machine interface and GPS clock, etc. (3) The IPP receives measurements from all locations in the substation through the communication network and information from other related substations through the communication gateway. Equipped with the advanced algorithms, the IPP then performs all the control and protection calculations to assess the system stability based on the information derived locally and from remote units in the transmission system, to on-line determine necessary action(s) to be taken to ensure the safety operation of the transmission systems.