Managing concurrent duties and time of wireless sensors in electrical power systems

This paper presents a new method for managing concurrent duties and time in low-power wireless sensor cells that monitor electrical power systems. The method is based on the co-operation of two interrupt levels, one generated locally in every sensor that is part of the cell, the other generated as the response to a signal that is sent out by some base station. With this method very precise synchronization of concurrent duties can be achieved at a very low energy cost. The same signal can also be used to provide an accurate timestamp of events that the system will generate. Experiments show that the method is successful in the case that the duration between two subsequent concurrent duties is relatively short. For longer periods it is predicted that the deviation among clocks can cause problems. A solution to this is presented in the paper. This solution is based on dividing the duration between two concurrent duties into shorter steps that the sensors may utilize to keep the synchronization at a feasible level.