Applications of precise time in electrical transmission and distribution systems

An electrical power transmission and distribution system can spread over many square kilometres. For stable and efficient operation, all nodes of the system are required to operate at the same frequency (50 or 60 Hz dependent upon the country) and must be held in synchronism with each other. However, dependent upon the electrical parameters of a circuit connecting two nodes (buses) many kilometres apart and on the instantaneous energy transfer, the peak voltage at the sending end can occur several milliseconds before the peak at the receiving end: a phasor difference of up to 40° can exist between the ends. The measurement of this phasor difference can be helpful in determining the state of the power system at any instant. It can be achieved by using a common time reference from the GPS. Another application of a precise time signal is in location of faults within a circuit. A short circuit on an overhead transmission/distribution line or cable will propagate a surge in each direction along the circuit which can be detected at monitoring points (usually located in a substation). By recording and timing the receipt of this surge with sufficient accuracy, its initiating position can be estimated. The authors describe these applications of precise timing in more detail