Application of the Global Positioning System to the Measurement of Overhead Power Transmnission Conductor Sag

This article describes a method to directly measure the physical sag of overhead electric power transmission conductors. The method used relies on the global positioning system (GPS) used in the differential mode. The direct measurement of sag is a main advantage of the concept. The digital signal processing required is described in detail in a four-level configuration. Typical accuracy, response time, problems, strengths, and weaknesses of the method are also described.