Application and Analysis of Synchrophasor-based Online Impedance Measurement Methods

Electricity generation from renewable energy sources can be constrained by the static thermal rating of existing overhead lines. A potential solution is dynamic line rating based on the line’s temperature. The conductor temperature can be calculated from the line’s resistance, if measured accurately and in real-time. In this paper three suggested methods for impedance determination from synchronized phasor measurements are compared: the linear, non-linear and total least squares estimators. All methods have previously been put forward for their robustness against noise in the synchrophasor measurements and for accuracy of the identified impedance. The purpose of the comparison is to assess how suitable the methods are for high accuracy applications such as temperature monitoring. The assessment was conducted by applying all three methods to identify impedance values from real synchronized voltage and current measurements. The methods performed similarly, but none was able to identify the impedance with the reliability required for high accuracy applications. The potential reasons for the inaccuracy and future work are discussed.