Location of sources of voltage unbalance in an interconnected network

Identification of principal contributors to voltage unbalance and hence the implementation of suitable corrective measures has become an issue of concern for some network providers. In order to comply with stipulated limits, these network service providers require the development of quantitative measures that are reliable. For simple radial networks, the identification of sources may be seen as a trivial task. However, for interconnected networks which contain untransposed transmission lines and unbalanced loads, the identification of sources of unbalance is a non-trivial task. This paper gives a systematic theoretical approach that can be used to study the voltage unbalance behaviour exhibited by line and load asymmetries in interconnected network environments. A study network is initially analysed, and the outcomes are employed to develop a new concept termed ‘voltage unbalance emission vector’ to ascertain the overall influence made by an asymmetrical line or a load on voltage unbalance in a global sense. Using the voltage unbalance emission vectors of individual lines and loads, a technique has been developed which enables the identification of dominant contributors to voltage unbalance levels. Assessments made employing the above technique on the study system are confirmed using unbalanced load flow analysis.