Development of an Approach to Verify, Calculate and Optimise Protection Settings in a DSO Electrical Network

The Provincial Electricity Authority (PEA) operates the distribution networks up to 115 kV of all geographical regions in Thailand, except the metropolitan area (Bangkok Nonthaburi and Samut Prakarn). PEA is working together with Chiang Mai University (CMU) on a research study on the topic of "Wide Area Protection and Coordination for the Electrical Grid of PEA". In this project, DIgSILENT GmbH supplied an approach to verify the effectiveness of the existing protection settings and to identify areas where the protection scheme fails.The region considered in this study is located around Bangkok and includes more than 150 protective relays at the 115 kV level. The Protection Audit Tool of the network calculation software PowerFactory was used to develop the setting verification methodology. This tool evaluates the existing settings independently from the applied protection function by running short circuit calculations in sweeps throughout the network. In order to improve identified performance issues in the protection scheme and to optimise the selection of new protection settings for such a large number of protection devices, Python scripts were developed.This paper summarises the approach used, and presents a comparison between the performance of the original and the newly calculated protection settings.