New methods for protection of future power networks incorporating high penetrations of distributed generation

Due to initiatives such as the EU (European Union) 2020 target of 20% of final energy consumption from renewable sources [1], and a target to reduce greenhouse gases from energy production by 80-95% by 2050 [2], the number of renewable generators being connected to power systems is increasing. Many modern renewable generators are inverter-interfaced [3] and many of these are being connected at the distribution level within power systems. This increase in generation at this level of the system can affect the operation of network protection, and with the continuing increase in generation, the impact on protection operation is expected to grow. In this thesis, the growing impact of inverter-interfaced generation on distribution network protection is investigated. Initially, protection problems resulting from increasing DG (Distributed Generation) penetration are investigated and the work of others in this domain is reviewed. A description of the development of an empirical model of an inverter, incorporating fault behaviour, is presented. The model is based on observations of laboratory testing and is developed to accurately model inverter fault behaviour. Three problems are subsequently considered and evaluated using simulation: protection "blinding", loss of protection coordination and sympathetic tripping. Sympathetic tripping is found to be the most 'imminent' problem and a comprehensive simulation based investigation is undertaken to evaluate the extent of sympathetic tripping for typical penetrations of distributed generation. In the latter sections of the thesis, a number of potential solutions are evaluated to ascertain their effectiveness in reducing or preventing the occurrence of protection problems such as sympathetic tripping. Firstly, it is demonstrated that sympathetic tripping can be avoided in most circumstances by modifying the settings specified in the UK Energy Networks Association's G59/2 recommendation. Secondly, the development and operation of an optimisation based technique is described - this can significantly improve the speed of protection operation and thus avoid the occurrence of sympathetic tripping; improvements in protection speed of up to 42 % are achieved with this method. Finally, a communication based blocking scheme is described which employs IP/MPLS (Internet Protocol Multiprotocol Label Switching) communication technology. The operation of this scheme is demonstrated via laboratory testing and it is shown that the selected technology may be effective when adopted within this blocking scheme. The thesis concludes with an overview of future work that is required to further advance the concepts demonstrated.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral-pg

Grantor dc:publisher.institution

University of Strathclyde

Year dc:date.issued

2013

Author dc:creator

• Jennett, Kyle I.

DOI

10.48730/m8pf-3x09

Identifier

T13469

OAI identifier oai:identifier

oai:strathclyde:0g354f213