System Protection Guidelines for Systems with Inverter Based Resources: Performance of Line Current Differential, Phase Comparison, Negative Sequence, Communication-Assisted, and Frequency Protection Schemes Under Inverter-Based Resources and Impact of German Grid Code

Haddadi A., Kocar I., Mahseredjian J., Karaağaç U., Farantatos E.

Technical Report, pp.1-64, 2019

  • Publication Type: Other Publication / Technical Report
  • Publication Date: 2019
  • Page Numbers: pp.1-64
  • Middle East Technical University Affiliated: No

Abstract

Inverter-based resources (IBRs), including wind turbine generators (WTGs), have different and in some cases complex fault current characteristics compared to conventional synchronous generators (SGs). Therefore, legacy protective relays—set under the assumption of a conventional SG-dominated power system—may malfunction under operating conditions with a high level of generation power from IBRs. It is therefore necessary to study the performance of the protection system to ensure its efficiency in the presence of IBRs.

This technical update studies the impact of wind generation on the following protection schemes:

  • Negative sequence components–based protection, including negative sequence overcurrent (50Q), negative sequence time overcurrent (51Q), directional negative sequence overcurrent (67Q), communication-assisted protection, and fault identification (FID) scheme
  • Line current differential (LCD), including both the traditional and the current-ratio (alpha plane) schemes
  • Phase comparison (PC) protection, including mixed excitation and negative sequence excitation schemes
  • Rate of change of frequency (ROCOF)
  • Power swing detection

The report provides examples of misoperation of these protection schemes due to WTGs. As a potential solution to these challenges, the report studies the effectiveness of WTG negative sequence current injection based on the recent German grid code VDE-AR-N 4120 technical connection rules. Conducted simulations suggest that the adoption of the German grid code may help resolve misoperation problems in certain cases.