Unsynchronized Phasor-Based Protection Method for Single Line-to-Ground Faults in an Ungrounded Offshore Wind Farm with Fully-Rated Converters-Based Wind Turbines

Abstract

This paper proposes a protection method for single line-to-ground (SLG) faults in an ungrounded offshore wind farm with fully-rated converter-based wind turbines. The proposed method uses the unsynchronized current phasors measured by unit protections installed at the connection point of the fully-rated converter (FRC)-based wind turbines (WTs). Each unit protection collects the unsynchronized current phasors from two adjacent nodes and synchronizes them by aligning the positive-sequence current to the same phase angle. The faulted section is identified by comparing the phase angles of the synchronized zero-sequence currents from adjacent nodes. Simulations of an ungrounded offshore wind farm with relay models were carried out using power system computer-aided design (PSCAD)/ electromagnetic transients including direct current (EMTDC).

Frequency-Dependent Pi Model of a Three-Core Submarine Cable for Time and Frequency Domain Analysis

“…This feature allows the inclusion of the cable model with the mathematical description of other power components (such as transformers, filters, power converters including their control loops and harmonics, and others). Thus allowing the creation of a global analytical model of scenarios such as onshore and offshore wind power plants [32,33], electrically propelled vessels [34,35], electric railways, electrical grids [36] and many more, in where different types of cables and elements are presented. With this modeling approach, different valuable studies can be performed in order to obtain a higher understanding degree and contributing to the analysis and results presented in the previous references, which consider cable models at power frequency and neglecting their frequency dependent behavior.…”