A systematic evaluation of network protection responses in future converter-dominated power systems

Abstract

This paper illustrates how converter interfaces, used to connect renewable energy sources, HVDC links and infeeds to the power system, may bring significant changes to the behaviour of protection systems in the future. A converter model, capable of providing adjustable fault responses, is used to investigate the response of power system protection to a range of fault conditions. Different scenarios have been simulated by applying different types of faults at different location of the transmission system with a variety of different converter response types. A dynamic, verified, relay model and a hardware relay device have been injected with the simulated results to ascertain network protection performance.A summary of results are presented and it is shown that, when the system is dominated by converter-interfaced sources (especially where the sources are modeled as being unable to provide "fast" and "high" fault currents), the responses of traditional protection systems could be delayed, lose discrimination, e.g. by tripping with a zone 2 delay for a zone 1 fault, or may be completely unable to detect faults at certain locations within the system. The outcomes of the paper and further work should act as a guide for on-going investigations and assist in informing the specification of national grid codes and related work.

Advanced Protection Schemes of Modern Transmission Grids with Large-Scale Power Electronics

“…At the NSG-sided system, these characteristics include the suppressed short-circuit current [12][13][14], the possibly unstable equivalent impedance of the power source [15][16], and sometimes the severe distortion of fault current and voltage, i.e. the harmonic characteristics [17][18], etc. In general, these fault characteristics are due to the vulnerability of power electronic converters (PECs) and the inherent control pattern of PEC devices themselves, which will affect the functions of conventional protections in a certain degree.…”