Search

Rate-of-change-of-frequency (ROCOF) is one of the most popular local islanding detection methods due to its simplicity and low cost. However, the method suffers from significant non-detection zone (NDZ) and experiences security issues due to non-islanding events. In this article, an enhancement of the ROCOF relay, improving frequency estimation is proposed and compared to standard methods. Results are obtained through real-time hardware-in-the-loop (RT-HIL) simulations using an IEC61850 compliant STM32F746NG microprocessor acting as a ROCOF relay. Feasibility of the method has been proven experimentally. As demonstrated, it has an ability to significantly mitigate a number of nuisance trippings for non-islanding events. For the CIGRE medium voltage benchmark distribution network, the proposed method provided full security at the setting of 0.5 Hz/s for adjacent feeder faults, whereas the standard methods happened to fail even at the setting of 1 Hz/s. Additionally, as shown, an improvement of the relay security can lead to reduction of NDZ. [ABSTRACT FROM AUTHOR]

This paper presents a power swing detection algorithm in multi-machine power systems, which uses wide-area synchrophasor measurements and is based on Zubov’s stability boundaries. Zubov’s boundary method, an approximation of the famous Lyapunov function, is very common for numerical analyses of power system stability. This work extends the concept of Zubov’s approximation boundaries to online protection applications. First, the proposed protection algorithm constructs a series of Zubov’s stability boundaries on power angle–frequency ($\delta$ – $\omega$) plane for generators based on real-time measurements from phasor measurement units/merging units. Then, it tracks the trajectory of each generator in the $\delta$ – $\omega$ plane after the disturbance to differentiate out-of-step (OOS) conditions from stable swings. The proposed approach is suitable for online applications, which is a significant improvement over the existing methods for swing detection since it does not require offline studies and network reduction. Effectiveness of the proposed method is shown using a single-machine infinite bus and New-England 10-machine 39-bus systems. The proposed method is also implemented in a hardware-in-the-loop setup with a customized IEC 61850-based OOS relay, and performance is compared with a commercially available relay. [ABSTRACT FROM AUTHOR]