V. Valverde

Influence of power quality on the performance of digital protection relays

The performance of protection relays depends on many factors and needs to be carefully evaluated. One of the significant factors impacting protection system behaviour is power quality. Depending on which of the power quality parameters is distorted, the influence on the performance of digital protection relays will be different. This paper analyses the influence of power quality deterioration on digital protection relays. In the first part of the paper, the historical limitations related to electromechanical relays and the signal processing algorithms used in digital relays are outlined. In the second part, the influence of distorted waveforms on the behaviour of digital relays is analyzed. Two aspects of power quality are taken into account: harmonics and frequency variations. Additionally, several simulation examples supported by laboratory measurements are presented in order to illustrate practical implications of poor quality of power.

Dynamic line rating forecasting based on numerical weather prediction

This paper describes the line rating forecasting techniques based on NWP models. Taking the wind power forecasting as a base for the overhead line rating forecasting, the paper identifies the differences between the wind power forecasting and the overhead line rating forecasting. Recent experiences about overhead line rating forecasting are also described. As a result, the requirements for the overhead line rating forecasting are defined. Finally, a pilot project of overhead line rating forecasting is presented and the results are discussed.

DC fault detection in VSC-based HVDC grids used for the integration of renewable energies

Considering the relevance that HVDC systems are expected to have in the future of power networks, this paper aims to provide a wide overview of the protection against DC faults. In particular, the detection and location techniques that have been proposed to date are analyzed, focusing on the approaches that are set to be applied in modern HVDC networks, which comprise VSC-HVDC and MTDC systems. Although these systems present a series of remarkable advantages compared to the traditional LCC-HVDC systems, they require a fast detection and tripping of the fault, which is an important challenge in the design of the protection system.

Behavioral patterns in voltage transformer for ferroresonance detection

Ferroresonance can severely affect voltage transformers, causing quality and security problems. The possibility of appearing a ferroresonance phenomenon is mainly based on an existing series connected capacitance and a nonlinear inductance. However, factors that may influence on it are not only limited to these considerations, but also to several constructive, design, operation and protective parameters. This paper analyses the process of obtaining the ferroresonant behaviour of a medium voltage (MV) phase-to-phase voltage transformer under different operation conditions. The study is developed by software simulation in order to characterize several ferroresonant behavioral patterns of the voltage transformer. This characterization may be essential for future methodologies to detect and suppress this phenomenon, frequently regarded as an unpredictable or random.

Influence of resonant coil tuning in the fault current magnitude

This paper analyses the behavior of the resonant grounding method in MV electrical distribution systems, and its influence in the fault current magnitude. It is necessary to take into account several aspects as the specific topology of the system. Thus, a comparative analysis of different systems with different characteristics is presented. The fault current magnitude is studied for different resonant coil tuning values, and the obtained results are compared with the solid grounding method. Finally, using a real MV network, the effect of resonant coil tuning is analysed.