Basil C. Papadias

Simulation of long transmission lines energization for black start studies

In this paper the energization of a transmission line, a phenomenon particularly related to black start studies, is simulated using the Electromagnetic Transient Program (EMTP). The effect of several parameters, such as the line models used in EMTP, the line transposition, the existence of a surge arrester and the transient behaviour of the synchronous generator are investigated.<<ETX>>

Operation and control of island systems-the Crete case

In this paper, an advanced control system for the optimal operation and management of isolated power systems with increased renewable power integration is presented. The control system minimises the production costs through on-line optimal scheduling of the power units, taking into account short-term forecasts of the load and the renewable resources. The power system security is supervised via on-line security assessment modules, which emulate the power system frequency changes caused by pre-selected disturbances. For each of the above functions, a number of techniques have been applied, both conventional and AI based. The system has been installed in the dispatch center of Crete since June 1999, and is under evaluation.

Control of shunt reactor inrush currents in the Hellenic-Interconnected Power System

Transients caused by shunt reactor switching have been an important parameter in the design of the relevant equipment (reactor, circuit breaker, insulation) of the Hellenic-Interconnected Power System. Next to the well-known damaging overvoltages produced by shunt reactor de-energization, high dc components of inrush currents with low damping factor have been observed during energization, resulting in excessive electromagnetic stresses to the windings and undesired activation of zero-sequence current relays. In the present study, inrush currents produced by shunt reactor energization are analyzed and the performance of the techniques used for their limitation is investigated.

Three phase transformer modelling for fast electromagnetic transient studies

In this paper the overvoltages produced by switching the primary side of reactor loaded transformers are simulated using the Electromagnetic Transients Program (EMTP). Attention is focused on transformer modelling. Five general three-phase transformer models are used and from the results obtained, and comparisons with field tests, positive conclusions concerning the reliability and the accuracy of these models in the study of switching fast electromagnetic transients are drawn. >

Application of a deep level knowledge model to dynamic behavior analysis of power systems

The feasibility of power system dynamic analysis using qualitative reasonings with deep-level power system structure models is demonstrated. State transition models of the power system network components are developed to encode deep-level power system expert knowledge into the computer. The dynamic behavior of the system is then analyzed using this knowledge. The developed computational method is used to analyze the dynamic behavior of the Hellenic transmission system. Both the transient stability data and the acquisition of knowledge relevant to reasons behind problems affecting system stability can be ascertained. >

The effects of ionization in wind turbine grounding modeling

In this paper, the effect of soil ionization due to lightning strike on wind turbine grounding electrodes is investigated. The developed ionization model is validated and subsequently used to investigate the influence of several parameters on the phenomenon studied, namely, the soil type, the electrode type and the crest value of the impulse current. All simulations are performed using EMTP computer program.

Fuzzy Clustering Applied To Transient Stability Evaluation Of Electric power Systems

The objective of the paper is to present a method which can be used to evaluate rapidly the transient stability of an electric power system. The stability evaluation is performed by using a fuzzy pattern recognition approach, incorporating fuzzy membership values for the system operating states. These values classify the operating states into the defined fuzzy sets representing the class of either the stable or the unstable states. The memberhsip evaluation is performed by considering the lack of a known mathematical expression for the membership values and by using the fuzzy ISODATA clustering algorithm. The developed computational method is applied to evaluate the transient stability of a sample electric power system.