Technical Presentations

Measurements and Simulations of Electromagnetic Transients in Wide Distribution Networks850

Abstract
This work shows the modeling of wide distribution networks for simulation of electromagnetic transients of atmospheric origin and due to maneuvers and faults. To carry out the modeling, a methodology ... see morefor automatic creation of simulation files was developed using the utility's georeferenced database. Several real events both from surges due to lightning and due to faults and maneuvers were measured in the field and compared with the values obtained by simulation.

Tag(s): scripting, georeference, database, measurements

Real Case of a Resonance in a Power Plant851

Abstract
Overvoltages were identified on the MV and LV networks of a Hydro Power Plant as the cause of the trip of the LV maximum voltage protection, compromising the normal operation of the system. Following ... see morethis event, measurements were conducted and the presence of a very high 23rd harmonic, potentially responsible for the various overvoltages, was identified associated to the operation of the Plant’s Synchronous Machine Frequency Control System (FCS). It was concluded then that this harmonic would have its origin in the FCS and would be amplified due to a possible resonance in the Power Plant internal network. A digital simulation study, using EMTP, was conducted to identify and characterize the resonance in the system and to propose mitigation solutions. The simulation models were developed using the equipment data and the system characteristics. The models were duly validated with measurements made both in time and frequency domains and it was possible to identify the origin of the overvoltages and their propagation in the system. It was concluded that the resonance occurred between a 30/11 kV Power Transformer and a 30 kV cable with 850 m.

This conclusion was supported by the results obtained in the measurements. Several alternatives were analyzed as mitigation solutions: - Installation of capacitors; - Different bonding techniques of the 30 kV cable sheaths; - Changing the 30 kV cable length; - Installation of a harmonic filter; The advantages and disadvantages of each solution were weighed also considering the ease of implementation, namely the available room. It was concluded that the installation of capacitors would be the best option. Measurements were conducted after the capacitor’s installation confirming the success of this solution.

Tag(s): harmonics, power uality, resonance

On Site Measurement and Simulation of Transferred Lightning Overvoltages780

Abstract
In this paper, three wideband transformer models are presented: black-box, grey-box and white-box. These models are validated using the transmitted overvoltage measurements at high voltage laboratory.... see more Then, the results of the simulation of the transient event recorded in 220/110 kV substation is presented and compared to the on site measurements results.

SSCI analysis: Assessment of Interactions Involving Wind Farm Systems755

Abstract
<p>This presentation provides an overview of recently proposed generic EMTP wind turbine models, which have been validated against field measurements, and a benchmark study system for th... see moree assessment of low-frequency interactions involving wind farms in radial series-compensated grids. Based on these models, detailed EMTP results are presented and modal analysis is applied to help explaining some of the identified issues and provide mitigation. Finally, a recently proposed Abstract : Recently, field events involving adverse interaction between grid-connected inverters and the existing power infrastructure have been reported. Hence, the ever increasing integration of such devices is yielding the need for detailed EMT-Type models to better understand such phenomena, as well as reliable screening methodologies for the efficient identification of potentially critical scenarios during new interconnection processes. This work provides an overview of recently proposed generic EMTP wind turbine models, which have been validated against field measurements, and a benchmark study system for the assessment of low-frequency interactions (sub-synchronous control interaction) involving wind farms in radial series-compensated grids. Based on these models, detailed EMTP results are presented and modal analysis is applied to help explaining some of the identified issues and provide mitigation. Finally, a recently proposed methodology aiming at the efficient identification of critical scenarios, namely, the DQ-Scanning technique, is outlined and its effectiveness demonstrated by its application to the aforementioned systems. Author: Aramis Schwanka Trevisan</p>

Simulation of switching Overvoltages and Field validations 754

Abstract
<p>This presentation is on the simulation of switching overvoltages on transmission lines with trapped charge, validation of EMTP line models, modeling of prestrike in statistical simula... see moretion studies and discussion of necessary simulation practices by means of validations with field tests.</p>
<p>Objectives: - Identify simulation practices to produce the field measurements en EMT simulation - Validation of line models - frequency dependence - Discussion on modeling approaches, simulation practices, sensitivity to electrical parameters - Evaluate maximum overvoltages - How to perform statistical simulations, model prestrike and include corona in statistical simulations efficiently.</p>