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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Danka Todorovic University of Belgrade, Faculty of Electrical Engineering, Serbia
Co-authors:
Danka Todorovic (1) F P Zeljko Djurisic (1)
(1) University of Belgrade, Faculty of Electrical Engineering, Belgrade, Serbia

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Danka Todorovic is a PhD candidate at the University of Belgrade, Faculty of Electrical Engineering, Module for Electric Power Systems, where she obtained her BSc and MSc degree in 2013 and 2014 respectively. She was wind farm grid engineering Intern in GE Wind Energy GmbH during the period between August 2014-February 2015. Her PhD research interests are in the fields of renewable energy sources and wind power integration into the electric grid.


Poster

Poster Download poster (8.81 MB)

Abstract

Forecasted line rating for improved wind power integration into power system

Introduction

Modern power systems with a big share of renewable energy sources require new approach regarding real net transfer capacity (NTC) of interconnecting overhead lines (OHL). Information about the NTC between certain regions one day in advance is of a great importance for the normal market operation and optimal system planning. This could have huge impact on optimal planning of transactions and congestion management, as well as a better integration of energy from the region with large penetration of wind generation.

Approach

Energy market is usually based on demand and supply principal for day-ahead and transactions are made on hourly basis. Thus, consideration of NTC one day in advance is of major importance. This paper develops day-ahead forecasting model of OHL cooling conditions on hourly basis. It establishes new term Forecasted Line Rating (FLR), which in fact represents forecasted transmission line capacity. Estimation of FLR might be significant in terms of optimal transaction and congestion planning, as well as optimal evacuation of energy from windy regions.

Main body of abstract

NTC forecast is based on a day-ahead forecasting model of the OHL cooling conditions. Proceeding forecasted wind and insolation parameters, with respect to spatial and vertical aspect, OHL cooling conditions can be estimated on an hourly basis for the following day. Cooling conditions are not the same along the entire OHL; consequently, conductor temperatures are not the same for all spans. It is required to identify the most critical span in terms of cooling conditions. Determination of hot parts of the OHL is crucial, since they define and restrict line ampacity.
FLR model should evaluate maximal allowable OHL ampacity for each hour of the following day. This model integrates:
• Wind speed and direction forecast along the OHL at the altitude of phase conductors,
• Ambient temperature forecast along the OHL
• Solar irradiation forecast along the OHL
• Identification of the most critical span in terms of conductor heating,
• Estimation of the line ampacity, using thermal model according to the IEC standard.
Wind climatology have the greatest impact on determination of OHL hot spot, whilst other parameters (solar irradiation, ambient temperature) are usually less variable along the OHL. For certain wind directions some spans of OHL will be exposed to wake effect, whereas other might be directly exposed to wind. In order to determine parts of OHL with the lowest wind speed, it is necessary to add OHL to the vector map of orography and terrain roughness. Using software for regional wind energy resource assessment, such as WAsP, for each wind direction it is possible to determine the most critical OHL span. The most critical span is the one with the minimal convection cooling power.


Conclusion

This paper describes problems regarding congestions in transmission grid, initiated by rapid growth of demand and generation, especially from renewables. It proposes methodology for day-ahead real net transfer capacity forecast based on real cooling condition. This method is demonstrated on the example of perspective 400 kV tie-line, that should connects substation in Pančevo (Serbia) with one in Reșița (Romania). Wind forecast error is acceptable for these analysis. For practical purpose of proposed methodology, measuring devices for all wind and solar parameters should be installed in all critical spans, which would eliminate error caused by spatial extrapolation.
Simulation analysis performed on perspective OHL verified theoretical assumptions and confirmed that such system could be a basis for development of real forecasting model. Estimation of FLR might be significant in terms of optimal transaction and congestions planning, as well as optimal evacuation of energy from region with large installed capacity of wind farms.



Learning objectives
It has been confirmed that implementation of cooling conditions in OHL can significantly improve their transfer capacity. This is of special importance for OHL connecting regions with significant wind power installation, in order to forecast real NTC and improve integration of energy produced in wind power plants.