Tuesday, December 11, 2007

Automation to Optimise Network Configuration in Real Time - to Optimise DG Contribution and Reduce Losses

The Distribution Working Group of the Electricity Networks Strategy Group (ENSG), – the United Kingdom Electricity Supply Industry focus group for electricicity network issues, commissioned a study to undertake an investigation and report on "Automation to Optimise Network Configuration in Real Time – to Optimise DG Contribution and Reduce Losses". The contract was awarded by Department for Business, Enterprise and Regulatory Reform (BERR) to the Institute for Energy and Environment at the University of Strathclyde in December 2006 with the final project report (click here to download) delivered now in November 2007.

The objectives of this work were to investigate the potential for network automation to:
• Maximise utilisation of distributed generation by assessing whether network automation can allow a prefault configuration that maximises generation output whilst allowing a post fault configuration that preserves network security
• Reduce network losses by reducing the constraints on prefault configuration to take account of post fault loading
• Identify the most promising automation solutions by using network simulations
• Specify a field trial

Two actual networks were used to simulate the impact of using network automation. There were several key assumptions in the work:
• A suitable communications infrastructure exists
• That transformers, cables and overhead lines all have emergency ratings
• That overcurrent protection does not operate for these post fault ratings
• Fault level issues were ignored
• That there are no restrictions on reverse power flow through transformers

A series of simulation were undertaken to assess the configuration that maximised generation output and reduced system losses whilst allowing network automation to reconfigure the network post fault to maintain system security.

The results of simulation studies have demonstrated that DG helps to reduce losses under high demand conditions but – if exports back to the grid can be tolerated on the network in question – operation of DG increases losses when demand is low. This result of this project has provided some quantification of the effect on losses, something that is rarely available in the existing literature. The results also confirmed that the contribution of DG can be significantly improved by the use of emergency ratings on circuits and automatic post-fault actions – mainly DG power output trimming or tripping of the generation – to restore loadings on overhead lines in particular to back below normal ratings after a fault outage. For high post-fault loadings on transformers up to their emergency ratings, automatic actions are less necessary due to there being more time available for corrective action (the emergency ratings being assumed to be applicable for up to 24 hours). One open question concerns the degree of tolerance for post-fault loadings on transformers above the emergency ratings for very short periods, e.g. 1-5 minutes. This is something that might need to be considered further.

It has been demonstrated that some moderate – but, over the course of a year of operation, potentially significant – reductions in losses for a given demand and a given level of DG output can be achieved with appropriate reconfiguration of the network. This suggests that further exploration through field trials may be worthwhile. Guidance has been offered on what the requirements of such a field trial should include. However, it should be noted that the full benefits depend on automation – mainly tripping or trimming of DG output – which may not currently be possible given contractual arrangements for existing DG. On the other hand, it has been shown that it cannot be generally assumed that increased penetration and utilisation of DG will lead to reduction in losses. It depends on the nature of the network in which the DG is located, where it is located within that network and the level of output of the DG at different levels of demand throughout a year.

Through the results of this study and those reported elsewhere, it has been argued that distribution network automation is now technically feasible and has the potential to be extremely cost-effective for the accommodation of increased levels of DG. However, unless appropriate commercial and regulatory arrangements are put in place to incentivise the appropriate actions by network operators and contracts with DG operators, it is not certain that the benefits will be realisable. Moreover, while such commercial and regulatory arrangements remain under development, it will not be possible to undertake a full and accurate economic appraisal of the benefits of distribution network automation. Resolution of these commercial and regulatory arrangements should now be regarded by those interested in DG as a priority.


Other posts related with this issue posted in this blog
February 02, 2007
Profiling and Mapping Intelligent Grid R&D Programs
March 05, 2007
Distribution and Microgrids.
March 30, 2007
MicroGrid Control System Implemented in CHP Product
May 14, 2007
GridWise Architecture Council Offers Interoperability Checklist.
August 29, 2007
US Legislation on Smart Grids
August 31, 2007
Global Talent to Develop the Smart Grid
November 15, 2007
Smart Grid Standards Are Being Set
November 29, 2007
Decoupling to Promote Energy Efficiency

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