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TNEI Designs Two New Analytical Software Tools for Northern Ireland Electricity

21 April 2009

TNEI's power systems team is working on a two phased programme to provide power systems analysis for Northern Ireland's electricity network operator.

The team is developing bespoke analytical tools that will allow Northern Ireland Electricity (NIE) to model its system more closely and develop a better understanding of how it operates currently and in the future with increasing amounts of energy being generated by wind farms. This greater knowledge will facilitate the connection of even higher penetrations of renewable generation and at the same time improve operational efficiency and security.

Phase one of the programme sees TNEI's team of power systems experts developing software to model the complex network of Special Protection Schemes, SPS that NIE operates. These SPS operate during abnormal system conditions and allow continued operation of the network by switching off, or constraining the output of generators or wind farms.

As NIE's system has become more complex with increased levels of generation, particularly from renewables, so too has the range of Special Protection Schemes. To enable the grid operators to assess how the whole system interacts and how new forms of power generation could be brought on-line, TNEI is developing software that will model the protection schemes individually and analyse how they interact. The software will identify the domino effect that may be triggered if one scheme is activated and will allow NIE to streamline its analysis of the whole system.

This requires a different approach to the modelling of the system and a multi-step load flow technique is being developed to handle the long simulation times and wide range of studies required. The software will allow the schemes to be modelled using commercially available power systems software such as IPSA+ or PSSe.

Greater knowledge and understanding of the system will enhance the design of new protection schemes and how they interact with the existing SPS network.

TNEI is one of only a handful of companies internationally to provide this type of software development and analysis service and will be working closely with NIE during the development period.

Phase Two – Probabilistic network assessment

TNEI is working with NIE on another innovative modelling and analysis project to develop a method of assessing network security for a power system with a significant wind penetration.

Traditionally, network operators design their systems to factor in the most onerous operational scenarios to ensure that the network covers the worst possible eventualities. However, this can result in the creation of overly complex and costly systems with excessive functionality and network reinforcement, especially for systems with a significant wind penetration.

TNEI is developing an innovative modelling tool that will allow NIE's whole network to be assessed including the probability of certain scenarios occurring. The modelling tool will create a statistically representative set of scenarios covering system uncertainties including wind power and demand fluctuation and unit availability with a high degree of certainty. Network security analysis will be carried out for each scenario to assess both the severity (for example required wind power curtailment to ensure that branch flows do not exceed their ratings) and their probability.

From this analysis TNEI hopes to assess the required wind power curtailment, identify the network bottlenecks and determine where reinforcements are both economical and needed to accommodate various level of wind penetration.

Using TNEI's new modelling device, NIE should be able to inform wind developers on the estimated annual wind power curtailment and help NIE's network designers to prioritise network reinforcements and ‘optimise' corresponding outage planning.

TNEI has already submitted a methodology report to NIE and is hopeful that the implementation will be completed by the end of July.