Network Reduction

Main Features

There is often a need to pass data between power analysis models to allow users to account for the effect of adjacent networks on their own network. For instance Distribution Companies need to provide the detailed information about the effective infeed from their networks to both external and internal customers.

National Grid Company - On an annual basis there is a NGC requirement to ensure that fault level and load flow studies can be performed accurately and reflect actual system conditions. This means that system data and suitable equivalent networks must be passed to NGC to allow proper system studies to be performed. Similarly NGC will provide the necessary data to allow Distribution Companies to model their network correctly. In cases where Distribution Companies run their Grid Supply Points either with solid or switchable interconnection at, for example, 132kV the facility provide by network reduction to calculate equivalent networks is especially valuable.

Customers and consultants - Enquiries for information which allows customers to calculate fault levels on their networks. In cases where customers have more than a single point of connection the facility to provide equivalent networks is especially beneficial as it can significantly reduce the amount of data a customer requires.

For large networks spanning a number of different voltage levels such as 11-33-132kV the size of the system model required may hinder the effective running of studies. For instance many companies model their 11kV system separately from their 33kV and 132kV networks. Under such circumstances it is essential to pass equivalent data between the two models to allow accurate system studies to be performed. For example where substations of 33/11kV voltage have parallel connections to the 11kV system deriving suitable equivalent infeeds is complex and a facility to carry out such reductions automatically is of benefit in terms of time and accuracy.

Under such circumstances for a real power system the amount of information required to allow accurate studies to be carried out can be considerable. Indeed it may be preferable to use reduced equivalent networks. These can have several advantages

	Reduced or equivalent networks contain far less data and are hence easier to transfer to another system
	Updating an equivalent network to account for changes on the real system is less complex
	The smaller the quantity of data that needs to be transferred between models reduces the risk of any errors occurring
	Analysis tools may have limits on the maximum number of nodes etc. that they can accommodate. A network reduction can provide an equivalent network requiring very few nodes thus allowing user's to accommodate any limitations in their computing facilities
	Distribution Companies will want to protect its competitive and commercial position and the ability to provide a network reduction equivalent rather than full detail of the actual system is essential.
	By reducing parts of very large networks to an equivalent enables analyses to be performed faster and more effectively than by using a full model

Other Features

	Selection of retained nodes by graphical means
	The facility to switch out manually parts of the network not required for inclusion in the reduction allows maximum flexibility to users
	The ability to select the type of machine impedance used in the reduction is essential when carrying out studies using IEC909 or G74 methodologies
	Optional inclusion of Loads, Shunts, Motors and Line Charging allows user's to account separately for these effects. This is necessary when deriving equivalent data for use in load flow studies