Demand Estimation in Planning Timescales (SPP:204):-

This Gridco document describes the Gridco internal procedure and responsibilities for State demand estimation at more than three months ahead.

Demand estimation is required to enable Gridco

• To carry out system simulation studies to meet the requirements of the Grid Code
• To prepare and submit a long term (10 years) plan to the Commission
• To make formal offers against connection applications
• To produce a yearly outage plan on an annual basis.
• To submit, on an annual basis a statement to the Commission, for the coming 5 years containing forecasts of circuit capacities, power flows and loadings, and also a commentary on those parts of the Transmission System most suited to new connections and transport of further quantities of electricity (which has been termed a Statement of Opportunity) to meet the requirements of the Licence.

Demand estimation for more than three months ahead shall be prepared based on historical data and corrected for load growth, holidays, demand shed, effects of weather etc. Computer programmes shall, where appropriate, be used to assist in the estimation process.

Demand estimation for more than three months ahead shall be prepared by the System Planning cell and for less than three months by SLDC (refer to SOP102).

The objective of this internal procedure is to enable Gridco to make accurate demand estimates on a monthly basis for the next two years, and annually for subsequent years. These estimates shall be used to conduct system studies for use in long term system and generation development purposes. To meet the objective (in compliance with section 4.5 of the Grid Code) the following steps are to be followed :

A. Prepare demand estimates from its historical data and likely domestic and industrial development.
B. Receive demands from Distcos and compare with the own estimate.
C. Differences, if any, shall be reconciled on examination of Distcos methodolgy.

Actual post-event demand shall be used to increase the accuracy of the predictions. This data shall then be used to accurately predict system demand and will eventually form the basis of a computerised database. From this graphical demand estimates may be produced with a high degree of confidence.

Both system maximum and system minimum shall be studied in order to evaluate the effects of system demand on system voltage.

Demand includes both real and reactive power data. Real power largely defines equipment ratings and reactive power largely controls voltage performance.