Upgrading London Underground´s generation to accommodate the changing pattern of load

London Underground´s Lots Road Power Station operators noticed a trend of increased variations in demand and system frequency. Excessive variations in frequency have undesirable effects on plant operation and, in the case of LUL, there are also serious safety implications as some of the signalling equipment is supplied by rotating frequency converters. The trend was suspected to correlate with the phased introduction of new rolling stock. Initial measurements indicated poor load sharing between the generators. It was therefore decided to investigate the problem by adopting the following procedure: measurements to quantify plant performance by monitoring electrical and steam quantities; develop computerised dynamic models of the generating units and the electrical plant; develop computerised probabilistic model of each type of traction equipment and determine the aggregate load as seen at the power station; undertake studies to evaluate the effect of the new traction equipment and the effect of anticipated changes-the latter includes greater usage of modern rolling stock with regenerative braking capability which accentuates sudden power changes; determine limitations of existing generation and possible corrective measures to improve response time, load sharing and overall system frequency stability both for the present and the future load; apply corrective measures; and verify the analysis with measurements following the completion of the corrective measures. This paper outlines each of the above aspects