Reduced DUOS Charges

A major heavy industry company in the north of England sold their manufacturing business abroad and let their workshop areas to a number of SME’s whilst retaining test and repair capability for what had been their core business. Under a new electricity supply agreement they reduced their Authorised Supply Capacity from16MVA to 8MVA. Later, they decided to apply for a further reduction to 6MVA and this was refused by the local distribution company. The project was to identify the reason for the refusal and propose a solution. Prior to a site visit, 4 years of half hourly kWh data was supplied by the distribution company but didn’t highlight the solution.

The overall site area was between 30 and 40 acres and electricity was supplied to the site from a sub-station owned by the company. There were four transformers in the sub-station, 2 x 66/11kV and 2 x 66/6.6kV. The 6.6kV network supplied a series of transformers serving the original manufacturing workshops; the 11kV network supplied the retained test facility. During the site visit it was explained to the facilities manager that portable energy monitoring would not be feasible at the point of supply and it was agreed that the HV metering of the four transformers would be read on day one and again 24 hours later. Also, it was agreed that 12 months electricity bills would be supplied for analysis.

On day two, when the meters were read, the chief engineer queried why the 11kV meter showed 600kWh usage over the 24 hours when the test facility had not been used. Subsequently, it was decided this was due to transformer losses.

The billing information was collated and analysed; the monthly consumption/demand data indicated that there were months when the kW and kVA demand coincided with power factors of less than 0.7 and maximum demand exceeded 8MVA. This identified the reason for the application being refused. A history of the test bay operation was requested from the company, this confirmed that the poor power factor coincided with test bay operation and it was identified that, although there was power factor correction (PFC) on the 11kV network, it was either insufficient or had failed. The recommendation was for this to be tested and repaired or 6.5MVAr of power factor correction installed.

A further application to the local distribution company was agreed, resulting in savings of £50k per annum.

DUOS Charges HV Schematics