System fault simulation studies combining cost-benefit analysis have been undertaken to determine the optimal substations in which to install the Discos sensors. To achieve the benefits required, some 500 substations will have Discos sensors that operate in the Type A sensor system mode and a further 660 substations that operate in the Type B sensor system mode.

In addition to improving quality-of-supply statistics, the access to on-line load measurements on the MV lines has an impact on long-term planning of the network, especially for radial distribution networks with tapered cable cross-sections.

Traditionally, on-line measurements were only available at the source end of MV feeders. The load distribution along the feeder is estimated using the energy consumption from each MV/LV substation. This method assumes that the peak load occurs simultaneously at all substations and depends on correlating customer energy consumption and peak load. The uncertainties meant it was difficult to locate the network hot spots, resulting in unnecessary investment and “hidden” network capacity.

The Discos system for three bays, two MV circuit bays and an MV/LV transformer is approximately 4000 euros, depending on the quantity purchased.

FURTHER DEVELOPMENT

Currently for DONG Energy, the Type A and B Discos systems are set up to provide current, voltage and power measurements every 10 minutes. In 2008, DONG Energy implements the Smart Power Grid IT (SmartPIT) solution from IBM to:

• Collect and analyze the on-line data from the Discos systems for some 20% of all substations

• Evaluate an on-line state estimation of the complete MV network

• Interface with DONG Energy's long-term planning tool NEPLAN.

The variation in calculated line-load profile is reduced as an increasing number of measurements are introduced into the computed estimation. Business case studies undertaken on network reinforcement confirm that approximately 80% of reinforcements can be avoided when the actual load data for individual circuits is available. The SmartPIT solution also forms the basis for short-term load and production forecasting, allowing DONG Energy to make use of the network components' inherent overload capability in the future.

DONG Energy approached distribution network automation by seeking a solution that would offer benefits throughout the business and be suitable for retrofitting to all the existing distribution equipment, irrespective of age. Operational experience with commercially available solutions proved only a limited success, so the utility has invested in an automation system, based on fiber-optic sensors, that is now being installed.

The plan is to automate more than 1100 MV/LV substations on the Northern Zealand distribution network. DONG Energy plans to install more than 300 units by the end of 2008. Planned further stages of development include data processing that seems set to offer the utility benefits in the form of reduced investment on network reinforcement to offset against the capital invested in system automation.

Peter Vinter received his MSEE degree from the Technical University of Denmark and joined DONG Energy Sales and Distribution 11 years ago. As a power grid specialist, Vinter has held several positions in the company, including transmission and distribution operations, planning, maintenance and SCADA/DMS supervision. Currently, he is responsible for establishing the strategies and implementation plans for distribution automation on DONG Energy's medium-voltage system and low-voltage network. petvi@dongenergy.dk