Common Application Platform for Low Voltage Network Management

In this proposal, both laboratory testing and thermal modelling will be carried out to refine and validate the dynamic thermal
rating (DTR) algorithm for low voltage (LV) distribution transformers in order to cope with future dynamic loading scenarios
caused by dispersed generations, electric vehicles, heat pumps and etc.
A specially commissioned 11kV/0.433kV three phase distribution transformer will be manufactured with multiple optical
fibre sensors embedded in the transformer winding during the manufacturing process. This transformer will be used as the
testing object in the laboratory. Thermal rating and life assessment of a transformer are dependent on the hotspot
temperature inside the transformer. While the hotspot location is usually assumed to be near to the top position of the
winding, due to the exposure to the maximum leakage field and the high surrounding oil temperature, previous experience
has shown that this is not necessarily the case and it could be located at lower conductor positions. Therefore multiple
sensors will be installed at the top region of each winding to capture the hotspot temperature. In addition, top oil and bottom
oil temperatures inside the transformer will be monitored. Extra condition monitoring measures used by the industry to
determine the health condition of transformers, e.g. on-line Dissolved Gas Analysis Monitor (already available in the
laboratory) will be applied during the tests to provide complementary information.
The temperature rise tests will be implemented in two stages. First, prolonged heat run tests will be conducted under
multiple levels of constant loadings, such as 70%, 100% and 120% of rated loadings. The thermal parameters required in
the IEC thermal model for calculating the hottest spot temperature, can be refined based on the heat run test results.
Second, a series of dynamic load profiles obtained from the load analysis and forecast algorithm will be applied in the heat
run tests to verify the thermal model and its parameters. The developed DTR algorithm of distribution transformers would
be able to cope with future predictable and un-predictable loading scenarios in LV networks.

Electricity distribution costs account for about 16% of customer's bills. This represents the cost of providing and managing
the infrastructure needed to supply electricity to the end user. Transformers are one of the most significant elements in the
distribution networks. Consequently accurate estimation of thermal behaviour and prediction of the operating life of
distribution transformers are essential to the calculation of the charge customers pay for the use of the network.
This work, which is conducted in association with EA Technology Ltd an employee owned SME based in the NW of
England, seeks to provide a clear understanding and a validated model of the asset management implications of uptake of
low carbon technology on distribution transformers.
EA Technology Ltd plans to deploy this model as part of the asset management advice service they provide for their
customers and in particular the Distribution Network Operators who own and operate distribution transformers.
Additionally the research will be available to the Transformer Research Consortium and multiple industrial seminars at the
University of Manchester which brings together transformer manufacturers, users and their supply chain to share learning
and developments in the field. This will ensure that the learning from the project is able to be used in the design and
development of new transformers.
The PI on the project is also involved with a number of international standards bodies including: Council on Large Electric
Systems (CIGRE), the International Electrotechnical Commission (IEC) and Institute of Electrical and Electronics Engineers
(IEEE) all of whom have a role in the development and implementation of international standards and engineering practice
guidelines that the outcome of this research will feed into.