Evaluation and mitigation of low voltage network thermal constraints

This paper investigates the thermal constraints imposed by low voltage underground cables on the growth of Small Scale Embedded Generators (SSEGs), within Small Scale Energy Zones (SSEZs). A small scale energy zone is defined as a section of Low Voltage (LV), network with a high penetration of SSEGs, controllable loads and energy storage units. SSEZs, coupled with active control techniques, have the potential to assist the growth of SSEGs by removing network constraints and enabling blocks of aggregated and controlled SSEGs to participate more effectively in energy markets and network operational tasks. This research focuses on identifying the thermal cable constraints which may be encountered as SSEGs grow. The analysis is performed using a dynamic PSCAD/EMTDC electrical network model, with varying levels of SSEGs. The simulation results show that, at certain SSEG penetration levels, the thermal ratings of the LV underground cables may be exceeded. It would therefore become necessary to reinforce the network assets affected or to devise an active network management system which could overcome these constraints. It was found that the first cable thermal limit was encountered for a SSEG penetration level of 190% (2.2kW per household).