Ennoidgy limited provided consultancy service to assess the prospective harmonic distortion due to the connection of the East London line to the DNO grid connection points and other relevant substations.

TfL installed three no. off new high voltage DC traction substations, with their power electronic inverters and 33 kV feeder cables. These works had a significant effect on the system harmonic characteristics and harmonic distortion levels on the grid.

These works improved the rail links in East London by upgrading the existing East London Line (ELL) from Dalston Junction station in the north to New Cross and New Cross Gate stations in the south.

Additional studies were also carried out on the possible consequences, effects, and feasibility of paralleling two major bulk supply points connected by ELL, by closing all the lines and circuit breakers adjoining the ELL substations.

Scope covered the following:

• Collected data and constructed suitable East London Line (ELL) and DNO network model on IPSA.
• Harmonic analysis involving impedance profiles and current injections.
• Presented study results in comprehensive reports highlighting problem areas where G5/4 Planning and Compatibility Limits were exceeded.
• Identified mitigation measures required to ensure compliance with G5/4.
• Liaised with DNO to assist in connection agreement.
• Studies to determine the technical feasibility of operating the ELL system network BSPs in parallel and also advice on the limitations of paralleling including day and night operation.