This project will trial MAAV in central London area that contains over 2,000km of LV underground cables along with joints. The MAAV will assess all accessible road surfaces in the survey for the presence of contact voltage faults from buried cables and accessories.
The aims of the project are:
The first survey will aim to cover all accessible carriageways in the central London Area. The “centreline distance” of the carriageways is approximately 926km and it is expected that the MAAV will have to drive over 1800km during each assessment. Any object or surface which is energised at more than 1V AC will be recorded and investigated.
The second survey will include the same coverage of the central London area using the MAAV approximately 4 to 6 months following the completion of the first survey. The second survey will identify newly generated contact voltage faults, which will be used to understand the generation rate of these types of faults in the area. The same investigation and reporting process will be followed, except for incorporating any improvements identified from the first survey and report.
The data collected will be analysed after each survey to provide a better understanding of the performance, behaviour and health of the central London network. The analysis will include an assessment of the underlying types of faults present, the root causes of the failures and the generation rate of new faults. The impact of proactive elimination of these faults will be assessed at the conclusion of the project along with the energy losses reductions achieved as a part of the programme.
Whilst contact voltage surveys have been conducted in some cities in the USA they have only once been trialled in the UK with a previous generation of the technology. The impact that system design differences may have on the efficacy of the testing using current technology in the UK is unknown. As an example many US cities use unshielded LV cables which are installed in underground ducts, while the vast majority of LV cable in the UK is shielded and directly buried. It is also possible that the electric fields associated with increased operating voltage (230 volts in the UK vs. 120 volts in the USA) will create interference which will desensitise the detector. The electrical signatures present at 100Hz and 150Hz are presently unknown and may provide for additional proactive detection capabilities in the future. Finally, an understanding of the instantiation rate of new cable faults and the underlying root causes of these faults will provide new information which will aid and improve the management of LV networks in the UK.