Voltage Reduction Analysis
| Duration | Sep 2015 - Jun 2016 |
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Project Description
Following promising results from the “Low Voltage Network Templates” LCNF tier 2 project as well as the “South Wales voltage reduction analysis” IFI report; this project looked to further investigate the effects of long term LV voltage reduction.
LV voltages must be kept within the statutory limits of 230V + 10% or - 6% (253.3V-216.2V). With minimal active voltage control beyond 33/11kV transformers and designs based on demand dominated networks, LV voltages are generally set as high as possible to allow for voltage drop along the network and ensure that voltages never drop below the limits.
However reducing network voltage can have significant benefits, particularly where there is a large concentration of resistive loads. For these types of loads reducing the voltage will reduce the maximum demand requirements and, depending on the control mechanism, can also reduce the consumption. The effect of voltage reduction on a substation depends on the specific make-up of the local load. As this is generally unknown, estimates of the benefits of voltage reduction vary drastically, ranging from consumption dropping by the square of the reduction to no drop at all.
Within such uncertainty the VRA project aimed to quantify the reaction of consumption, maximum demand and voltage profiles to voltage drop on real monitored networks. This could then ease the implementation of voltage reduction across network licensees and derive benefits to customers.
Initial analysis of voltage profiles in South Wales was conducted as part of the “Low Voltage Network Templates” trial. This showed that voltages at both substations and feeder ends sat at the higher end of the allowable range, with very few (only 0.015%) measurements below the statutory limits. As such a program of voltage reduction was carried out in the area covered, altering the AVC settings at the 33/11kV transformers. These were shifted from a target of 11.4kV (±200V) to 11.3kV (±165V), approximately 0.88%. The majority of the voltage changes occurred in November and December of 2014.
The VRA project sought to analyse the effect of this change on the monitored network through the use of statistical techniques. The analysis work was conducted by the University of Bath in late 2015 and early 2016. The results are summarised in the report below.
