VOLTAGE OPTIMISATION
VOLTAGE OPTIMISATION: IMPLEMENTATION
Ian Reeves, Marketing Manager Watford Control Instruments Ltd O Fig.1
nce the decision has been taken to look at voltage optimisation as a possible energy saving measure, a professional site survey
must be completed. This will give a reasonable estimate of possible savings, which in turn will hopefully achieve the return on investment your company requires to proceed with the project. It is worthwhile remembering three important facts regarding voltage optimisation that may assist you during this process. Firstly, whichever optimiser you finally purchase, that unit within itself will not make any energy savings. The optimiser will only set the conditions for any possible saving to be achieved. Secondly, only the loads attached to the supply under scrutiny can make any energy savings. These loads are normally classified as (uncontrolled) voltage
dependent and as time progresses they are becoming fewer. It is therefore very important to the whole process that any site survey as a priority takes into account (in detail) the existing loads. Any estimate of savings without a load survey is a guess and therefore worthless. Thirdly, the optimiser that can control closest to the required specified optimised voltage and maintains it must extract the maximum savings from the appropriate loads. This does not necessary give you the best return on your investment as the cost of these units can be higher than that of a fixed reduction optimiser.
The most important element within the whole process is the site survey. If your site has a 3 phase supply, insist upon a 3 phase logging, not only of the voltage but also the current. The present practice by some suppliers of monitoring a single phase voltage close to the incoming supply for a week and then moving the logger to a 13A socket furthest away for another week, would be fine for a site with only a single phase incomer, at least you would know you are logging the same phase on both occasions. However, this practice is not acceptable for a site with a 3 phase supply. Figures 1 and 2 (from actual sites) show how ill
Fig.2
advised it is to assume that phase voltages or currents are balanced. Voltage optimisers should always be rated on maximum phase current.
A reasonable expectation of a survey would be to monitor as a minimum all voltages and currents for at least a 7 day period to obtain a week’s working profile, all site voltage measurements can then be referred back to this logging. The annual consumption profile and maximum demand can be obtained from the half hourly data. Perhaps the most critical element of the whole process is the inspection of loads connected to the surveyed supply. Identifying not only loads that can and cannot make a saving but also for “critical loads” such as high torque start motors and assessing the effects of voltage reduction on that item. There are also an ever increasing number of different types of loads, that due to their design make negligible or no savings. These loads must be catalogued by “on time”, “rating” and “duty cycle”, this forms a critical part of any estimate of savings for a site. However, in all cases equipment will generally benefit from the reduction of the supply voltages. Installation of a voltage optimiser will normally improve your power factor and perhaps harmonics but only by an indeterminable amount. These are by-products of voltage reduction and not a function of the voltage optimiser. If you have power factor or harmonic issues, seek professional assistance.
The final part of the survey is where to physically locate the optimiser, how to get into position and where to connect within the existing switchgear. Many sites now have their own generator, CHP or possibility solar power, the latter with the potential to export and all must be taken into consideration. The overall objective is that all possible issues are resolved at installation.
Once the survey is complete, the submitted report should identify any problems areas or equipment and offer a solution on how it can be resolved. Included within the report is an acceptable end of site voltage normally 216V to 220V
32 PUBLIC SECTOR SUSTAINABILITY • VOLUME 3 ISSUE 3
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