Can we say connect a single phase customer(instead of all, just a few customers in a LV Distribution network) to all 3 phases but use some sort of relay to select one at any time and then switch the customer at the customer's end to a different phase to control Voltage Unbalance?
Can we preset for certain times?
And if yes then what sort of problems we would face when switching phase? will there be a short time interval where the customer's appliances will be out of power or can we neglect that time? Or may be it is a slow transition?
Dera Karam, your question is very interesting. So far anybody has discuss this question. There is not commercial equipment for this function. I think the cost of equipment and the assembly at last is a problem.
Dear Christian, Thanks for the interest. I thought so too because I tried searching this using a multitude of different keywords but nothing brought up an answer for this. Either it is going to be a breakthrough or may be not possible at all and we are missing something. Eitherway it will be nice to know.
You are absolutely right about the cost factor but I think using this instead of expensive ESS or DSTATCOM or DG systems might be a better option or something to look into as it not only solves the problem of Voltage unbalance but will also save Labour costs when connecting new consumers to the grid as any changes required on the previous setup can be done remotely.
Yes using microcontroller it is possible and economical, refer my paper, " Microprocessor based load balance control and fault type detection...." and "Microprocessor based load shedding controller....."
Right, Prof. Dr. Desai, the Microcontroller application is very appropriate for such type of need.
We have done this as a phase swapping computer command exercise as a student project about 10 years back based on current measurements. The make- before break contacts for the contactors were required and required a tricky logic is how I remember it. However pre-set phase swapping may requite too many switching episodes, which in itself would be destructive.
I think this is possible in principle, although obviously if single loads must be individually switched, you do need to install a lot of extra cabling.
As to switching, the best way to do this, when "break before make" is infeasible, I would think, is to switch when the AC is at 0 crossing, at the two power sources you're contemplating. Microprocessor control should be up to the task. This is doable, although I've never seen the technique applied for individual loads.
Mr Desai, Mr Aung, Ms Sudha and Mr Albert, thank you very much for your time and your comments.
The reason for my late reply is that I wanted to come back with either the answer or another question to keep this string alive.
Ms Sudha you are right about it being destructive and I am trying to find what is the allowable range (voltage transients/spikes) and then try and develop a product that swaps the phase while keeping within these allowable limits.
I have not been able to completely answer the question myself yet, as it would require testing and simulations which I am currently working on. Thank you all for suggesting microcontroller, the only problem with that would be getting it past the strict Electricity distribution laws currently in place in Australia and around the world, I could be wrong as well but from my understanding, the Power industry still does not trust the electronics 'that' much. It has to be a physical switch as is the case with many devices used in the Power industry.
I do need to address something else first. As this is required before the phase switching device would come into place.
How would we able to accurately model a grid system so the voltage unbalance at the customer's end can be calculated accurately?
What if smart meter data cannot be used to calculate voltage unbalance or the fact that smart meters are not sending data as frequently as required and rather than upgrading the current infrastructure (new/upgraded smart metres and improved communications), the current system needs to be modelled accurately to get the results? How can it be done for a 4 wire grid with a neutral and several grounds (meaning a lot of the current will be unaccounted for)?
The reason this question is important is because the phase switching technique is only useful if we are able to accurately answer this question as this is how the current Grid is designed. According to my current knowledge, there is no software available at the moment which can accurately model this.
The reason this question is important is because normally the power quality meters installed on the feeders do not show a lot of voltage unbalance as it gets balanced as we move along the conductor, but, it is the voltage unbalance at the customer's end which is problematic and needs to be addressed.