Power conditioning

The first question is what kind of loads do you want to protect, computer or active machines that must be maintained at al times? What is the kw value of the loads supported? Are loads 50 hz or 60 hz and do you need frequency conversion? Is the enviroment capapable of operating a battery plant or is the area to hot for batteries. Do you have multiple "like" Power sources available that may not go down at the same time? And the most important can you accept the 5% outage time that may be effective upon completion of the project?

Dear Sir's

although these papers are for aideas

please whatever information or discussion it should have a schematic, because there is no circuit diagram it is deficult to under stand for me

Abdul Majeed Awan

Dear Sir,

I feel it is essentially to design entire circuit to protect against voltage interruptions, Over Volatages, Harmonics,Variation and fluctuations and finally unbalance. We may have to consider all instantaneous, momentary and temporary disturbance(dt and dv)

I do not feel we can get best quality of power unless we have good stability of the system.

The selection of UPS also plays very important role for better quailty.

Regards,

Hareesha

Yes, poor power quality lead to not only power loss but also to frequent plant shutdowns/ breakdowns. CEOs simply procure cheap machinery with built0in VFDs etc, and the maintenance people are made busy to rectify. Particularly in developing countries the problem is very high. I know few manufacturing units that are running with ITHD up to 42%. They struggle (wakeup) whenever their PF capacitors fail and penalized for poor PF maintenance. Harmonics problems cannot be solved in isolation or in vacuum. The solutions involve designing of proper filtering circuits and needs to be maintained on day-to-day basis depending upon the varying plant load conditions. One best method is ACTIVE filters, but they are very costly. Cheap are Series blocking or parallel filtering.

The quality of power is very important requirement for CNC machines , computers , modern sophisticated machines with robotic , computer and electronic controls . In USA what I have experienced is UPS and Voltage stabilisers are a formality rather than necessity as I have not experienced any power failure or voltage fluctuations. The only major power failure I came across was that of NY and NJ during summer of 2006 and that too only in residential area due to cable fault and the entire state reacted with war footing actions .So this problem is not very much applicable there. I do not know about the conditions in Europe or Middle East countries. But In India definitely it is a big issue. where power failure and frequent planned and un planned power shutdown is routine.Voltage and Frequency fluctuations and harmonics are another problem faced there. There power conditioning is very essential for breakdown free working of plant and machinery.When ever I used to finalise electrical specification for ordering machine tools and process plant specially from Developed countries either the manufacturers were asked to incorporate power conditioning and isolation transformers for controls and systems where good quality power is required . If they are not able to provide that ,then depending up on capacity and requirement Voltage stabilisers and UPS are ordered Indigenously before erection of the machine or plant.

In general it is always advisable to Install Automatic Voltage regulators with harmonic suppressors and Power factor correctors at substations if finance is available. It will help save recurring loss in power bills. Redesign your substations and power distribution by Installing automatic power factor correctors , Voltage stabilisers ,Providing proper size of cable and appropriate voltage ,and duplicate feeder for distribution with bus couplers.It will reduce your in house breakdowns and down time. The cost of initial expenditure can be recovered in five to six years from power saving .Providing hundred percent standby in house generation will be very costly .It is cheaper to provide UPS and diesel MG sets for machines and installations where ever interruption free power is required.

The harmonics will not be reduced, if you add the ups in the system.Because, ups is also one of the equipment to create harmonics, due to more electronic componants.This improvement is possible by the provision of harmonic suppression on each UPS.I have recorded the percentage of harmonics with & without UPS on the supply side and load side.Hence the all the manufacturer of UPS should introduce the device to reduce the harmonics.I am telling about the harmonics only.The outages is not considered here.

Mr. G Swaminathan

You are right Use of any electronic oscillators produce harmonics .But we have to use them when required. So Harmonic suppressor has to be incorporated with those equipments to have quality power. Thanks and good day