Capacitor Bank

LT.

But my coin says HT side. What does LT mean to you?

LT = 0-1000v; HT > 1000v (where they say "tension" rather than "voltage") [?]

I don't know what the KPU (Ketchikan Public Utilities) voltage into our transformers is; but our 80kvar PF capacitors are on the 480 low voltage side, paralleled to their respective 450-hp motors.

GA

Adding: In theory, correcting the PF for the Power Utility benefit, it does not matter where you correct it as long as it reduces the losses on the distribution lines. BUT It is cheaper and easier to produce LT capacitors.

Also, usually, the LT is toward the consumer, and the PF correction must be nearest to the point where it is most consumed, otherwise, it is still feeding down the line and still produces losses upstream!

Regards.

Your points are valid but I have been working on Users systems; not on Power Suppliers; in all cases the PF Correction on LT side is the responsibillity of consumers and Suppliers ensure it on their side on HV side [In my country it is 11KV].

About GenSets I have little info but on UPS Systems we have PF Correction Module on almost all systems greater than 110KVA systems.

I agree with you as in Pakistan we see on the 11KV Poles not on Street poles distributing to houses.

Dear Sandeep, Did you calculated cable for lighting load?... Didi you have any design drawings for your project?...Are you the responsible person for designing?...

No, i have yet decided type of fixtures and lumainaires for the project

Normally consumer installs cap at LT side, they are not responsible for HT. The power supply company installs cap at HT side.

But since we have to improve power factor on 11KV side as our major load is on 11kv side, so it has been considered to install capacitor at 11KV side instead of 415V side.

I'm sure someone more knowledgeable will reply, but I can make a few observations. First, to perform its power-factor-correction job, considering impedance-scaling through the transformer, in theory the physical bulk size of the required capacitor will be the same on either side, and hence the cost the same. This is because of the scaling of the capacitor-insulation thickness, etc., and the way capacitors of different voltages but with equal stored energy tend to have the same volume. All other things being equal.

But I speculate that two things argue in favor of the secondary side. First, caps on the HV side will probably need more insulation because they're closer to HV transients, whereas the leakage inductance of the transformer limits its high-frequency response, protecting the secondary capacitors. So primary-side caps will need higher safety margins and be more expensive. And second, the transformer will experience a better power factor if you apply the correction on the secondary side, so it can have lower peak-current ratings.

Maybe they do things differently in your location, but here the electrical meters are on the secondary side, as are the PF capacitors, if any.

People here have forgotten one critical thing that I think tips the choice to putting the capacitor bank on either side of the transformer. The transformer core reluctance limits the amount of fault energy that can be transferred per cycle. So I believe the capacitors should reside on the load and not the power distribution side of the transformer. So if this transformer is stepping up the line voltage from the grid then the capacitors should be applied to the HT side.

THIS DEPENDS ON SYSTEM REQUIREMENT.

1.CAPACITOR BANKS ARE BASICALLY LOCATED NEAREST TO THE INDUCTIVE LOAD CENTRE AND IN THAT CASE IF THERE IS HT LARGE MOTORS THIS CAPACITOR BANK SHOULD BE LOCATED NEAR HT SWBD OR THERE SHOULD BE SVC UNITS.

2.FOR LT LARGE MOTORS THIS CAPACITOR BANKS SHOULD BE NEAREST TO THE MOTOR OR LT SWITCHBOARD.

3.FOR LARGE FURNACE TRANSFORMERS SAY 33KV/---V 150MVA RATINGS AND ABOVE CAPACITOR/SVC UNITS WITH PROPER HARMONIC SUPPRESSOR UNITS ARE LOCATED IN 33KV BUS ONLY.

IN A NUTSHELL CAPACITOR BANKS TO BE LOCATED NEAREST TO THE LOAD CENTRE .

Mr. Sandeep k.v,

Mr. Winfield Hill and Mr. redfred imparted their brilliant engineering knowlwdge, so you've got the perspective view to exactly where to install the capacitor/s and what capacitor bank meant to you in relevance to power factor correction. The transformers are getting its power source directly from power generating plants and need to step-up the line voltage/s into transmission lines over head system, first we installed reactor on HV 132kv side to maintain primary line currents. Again in our case here we have 5000MW power plant(PP9)(Saudi Electric-SCECO) that delivers 2.40kv and then step-up into 132kv, then steps down to sub-distribution voltage system at 13.80kv 3-phase in HV/MV substation/s. The capacitor bank are installed at 13.80kv load distribution side feed to another MV/LV substations at 13.80kv/380v-3-phase for consumers... reason why it need to install capacitor bank on load side is to maintain or correct the power factor of the line that feed to consumers/load.

Normally, the use of capacitor bank is for correction of power factor. The more closer to load , more is the effect of Capacitor bank. Now, irrespective of that, if we put capacitor bank to HT side for the same effect, voltage rating of Capacitor bank will increase, which will further increase the cost of capacitor bank,requiring greater insulation level, protection for capacitor bank, termination, cable for capacitor bank etc. Hence techno-economically, It is best to put Capacitor bank LT side.

in the load side

Dear Mr. sandeepkv,

There are 2 isssues here.

1st issue is the LT supply consumer - responsibility lies with the consumer and hence the capacitor bank as for as possible should be closer to the motor and the KVAR required, as thumb rule, in general will be (0.4) x H.P. of Motor or (0.543) x KW - where the PF will be around 0.8

2nd Issue is in the limits of Power Supply Agency who maintains HT Transformers for Distribution and they have to install the Capacitor in their premises on HT input side.

Dhayanandhan.S