Each type of capacitor has its advantages and disadvantages.

Low voltage capacitor require simpler switches, are safer, does not require a separate room, is closer to the consumer 400V, reduce losses in power lines and transformers of distribution network, can be used in Automatic capacitor banks.

High voltage capacitors are cheaper, have smaller dimensions, but require expensive switches, separate room, do not withstand frequent switching.

Furthermore, the high-voltage network is excess capacitance of line.

The Capacitor Banks in general are used for not only improving the Power Factor,but for improving the voltage profile and reducing the Real Power Loss. It is the simplest,best and cheapest Method and almost maintenance-free..

There are other Facts Devices for improving the Power Quality,but go with a price and some technical problems,for which there are solutions.

You can also go for lightly loaded Over Excited Synchronous Motor ,also called Synchronous Condenser for the Purpose if you can spare,though it is old fashioned.

Generally 3 Phase Capacitor Banks are used at 11 K.V. Substations or at 11 K.V Distribution points at Factories or Heavy Load Consumer Points.At Higher voltage levels Insulation and consequently cost of the Capacitors will be high and are to be specially manufactured

400V Three Phase Capacitor Banks are generally located at Consumer Premises.

Standard Capacitor Banks are available in the Market.

While installing Capacitor Banks one has to be careful about Designing the Capacity or else the P.F. may go to leading side and the Supply Utility or the consumer installing the bank will be Losing.

The following Reference LINK gives a very good idea on Installation and Types and Protection of Capacitor Banks.

2003 Conference for Protective Relay Engineers - Texas A&M University

April 8-10, 2003, College Station (TX)

Shunt Capacitor Bank Fundamentals and Protection

Gustavo Brunello, M.Eng, P.Eng Dr. Bogdan Kasztenny Craig Wester

GE Multilin, Canada GE Multilin, Canada GE Multilin,USA

[email protected]

[email protected]

[email protected]

http://www.geindustrial.com/publibrary/checkout/Shunt%20Capacitor?TNR=White%20Papers|Shunt%20Capacitor|generic

P.S.

Ideal location of capacitors placement is near loads. Generally utilities prefer to place capacitor at the voltage level next to the consumers voltage level.Because if reactive support is being given from far end it will incurr additional line losses. However, it is difficult & not cost effective to place capacitor very near to loads. Higher the voltage level less effective is capacitor placment but is more cost effective. Therefore capacitor placement problem at different voltage level should be investigated as a multiobjective optimization problem with minimum cost and max loss reduction as objectives at all operating voltage of a given network.

Prof. K.R.Niazi Elect Engg Dept. MNIT Jaipur

The capacitor bank instalation into power system has two objective, depending of the voltage level. If the issue is with distribution or subtransmission network (could be up to 100 kV) then the objective is to compensate the inductive reactive power; in contrast if we are talking on transmission system (above 100 kV), in this case the problem could be another at all, and it could be related to voltage stability, and the solution is not only the capacitir instalation but could a mix between capacitor and reactor, depending on the load flow along the line.

Regarding the remarks of Dimitrios Koupatsiaris and Fredy Saravio Poican,I would like to state that the observations made regarding the location or voltage of Capacitor Banks for improving Voltage Profile of the Buses or Power Factor or for Reducing the Power Losses apply to Distribution System,particularly, for Radial Distribution Systems.

Coming to Cables or EHV High Voltage cables,the High Capacitance of these come into Picture and the Voltage at the Receiving end will be more than the Sending End Voltage and this is called Ferranti Effect.To overcome this problem you have to go for installing Shunt or Series Inductors instead of Capacitors.

You can observe that EHV Substations use Shunt Inductors and not Shunt Capacitors for compensation.

P.S.

.

caPACITORS can also be used for filtering Harmonics .

So , there is no specific Thumb rule for placement of Capacitor . Rather, one has to decide the specific objective in order to decide the location of the capacitor . A capacitor should be placed as close as possible to the Load , the limitatio of voltage / current of the load is also to be seen ..

A capacitor is a bank of number of capacitor elements connecetd in Series-parallel combination the economy of the bank uis to be seen .

CAution - Unless the capacitors are over designed , they are NOT MAINTANCE FREE

Capacitor banks indeed are used to improve the power factor of the electrical system as installed on load sides whether in high voltage levels or in low voltages as it counteract the lagging p.f. Which the inductive loads such as motors and reactors have contributed to these lagging p.f. And it works by injecting leading p.f. And the end result is improved overall power factor lets say from 85% to 90 % and higher as desired. Since capacitor banks have the ability to store electrical energy same as the inductive loads (i.e. Transformers an dmotors) which store magnetic energy and these two (2) energies will then counteract with each other and/or balance each other until one is more than the other to a certain level that the ave. P.f. Is achieved towards the desired level. Usually in big industrial oil and gas plants or in a manufacturing plant when more inductive loads (i.e. Motors) are connected @ lv bus which contributes more inductive reactance (hence reactive power=kvar) which brings down to 80 % below the p.f. (for example) then this low value of p.f. Is a nuisance as it brings over supply of apparent power (kva) from the utility company's source to drive electrical energy up to the end users switchgear and so in the process charge more tariff or penalty to that end users. Therefore, with the help of the capacitor banks, this 80 % low p.f. Can be increased to higher value, say to 90 % level depending on the required kvar supplied by this capacitor bank and so when an end user install it's own capacitor bank as required in fact by the utility company, it will save on it's own power bills paid on the utility company monthly or annually, depending of course on how long the capacitor bank is connected. So, now as a rule, if there are more motors connected on the lv bus, then capacitor banks are normally installed on these lv bus. But if otherwise, if more motors are connected on the mv or hv bus (such as big hp motors) then usually the capacitor banks of mv or hv rated level are herein installed to do the same function of improving the low p.f. Of the electrical system.

By felix m.s.jr. / ch2m hill - veco engineering, abu dhabi, uae

In short we can say wherever you have more Inductive Loads you connect the Capacitor Bank at that voltage level.

The Loads at L.V.side are also reflected on the M.V.or H.V. side. But their contribution at higher Voltage Level is less because it will be only a small fraction of the total load at that level.

At the user end we have even capacitor start and capacitor run single phase Induction Motors as single phase Induction Motors are widely used.

P.S.

The answers already offered cover the question well. I can add only two thoughts.

While loss prevention is often mentioned, CBs also release capacity. Generators, lines, and transformers are all current limited. If they have to carry the var requirements of the load, their capacity to carry real power is diminished.

Regarding synchronous condensers, being "old fashion", I have seen a movement to repurpose older, less efficient generators, in urban environments as synchronous condensers. This provides var support close to the load and allows the use of newer, more efficient, but remote generation.

hi

I must mention that for "voltage level of capacitor placement" we must consider 2 objective:

1) the cost

2) the effectivity

so, you must consider capacitor in both LV and HV side, and with financial study choose of  them.

Hi,

I have a practical scenario to solve. Due to the increase in the additional load, We need to upsize our capacitor bank from 2000KVAr to 3800kVAR. Our voltage distribution scheme is 22kV (grid connection)/ 11kV(80% load at this voltage level)/690V (15% load at this voltage level)/400V(5% load at this voltage level). Our present capacitor bank is 2000kVAr at 11kV level. In order to meet 3800 KVAR compensation, we need to add further 1800KVAr. However, we have a space concern for adding another 1800kVAR at 11kV level (it is not economical either). I would like to check whether we can add the capacitor bank to the 690V (instead of 11kV) level to improve overall pf. Inductive kVAR at 690V level is about 800 kVAR. When we add 1800kVAR at 690V level, it will overcompensate reactive power. Will it contribute any problem to the upstream network? any disadvantage for this approach?