capacitormanual(1)

8/12/2019 CapacitorManual(1)

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ENERGE CAPACITORS PVT. LTD

d. Neutral Displacement:Voltage Unbalance 9elay% 9equired in case of a single star connected capacitorbank. The secondary of the 9esidual Voltage Transformer 29VT3 in connected in opendelta. Under balanced condition of the capacitor bank the voltage across the opendelta terminals is almost 8ero. But in event of failure of one or partial unit in acapacitor bank the neutral is shifted and this is reflected on the open delta

terminals which should be set to a specified value which can differ depending on thenumber of units in a capacitor bank. &'(T) relay is suggested to avoid spurioustripping.Current Unbalance 9elay% 9equired in case of a double star connected capacitorbank. The neutral points of both the stars are connected through a :eutral CurrentTransformer 2:CT3. Under balanced condition the current at the star points is almost8ero. But in event of failure of one of partial unit in a capacitor bank the neutral isshifted causing flow of current in the neutral. Current Unbalance 9elay is connectedto the secondary of the :CT0 which is set at a specified setting depending on thenumber of units in the capacitor bank. ;n instantaneous type relay with fi*ed timedelay is suggested for this purpose.

e. Timer for reenergisation after ! minutes:This is provided to block the re-switching of capacitor bank in less than 6 minutes.

f. "eading #o$er factor %ela& 'Optional(:&n case it is envisaged that the power factor of the electrical system is close to unityand due to sudden variation in the load the power factor shoots above unity it isrecommended that a leading power factor relay be provided to avoid leading powerfactor condition.

,. !or ++


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&deal method under circumstances%i. The si8e of the inductive load is large enough to select the minimum si8e

of capacitors that is practical. !or #T capacitors the minimum ratingsthat are practical are as follows%

ystem Voltage (inimum rating of capacitor bank,.,


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c) Central Compensation % The compensation will be as shown in the diagram given

below%Capacitors of central compensation could be of high or low voltage. #ere alsocapacitors sections will have to be decided depending on the variation in theloads and the power factor of the loads to be compensated. ven in case ofcentral compensation the capacitors should be located as close to the loads as ispracticably possible.

&n short the compensation of reactive power should be made udiciously taking intoconsideration the composition of loads and practical situation. The prime factor to beconsidered is that compensation of reactive power should be as close to the load aspossible and if required all the three types of compensation can be adopted in certainindustries.

5. election of rated voltage of Capacitor Bank % ?hile selecting the rated voltage of a

capacitor bank it should be note that the rated voltage of the capacitor bank should beas close to the highest service voltage of the system as possible. &f the actual servicevoltage varies up to +/ of the system voltage it should be brought to the notice to themanufacturer. The following aspects have to be taken care while selecting the ratedvoltage of the capacitor bank%

a3 ervice voltage higher than the rated voltage of the capacitor bank couldadversely effect the life of the capacitor due to over stress on the capacitordielectric

b3 ervice voltage lower than the rated voltage of the capacitor bank results inoutput lower than the rated value of the capacitor bank.

c3 1ver voltage should not e*ceed +/ of the rated voltage of the capacitor bank.d3 Capacitor will cause voltage rise at the point where it is located.e3 The voltage on capacitor might increase in light load conditions.f3 eries 9eactor will cause rise in voltage on the capacitor terminals.

6. Temperature category of Capacitors %

?hile selecting the temperature category0 it should be borne in mind that higher

temperature might cost more at the same time temperature category lower than theactual temperature in the service condition can endanger the operation of capacitors.!or tropical climate like in &ndia 6deg C temperature category is considered as mostideal. #owever if capacitors are installed close to heat-generating equipment forced air-cooling must be seriously considered. ?hile selecting the temperature category all thetwo means i.e. $7 hours and +year should be considered simultaneously. ;s a guide linethe table for selection of temperature category as per & are given below%

DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD*mbient *ir Temperature in degrees centigrade(a*imum #ighest (ean over period of

$7 hours + yearDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD

7 , $76 ,6 $66 7 ,66 76 ,6

DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD

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>. Capacitors unless specially designed should not be installed highly harmonic infestedsystem. &n case of capacitors to be installed in system having ;rc !urnaces0 9ectifiers0'C drives0 etc0 the same will have to be designed specially to take care of the overloadconditions due to the effect of harmonics.

8. eries 9eactors used for different applications are as under %

a. +nrush suppression ,eries reactor% &t is used to suppress the inrush current duringswitching of capacitor bank and transients. The series reactor should be of rating of.$/ of the capacitor bank reactance and should be connected on the neutral end ofthe capacitor bank.

b. Detuned ,eries %eactors% The eries 9eactor of rating of "/ of the capacitor bankreactance in connected on the line end of the capacitor bank. The capacitor bankand reactor group id tuned 7thharmonic such that it will be inductive at $6 #8 andprevent the possibility of occurrence of any resonant condition. This capacitor willblock the higher order of harmonics and protect the capacitor bank from harmonics.

c. Tuned ,eries %eactors 'Filter circuit reactor(:The eries 9eactor is designed suchthat the capacitor bank and reactor combination filters out any particular order ofharmonic that is predominant in the system by creating a low impedance path of theorder of harmonic that it predominant. The reactor and capacitors in such cases aredesigned to withstand the overloads due to harmonics. ;n electrical system can beprovided with one or more filter circuit depending upon the presence of harmonics.

The rating of series reactor is crucial and has to be selected properly which should be basedon the application of capacitors. &mproper selection of series reactor rating can adverselyaffect the life of the capacitors.

Surge Arresters :

&nrush surge current and voltage are notorious factors which determine the life of capacitorbanks and hence these factors have to be tackled appropriately. (aority of failures cases incapacitors are under switching surges. !or precisely this reason it is mandatory to providesurge arresters in the capacitor circuit. !or capacitor bank application it is recommendedto provide (etal 1*ide0 Aapless type urge ;rresters with discharge class &&&. &t is alsoimportant that $ nos. earthing pits are provided which will be dedicated only for surgearresters to have an effective functioning of the arresters.

Externa !uses:#T capacitors are categori8ed under $ basic designs vi8. internal fuse design and e*ternalfuse design. &n case of internal fuse design providing e*ternal fuses is not mandatory as theinternal element fuses takes care of capacitor unit protection. !or e*ternal fuse design thefuse must be de-rated by a factor of $. There are $ types of fuses that are used forcapacitor unit protection as under%E-pulsion fuses :These are drop out type fuses with fuse links which can be replaced. Butit should be ensured that the fuse links are of the precise rating and should not besubstituted with commonly available copper wires.%C fuses :These are provided with a porcelain body and are more reliable than e*pulsionfuse although they are very uneconomical.

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INSTALLATION GUIDELINES

+. &t is very important that the capacitors are stored securely after its receipt from thetransporter. The capacitor should be thoroughly checked for damage or leakage. Thebushings of the capacitor should be intact. ;ll the welded soldered oints should bee*amined.

$. &n case it is observed that in any capacitor unit the bushing2s3 are broken or anyleakages are observed the same should be covered with a clean and dry polythene coverto avoid ingress of dirt0 dust or moisture inside the capacitor container. &t must beassured that capacitors with leakage are not put in service. ;t times very minor leakagecan be attended at site by application of sealing compound. This should be done onlyafter ascertaining that very little oil has leaked. The oil level inside the capacitor shouldbe sufficient that it immerses the dielectric column. The dielectric columns aregenerally + to +6 mm from the top of the container. &t is essential that arecommendation of nerge Capacitors 4vt. )td. is taken in such cases.

,. &n case capacitors are installed indoor there should be proper ventilation is provided.?hile installing capacitors inside a panel care must be taken to provide sufficient apacebetween adacent capacitors 2minimum + mm3 and capacitor unit and the panel body.This will ensure free circulation of air. Ventilating louvers should be provided on the twoopposite ends of the panel. &f required even e*haust fans should also be provided. ;s perguidelines and & standards the highest operating temperatures should be less than 6deg. C. The temperature rise in capacitor bank is ma*imum +6 deg. C above theaverage ambient temperature. &ncase the temperatures at the container are above thespecified temperature providing forced ventilation if mandatory. &f the temperaturescontinue to be higher the matter should be reported to nerge Capacitors 4vt. )td.

7. !or outdoor clearances ground clearances and sectional clearances as per & rules mustbe maintained for safety purpose. The clearances between phases and phase and earthare maintained as per & rules. The installation and connections should be strictly as perdrawings provided. !or your guide lines the minimum electrical clearance to be providedas per B +"$ is given below%

MINIMUM ELECTRICAL CLEARANCES AS PER "S : #$%

# INDOOR:Voltagein ".$ +$>.

+6 ++." +"6.+

$$ +,@.> $7+.,,, $$$.$6 ,66."

% OUTDOOR"." +,@.> +>>.E

++ +>>.E $$E."

$$ $>@.7 ,,.$

,, ,E+ 7,+.E

"" "E6.E >E>.7

++ E",." @@."

+,$ +"".E +$+@.$

$$ +>>E $6>.7

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MINIMUM 'OR(ING CLEARANCES IN OUTDOOR S'ITCH)ARD

Voltagein 6 $6

,, ,> $E

"" 7 ,

+,$ 7" ,6

$$ 66 76

6. &n case capacitors are installed in location which is dominated with chemical industriesand the pollution levels are high the same should be informed to nerge Capacitors 4vt.)td.0 prior to manufacture so the special care could be taken in the surface treatmentof the C9C; containers of the capacitor units.

". ?hile tightening the connection in the capacitor bushings necessary care should betaken to avoid undue stress on the on bushings. To be precise there should not be anyattempt to over tighten and at the same time there should not be loose connection. Theconnectors0 busbars0 conductors0 cables etc. should be adequate current carryingcapacity.

>. The series and parallel connections in case of outdoor capacitors should be strictly asper approved drawings. This is very important as any faulty connection could lead tomassive failure. The series groups in the capacitor bank increases with higher ratedvoltage and this aspect should be carefully checked at the time of erection. &n case ofany doubt please immediately contact nerge Capacitors 4vt. )td.

E. ;ll the three phases of the capacitors should be in balanced condition in case ofe*ternally star=delta connected capacitor banks wherein the basic unit is of singlephase. This balancing can be carried out based on the capacitance value of eachcapacitor unit. The capacitance value of each unit is given in the routine test certificateof the capacitor units.

9. The capacitor bank and all the associated equipment should be properly earthed in two

points of each equipment as shown in the respective drawings. &f capacitors areprovided with base insulators 2generally provided for $$


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arth continuity conductor along with sub-main wiring from (ain=ub'istribution boards to various distribution boards shall be of copper. arthcontinuity conductor from distribution board onward upto outlet point shall alsobe of bare copper. arth continuity conductor connecting (ain ub 'istributionboards to earth electrode shall be with galvanised ( strip.

ingle phase distribution board shall have one earth continuity conductor while

three phase distribution board shall be provided with two earth continuityconductors. arthing of main switch board and sub switch boards shall beearthed with two independent earth electrodes or as indicated elsewhere. arthconductor laid in ground shall be protected for mechanical inury corrosion byproviding A& pipe. E.7 A& pipe shall be of medium class 7mm dia and 7.6 metrein length. Aalvanising of the pipe shall conform to relevant &ndian tandards. A&pipe electrode shall be cuttapered at the bottom and provided with holes of +$mm dia drilled not less than>.6cm from each other upto $ metre of length from bottom. The electrode shallbe buried in the ground vertical with its top not less than $cm below groundlevel as per detail enclosed. arth electrode shall not be situated less than$metres from the building. The location of the earth electrode will be such that

the soil has reasonable chance of remaining moist as far as possible. (asonrychamber of si8e , * , *,mm shall be provided with water funnelarrangement a cast iron or ( frame cover having locking arrangement at thetop.

arthing shall be provided with either A& plate electrode or copper plateelectrode of following minimum dimensions.

A& 4late lectrode % "mm * "mm * "mm thick

Copper 4late lectrode % "mm * "mm * ,mm thick

The electrode shall be buried in ground with its faces vertical and not less than ,metres below ground level. $mm dia medium class A& pipe shall be provided and

attached to the electrode. ; funnel with mesh shall be provided on the top ofthis pipe for watering and earth electrode. arth electrode the watering funnel

attachment shall be housed in masonry enclosure of not less than , * , *,mm deep. ; cast iron or ( frame with cover having locking arrangement

shall be provided at top of metres from the building. Care shall be taken that thee*cavation for earth electrode may not affect the column footing or foundationof the building. &n such cases electrode may be further away from the building.

&f the earth resistance is too high and the multiple electrode earthing does notgive adequate low resistance to earth0 then the soil resistivity immediatelysurrounding the earth electrodes shall be reduced by addition of sodium chloridecalcium chloride0 sodium carbonates copper sulphate0 salt and soft coke orcharcoal in suitable proportions.

The resistance of earthing system shall not e*ceed +21ne3 1hm.

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T)PICAL EARTHING PIT DIAGRAM

10. &f it is envisaged that the outdoor locations are prone to bird faults0 the complete

capacitor bank should be covered with fine wire mesh enclosures 2opening of minimumone inch opening3 or all the live parts should be covered with sheet steel of wire meshenclosures. &n case this is not possible due to practical reasons0 all live busbars and liveparts should be insulated with heat shrinkable sleeves or insulating tapes of adequatevoltage grade.

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COMMISSIONING AND OPERATION:

+. Check that all the connections are made as per the drawing and required clearances areas per & rules and drawings are maintained. 4lease ensure that there are no looseconnections at any point0 which can lead sparking.

2. Check if all the porcelain parts i.e. bushings0 post insulators etc. are thoroughly cleaned

and free from cracks breakage etc.

,. The insulation resistance of the complete installation should be checked with a meggerbefore put the capacitor bank into service. 4lease do not switch on the capacitor bank ifthe megger values are low and once clean the bushings and other porcelain parts of thecomplete installation.

7. Connect the capacitor bank to a ,-phase low voltage supply 27+6=773 for checking thebalancing. The current across all the , phases should be measures0 which must bealmost equal.

6. 'isconnecting one unit must create an unbalance condition at low voltage supply.(easure the voltage 2incase of e*ternal single star connected capacitor bank3 or current2incase of e*ternal double star connected capacitor bank3 at the terminal of the :'9relay. Under healthy condition the voltage or current will be almost 8ero but onunbalance condition some voltage or current will appear in the terminals of the :'9relay. This test will assure that the connections are proper and the :CT or 9VToperations are proper.

". ;ll the protective relay of the relay panels should be tested with a relay testing kitbefore commissioning of the capacitor bank.

>. The load current and the voltage of the system should be noted prior to thecommissioning of the capacitor bank.

E. ;fter all the pre-commissioning test results are satisfactory the capacitor bank can becharged at high voltage. ;fter switching 1: the capacitor bank all the reading likecapacitor bank current0 load current0 system voltage and power factor must berecorded. The parameters like power factor0 load current and voltage will changecompared to the reading prior to the commissioning of the capacitor bank. The loadcurrent will reduce0 power factor will improve and slight improvement in the voltage ofthe system will be e*perienced. The current of all the three phases on the capacitorsmust be equal.

@. ; couple of hours after the commissioning0 the capacitor bank must be switched 1!!and after + minutes 2time taken for capacitor to discharge to a safe value3 thecapacitor bank should be grounded with A1' if available. &f A1' is not available thegrounding can be done with a discharge rod. Check if any connections are gettinge*cessively hot and tighten the connection at that point. ;lso check for any leakagesetc. or any other abnormality. &f any abnormality is observed please immediatelycontact nerge Capacitors 4vt. )td.

+. &t is recommended that all the tests mentioned above are carried out periodicallyespecially during shut down condition to ascertain the healthiness of the capacitor bankand for a long and trouble free service of the capacitor bank.

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MAINTENANCE O* CAPACITOR "AN(:

+. 'aily records of capacitor current0 load current0 power factor0 system voltage etc.should be maintained on hourly basis. The tripping of relays and the number ofswitching operations must be systematically recorded. These information are necessaryto ascertain the causes of any fault in future and will help in taking precise remedialmeasures.

$. &t is advisable to restrict the number of switching operations of the capacitor bank.&ndian tandards specifies that the switching operation should be less than +operation per year.

,. The voltage across the capacitor bank must be within permissible limits. &t is goodpractice to switch 1!! large rating capacitor bank during light load conditions to overleading power factor conditions.

7. 'uring shut down conditions maintenance work like cleaning the bushing tightening theconnections etc. must be carried out. ;lso leakages0 damages0 crack on bushings andinsulators must be checked.

6. &n case the corrosion is observed in the capacitor container in a period of time the samemust be attended by re-painting the surface of the capacitor container. &n humid andpolluted atmosphere repainting of the capacitor container must be done periodically.

". (aintenance of breaker and all other equipment must be carried out periodically alongwith all other equipment in the switchyard.

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