Installation Troubleshooting Capacitors APFC System

The Capacitor are not switched off when the load is not working, under such condition the average power factor is found to be lower side.. The capacitor required should be calculated tak

INSTALLATION & TROUBLE SHOOTING

CAPACITOR AND APFC SYSTEM

SERVICE MANUAL

1 Please check if required kVAr of capacitors are installed.

2 Check the type of capacitor installed is suitable for application or the capacitors are derated

3 Check if the capacitors are permanently ‘ON’ The Capacitor are not switched off when the load is not working, under such condition the average power factor is found to be lower side

4 Check whether all the capacitors are operated in APFC depending upon the load operation

5 Check whether the APFC installed in the installation is working or not Check the

CT connection is taken from the main incomer side of transformer, after the fix compensation of transformer Refer Fig No.1

6 Check if the load demand in the system is increased

7 Check if power transformer compensation is provided

Fig No.1

1 P O W E R F A C T O R I S N O T I M P R O V I N G

Calculation of required capacitor.

The capacitor required should be calculated taking the data from electrical bill copies

of last 4-6 months if bill is not available please take initial power factor as 0.75 lag

Please note that the max demand given in electrical bill is in kVA not in kW

Power factor = kWH / kVAH (these data are generally provided in electricity bills)Initial Power factor - (Before installation of capacitor)

Recorded demand - 516kVA (Highest recorded demand)Req power factor - 0.95lag (To be decided by customer)

kW = kVA x Power Factor

= 516 x 0.75 = 387Required capacitor = kW x Multiplying Factor

Cable

Transformer Compensation ACB

CR

SDF

F1 1-M

1-M F2

K 1-M

C1-M

APFC Panel

H1 F2 1-M F1 C1-M

1-M K SDF

CR CT

TR Power transformer Current transformer Power factor controller Switch disconnector fuse Contactors

Capacitor stop fuses Control fuses Capacitor stops

Load

0.66 0.654 0.683 0.712 0.743 0.775 0.810 0.847 0.888 0.935 0.996 1.138 0.67 0.624 0.652 0.682 0.713 0.745 0.779 0.816 0.857 0.905 0.966 1.108 0.68 0.594 0.623 0.652 0.683 0.715 0.750 0.787 0.828 0.875 0.936 1.078 0.69 0.565 0.593 0.623 0.654 0.686 0.720 0.757 0.798 0.846 0.907 1.049 0.7 0.536 0.565 0.594 0.625 0.657 0.692 0.729 0.770 0.817 0.878 1.020 0.71 0.508 0.536 0.566 0.597 0.629 0.663 0.700 0.741 0.789 0.849 0.992 0.72 0.480 0.508 0.538 0.569 0.601 0.635 0.672 0.713 0.761 0.821 0.964 0.73 0.452 0.481 0.510 0.541 0.573 0.608 0.645 0.686 0.733 0.794 0.936 0.74 0.425 0.453 0.483 0.514 0.546 0.580 0.617 0.658 0.706 0.766 0.909 0.75 0.398 0.426 0.456 0.487 0.519 0.553 0.590 0.631 0.679 0.739 0.882 0.76 0.371 0.400 0.429 0.460 0.492 0.526 0.563 0.605 0.652 0.713 0.855 0.77 0.344 0.373 0.403 0.433 0.466 0.500 0.537 0.578 0.626 0.686 0.829 0.78 0.318 0.347 0.376 0.407 0.439 0.474 0.511 0.552 0.599 0.660 0.802 0.79 0.292 0.320 0.350 0.381 0.413 0.447 0.484 0.525 0.573 0.634 0.776 0.8 0.266 0.294 0.324 0.355 0.387 0.421 0.458 0.499 0.547 0.608 0.750 0.81 0.240 0.268 0.298 0.329 0.361 0.395 0.432 0.473 0.521 0.581 0.724 0.82 0.214 0.242 0.272 0.303 0.335 0.369 0.406 0.447 0.495 0.556 0.698 0.83 0.188 0.216 0.246 0.277 0.309 0.343 0.380 0.421 0.469 0.530 0.672 0.84 0.162 0.190 0.220 0.251 0.283 0.317 0.354 0.395 0.443 0.503 0.646 0.85 0.135 0.164 0.194 0.225 0.257 0.291 0.328 0.369 0.417 0.477 0.620 0.86 0.109 0.138 0.167 0.198 0.230 0.265 0.302 0.343 0.390 0.451 0.593 0.87 0.082 0.111 0.141 0.172 0.204 0.238 0.275 0.316 0.364 0.424 0.567 0.88 0.055 0.084 0.114 0.145 0.177 0.211 0.248 0.289 0.337 0.397 0.540 0.89 0.028 0.057 0.086 0.117 0.149 0.184 0.221 0.262 0.309 0.370 0.512 0.9 0.029 0.058 0.089 0.121 0.156 0.193 0.234 0.281 0.342 0.484 0.91 0.030 0.060 0.093 0.127 0.164 0.205 0.253 0.313 0.456 0.92 0.031 0.063 0.097 0.134 0.175 0.223 0.284 0.426 0.93 0.032 0.067 0.104 0.145 0.192 0.253 0.395 0.94 0.034 0.071 0.112 0.160 0.220 0.363 0.95 0.037 0.078 0.126 0.186 0.329

KVA rating of the transformer

Upto and including 315 kVA315kVA - 1000 kVAAbove 1000 kVA

Thumb Rule if HP is known.

The compensation for motor should be calculated taking the details from the rating plate of motor Or the capacitor should be rated for 1/3 of HP Refer Fig,No 2 for the connection of capacitor

Where to connect capacitor

1 Fix compensation should be provided to take care of power transformer Power and distribution transformers, which works on the principle of electro-magnetic induction, consume reactive power for their own needs even when its secondary is not

connected to any load The power factor will be very low under such situation To improve the power factor it is required to connect a fixed capacitor or capacitor bank

at the LT side of the transformer For approximate kVAr of capacitors required

Refer Table No-1.1

2 If the installation is having various small loads with the mixture of large loads then the APFC should be recommended Note that APFC should have minimum step rating of 10% as smaller step

3 If loads are small then the capacitor should be connected parallel to load The connection should be such that whenever the loads are switched on the capacitor

also switches on along with the load Refer Fig No-2

4 Note that APFC panel can maintain the power factor on L.T side of transformer and it

is necessary to provide fix compensation for Power transformer Refer Fig No-1

5 In case there is no transformer in the installation, then the C.T for sensing power

factor should be provided at the incoming of main switch of the plant Refer Fig No-3

3 In case of star-delta starter the capacitor

should switch ‘ON’ on delta mode.

CT Meter

CR

CT Current transformer Power factor controller Switch disconnector fuse Contactors

Capacitor stop fuses Control fuses Capacitor stops

Load

11 Pharmaceutical industries etc.

Following industries are presently installed with MD-XL Capacitor.

1 Steel rolling mills

2 Cement plants

3 Sugar plants

4 Govt research institutes

5 Plastic moulding units

13 Automobile Industry etc

Apart from above Capacitors MPP-S are generally used in

various industries having pure steady inductive loads

Do not use in the industries having harmonic generating loads such as welding, drives, ups, rectifiers, furnace etc

Note : The industries like cement, sugar, software industries and steel plants need data of harmonics for designing suitable compensation components.

The recommendation for heavy industries should be given in consultation with L&T / MEHER Engineers

as the harmonic generating loads are found to be increasing in all the industries

2 T E S T I N G O F C A PA C I T O R S AT S I T E

Measurement of Voltage

Check the voltage using tongtester at capacitor terminals Ensure that the tong tester / multimeter

used is of “True RMS type” Please note that the

current output ot 440 volt capacitor connected to a system of 415 volt will be lesser than rated value

Table no - 2.1 & 2.2 gives you the resultant kVAr

output of the capacitor due to variation in supply

voltage Refer formula no 1

Caution:

Please ensure customer is not comparing wrong technologies such as our MPP-S Capacitors with other makes APP/MD/ or heavy duty MPP Capacitor Please also ensure that the customer is comparing with similiar voltage rated capacitor

TABLE – 2.1 Three phase 440V Capacitor.

Measured capacitance across two terminals with third terminal open

(Micro farad) 440V

kVAr 440V

Line current 440V

kVAr

at 415V

Line Current

Line current 415V

kVAr

at 440V

Line Current at 415V

“True RMS Clamp Meter” sticker) Make a

record of measurement data of individual phase and other parameter as given in the table no 2.3

Check wether the current measured is within the limit value with respect to supply voltage &

data given in the name plate of capacitor

Refer formula no -2 and 2.1 for calculation.

L.T power capacitors are provided with discharge resistor to discharge the capacitor which is limited to one min The resistor are

provided as per clause No-7.1 of IS

13340-1993.

Switch off the supply to the capacitor and wait for 1 minute and then short the terminals of capacitor to ensure that the capacitor is completely discharged This shorting of terminals ensures the safety while handling the capacitor

Discharge of capacitor also becomes necessary for the safety of meter used for capacitance measurement.

After discharging capacitor measure capacitance between two terminals and repeat for other terminals (RY YB and BR)

Check the value from the Table No-2.1 & 2.2

Please refer to the corresponding table for rated voltage

You can also calculate the kVAr from the

formula No - 4 for the capacitor which may be

RATED VOLT CAP

RATED CURRENT

INSTALLED DATE

MEASURED VOL AND CURRENT

MEASURED CAPACITANCE VALUES

Formula - 1

The kVAr of capacitor will not be same if voltage applied to the capacitor and frequency changes The example given below shows how to calculate capacitor current from the measured value at site

Example :

1 Name plate details – 15kVAr, 3 phases, 440v, 50Hz capacitor

Measured voltage - 425vMeasured frequency - 48.5Hz

The current of capacitor will not be same

if voltage applied to the capacitor and frequency changes The example given below shows how to calculate capacitor current from the measured value at site

I = IM R

Example - Consider a capacitor of 15 kVAr 440V, 50 Hz, 19.68 Amps Three phase Capacitor

IM = 19.68

= 18.43 Amps

Note: Please ensure that the measurement is done using true RMS clamp meter.

3

l = kVAr x 10 / ( 3 X V ) L L Example:

3 15kVAr, 3 phase, 440v, 50Hz capacitor

Formula - 3

Formula - 4

The capacitance value of a capacitor can be calculated using following formulae for delta connected 3-ph capacitor Please not that the value given below is between two terminals with third terminal open circuit

6 15kVAr, 3 phases, 440v, 50Hz capacitor

C = 15 x 1000000000 / ( 4 x 3.142 x 50 x (415 x 415)) = 138.62 µf (micro farad)

KVAr calculation from the measured capacitance value of a capacitor

KVAr = 2/3 (Ca + Cb + Cc) x V 2 f / 10 - for three phase capacitor

Consider you have measured a capacitor rated for 440 volts where in measured capacitance value is as follows

1 197 µf (between R & Y phase)

2 196 µf (between B & Y phase)

3 200 µf (between R & B phase)

9

KVAr = 2 / 3 x (Ca + Cb + Cc) x v2 x 2 f / 10KVAr = 2 / 3 x (197 + 196 200) x (440 x 440) x 2 x 3.14 x 50 / 1000000000

= 24.04

Consider you have measured a capacitor rated for 415 volts where in measured

capacitance value is as follows

4 197 µf (between R & Y phase) -Ca

5 196 µf (between B & Y phase) -Cb

6 200 µf (between R & Y phase) -CcKVAr = 2 / 3 x (197 + 196 + 200) x (415 x 415) x 2 x 3.14 x 50 / 1000000000

= 21.39Please note while calculating kVAr of capacitor using above formula the voltage rating should be taken from the name plate of capacitor

The tolerance of capacitance of a capacitor is -5% to +10% of capacitor as specified in the Indian Standard IS 13340-1993.

Service condition

Termination and Mounting

1 Installation area should be dry, free from excessive dust or chemical fumes and vibration

Refer Annexure - D point Number D-4.1 of I.S 13340-1993

2 Ensure that the installation area / enclosure have provision of cross ventilation

Refer Annexure - D point Number D-3.1 of I.S 13340-1993

1 Use suitable size lugs for connecting the cable to the terminals of capacitor

2 Ensure that there is no loose connection: As loose connection may lead to failure of capacitor / insulation break down of cable

3 Use proper tools for connection / tightening

4 Ensure that the capacitor is mounted vertically

5 The earthing of capacitor should be done before charging

6 The applied voltage should not exceed more than 10% Refer technical specification of capacitor

7 The capacitor should be provided with the short circuit protection device as indicated in Table number 5.1 Do not connect higher rating protection device

Annexure - D point Number D-7.1 IS 13340-1993

4 G U I D E L I N E F O R I N S T A L L A T I O N O F C A P A C I T O R

Table 5.1 Recommended switchgear

KVAr

57.51012.51520255075100

I / CFNX / FN32FNX / FN32FNX / FN32FNX / FN32FNX / FN63FNX / FN63FNX / FN63FNX / FN125FNX / FN200FNX / FN200

Use of capacitor in APFC panel

Maintenance

1 The capacitor should be provided with suitable designed inrush current limiting

inductor coils or special capacitor duty contactors Annexure d point no d-7.1 of

IS 13340-1993

2 Once the capacitor is switched off it should not be switched on again within 60 seconds so that the capacitor is completely discharged The switching time in the relay provided in the APFC panel should be set for 60 seconds for individual

steps to discharge Clause No-7.1 of IS 13340-1993

3 If the capacitor is switched manually or if you are switching capacitors connected

in parallel with each other then “ON” delay timer (60sec) should be provided and

in case of parallel operation once again point No 1 should be taken care Clause

6 The panel should have provision for cross ventilation, the louver / fan can be provided in the care Annexure d point No d-3.1 IS 13340-1993

7 For use of reactor and filter in the panel fan should be provided for cooling

8 Short circuit protection device (HRC fuse / MCCB) should not exceed 1.8 x rated current of capacitor

9 In case of detuned filter banks MCCB is recommended for short circuit protection

1 Check the current of capacitor and cable connection

2 Tighten the connections if termination is found loose Clean the area around the capacitor

3 Make use of table no-2.3 for recording the data of measurements Check the capacitance of capacitor once in three month

4 Disconnect capacitor drawing over 30% current than rated Contact us on help line for further action

5 Disconnect the capacitor having leakage problem and replace

3 Rating of cable is not adequate.

4 Lugs having bad crimping

5 Capacitor drawing over current

1 Poor ventilation

2 Drawing excessive current

3 Over voltage

1 Low voltage

2 Failure of capacitor elements

3 Improper rating of short circuit device

4 Presence of harmonic causing

1 Capacitor installed is not operated as required

2 Capacitor is permanently switched on

3 Transformer fix compensation

1 Fuse rating improper

2 Harmonic over loading

3 Over voltage

4 Switching timer not provided

(On delay timer.)

5 High ambient temperature

capacitor

1 Check the size of lug used and replace with suitable size

2 Tighten the loose connection

3 Check the cable current carryingcapacity and if req change

4 Rectify the crimping

5 Check the voltage and reduce it ifpossible Check for any harmonic

in the supply voltage

1 Ensure cross ventilation for theinstallation area / inside the panel

2 Check for any harmonic presence in the network

3 Maintain the voltage within limits (Refer the specification of capacitor)

1 Voltage to be maintained

2 Should be checked if the capacitor are installed and operated as per guide line given above

3 In case of improper HRC fuse rating the capacitor element would have failed during over current condition

1 Check the operation of capacitors

2 Capacitor should be allowed to switch on only when it is required

3 Transformer should be provided with fix compensation

4 Check the rating of capacitor installed is sufficient or not

1 Fuse rating should be properly selected refer Table No - 5.1

2 Check for harmonic over loading and if required install detuned filter banks

1 Fuse rating should be properly selected refer Table No-5.1

2 Check for harmonic over loading and if required install detuned filter banks

3 Replace capacitor in case it has

no other problems