Manual for MV Power Capacitors

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MV Power Capacitors Power Factor Correction Installation and Maintenance instructions for MV-Power Capacitors Series/Type : Ordering Code : B2516 Date : Feb 2009 Version : 1.1 EPCOS AG 2008, Reproduction, Publication and dissemination of this data sheet, enclosures hereto and the information contained therein without EPCOS prior consent is prohibited

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Installation and maintenance instructions for MV Power Capacitors Preliminary data Installation and Maintenance Instructions Read This First : Read the following >> Installation and maintenance instructions

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Installation and maintenance instructions for MV Power Capacitors Preliminary data

Caution:


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Installation and maintenance instructions for MV Power Capacitors Preliminary data Unpacking & Inspection While taking the delivery of capacitors, check for any

visual damage to the boxes/crates and for any trace of oil on the cases. In case of damage or leakage insist on open delivery and obtain open delivery certificate.

Open the cases carefully and check whether the ratings of capacitors are in line with the order, packing list or bill of materials.

Check for any damage especially for

a) Any breakage of bushings or insulators

b) Leakage of oil from the bushing top/base or from capacitor container and

c) Any denting or damage to terminal cover, bank frames, bus bars and other accessories.

In case capacitor units/other material found damaged insurance claim must be lodged. If insurance is done by EPCOS, intimation should be sent within 10 days giving details of damage. Open delivery certificate should accompany if the cases were damaged. If the cases were intact and damage was found subsequently after opening the cases it should be mentioned in the letter and the cases should be kept in safe custody for inspection and further advice from insurer.

If the bushings are broken or lot of oil has leaked out from the capacitor making it un-repairable at site, such capacitors should be sent back to EPCOS for possible repairs after taking consent of EPCOS.

Minor leakage can be repaired at site by applying EPCOS recommended adhesive.

If site for installation is not ready, capacitors should be stored at a proper place with bushing in upward position. Any hair crack developed during handling may not show the leakage at the time of storing the capacitor and may show up afterwards; hence it is advisable to check once again after a week. Store in a place where capacitors are not required to be handled for removing or keeping other


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equipments in the Store. Do not keep anything on the capacitors to avoid damage to the bushing.

Installation Install capacitors in cool dry place, which should also be

free from excessive dust and chemical fumes. Capacitors should be installed away from the heat generating bodies.

Clean the bushings of capacitors with cloth for dust and oil stains.

Tighten all electrical and mechanical connections. Avoid over tightening of capacitor bushing terminals. Also take care while connecting bus bars so that no stress comes on capacitor bushing. Ensure that the ambient temperature at capacitor location does not exceed beyond the limits specified in the table below:

Maximum ambient temperature in C Upper limit of

temperature category in C,

Mean over 1 hour

Mean over 24 hours

Mean over 1 Year

40 40 30 20 45 45 40 30 50 50 45 35

EPCOS Capacitors are made as per 50C upper limit of temperature category. Ambient temperature at capacitor location should be measured 1 to 2 meters away from capacitors.

Ensure free circulation of air around the capacitors. Adequate clearance (minimum 300 mm) should be provided between walls and capacitors for heat radiation. Cooling temperature should not be more than 5C above ambient measured at the hottest point in the bank i.e. mid way between two capacitor units or at 30 cm away from a capacitor at its 3/4 height in case one capacitor is involved.

The site work such as banking of capacitor units, connections of bus bars / fuses should be done as per the drawings provided. Adequate clearances should be maintained. Minimum clearance required as per BS: 162 are given below for guidance.


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Clearance in mm. Indoor Out door

Rated Voltage In KV

Phase to Phase

Phase to Earth

Phase to Phase

Phase to Earth

Up to 6.6 89 64 178 140 11 127 77 229 178 22 242 140 330 280 33 356 223 432 381

When capacitors are mounted on an open structure of angles and channels, their live parts are exposed and accessible. Such banks are required to be elevated to minimum 2.5 mtrs from ground level by providing elevating structures or fencing is erected all round the capacitor bank keeping adequate clearances as given above to eliminate the possibility of any one touching the live parts of the bank. Elevating structure or the fencing should be earthed as per IS:3043.

When capacitor has an external fuse protection it should be ensured that fuse is connected to individual capacitor unit. Do not connect one fuse to more than one capacitor unit.

It should be ascertained that the breaker used for capacitor switching is restrike free, if on-load isolators are used for pole mounted capacitors or for small banks, it should be ensured that they are suitable for capacitor duty. Whenever off-load isolator is connected between capacitors and the breaker, it is advisable to interlock the isolator with the breaker in such a way that the isolator can be opened or closed only when the breaker is in open condition.

When capacitors are directly connected to the motors, it is advised that the capacitor current is not more than 90% of the no load motor current. Motor draws lesser current from the source when connected with the capacitors. Hence its over current setting should be reduced accordingly.

Unless specifically agreed capacitors are provided with discharge resistors to discharge the capacitors within 600 seconds to safe voltage. When capacitors are required to be reswitched earlier than 600 seconds PT/RVT can be provided for quick discharge. PTs/RVTs have secondary winding which can be connected to indicating lamps to show that capacitors have discharged. When capacitors are required to be reswitched within couple of seconds


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an interlock through secondary winding of PT/RVT can be provided to ensure that at the time of reswitching capacitors have discharged to safe value.

Capacitor units and the bank should be earthed at earth points provided. Capacitors with live containers and banking structure should not be earthed. All auxiliary equipments should also be earthed at earthing points provided.

Commissioning Before energizing the bank check all the

equipments as per the checks mentioned in commissioning report format given at the end.

Megger the capacitor bank between phases and earth. The megger reading for individual capacitor should not be less than 50 Mega ohms, for more than one unit in parallel minimum acceptable megger value can be derived by dividing 50 Mega ohms by the number of units connected in parallel.

Complete installation with all the equipments connected to capacitors should be meggered between shorted phases and earth and should be in line with acceptable capacitor megger value.

Now the capacitor bank is ready for energization. Before switching on capacitor bus voltage, system incoming load current and power factor (if meter available) can be noted.

After energizing check that capacitor draws

almost balance current in all the 3 phases and is near to its rated value. Note the change in bus voltage, load current and system power factor. Normally after capacitors are energised, there will be little rise in the bus voltage and some reduction in the system load current and naturally improvement in power factor. In case load current increases instead or reducing, it shows that capacitors connected are more than required for the load and in this case the power factor shall be leading.

When PT/RVT is used for unbalance

protection, measure open delta voltage, which should be negligible. In case capacitors are connected in double star with neutral CT, the current on the secondary side of neutral CT can be measured, which should also be negligible.


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After a few hours (12 to 24 hrs.) of continuous operation capacitor bank can be switched off and the capacitor units should be checked for any leakage, excess temperature rise of the container and of other equipments. Series Reactors if provided should have temperature rise within prescribed limit. In an event everything is in order then capacitor bank can be re-energized and kept in operation.

Operation Voltage on the capacitors should be near to

its rated voltage. It should be ensured that the voltage including fluctuations in the system do not exceed 110% of the capacitor name plate voltage.

Variation in currents in the three phases

should be within 5% and rating should be within 5 to +10% of rated current. If there are harmonics present in the system, it may increase the current in capacitor. However, this current should not exceed 13O% of rating mentioned on the name plate.

Temperature of capacitor container can be measured by fixing a thermometer on the wall of the container, its bulb being at one fourth of the height of capacitor down from the top.

Hourly readings of capacitor current,

voltage should be maintained. Open delta voltage of RVT or current of neutral CT can be measured once in a day and logged. If capacitors installed are for indoor applications, their ambient temperature should be logged at least three times a day, morning, noon time and in the evening. If exhaust fans or air circulators are provided to maintain ambient, it should be ensured that they are always ON, when capacitors are in operation.

Internal discharge resistances are fitted

across capacitor terminals to reduce the voltage on switching off to less than 50 volts within 10 minutes. Capacitor should not be handled during this period. For human safety it is advisable to ground the capacitor bank with grounding rod before handling.

Preventive Maintenance Capacitors should be maintained periodically,

preferably once a month. Capacitors including bushings should be cleaned of dust etc. All connections should be checked for its proper tightness.


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Any rusty portion should be cleaned and then given a coat of paint.

Capacitor units should be checked for any leakage.

Other associated equipments specially breakers should be maintained as per manufacturers recommended practice.

Oil of series reactor and RVT should be checked for its breakdown strength periodically.

Normally capacitors once installed and

operated as recommended practice should give long and trouble free service. However, in the event of encountering any trouble, users may refer to the table below which gives some of the common troubles encountered with its causes and remedies to take appropriate action.

Trouble Cause Remedial action

a) Minor transit damage which remained undetected.

a) For minor leakage apply adhesive or solder on leaky welded joints. if leakage does not stop replace the unit and refer to manufacturer for possible repairs. (Refer Note 1)

b) Due to tension coming on bushing.

b) Check & tighten the connections to avoid tension coming on bushing, repair capacitor as stated above.

1. Leakage of oil from capacitor bushing or welded joints.

c) Due to overheating of unit

c) Refer Serial No. 2 for action.

a) Poor ventilation,

a) Provide free circulation of cooling air.

b) Excessive ambient.

b) Arrange forced ventilation

c) Drawing excessive current.

c) Refer Sr. No. 3 for action

2. Over heating of units

d) None of the above causes.

d) Refer to the manufacturer

3. Capacitor drawing high current

a) High voltage,

a) Reduce voltage by changing transformer taps or switch off the bank.


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b) Harmonic current flowing

b) It current beyond permissible limit, switch-off capacitor bank and take remedial measures to reduce harmonics flowing in capacitors.

a) Low voltage,

a) Current directly proportional to voltage No repairs required.

b) Failure of capacitor unit with blown fuses.

b) If one or more units have failed and it has not been detected by neutral unbalance relay, check whether unit has failed or fuse has spuriously blown. If unit fails replace the unit. Refer Note 2.

4. Capacitors drawing less current.

c) Partial failure of unit.

c) In case of internal fused capacitors sometimes partial failure in various units may occur which cannot be detected by neutral unbalance relay. Check the whole bank for capacitance and regroup them. Remove units having capacitance less than 95% of the rated value. Also check if neutral unbalance limit is set Correctly. Refer Note 2.

a) Expulsion fuse rating may not be of adequate value.

a) Check expulsion fuse rating. Consult manufacturer by providing complete bank details. Refer Note 3(a).

5. Expulsion fuses blowing too frequently but unit is healthy.

b) Expulsion fuse for one unit connected to more than one unit.

b) Connect one fuse with one unit.

6. Expulsion fuse not blowing but unit has failed.

a) Expulsion fuse rating may be high.

a) Check expulsion fuse rating. Consult manufacturer by providing complete bank & system details. Refer Note 3(a).

7. Abnormal bulging/bursting.

a) Gas formation due to internal arcing Causing unit to bulge or burst.

a) Replace the unit and refer to the manufacturer.

8. Abnormal sound and black marks noticed on bushing

a) External earth fault between terminal and container.

a) Clean the bushings and check installation for any short circuit.


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and near by. b) High voltage surges due to lightning or due to restriking of breaker.

b) Consult the manufacturers application engineer. Refer Note 3(b).

9. Terminal over-heated or melted

a) Loose contact.

a) Tighten the connections. Replace the damaged capacitors.

10. Capacitor bank tripping on unbalance protection but expulsion fuse not blown.

a) Co-ordination of expulsion fuse blowing with neutral protection is not proper.

a) Check and consult with manufacturers application Engineer.

Note:

1. Minor leakage from bushing can be repaired as follows:

Turn the unit and place in such a way that the leaky portion will remain on the top. Clean the area by carbon tetra chloride and wipe of with a clean cloth. Apply Araldite and then allow it to cure in that position for 8 hours. Put the unit back in to the circuit after 24 hours.

For minor leakages on the welded joints or metal

terminals turn the unit to keep the leaky portion on the top. Clean the surface with carbon tetra chloride and wipe the area with clean cloth. Solder the leaky portion using soldering iron of suitable wattage. Avoid using excess solder. Wipe/ clean the soldered area for any residual flux. Keep the unit for 10 minutes in that position and then put the unit back in to the service.

2. Following methods can be adopted to check failure of a capacitor unit:

(a) Capacitor with external fuse:

Megger with 500V megger between 2 terminals of capacitors. Completely failed unit will show zero megger value and healthy unit will show megger value of a few M.ohms, which corresponds the value of internal resistors.

(b) Capacitor with internal element fuse:

In case of capacitors with internal element fuse, megger will always show a few M. ohms corresponding to internal discharge resistors value, whether unit is healthy or partially/completely failed. However, if the terminals are shorted immediately by shorting link, the spark can be noticed in case of healthy or partially failed unit. To distinguish between healthy and partially failed unit,


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capacitance can be measured. If Capacitance Bridge is not available at site then 440 volts supply can be given across the two terminals and current drawn by the unit can be measured, which should be in direct proportion to the voltage applied. For example a 200 KVAR 7300 volts, 1-Phase capacitor has rated current of 27.39 Amps. When tested at 440 volts the current will reduce in the ratio of 440/7300 to 1.65 Amps. Current drawn lower than this will show partial failure.

3.(a) While referring to the manufacturer, provide the

details of complete capacitor bank rating, individual unit rating, expulsion fuse rating whether series reactor used or not, if not cable length from breaker to capacitor, bank details of any parallel connected bank on the same bus, actual system fault level or incoming transformer rating with % impedance. Also arrange to furnish the single line diagram of the power system along with harmonic details if available.

(c) Please furnish full particulars of capacitor bank as well as

the breaker used. Provide the complete details of lightning arrestors and its location with respect to capacitor if used for surge protection. If lightning arrestors are not used, state so.


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Important Notes : The following applies to all products named in this publication: 1. Some parts of this publication contain statements about the suitability of our products for certain areas of application. These statements are based on our knowledge of typical requirements that are often placed on our products in the areas of application concerned. We nevertheless expressly point out that such statements cannot be regarded as binding statements about the suitability of our products for a particular customer application. As a rule, EPCOS is either unfamiliar with individual customer applications or less familiar with them than the customers themselves. For these reasons, it is always ultimately incumbent on the customer to check and decide whether an EPCOS product with the properties described in the product specification is suitable for use in a particular customer application. 2. We also point out that in individual cases, a malfunction of electronic components or failure before the end of their usual service life cannot be completely ruled out in the current state of the art, even if they are operated as specified. In customer applications requiring a very high level of operational safety and especially in customer applications in which the malfunction or failure of an electronic component could endanger human life or health (e.g. in accident prevention or life-saving systems), it must therefore be ensured by means of suitable design of the customer application or other action taken by the customer (e.g. installation of protective circuitry or redundancy) that no injury or damage is sustained by third parties in the event of malfunction or failure of an electronic component. 3. The warnings, cautions and product-specific notes must be observed. 4. In order to satisfy certain technical requirements, some of the products described in this publication may contain substances subject to restrictions in certain jurisdictions (e.g. because they are classed as hazardous). Useful information on this will be found in our Material Data Sheets on the Internet (www.epcos.com/material). Should you have any more detailed questions, please contact our sales offices. 5. We constantly strive to improve our products. Consequently, the products described in this publication may change from time to time. The same is true of the corresponding product specifications. Please check therefore to what extent product descriptions and specifications contained in this publication are still applicable before or when you place an order. We also reserve the right to discontinue production and delivery of products. Consequently, we cannot guarantee that all products named in this publication will always be available. The aforementioned does not apply in the case of individual agreements deviating from the foregoing for customer-specific products. 6. Unless otherwise agreed in individual contracts, all orders are subject to the current version of the General Terms of Delivery for Products and Services in the Electrical Industry published by the German Electrical and Electronics Industry Association (ZVEI). 7. The trade names EPCOS, BAOKE, Alu-X, CeraDiode, CSSP, CTVS, DSSP, MiniBlue, MKK, MLSC, MotorCap, PCC, PhaseCap, PhaseMod, SIFERRIT, SIFI, SIKOREL, SilverCap, SIMDAD, SIMID, SineFormer, SIOV, SIP5D, SIP5K, ThermoFuse, WindCap are trademarks registered or pending in Europe and in other countries. Further information will be found on the Internet at www.epcos.com/trademarks.


Manual for MV Power Capacitors

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