abb lv capacitor

34 Low Voltage Products

CNABB/LV/TC/01 10-1999

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CONTENTS

DescriptionLow Voltage Network Quality

Capacitor Construction

Fixed Capacitor Units CLMDProduct Description

Technical Specification

Product Range and Ordering Data

Automatic Capacitor Bank CLMH-HKProduct Description



Automatic Capacitor Bank CLMT

Compact Wall-Mounted or

Free Standing SystemProduct Description



DimensionsCLMD

CLMH-HK

CLMT

Capacitor Application Manual

AppendixHarmonic and Capacitor

Page

3

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11

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3Low Voltage Products

Internally Protected Elements (IPE)ABB’s sequential protection system featuring our patented

Internally Protected Element (IPE) design provides increased

protection to facilities and personnel not available from other

capacitor designs. This proven design allows for self-healing

throughout the life of the capacitor to insure the maximum length

of reliable service and still provide short circuit protection in

each element when self-healing can no longer continue. This is

accomplished by a combination of unique winding construction

and an internal fuse link (See Fig. 3) within each element which

safely and selectively disconnects each individual element. ABB

capacitors do not rely on mechanical pressure interrupters and

additional line fuses which have disadvantages associated with

that type of construction.

Low Voltage Network Quality

Advanced design features inherent in all ABB capacitor products

include :

• Dry type design

• Self-healing elements

• Internally Protected Elements (IPE)

Dry type designAll ABB low voltage capacitors utilize elements that are

completely dry and contain no free liquid.

Self-healing elementsABB capacitors are constructed from a completely dry

metallized polypropylene film. A short circuit between electrodes

(See Fig. 1) is short lived. The electrode is instantaneously

vaporized (See Fig. 2) clearing the fault, resulting in only a minor

degradation in performance. The self-healing design significantly

lengthens the life of ABB capacitors.

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Capacitor Construction

Principal Components of a 3-Phase CapacitorThe principal components of a 3-phase ABB capacitor include :

1. Sequential Protection System :

• Self-Healing Capacitor Elements

One or more self-healing capacitor elements are installed

for each phase. These elements are connected in Y or delta.

In case of dielectric breakdown, the fault is cleared by

evaporation of the metallized layer around the breakdown

with negligible loss of capacitance and continued operation

of the capacitor!

• Internally Protected Elements

A unique Sequential Protection System including the IPE

design (IPE - internally protected elements) ensures that

each individual element can be disconnected from the

circuit at the end of the element’s life.

• Nonflammable Dry Vermiculite Filler

Vermiculite is a dry, granular insulating material that is solid,

inert and fire proof. This material fills all open spaces in

the enclosure to isolate the capacitor elements and exclude

free oxygen.

2. Discharge Resistors

Discharge resistors (one for each phase) are sized to ensure

safe discharge of the capacitor to less than 50 volts in one

minute or less as required.

3. Terminal Studs

Large terminal studs are located inside the enclosure at the

top of the capacitor for quick and easy cable connections.

4. Enclosure

All ABB enclosures are made of welded heavy gauge steel.

Available enclosure types include Indoor, Outdoor Raintight,

and Indoor Dusttight.

Design Features

1) Robust terminals, easy connection

2) Discharge resistors

3) Self-healing

4) Dry dielectric

5) Thermal equalizer

6) Inert and non-toxic granules

7) Knock out

8) Earth terminal

9) Heavy-duty enclosure (Also

available for outdoor installation)

10) Very low losses

11) Easy to install

1

2

3

4

5

6

7

8

9

10

11

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What is a Metallized-Film Elements?Metallized-film is a microscopically thin layer of conducting material(called an electrode), usually aluminum or zinc on an underlying layerof insulating film. The electrode thickness averages only 0 .01 micronswhile insulating (polypropylene) film ranges from 5 to 10 microns inthickness depending upon the design voltage of the capacitor (thehigher the voltage rating, the thicker the insulating film).

Advantages of Metallized-Film ElementsThere are two electrode layers separated by one layer of insulatingfilm. Thousands of these layers are tightly wound around a core insuch a manner that the edge of one electrode is exposed on one sideof the element and the edge of the other electrode is exposed on theother side of the element (See Fig. 4 & 5). Wires are then connected toeach side of the element. The element is enclosed in a container andthen filled with a hardening protective sealant.

1. Self-Healing DesignSelf-healing refers to a process where a short circuit betweenelectrodes vaporizes the electrode around the fault (See Fig.6) until the fault is eliminated. The element continues tofunction with negligible loss of performance (See Fig. 7).

2. Low Internal LossesDue to the high dielectric efficiency of the metallized-film,the internal losses are extremely low. ABB metallized-filmdesign losses are limited to 0.5 watts per kvar including thelosses across the discharge resistors.

3. Small Element SizeDue to the thin electrode and dielectric, metallized-film elementsare small and compact in size resulting in smaller, more powerfulcapacitors. The capacitance of any element design is inverselyproportional to the separation between electrodes. In otherwords, if the separation between conducting surfaces is cut inhalf, the effective capacitance is doubled in addition to reducingthe physical size of the element by half.

More About Self Healing Elements“Self-healing” is a characteristic which is unique to metallized electrodecapacitors. All capacitor normally experience insulation breakdownas a result of the accumulated effect of temperature, voltage stress,impurities in the insulating medium, etc. When this happens in a “non-metallized” design, the electrodes are short-circuited and the capacitor

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ceases its production of reactive power. In an ABB metallized-film unit,however, these individual insulation breakdowns do not mean theshutdown of the capacitor. The faults self-heal themselves and thecapacitor continues operation.

The conducting electrode is very thin; when a short circuit developsas a result of a fault in the insulating dielectric, the thin electrodevaporizes around the area of the fault. This vaporization continues untilsufficient separation exists between the faulted electrodes to overcomethe voltage level. Fig. 7 illustrates the process of self-healing.

The entire process of self-healing takes ‘microseconds” and the amountof electrode which is lost is negligible in comparison to the total surfacearea of the element. The result is the metallized-film unit may self-healhundreds of times during its long life and still retain virtually all of itsrated capacitance.

The IPE Sequential Protection SystemABB’s metallized-film self healing capacitor elements will have a longerlife than their conventional foil design counterparts for the above reason.However, accumulated effects of time, temperature, voltage stress,etc., eventually effect capacitor life.

ABB’s sequential protection system featuring patented InternallyProtected Elements (IPE) design provides increased protection tofacilities and personnel not available from other capacitor designs.This proven design allows for self-healing throughout the life of thecapacitor to insure the maximum length of reliable service and stillprovide short circuit protection in each element when self-healing canno longer continue. This is accomplished by a combination of uniquewinding construction and an internal fuse link (See Fig. 8) within eachelement which safely and selectively disconnects each individualelement. ABB capacitors do not rely on mechanical pressureinterrupters and additional line fuses have disadvantages associatedwith that kind of construction.

What are Discharge Resistors?As all the capacitor elements store electrical power like a battery, thecapacitor will maintain a near full charge even when not energized. Asthis is a potentially dangerous condition to unsuspecting plantpersonnel that might be inspecting the capacitor terminals and wiring,discharge resistors are connected between all of the terminals. Whenthe capacitor is shut off, these discharge resistors drain the capacitorelements of their stored electrical charge. It is recommended, however,that capacitor terminals should ALWAYS be short-circuited beforetouching the terminals.

What is the Significance of Dry Type Design?ABB low voltage capacitors contain no free liquids and are filled with aunique nonflammable granular material called vermiculite.Environmental and personnel concerns associated with leakage orflammability of conventional oil-filled units are eliminated; and kvar forkvar, vermiculite filled units weight 30% to 60% less than their oil filledcounterparts.

Vermiculite is routinely used in the United States as an insulatingmaterial in the walls and ceilings of new buildings. Its properties havebeen extensively documented and recognized as an ideal material forsafety and environmental considerations.

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Fixed Capacitor Units CLMD

From 220 to 1000 Volts 50Hz and 60Hz

Product DescriptionThe ABB CLMD capacitor consists of a number of wound

elements made with a dielectric of metallized polypropylene

film. These dry windings are provided with a Sequential

Disconnector ensuring that each element can be reliably and

selectively disconnected from the circuit at the end of its life.

They receive then a treatment under vacuum in order to ensure

perfect electrical characteristics. Each winding is placed in a

plastic case and encapsulated in thermo-setting resin in order

to obtain a perfectly sealed element. The elements are placed

inside a sheet steel box and connected in such a way as to

supply the single or three-phase power at the required voltage

and frequency. The sheet steel box is filled with inorganic, inert

and fire proof granules in order to absorb the energy produced

or to extinguish any flames in case of a possible defect at the

end of an element’s life. The CLMD is also provided with thermal

equalizers to ensure effective heat dissipation.

CLMD 63 CLMD 83

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°C°C°C

Voltage range : From 220 to 1000 VFrequency : 50 and 60 HzConnection : 3-phase as standard construction

(Single-phase on request)Discharge resistors : permanently connected built-in discharge

resistors are sized to ensure safedischarge of the capacitor to less than 50Vin 1 minute after a switch off

Terminals : with threaded rods M6, 8,10 or 12 according to the power of the capacitor

Earth : a M8 terminal is included under the coverCable input : by a knock out : 37mm-CLMD 43-53

47mm-CLMD 63-83Case material : zinc electroplated mild steelColour : Beige RAL 7032Fixing : with two slots 26 x 12 mmExecution : indoor (outdoor on request)Protection : IP 42 (IP 54 on request)Maximum ambient temperature : +50°C according to IEC 831Minimum ambient temperature : indoor type : -25°C

outdoor type : -40°C

CLMD 43 CLMD 53



Minimum distance between units : 50mmMinimum distance between units and wall : 50mmLosses (discharge resistors included) : less than 0.5 Watt/kvar

for 380 V nominalvoltage and above

Tolerance on capacitance :-5% +10%Voltage test :

- between terminals : 2.15 Un for 10 seconds- between terminals and earth : 3 KV for 10 seconds

The acceptable overloads are those specified in IEC 831-1&2 :- overvoltage tolerance : 10% max. at intervals- overcurrent tolerance : 30% permanently- maximum overload : stable operation at 135% of the

nominal rating (generated byovervoltages and harmonics.)

IMPORTANT NOTICEThe installation of capacitors on networks disturbed byharmonics may require special precautions, especially whenthere is a risk of resonance.

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Product Range and Ordering Date


System Power (kvar) Type UF / Phase A / Phase Terminal Weight

* Other ratings are on request

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CLMD 33 400/415 V 50Hz


Fixed Capacitor UnitBasic Modular Unit for Cubicle System* discharge resistors are supplied separetely

System Power (kvar) Type UF / Phase A / Phase Terminal Weight

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Automatic Capacitor Bank CLMH-HK


Product Description

The CLMH-HK is supplied as a complete unit, factory tested

and ready for connection. The design gives high modularity and

compact overall dimensions. The CLMH-HK includes up to 8

power modules (4 modules max. for CLMH-HK-1 and 8 modules

max. for CLMH-HK-2). The power modules are composed of

CLMD33 capacitors and contactors mounted on a common

mounting plate. The number of capacitors and contactors

included in the power modules depends on the automatic

capacitor bank total power and the possible presence of

reactors. The CLMD 33 capacitors are provided with a unique

Sequential Protection System ensuring that each individual

capacitor element is selectively and reliably disconnected from

the circuit at the end of its life.

The CLMH-HK is equipped with an ABB microprocessor based

PF controller which maintains the selected power factor by

switching on or off one or more capacitor steps depending on

the load conditions of the system.

The CLMH-HK modular design allows for the installation of

additional power and switch modules as well as various other

options. Additional auxiliary units can also be connected in

parallel to the CLMH-HK.

The CLMH-HK is supplied with an elevated roof. A separately

mounted current transformer of a X/5 ratio, minimum precision

class 1, is required but not included in our offer.

Consumption is less than 3VA.

Lifting lugs

Elevated roof

Busbar system

Power factor controller

Installation, operation andmaintenance instructions

Power module

Mounting plate

Louvres

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Rated voltage : from 220 to 660V - 50Hz/60Hz, 3 phaseAdmissible overloads according to IEC 831. P.F setting :

between 0.90 capactive and 0.7inductive.

C/k setting : between 0.07 A and 1 A.Operation : automatic or manual with step

indication. LED indication of the numberof capacitors energized and thecapacitive or ınductive demand.

Discharge resistors included.Dielectric losses : less than 0.2.Watt/kvar.Capacitor total losses : less than 0.5 Watt/kvar.Automatic bank total losses (without reactors) includingaccessories such as contactors and PF Controller :Iess than 1.5 Watt/kvar.Dry type self healing capacitors.Capacitor voltage test : between terminals : 2.15 Un during 10

sec. at rated frequency (above IEC 831).between terminals and container : 3 kV during 10 sec.Automatic capacitor bank test : functional test

insulation testExecution : indoor.Cable entry : Top or Bottom (on request)Colour : beige RAL 7032.

Automatic Capacitor Bank CLMH-HKProtection : IP 31 or higher protection on requested.Ambient temperature: -10°C / +40°C according to IEC 831.Installation : floor fixation. Lifting lugs provided. A

leaflet for erection, connection andstarting up is supplied with each unit.

IMPORTANT NOTICE :Placement and orientation of the current transformer arevery important for a correct operation of the automaticcapacitor bank.

The installation of capacitors on networks disturbed byharmonics may require special precautions, especiallywhen there is a risk of resonance.

The CLMH automatic capacitor bank is only one of severalproducts ABB proposes to improve the Low VoltageNetwork Quality. ABB makes products and suppliessolutions to improve LVNQ by power factor compensation,harmonic filtering and dynamic compensation.

°C °C


C1...C12 capacitor steps

F1 main fuses or protective devices

F2 control fuses

F3 capacitor step fuses

K1...K12 contactors

P1 PF controller

T1 power transformer

CT current transformer



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Rated voltage 400V, 50 Hz, three-phaseSwitching sequence 1:1: . . . 1:1

Compensation system

CLMH without Switch- Power Factor Controller, Contactors, Discharge resistors

- HRC Fuses, control Fuses

Type Steps Power (Kvar) Rate current (A) Weight (kg)

CLMH-HK-1 5x20 100 144 140

CLMH-HK-1 5x25 125 180 160

CLMH-HK-1 5x30 150 217 180

CLMH-HK-2 5x40 200 289 260

CLMH-HK-2 5x50 250 361 280

CLMH-HK-2 6x50 300 433 300

CLMH-HK-2 8x50 400 577 320

CLMH with Switch- Load Break Switch

- Power Factor Controller, Contactors, Discharge resistors



CLMH-HK-1 5x20 100 144 160

CLMH-HK-1 5x25 125 180 180

CLMH-HK-1 5x30 150 217 200

CLMH-HK-2 5x40 200 289 280

CLMH-HK-2 5x50 250 361 300

CLMH-HK-2 6x50 300 433 320

CLMH with Reactors and Switch- Series Reactor

- Load Break Switch

- Power Factor Controller, Contactors, Discharge resistors



CLMH-HKX-1 3x25 75 110 170

CLMH-HKX-1 4x25 100 144 190

CLMH-HKX-1 2x50 100 144 190

CLMH-HKX-2 5x25 125 180 260

CLMH-HKX-2 6x25 150 217 280

CLMH-HKX-2 3x50 150 217 300

CLMH-HKX-2 4x50 200 289 320


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The CLMT automatic capacitor bank is a ready-to-connect

system for wall mounted or floor fixation (by means of fixation

rails supplied optionally). The CLMT is provided with top/bottom

entry cable accesses. The CLMT unique design allows optimum

heat dissipation without forced ventilation. The Sequential

Protection System ensures that each individual capacitor

element is selectively and reliably disconnected at the end of

its life. The capacitors are filled with vermiculite (a mineral, inert,

non-toxic and non-flammable material). The CLMT is equipped

with an ABB microprocessor-based and programmable power

factor controller which provides for the setting of the target

power factor and the sensitivity of the regulation (please refer

to our specific documentation).

The CLMT consists of

- three-phase capacitor steps,

- one ABB Power Factor Contoller,

- discharge resistors,

- fuses,

- busbar system, terminals for connecting the mains

(from 16 mm2 to 120 mm2),

- terminal for connection to the C.T.,

- terminal for connection to auxiliary units.

Auxiliary units have similar characteristics as pilot units but are

not equipped with PF controller.

Product Description


Compact wall-mounted for reactive powercompensation400V 50Hz

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Compact wall-mounted orfree standing system

Technical SpecificationRated voltage/frequency : 400V - 50 Hz, three-phase

Admissible overloads according IEC 831P.F. settings : between 0.90capacitive and 0.7

inductiveC/k setting : between 0.05 A and 1AOperation : automatic or manual with step

indication. LED indication of thenumber of capacitors energized andcapacitive or inductive demand

Discharge resistors includedDielectric losses : less than 0.2 Watt/kvarCapacitor total losses : less than 0.5 Watt/kvarAutomatic bank total losses: less than 2 Watts/kvar

Dry type self healing capacitorsCapacitor voltage test :

- between terminals : 2.15 Un during 10 sec. at rated frequency- between terminals and container : 3 kV during 10 sec

Automatic capacitor bank test : functional testinsulation test

Execution : indoorTop/Bottom cable entryColour : beige RAL 7032Protection : IP42 (IP 20 open door)

Max ambient temperature :-10°C / +45°C for units of max. 100 kvar-10°C / +40°C for units higher than 100 kvar

Installation : wall-mounted or floor fixation

Options : Fuse disconnect switchAuxiliary unitFloor fixation RailPF Controller with lockable door

Important Note :A separately mounted current transformer of a X/5 rating, min.precision class 1 is required but not included in our offer.

Placement and orientation ofthe current transforrner are veryimportant for a correct operaton of the automatic capacitor bank.

The installation of capacitors on networks disturbed byharmonics may require special precautions, especially whenthere is a risk of resonance.

The CLMT automatic capacitor bank is only one of severalproducts ABB proposes to improve the Low Voltage NetworkQuality. ABB makes products and supplies solutions to improveLVNQ by power factor compensation, harmonic filtering anddynamic compensation.

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Compact wall-mounted orfree standing system- Power Factor Controller, Contactors, Discharge resistors

- Fuses


CLMT 3x25 75 110 70

CLMT 3x30 90 130 75

CLMT 4x25 100 144 85

CLMT 4x30 120 173 130


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Dimensions

CLMD

CLMD-33

CLMD 13

CLMD 43

CLMD 53/63/83

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CLMH-HK

CLMT

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Table 1. Reduction of current and ohmic losses by the installion

of static capacitors.

ϕϕ

ϕϕ

Capacitor Application Manual

General Technology of low voltage powercapacitors for reactive power compensation

Picture 1. Without a capacitor, the reactive current flows from thegenerator through the lines and transformers to the motor. Picture 2. With a capacitor, only active current flowsi in the feed lines

and transformer. With this relief, the trandgormer and the transmissionlines can be dimensioned smaller.

Inductive electricity consumers, i.e. motors, transformers,

welding machines etc., require magnetization energy to establish

a magnetic field. This energy - generally referred to as lagging

reactive energy - is not converted into mechanical work or heat

as is the active energy, but reciprocates between the generator

and consumer. The active energy and reactive energy are

registered on the power consumers’ premises with different

meters, i.e. active energy with kilowatt-hour meters and reactive

energy with kilovar hour meters. Reactive current is the cause

of various adverse phenomena. It places a load on the

transmission lines, the transformers and generators, it causes

additional ohmic losses and voltage drops, and requires larger

dimensioning of all transmission components. By installing

static capacitors, the transport of reactive current from the

generator to the consumer can be extensively reduced or

corrected (pictures 1 and 2). Table 1 shows the reduction of

current and losses with an improved cos ϕ.

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Graphical representation of the powers and currentsReactive current and active current are added geometrically

(picture 3). The reactive current is at an angle of 90° to the active

current. The resultant of the two current components OA and

OB is designated the apparent current OC, and all transmission

components have to be dimensioned for this apparent current.

The capacitor current is in phase opposition to the inductive

reactive current, and is thus entered in the graph in the reverse

direction CA. The capacitor can be dimensioned in such a way

that the two currents cancel each other out, thus making the

phase angle ϕ zero and the apparent current OC equal to the

active current OA, with the power factor cos ϕ being corrected

to 1.

When this condition has been achieved, the lines and

transformers are then only subjected to active current.

°

ϕ

Graphical repesentation of the powers and

currents

O A = Active current IA (A)

O B = Inductive reactive current IB (A) = AC

O C = Apparent current IS (A)

C D = Capacitor current or capacitive reactive current

ϕ = Phase angle, uncompensated

ϕ1 = Phase angle, compensated

O A = Power factor cos ϕO C

O D = Compensated current IS cos ϕ

cos ϕ1

The powers are proportional to the currents and can begraphically representd in the same manner.

ϕϕ

ϕ

ϕϕ

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Qc = U2 w • C • 10-9 (kVAr)Qc = Reactive power in kVArU = Terminal voltage in V

Determination of the power requirement :Power factor improvement from cos ϕ1 to cos ϕ2

Qc = Active power x (tan ϕ1 - tan ϕ2)Qc = P x (tan ϕ1 - tan ϕ2)orQc = P [kW] x F (F = see table 2)

Example 1

Given : Active energy consumption Ea 300,000 kWh, reactive energy

consumption Er 400,000 kVAr h, number of working hours

600 h

Average cos ϕ1 = = 0.60 tan ϕ1 = 1.33400 000300 000( ) 2

+ 1

1

cos ϕ1 =Er

Ea( ) 2

+ 1

1

Required :

Desired cos ϕ2 = 0.9

Qc = P x (tan ϕ1 - tan ϕ2)

Qc = 425 kVAr

or

Qc = P [kW] x F

Qc = 425 kVAr

Result:

tan ϕ2 = 0.48

500 (1.33 - 0.48)

= 500 x 0.85

ω = Angular frequency = 2 π f

C = Capacitance in µF

f = Network frequency in Hz

tan ϕ =

Qc =

react. current meter reading 2 - react. current meter reading 1active current meter reading 2 - active current meter reading 1

Meter readings 1 and 2 : To be taken at the start and finish of work

respectively.

h = Time in hours between meter reading 1 and 2

F = The calculated tan ϕ value is to be located in table 2, column 1,

and the factor F read off under “desired cos ϕ2 value” in column 2.

From example 1 : tanϕ = 400 000 kVAr h300 000 kW h

= 1.33

Qc = 300 000 kW h600 h

x 0.85 = 425 kVAr

Meter reading

Determination of the power of a capacitor Qc

cos ϕ1 =Er

Ea( ) 2

+ 1

1

cos ϕ2 = 0.9

Qc = P x (tan ϕ1 - tan ϕ2)

Qc = 425

Qc = P [kW] x F

Qc = 425

tan ϕ2 = 0.48

500 (1.33 - 0.48)

= 500 x 0.85

tan ϕ =

Qc =

h =

F = tan ϕ

F ϕ2

Qc = 300 000 600

x 0.85 = 425

cos ϕ1 = = 0.60 tan ϕ1 = 133400 000300 000( ) 2

+ 1

1

1 tanϕ =400 000 300 000

= 1.33

Qc = U2 w • C • 10-9 (kVAr)Qc =U =

cos ϕ1 cos ϕ2

Qc = x (tan ϕ1 - tan ϕ2)Qc = P x (tan ϕ1 - tan ϕ2)

Qc = P [kW] x F (F 2)

ω = = 2 π fC = µF f =

300,000Average active power

600 = 500 kW 300,000

600

= 500 kW

x F ( ) active current meter reading 2 - active current meter reading 1h

x F (kVAr)

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Column 1 Column 2Existing Desired cos ϕ2

tan ϕ cos ϕ 0.80 0.82 0.85 0.88 0.90 0.92 0.94 0.96 0.98 1.0Factor F

3.18 0.30 2.43 2.48 2.56 2.64 2.70 2.75 2.82 2.89 2.98 3.182.96 0.32 2.21 2.26 2.34 2.42 2.48 2.53 2.60 2.67 2.76 2.962.77 0.34 2.02 2.07 2.15 2.23 2.28 2.34 2.41 2.48 2.56 2.772.59 0.36 1.84 1.89 1.97 2.05 2.10 2.17 2.23 2.30 2.39 2.592.43 0.38 1.68 1.73 1.81 1.89 1.95 2.01 2.07 2.14 2.23 2.432.29 0.40 1.54 1.59 1.67 1.75 1.81 1.87 1.93 2.00 2.09 2.292.16 0.42 1.41 1.46 1.54 1.62 1.68 1.73 1.80 1.87 1.96 2.162.04 0.44 1.29 1.34 1.42 1.50 1.56 1.61 1.68 1.75 1.84 2.041.93 0.46 1.18 1.23 1.31 1.39 1.45 1.50 1.57 1.64 1.73 1.931.83 0.48 1.08 1.13 1.21 1.29 1.34 1.40 1.47 1.54 1.62 1.831.73 0.50 0.98 1.03 1.11 1.19 1.25 1.31 1.37 1.45 1.53 1.731.64 0.52 0.89 0.94 1.02 1.10 1.16 1.22 1.28 1.35 1.44 1.641.56 0.54 0.81 0.86 0.94 1.02 1.07 1.13 1.20 1.27 1.36 1.561.48 0.56 0.73 0.78 0.86 0.94 1.00 1.05 1.12 1.19 1.28 1.481.40 0.58 0.65 0.70 0.78 0.86 0.92 0.98 1.04 1.11 1.20 1.401.33 0.60 0.58 0.63 0.71 0.79 0.85 0.91 0.97 1.04 1.13 1.331.30 0.61 0.55 0.60 0.68 0.76 0.81 0.87 0.94 1.01 1.10 1.301.27 0.62 0.52 0.57 0.65 0.73 0.78 0.84 0.91 0.99 1.06 1.271.23 0.63 0.48 0.53 0.61 0.69 0.75 0.81 0.87 0.94 1.03 1.231.20 0.64 0.45 0.50 0.58 0.66 0.72 0.77 0.84 0.91 1.00 1.201.17 0.65 0.42 0.47 0.55 0.63 0.68 0.74 0.81 0.88 0.97 1.171.14 0.66 0.39 0.44 0.52 0.60 0.65 0.71 0.78 0.85 0.94 1.141.11 0.67 0.36 0.41 0.49 0.57 0.63 0.68 0.75 0.82 0.90 1.111.08 0.68 0.33 0.38 0.46 0.54 0.59 0.65 0.72 0.79 0.88 1.081.05 0.69 0.30 0.35 0.43 0.51 0.56 0.62 0.69 0.76 0.85 1.051.02 0.70 0.27 0.32 0.40 0.48 0.54 0.59 0.66 0.73 0.82 1.020.99 0.71 0.24 0.29 0.37 0.45 0.51 0.57 0.63 0.70 0.79 0.990.96 0.72 0.21 0.26 0.34 0.42 0.48 0.54 0.60 0.67 0.76 0.960.94 0.73 0.19 0.24 0.32 0.40 0.45 0.51 0.58 0.65 0.73 0.940.91 0.74 0.16 0.21 0.29 0.37 0.42 0.48 0.55 0.62 0.71 0.910.88 0.75 0.13 0.18 0.26 0.34 0.40 0.46 0.52 0.59 0.68 0.880.86 0.76 0.11 0.16 0.24 0.32 0.37 0.43 0.50 0.57 0.65 0.860.83 0.77 0.08 0.13 0.21 0.29 0.34 0.40 0.47 0.54 0.63 0.830.80 0.78 0.05 0.10 0.18 0.26 0.32 0.38 0.44 0.51 0.60 0.800.78 0.79 0.03 0.08 0.16 0.24 0.29 0.35 0.42 0.49 0.57 0.780.75 0.80 0.05 0.13 0.21 0.27 0.32 0.39 0.46 0.55 0.750.72 0.81 0.10 0.18 0.24 0.30 0.36 0.43 0.52 0.720.70 0.82 0.08 0.16 0.21 0.27 0.34 0.41 0.49 0.700.67 0.83 0.05 0.13 0.19 0.25 0.31 0.38 0.47 0.670.65 0.84 0.03 0.11 0.16 0.22 0.29 0.36 0.44 0.650.62 0.85 0.08 0.14 0.19 0.26 0.33 0.42 0.620.59 0.86 0.05 0.11 0.17 0.23 0.30 0.39 0.590.57 0.87 0.08 0.14 0.21 0.28 0.36 0.570.54 0.88 0.06 0.11 0.18 0.25 0.34 0.540.51 0.89 0.03 0.09 0.15 0.22 0.31 0.510.48 0.90 0.06 0.12 0.19 0.28 0.480.46 0.91 0.03 0.10 0.17 0.25 0.460.43 0.92 0.07 0.14 0.22 0.430.40 0.93 0.04 0.11 0.19 0.400.36 0.94 0.07 0.16 0.360.33 0.95 0.13 0.33

Determination of capacitorpower Qc by table 2

Table 2

Qc = P x (tan ϕ1 - tan ϕ2)Qu = Active power [kW] x F [kVAr]tan ϕ 1 + 2 = Column 1 for the corresponding cos ϕ valuesor F = "Existing cos ϕ" in column 1 and "desired cos ϕ2" in column 2

A/W 7/99 8/2/00, 10:07 PM22


Single compensation for motorsAll AC motors are consumers of active and reactive power.-The reactive power consumption depends on the size, loading,rated speed, frequency, voltage and construction. Whenimplementing compensation systems for large motors, it isadvisable to obtain the values from the manufacturer of themachines concerned.

The reactive power of the capacitor should not be higher thanthe no-load reactive power of the motor. If it were greater, motorsslowly running down after switch-off could be subject to self-excitation in the motor windings as a result of the discharge ofthe parallel capacitor, which would lead to impermissible voltagesurges.

The capacitor power is to be as follows :QC = 0.9 • 3 • UN • l0 sin ϕ0 • 10-3 [kVAr]l0 = No load current in AUN = Rated voltage in Vsin ϕ0 = Phase angle at no load (approx. 1)0.9 = 90% of the no-load reactive power requirement of themotor

As a guideline : Qc - 0.9 • 3 • UN • 10 • 10-3 [kVAr]

Table 4 provides guideline values on the no-load reactive powerrequirement of motors.

QC = 0.9 • 3 • UN • l0 sin ϕ0 • 10-3 [ ]

l0 =

UN =

sin ϕ0 =

0.9 = 90%

Qc - 0.9 • 3 • UN • 10 • 10-3 [ ]

Single or direct compensationSingle compensation is used for large motors, inductionfurnaces, transformers and welding machines in use for a largenumber of operating hours. The capacitor required for each unitis connected direct to the terminals in parallel, and switched onand off together with the machine (see picture 4).

DischargeThe discharge resistors are configured in accordance withinternational standards and permanently installed in the fixedcapacitors of type CLMD. These ensure that the CLMDcapacitors are discharged to a safe residual voltage below 50 Vwithin one minute of the system being shut down.

Picture 4. Principle of single or direct compensation

Single or direct compensation has the great advantage that allfeed lines up to the load are relieved of reactive current.

A/W 7/99 8/2/00, 10:07 PM23


Group or central compensation with automatic

control

If a large number of small inductive loads are installed in a works,

single compensation for these units becomes uneconomical. If,

in addition, the simultaneity factor, i.e. the percentage of motors

simultaneously in operation, is low, group compensation achieves

better exploitation of the total capacitor power installed.

Group or central compensation (picture 5) represents the easiest

solution to install and also the cheapest. The entire reactive

power required is directly connected to the busbars in the

distribution stations.

The energy suppliers require overcompensation to be avoided.

The capacitor power must therefore continuously be adapted

to reflect the greatly fluctuating energy requirement. This

adaptation is effected by controlled reactive power systems.

The total reactive power installed is divided into an appropriate

number of control steps. The number of switching steps affects

the time for connection and disconnection of the total power

and the number of contactor operations. With small switching

steps, the acting time is prolonged and the operating frequency

of the contactors increased. The selection of the power steps

and number of switching steps must take these criteria and the

necessary control accuracy into account.

Picture 5. Principle of group or central compensation

A basic step, which is permanently active, can be provided to

cover the no-load reactive power of transformers and

permanently activated machines. The control steps are then to

be connected or disconnected by the reactive power relay as

required, until the set power factor (cos ϕ) is reached.

The controller is set in such a way that the switching command

from step to step is delayed by approx. 20 seconds. This delay

is necessary to prevent continuous switching on and off of the

capacitor bank in response to short-term load peaks.

The controller is fitted with a no-volt relay which returns the

control apparatus to its initial status on interruption of the power

supply. This avoids the entire capacitor bank power previously

active being switched on again immediately on restoration of the

power supply, and avoids undesirable current and voltage peaks.

A/W 7/99 8/2/00, 10:07 PM24


Appendix

Harmonics and Capacitors

PROBLEMS CREATED BY HARMONICS• Excessive heating and failure of capacitors, capacitor fuses,

tansformers, motor, fluorescent lighting ballasts, etc

• Nuisance tripping of circuit breaker or blown fuses

• Presence of the third harmonic in neutral grounding systems

may require the derating of neutral conductors

• Noise from harmonics that lead to erroneous operation of

control system components

• Damage to sensitive electronic equipment

• Electronic communications interference

ORIGINS OF HARMONIC DISTORTIONThe ever increasing demand of industry and commerce for

stability, adjustability and accuracy of control of electrical

equipment led to the development of relatively low cost power

diodes and thyristors. Now used widely for rectifier circuits for

U.P.S. systems, static converters and DC motor control, these

modern devices replace the Mercury Arc Rectifiers of earlier

years and in consequence create new and challenging

conditions for the power engineer of today.

Although solid state devices such as the thyristor have brought

significant improvement in control techniques, they have the

disadvantage of producing harmonic currents.

Harmonic currents can cause an unacceptable disturbance on

the supply network and adversely affect the operation of other

electrical equipment including power factor correction

capacitors.

Typical D.C. Current Waveform

Transformer

HarmonicGenerator Capacitor

f

h3

h5

h7

h9

t

t

t

t

t

A/W 7/99 8/2/00, 10:07 PM25


WAVEFORMAll complex waveforms can be resolved into a series of

sinusoidal waves of various frequencies hence any complex

waveform is the sum of a number of odd or even harmonics of

lesser or greater value. (Fig.3)

HARMONICS CONTENTThyristor convertors or rectifiers are usually referred to by the

number of DC current pulses they produce each cycle the most

commonly used being 6 pulse and 12 pulse (Fig.4). There are

many factors that can influence the harmonic content but typical

harmonic currents shown as a percentage of the fundamental

current are given in the Table. Some content of the harmonics

not listed will always be present to some degree but for practical

reasons they have been ignored.

1 100 1005 20 –7 14 –11 9 913 8 817 6 –19 5 –23 4 425 4 4

HARMONIC OVERLOADING OF CAPACITORThe impedance of a circuit dictates the current flow in that circuit.

As the supply impedance is generally considered to be inductive,

the network impedance increases with frequency while the

impedance of a capacitor decreases. This encourages a greater

proportion of the currents circulating at frequencies above the

fundamental supply frequency to be absorbed by the capacitor

and all equipment associated with the capacitor.

In certain circumstances such currents can exceed the value of

the fundamental (50Hz) capacitor current.

These currents in turn cause increased voltage to be applied

across the dielectric of the capacitor. The harmonic voltage due

to each harmonic current added arithmetically to the

fundamental voltage dictates the voltage stress to be sustained

by the capacitor dielectric and for which the capacitor must be

designed.

Capacitors of the correct dielectric voltage stress must always be

used in conditions of harmonic distortion to avoid premature failure.

A/W 7/99 8/2/00, 10:08 PM26


HARMONIC RESONANCEAs frequency varies, so reactance varies and a point can be

reached when the capacitor reactance and the supply reactance

are equal. This point is known as the circuit or selective resonant

frequency. (Fig.6)

L1 L2 L3 L1 L2 L3

Whenever power factor correction is applied to a distribution

network, bringing together capacitance and inductance, there

will always be a frequency at which the capacitors are in parallel

resonance with the supply.

If this condition occurs at, or close to, one of the harmonics

generated by any solid state control equipment, then large

harmonic currents can circulate between the supply network

and the capacitor equipment, limited only by the damping

resistance in the circuit. Such currents will add to the harmonic

voltage disturbance in the network causing an increased voltage

distortion. This results in an unacceptably high voltage across

the capacitor dielectric coupled with an excessive current

through all the capacitor ancillary components. The most

common order of harmonics are 5th, 7th, 11th and 13th but

resonance can occur at any frequency.

AVOIDING RESONANCEThere are a number of ways to avoid resonance when installing

capacitors. In larger Systems it may be possible to re-position

the proposed capacitor installation onto another part of the

system. The same value of kvar installed at high voltage rather

than at low voltage may eliminate a resonant difficulty or there

may be other low voltage busbars where there is no harmonic

generating load.

Varying the output rating of the capacitor bank will alter

the resonant frequency. With multistage capacitor

switching there will be a different resonant frequency for

each stage. Changing the number of switching stages

may avoid resonance at each stage of switching.

Fig. 7 Detuned Capacitor / Reactor / System

XX L

X L X C+

X C

fO fHZ

X C

X L

fhz

fo

W†v

¤ „q§ „

„q „“ §

ƒ@ _ W†v

frequencySupply ReactanceCapacitor Reactance

resonant frequency

–––

–

A/W 7/99 8/2/00, 10:08 PM27


OVERCOMING RESONANCEIf resonance cannot be avoided an alternative solution isrequired. A reactor must be connected in series with eachcapacitor switching section such that the capacitor/reactorcombination is inductive at the dangerous frequencies butcapacitive at fundamental frequency. To achieve this thecapacitor and series connected reactor must have a tuningfrequency below the lowest order of harmonic to heexperienced, which is usually the 5th This means the tuningfequency is usually in the range of 175Hz to 230Hz, althoughthe actual frequency will depend upon the magnitude of theharmonic currents present. The actual tuning frequency will bevaried to suit the specific needs of each case.

The inclusion of a reactor in the capacitor circuit increases thefundamental voltage across the capacitor in the order of 5 to

9% in addition to the harmonic voltages previously mentioned.

LIMITS OF HARMONIC DISTORTIONHarmonic distortion can cause severe disturbance to certainelectrical equipment and as it is the duty of the electrical utilityto provide a “clean supply, many countries now set limits to theharmonic distortion allowed on the distribution networks. In theU.K. the Electricity Council Engineering Recommendation G5/3 provides for three levels of acceptance for the connection ofharmonic generating equipment, defined as stages.

h<11 11≤h<17 17≤h<23 23≤h<35 35≤h THDI<40A 15 7 6 2.5 1.4 20

40A≤I<400A 12 5.5 5 2 1 15400A≤I<800A 10 4.5 4 1.5 0.7 12

800A≤I<2000A 7 3.5 2.5 1 0.5 8I>2000A 4 2 1.5 0.6 0.3 5

STAGE 1 : permits the connection 14kVA at 415 volt and 250kVAof individual loads up to at 11 kV without specialconsideration.

STAGE 2 : limits the total harmonic current which any installationmay produce at the point of connection with thesupply authority, as follows:

STAGE 3 : Individual analysis of systems is required to ensuretotal harmonic distortion does not exceed 5% at 415volt and 4% at 11kV

Before accepting harmonic generating loads, the existingharmonic voltage distortion on the supply network is taken intoconsideration in setting the individual limits of Stage 3, andmay also restrict the maximum limits as tabulated for Stage 2.Where these limits are exceeded, it may be necessary to reduceor eliminate the harmonics produced.

In Hong Kong, the EMSD and the power companies recommendthe maximum allowable total harmonic distortion (THD) of oddharmonic currents shall be limited to those figures as shown inthe table below. This is known as the Code of Practice for EnergyEfficiency of Electrical Installation.

Maximum circuit harmonic current distortion in % offundamental

Table 8 Maximum circuit harmonic current distortion in % of fundamental

A/W 7/99 8/2/00, 10:09 PM28


REDUCTION OF HARMONIC DISTORTIONHarmonic currents can never be totally eliminated from an

electrical system by passive filtering systems. Using an active

harmonic filter can however, very significantly reduce them. The

Power Quality Filter (PQF) is developed by ABB to reduce

harmonic distortion.

The active harmonic filter monitors the line curent in real time

and processes the measured harmonics as digital signals in a

high-power DSP (Digital Signal Processor). The output of the

DSP controls PWM (Pulse Width Modulated) power modules

that through line reactors inject harmonic currents with exactly

the opposite phase to those that are to be filtered.

CT

Fundamental only

When it is necessary to reduce third harmonic currents in the

neutral conductors, a THF third harmonic filter may be required.

TYPE OF FILTERThe effectiveness of any filter scheme depends on the nett

reactive output of the filter; filter tuning accuracy add the

impedance of the network at the point of connection.

Harmonics below the filter tuning frequency of the passive filter

will be amplified. The experience of the filter designer is therefore

important to ensure that insignificant distortion is not amplified

to unacceptable levels. Where there are several harmonics

present, a single arm filter may reduce some haImonics whilst

increasing others, e.g. a filter for 11th harmonic may create

resonance in the vicinity of 7th harmonic and high magnification

of any 5th harmonic already on the network.

In these cases it may be necessary to use an active filter which

offers unprecedented ability to clean the net work from

harmonics. The PQF eliminates harmonics in a controlled way.

It is easy to extend and adapt to changes in the network.

A/W 7/99 8/2/00, 10:09 PM29


The extensive international experience of ABB Capacitors

in the design and operational performance of such filters

has created a wealth of knowledge and back-up

programme data. This enables our design engineers to

assess the effects of variations such as component

manufacturing tolerances, temperature variations etc. and

accommodate these within the design proposed to ensure

the filter provides the performance required.

LOAD ALTERATIONWith the PQF, limitation of the filtering capacity will not

be the barrier for load alternation. Whenever load

expansion is considered, with or without additional power

factor correction equipment, the network impedance is

l ikely to change and PQF fi lter equipment wil l

automatically filter the most critical harmonic components

up to PQF’s maximum capacity.

HARMONIC ANALYSISTo determine capacitor and filter requirements to meet

specific harmonic conditions, it is necessary to establish

with accuracy the impedance of the supply network and

the value of each harmonic current experienced at the

point of intended connection of any filter or power factor

correction capacitor. ABB Industrial and Building Systems

Ltd. is the China and Hong Kong’s leading manufacturer

and supplier of Harmonic Filter Systems at all voltages.

Site analysis and scheme design are undertaken on an

individual basis to utilize our technical expertise to the

best advantage of our customer in each case.

INFORMATION REQUIREDIn considering the application of power factor correction

equipment where harmonics are evident or suspected,

detailed site information will assist design of the most

economic and technically acceptable scheme.

Such information should always include:

- Simplified line diagram of system;

- Supply Transformer(s) rating and impedance;

- Summary of system load including:

• Source of harmonics (AC Drives-DC Drives),

• Type of harmonic generating equipment (e.g. 6

pulse),

• Details of additional proposed harmonic current

generating equipment;

- Ratings of existing capacitors;

- Rating of proposed power factor correction capacitors.

A/W 7/99 8/2/00, 10:09 PM30


ϕ

ϕ

ϕ

ϕ

Transformer

Existing capacitor

Transformer-busbar cable

Network

(Power electronics)

Motor

Busbar

Load

Indication of currentsfor X: measuring point

Automaticbank

¯ „q „

†{ƒs„qfie „

¯ „q „ß¿‹y–˘„q˘l

„q”ß¿‹y–˘

„q

„L‚

A/W 7/99 8/2/00, 10:10 PM31


CN

AB

B/L

V/T

C/0

1 1

0-19

99

40006015

2(023) 6282 6688(023) 6280 5369

310009

22 A(0571) 7225 333(0571) 7225 178

610072

28 C,D(028) 7786 688/5574 719-21(028) 7795 399/5574 722

2660716122 2208

(0532) 5715 260/217/219(0532) 5715 190

110001206

3-166(024) 2334 1818(024) 2334 1306

3(852) 29293838(852) 29293505

710054

(029) 7857 422-3/426-7(029) 7857 420

1000542

(010) 6353 3355(010) 6353 7949

510075183

21 1-8 16(020) 8755 0873(020) 8755 0172

210005

(025) 4791 479(025) 4791 799

15000126

1001-2(0451) 3605 460/465-66(0451) 3602 731

300141290

2505(022) 2621 6488(022) 2621 6485

2000021006 605

(021) 6320 3333/6323 2032(021) 6320 1132/6323 2697

25001117

8(0531) 6092 726(0531) 6092 724

350003158

16 2(0591) 7844 824(0591) 7814 889

430079200-1

7(027) 8740 7421/8749 1288(027) 8740 7426

116001681305

(0411) 2709 679/649/716(0411) 2709 659

10 1999 8500 CHM

While all care has been taken to ensure that the information

contained in this publicaton is correct, no responsibility can be

accepted for any inaccuracy.

The Company reserves the right to alter or modify the inforrnaton

contained herein at any time in the light of technical or other

developments. Technical specifications are valid under normal

operating conditions only. The Company does not accept any

responsibility for any misuse of the product and cannot be held

liable for indirect or consequential damages.

A/W 7/99 8/2/00, 10:10 PM33

abb lv capacitor

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