Total Power Factor Example

VFD ( Six Pulse )DPF = .95TDD = 90% ( No Line Reactor) Harm coefficient =

TPF = .95 x .7433 = .7061

**Power Quality Correction

Caps at Motors or at SWBD / MCC:Disadvantage:If Drives are present anywhere, the harmonic currents they produce can flow back to the point of lowest impedance: the capacitor! This will cause premature failure of the capacitor.VFDMMMMMApplying Capacitors:

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How Harmonics Affect CapacitorsCapacitors are naturally a low impedance to high frequencies:Caps absorb harmonicsCaps do not generate harmonicsAs capacitor absorbs harmonics, the capacitor heats upReduced life expectancyVoltage harmonics stress the capacitor dielectricReduced life expectancyParallel combination of capacitors with motor or transformer can cause resonance condition

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ResonanceThe installation of standard capacitors can magnify harmonic currents on the network

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How Harmonics Affect Capacitors:Resonance:( XL-Xc )

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Capacitor ResonanceMagnification of Harmonic Current when Standard Capacitor are Added to the NetworkResonant Point likely to amplify dominant harmonic (typically 5th)

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Power Factor Correction With Harmonics:De-tuning a network:Force the resonant point away from naturally occurring harmonicsIh5IZfAf5f3f7f9f14.2 Harmonic (252 Hz)We control the impedance of these two elements

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UTILITY RATE & PFCC

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Most utilities penalize for bad Power Factor...If the consumer does not correct the power factor, the utility may have to Build more power plants Install New/ Large transformers Use larger utility cables/ Wires, Switchgear,etc.Many different rate structures across the country. Typically, penalties are imposed for PF < 95%.Thousands of Customers across the country are currently unaware that they are being penalized for low power factor!!!

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How do utilities charge for Power Factor?Utilities recoup the cost of providing reactive power in different ways.. kVA billing: utility measures and bills every ampere of current including reactive current.kW demand billing with Power factor adjustment: utility charges according to kW demand and adds a surcharge for power factor, typically in the form of a multiplier applied to kW demand. kVAR Reactive Demand charge: A direct charge for use of magnetizing power. (example:$ 4.50/kVAR)Two utilities recently introduced substantial Power Factor Penalties TXU (Texas) $3.50 - $5.50 per kW Demand to 95% pf TVA (Tennessee) $1.46 per kVAR lagging, $1.14 per kVAR leading (April 1, 2004)

MOST COMMON POWER FACTOR RATE CLAUSEBILLING KW DEMAND =

ACTUAL KW DEMAND X BASE PF/ ACTUAL PF

Penalty Calculation From Utility Bills In TXBILLING DEMAND (apfa) = KW2 & ACTUAL DEMAND = KW1

Due to PF Adjustment, KW2 > KW1

*Distribution System Charge = (KW2-KW1) x $3.55 / apfa = M1*Nuclear Decommission Charge = ( KW2-KW1) x $0.044/apfa = M2*Transition Charge-1 = (KW2-KW1) x $0.177/ apfa = M3*Transition Charge-2 = (KW2-KW1) x $0.272 / apfa = M4*Transmission Service Charge = (KW2-KW1) x $1.19 / apfa = M5*Transmission Cost Recov Factor = (KW2-KW1) x $0.27103 /apfa =M6

Total / Month = M1+M2+M3+M4+M5+M6 = $ / Month

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CAPACITOR LOCATION & TYPE

**Power Quality Correction

Capacitor LocationsThree Options for Applying Power Factor Capacitors:A) Fixed capacitors @ individual motors or @ MCCB) Automatic Banks at Main Switch BoardC) De-tuned Automatic Capacitor Bank at Main Switch BoardMMMMMABCAHarmonic Source e.g. Variable Speed Drive

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Fixed Capacitors - Low VoltageMain Benefitpf correctionSide Benefitvoltage supportSmall I2R reductionUsageCorrecting pf on individual loads such as motorsDisadvantagesOvercompensation (correct past unity)Not to be used on non-linear loadsUnable to track minute by minute load changes occurring on non-compensated feeders

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Standard Automatic Capacitor SystemsMain Benefitpf correctionSide Benefitvoltage supportSmall I2R reductionUsageCorrecting pf on entire MCCs or substationsApplication alertNot to be used on non-linear loads

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Anti-Resonant Automatic Cap. BankAutomatic Cap. Bank with a reactors in seriesReactors tuned to 4.2 or 4.4Use where Non-Linear Loads less than 50% of total loads.

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Transient Free De-Tuned Automatic Cap. BanksFor sensitive networksSimilar to Anti-resonant Automatic Capacitor System except solid state switchingReactor tuned to 4.2 or 4.4Response time < 5 secUse where Non-Linear Loads < 50% of Total Loads.

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Electronic Switch Transient Free

**Power Quality Correction

Rule Of Thumb For PFCC Applications* When Non-Linear Loads < 15% Of Total Loads Select Standard Automatic Cap. Bank

* When Non-linear Loads >15% But < 50% Of Total Loads Select Anti-Resonant (Detuned) Auto. Cap. Bank

* When Non-Linear Loads > 50% Of Total Loads Select Active Harmonics Filter For VAR Correction

* When Transformer KVA To Cap. KVAR Ratio < 3 Select Anti-Resonant ( Detuned) Auto. Cap. Bank

* When Soft-Starters are present, select Detuned Auto. Cap. Bank

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ACTIVE FILTER in VAR Correction Mode

Division - Name - Date - Language*

WELDING OPERATIONSLARGE HP MOTOR STARTINGPROCESS LOADS (i.e. MIXERS, CRUSHERS, CHIPPERS, SHREDDERS)ARC FURNACESCAUSESCyclical Loads & Loads With Dynamic VAR MovementsRESULTING INVOLTAGE FLICKERVOLTAGE SAGSPOOR POWER FACTORINABILITY TO START MOTORS

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Active Filter (AHF)For Power Factor Correction For System where Non-Linear Loads > than 50% of Total Loads.When Fast VAR Movements NecessaryAHF-New breed of power quality productHarmonics cancellationPower factor correctionVAR compensationResonance eliminationIndependent or simultaneous modes of operation

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Active Harmonics FilterElectronic filtering up to the 50th harmonic

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Hybrid Filters Combination of passive & active technologies+

Division - Name - Date - Language*

MV HVC Banks General Layout

Division - Name - Date - Language*

HVC Banks GeneralMarriage of two technologiesFixed capacitor banks and AHFAuxiliaries: MV/LV SWGR

Chart1

-6000060000

-6000200040000

-6000500010000

-60008000-20000

-600010000-40000

-600012000-60000

-600012000-60000

-600012000-60000

-600011000-50000

-60009000-30000

-60007500-15000

-6000150045000

-6000060000

-6000060000

-6000300030000

-60008000-20000

-600011000-50000

-60007000-10000

-600012000-60000

-6000200040000

Fixed Kvar

Load

Accusine

Result Kvar

Time in cycles

Vars Leading/Lagging

HVC

Sheet1

Fixed KvarLoadAccusineResult Kvar

0-6000060000

1-6000200040000

2-6000500010000

3-60008000-20000

4-600010000-40000

5-600012000-60000

6-600012000-60000

7-600012000-60000

8-600011000-50000

9-60009000-30000

10-60007500-15000

11-6000150045000

12-6000060000

13-6000060000

14-6000300030000

15-60008000-20000

16-600011000-50000

17-60007000-10000

18-600012000-60000

19-6000200040000

Sheet1

Fixed Kvar

Load

Accusine

Result Kvar

Time in cycles

Vars Leading/Lagging

HVC

Sheet2

Sheet3

Division - Name - Date - Language*

WELDING OPERATIONSLARGE HP MOTOR STARTINGPROCESS LOADS (i.e. MIXERS, CRUSHERS, CHIPPERS, SHREDDERS)ARC FURNACESAPPLICATION OF:HYBRID VAR COMPENSATION (HVC)DYNAMIC VAR INJECTION ON PER CYCLE BASISPASSIVE/ACTIVE SYSTEM ARRANGEMENTWITH INRUSH OR DE-TUNED REACTORSCUSTOM-ENGINREERED FOR SPECIFIC SITE, NETWORK, LOAD CHARACTERISTIC NEEDSCAUSESSOLUTIONSCyclical Loads & Loads With Dynamic VAR MovementsRESULTING INVOLTAGE FLICKERVOLTAGE SAGSPOOR POWER FACTORINABILITY TO START MOTORS

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CAPACITOR APPLICATIONS AT MOTOR TERMINAL

> Motor Overload Protection

> Re-closure Issue Jogging , Reversing, Inching , Plugging Applications

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Capacitor At Motor Terminal Motor Over Load Protection Issue

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Motor Self-Excitation Voltage Influenced By Capacitor Ratings

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Reclosed Breaker & Net Voltage

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CAPACITOR APPLICATION ISSUES

**Power Quality Correction

Multi-Energy Power System of the Future ?

**Power Quality Correction

Utility & Customer Owned

Solar Power System WorkingIn Parallel

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Key Questions to ask Customer For Capacitor Applications

Are you being charged for poor power factor by your utility (ask for a copy of their electric bill - kW, kVA, Power Factor)?Do you have a large number of drives, rectifiers or other harmonic generating equipment? Do you have nuisance tripping of overloads ?Do you have welders, chippers, or other large cyclical loads?Do you have problems with voltage sags or flicker? How sensitive is your equipment to these power issues?Do you have capacity issues on any of your substations?Do you have HID lighting or critical processes with low tolerance to brownouts?Have you been experiencing poor weld quality?Do you have Soft Starters in the System?Do you have Motors subject to reversing, jogging, inching, or plugging?

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Capacitor Standards

NEMA CP-1 for Shunt CapacitorsUL 810 Standard for CapacitorsNFPA 70, National Electrical CodeIEEE Standard 399, Power System AnalysisANSI / IEEE Standard 18, Shunt Power CapacitorsIEEE Standard 141, Recommended Practice for Electrical Power Distribution for Industrial Plants

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Other Capacitor Application Issues

NEC & NEMA : * The Ampacity of Capacitor Circuit Conductors shall not be less than 135% of rated Capacitor Current * Breaker Rating based on 135% Rated Capacitor Current * Fuse Rating based on 165% Rated Capacitor Current for Class R Time Delay * Fusible Switch Rating based on 165% Rated Capacitor Current

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Capacitor Operating Environment Issues

Capacitor When Properly Applied Will Have Long Life.Conditions that affect the Life of Capacitor: * Ambient Temp. < 46Deg C or 115Deg F * Case Temp. of Capacitor < 55Deg C or 131 Deg F * Shunt Capacitor designed to operate at 110% Rated Voltage. * Avoid sustained Over Voltage * High System Harmonics

**Power Quality Correction

Summary of Benefits:Reduced Power Costs:Since Capacitors supply reactive power, you dont pay the utility for itDepending up on location of Cap. Bank, Line Loss can be reduced.You can calculate the savingsOff-load transformersDefer buying a larger transformer when adding loadsReduce voltage drop at loadsOnly if capacitors are applied at loads(minimal benefit at best)

A2

**Power Quality Correction

Thank You ! Questions?

22Power Factor CorrectionCapacitors offload the utility grid by supplying the reactive power required by inductive loads. Power factor is improved by reducing the reactive power component. Capacitors provide the reactive power required by inductive loads.

The installation of capacitors will improve the power factor from the point of connection back to the source as shown. In this example, the load is 10 000 kVA at a power factor of 80%. This results in demand for 8000 kW of active (real) power and 6000 kVAR of reactive power. With the installation of a capacitor in figure 2 (b) most of the reactive power is supplied locally and the power supply sees a power factor of 97%.

Since the power supply provides reduced reactive power with the installation of power factor capacitors, peak currents are reduced. Power factor capacitors are rated in kVAR. Power factor capacitors help bring the network current in phase with the network voltage by supplying leading current to effectively cancel lagging inductive current. Reactive energy is continuously swapped between the capacitor and inductive load.

The result of improved power factor is reduced utility demand resulting in lower utility demand bills, released system capacity and lower system losses.Total or True Power Factor has two components displacement power factor and harmonic power factor. However, harmonic PF is not a term used today. We call it the harmonic coefficient.

The product of these two values equals the true PF.In this example well use a PWM VFD that has no DC bus choke or input line reactor. Typically these drives can cause 90 to 120% TDD.

PWM VFD have diode rectifiers so the DPF is .95 or better.

When the harmonic coefficient is calculated using 90% THD(I) the factor is .7433. The total PF is .7061.The second and potentially more serious concern, is network resonance. When capacitors are added to the network, they set up a parallel resonance circuit between the capacitors and the network inductancesHarmonic current components that are close to the parallel resonance point are magnified. The magnified current can cause serious problems such as excessive voltage distortion, nuisance fuse and breaker operation, overvoltage tripping of drives and insulation breakdown within motors, transformers and conductors.

5th harmonic typically dominates on three phase networks. Three phase capacitors connected with solid state switching elements which are controlled by a Transient Free Controller Solid State Capacitor Switching Modules provide reliable, high speed, transient free operation. Each Capacitor switching Module switches up to three capacitor groups (450kVAR) using double phase electronic switches for each three phase capacitor group. Fuses protect the electronic switching elements against short circuit currents. Custom designed Iron Core reactors in the AT6000 de-tune the network, prevent resonance and remove up to 50% of the 5th harmonic. AT6000 is recommended for power factor correction in networks with greater than 15% non-linear loads. For a non-linear load percentage of less than 15%, the standard AT5000 bank is suitable. AT6000 provide the following: Tunes the network below the first dominant harmonic, usually the 5th or 300 Hz May absorb up to 50% of the 5th harmonic current depending on network characteristics A heavy steel welded yoke to clamp the top and bottom laminations as opposed to traditional bolt through clampingAT5000 vs AT6000 example: suppose a transformer supplies 2000 kW. Of this, 400 kW is used by non-linear devices (AC or DC Drives, power converters etc.) The non-linear load percentage will be greater than 15% (400/2000) and, therefore, an anti-resonant TFRC (AT6000) system is recommended.Capacitors - Heavy Duty Dry Capacitors feature self healing metalized polypropylene film elements provide good heat dissipation resulting in longer lifeElements for 480V networks are rated 590V +10% overvoltage; elements for 600V networks are rated 690V +10% overvoltageUnique open air-element design - modular design22224