medium voltage real time & transient free capacitor systems
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Medium Voltage Real Time & Transient Free Capacitor Systems
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Outline
Introduction Why RTRC or TFRC? Limitations of Conventional Solutions The RTRC and TFRC Solution Applications Benefits Product Characteristics
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Capacitor Offering Schneider Electric is the world’s largest LV capacitor
manufacturer by market share Power Quality Correction Group (PQc) located in
Toronto, Canada has marketing, sales, application engineering, design and technical support responsibility for North America
Low Voltage Equipment is manufactured at the Waterman facility
Medium Voltage Equipment is assembled at Square D facility outside of Cincinnati
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Capacitor Offering Fixed Capacitors Standard Automatic Capacitor Banks Anti-Resonant Automatic Capacitor Banks Filtered Automatic Capacitor Banks Real Time Reactive Compensation Systems Transient Free Reactive Compensation
Systems MV Metal Enclosed Systems MV Real Time & Transient Free Systems
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Service OfferingOn-site measurementComputer Network
SimulationsAnalysis of ProblemReportSpecificationsCustom Engineered
EquipmentCommissioningVerification of
PerformanceTrainingAfter Sale Servicing
Solution Cycle
Measure
Simulate
Analyze & Report
Specify & Propose
Commission
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Power Factor
Ratio of Active (Real) Power to Total (Apparent) Power (kW/kVA)
A measure of efficiencyDepends on the phase angle between
voltage and current waveforms
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Power Factor DefinedReactive
Power develops the magnetic field required by machines to perform useful work
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Power Factor FundamentalsIn this example,
demand was reduced to 8 250 kVA from 10 000 kVA.
The power factor was improved from 80% to 97%
Before After
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Increased System Capacity
Apparent Power2500 KVA
Real Power1500 KW
Reactive Power2000 kVARUncompensated
cos 1 = .60cos 2 = .882
1
2
1700 KVAReactive Power800 kVARCompensated
Any capacitor based system reduces apparent power (KVA) and load current
Potential savings in capital investment
Alternately, additional load can be added to the network without the risk of overload
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HarmonicsCurrent Limiting Reactors in
multi-step MV standard systems limit capacitor inrush currents
Air or Iron Core reactors in MV Anti-Resonant and Filtered systems detune the system to prevent resonance and remove up to 50% of the 5th harmonic
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Harmonic Current Waveform(Typical 6 Pulse Drive)
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Resonance
The installation of standard capacitors can magnify harmonic currents on the network
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Resonance
Magnification of Harmonic Current when Standard Capacitors are Added to the Network
Resonant Point likely to amplify dominant harmonic (typically 5th)
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Detune to Avoid Resonance
Effect on Harmonic Current when Anti-Resonant Capacitor Bank is Applied
Resonant Point where no Harmonic Content present (3.7th typical)
5th Harmonic on Network is reduced(4.4 Tuning)
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The Real Time ChallengeTo compensate reactive power required by
rapid and frequent load variations
• motivation:
– increased productivity
– elimination of voltage flicker and sags
– increased system capacity and energy efficiency
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Conventional TechnologyCompensates reactive energy of stable loads only
Unable to cope with rapid and frequent load variations
Limited Speed - Why?
To reduce wear of vacuum switchesTo allow capacitors to discharge before reconnectionConventional Controller speed limitation
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Conventional Switch Structure
HRC Fuses
VacuumContactors
OptionalDe-tunedInductor
L1 L2 L3Vacuum (or SF6)contactors or breakers are used to connect a capacitor group.
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Real TimeReactive Compensation
One cycle (17 ms) or less response to load fluctuations
Transient Free Connection of Capacitors
Minimal wear of electronic switching elements
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Transient Free Reactive Compensation
3-4 second response to load fluctuations
Transient Free Connection of Capacitors
Minimal wear of electronic switching elements
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Electronic Switch Structure
Fuses
SCR-Diode
De-tunedInductor
L1 L2 L3
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Transient Free Switching
RTRC - Smooth Connection
Current inrush with vacuum switching can be 15 - 20 times steady state current
Resultant voltage transient can effect sensitive electronics
RTRC and TFRC systems generate no network voltage transient
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RT Acquisition & Response
Acquisition Time 17 ms
A
B
RTRC Bank Current
System Voltage
Load Current V
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End Result Any variation in reactive power is
compensated within one cycle (16.7 ms) using transient free switching of capacitor stages resulting in:
•increased productivity
•elimination of voltage flicker & sags
•increased system capacity & energy efficiency
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Real Time ApplicationsUnstable Loads (rapid changes):
•Injection molding machines•Elevators•Presses•Rock Crushers
Motor Starting•compensation of inrush current for many motors•allows normal starting torque
Spot Welding (typically at low voltage)extremely fast changes - less than one
second (typically at low voltage)•Re-enforced Mesh for concrete•Automotive industry
•Wood Chippers•Mining Conveyors•Induction Heat Treating•DC Hoisting
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Results of RTRC Installation• Gas Pumping Station in Colorado
• 25 KV Line to 2.5 MVA Transformer step down to 2.4 KV
• Three FVNR Motors (500 HP, 700 HP, 700 HP)
• Motor start causing unacceptable voltage drop on 25 KV line (16-18%)
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• Solution was a 3.6 MVAR, 2.4 KV Real Time System
• Three equal steps of 1.2 MVAR each
• Utilized air cooled SCR/Diode modules
• Installed outdoors
• Goal to obtain less than 5% voltage drop on the 25 KV line
Results of RTRC Installation
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Results of RTRC Installation500 HP & 700 HP Running
Starting 2nd 700 HP Motor
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Objective to limit voltage drop to less than 5% on the 25 KV line has been met
• initial voltage drop is only 4.2% on the 2.4 KV line• secondary voltage drop of 7.3% at 2.4 KV line (as stages turn off)
– modifications to the control will improve this further
Motors previously took 4-6 seconds to come up to speed
• with RTRC, motors are up to speed in less than 2 seconds
Results of RTRC Installation
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Transient Free ApplicationsSensitive Networks
Hospitals Data Processing Centers Microelectronics Fab Facilities Pharmaceutical Facilities Airports Research laboratories Other Industrial and commercial facilities with high concentrations of sensitive electronic loads
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Voltage Sag and Flicker Reduction
With
•Voltage sag is reduced as a result of reactive compensation during the load fluctuation.
•The voltage sag during is affected more by the power factor than by current amplitude reduction.
VVS
VL
Without
V
VS
VL
With
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Energy SavingsEnergy saving due to reduction of losses and harmonics:
Losses in cables:
• Copper losses - I2R.
• Skin effect losses due to reduction of harmonics.
Losses in transformers:
• Copper losses - I2R.
• Skin effect losses due to reduction of harmonics.
• Iron losses due to reduction of harmonics.
Total estimated saving: 3 - 5%
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RTRC Advantages Flicker Reduction
Compliance with flicker standards
Network Stabilization and reduced equipment outages
Voltage Regulation Improvement Reduced duty on tap changers
Improved Network Utilization Reduced Transformer loading
Current reduction on Bus Bars, Breakers and Cables
Energy Saving, Power Factor Correction & Harmonic Reduction
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Process Productivity Improvements
The RTRC will eliminate:failed motor starts due to voltage sagsundervoltage tripping of sensitive loadslighting flicker and HID lighting shutdownoverloaded distribution equipmentcapacitor switching transients
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RTRC SummaryADVANTAGES
•Increases network capacity•Minimizes voltage sags•Minimizes voltage flicker•Reduces load current•Avoids wear of vacuum
contactors & capacitors•Transient free switching in
sensitive networks•Avoids use of reduced voltage
starters•Saves energy and improves
Power Factor
DISADVANTAGES•Costly solution
compared to standard capacitor systems (but often the only viable solution)
•Physical space requirements
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MV RT & TF Product Overview
Metal Enclosed Systems up to 15 kV
Three-Bushing, delta capacitor units available up to 5 kV. Two-bushing capacitors connected in Delta for higher voltages
Type 1 indoor or Type 3R outdoor enclosure types.
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Real Time Reactive Compensation Systems MV9000 Series Power Factor Correction of
highly cyclical loads
Transient Free Reactive Compensation Systems
MT6000 Series Power Factor Correction of
networks with sensitive electronic loads
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Standard, Detuned or Filtered? MT6000 & MV9000 are typically Anti-resonant
or filtered but may also be standard with current limiting reactors only
Filtered used for Power Factor Correction of networks with more than 50% Non-Linear Loads
Anti-resonant and filtered systems are manufactured with higher than nominal voltage capacitor elements to ensure long term system stability.
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Status Indicators
Readings Display
Function Keys Description
Function Keys
Controller
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Protection Unbalance and Overload protection via
phase current sensing standard for either wye or delta capacitor steps
Optional unbalance protection by neutral current sensing on wye connected capacitor steps
Optional Neutral to Ground Potential transformer for unbalance protection for wye connected banks
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Capacitors
Merlin Gerin PROPIVAR or Cooper (McGraw Edison)
External Fusing Standard
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Merlin Gerin Capacitors Available as
Three Phase, Three-Bushing Delta Connected, up to 5 kV or Single Phase, Two-Bushing for voltages higher than 5 kV
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Merlin Gerin Capacitors
Environmentally safe biodegradable non PCB dielectric liquid
Good Heat Dissipation and Low dielectric losses result in long element life
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Merlin Gerin Capacitors
High Overvoltage and Overcurrent withstand:
• 10% Overvoltage for 12 hours a day
• 30% Continuous Overcurrent Highly resistant to transient
overvoltages and partial discharge levels
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Merlin Gerin Capacitors
Suitable for harmonic filtering applications and networks with poor voltage regulation
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Cooper Capacitors Single Phase, Two-Bushing for
Wye or Delta connection 125% Continuous rms Overvoltage
withstand and 135% peak overvoltage capability
Wide operating temperature range:• -40 to 131ºF (-40 to 55ºC)
Environmentally acceptable dielectric fluid
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Cooper Capacitors
Standard unit power rating from 50 to 400 kVAR single phase from 2.4kV
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Current Limiting Fuses
To protect capacitors, fuses are rated as closely as possible to the capacitor steady state current
Blown fuse indication directly on the fuse (pop-up indicators)
Visible via viewing windows in enclosure
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Conventional Switching Stage
Three Phase Reactor
Capacitors
Current Transformers for unbalance detection
Vacuum Contactor
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Electronic Switching Modules Switching two phases with
Delta connected capacitors Air or Liquid Cooled Stick
Stacks of anti-polar SCR/Diodes with failsafe cooling systems
•temperature, air flow, pressure monitoring
Multiple modules connected in series for higher voltagesLiquid Cooled Stick Stack
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HVL Interrupter Switch
Direct Drive Operator Fused for short circuit
protection or Unfused available
Load Break to max 2400 kVAR @ 5 kV or 15 kV
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Iron Core Reactors
Necessary to Detune network to prevent resonance when large harmonic producing loads are present
Reactors Filter dominant harmonic (usually the 5th)
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Iron Core Reactors Single or Three phase
laminated low hysteresis reactors with precision air gap
All copper windings, mounted on insulated bushings up to 95 kV BIL
Current Limiting Reactors in standard systems are Air or Iron Core
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Enclosure
Modular Style Design either indoor NEMA 1 or outdoor NEMA 3R (others available)
All Silver-Flashed Copper Bus
• Better fault withstand ratings (50kA IC standard)
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Enclosure Removable Panels over bolted
steel frame
• Rigid construction while allowing ease of servicing
Standard ASA49 Gray paint finish. Other finishes available upon request.
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Enclosure Key interlocks standard
• Electrical interlocks standard Tamper resistant interlocked
ground switch for each capacitor stage
Viewing windows to ensure ground switch and main switch operation
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Enclosure Control Cabinet mounted rear or
side of main (remote mounting optional)
Optional thermostatically controlled, ball bearing fans
Welded lifting eyes Three point door latch
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7Division - Na me - Da te - Lan gua ge 20 © 2001 Schneider Electric Canada, All Rights Reserved June, 2001
Schneider Electric Canada Inc.19 Waterman AvenueToronto, Ontario, M4B 1Y2www.schneider-electric.caTel.: (416) 752-8020Fax: (416) 752-6230
Schneider ElectricPower Quality Correction Group255 Orenda RoadBramalea, Ontario, L6T 1E6www.reactivar.comTel.: (905) 459-8805Fax: (905) 454-3603