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Introduction to Power Quality: Problems, Analysis & Solutions
Presented by:
PowerCET® Corporation3350 Scott Blvd., Bldg. 55 Unit 1Santa Clara, CA 95054 USA408/988-1346 | FAX 408/988-4869E-mail: training@powercet.comE-mail: consulting@powercet.comWeb Page: http://www.powercet.com
Course: PQ103
© 2007 by PowerCET Corporation. All rights reserved. (070320)
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)1
Introduction to Power Quality: Problems, Analysis & SolutionsCourse: PQ103
ByPowerCET Corporation
2
The Electrical Environment & Power Quality• What is it? ...Quality or Reliability?• Why is it important?• How do we measure it?• Is it getting better?• Utility deregulation, what's going to happen?• Where do electrical problems come from?• What can we do about it?
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2
3
Power Quality (def.)
• "Poor Power Quality" generally mean there is sufficient deviation in the power (electrical) supply to cause equipment/process mis-operation or failure.
• "Good Power Quality" means that the power (electrical) supply is sufficient for the equipment/process to operate satisfactorily.
• Equipment design is a major determinant between good and bad power quality.
4
Power Quality & Reliability
• Power Reliability is the presence of sufficient voltage at the meter.
• Power Quality is the value of the voltage (and other electrical parameters) as a percent of nominal at the meter.
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)3
5
Power Quality - Translated
• If you can achieve what you want--making widgets, etc.--in the existing electrical environment then power quality would be considered good!
• If you can not achieve the desired results in the existing electrical environment then power quality would be considered bad!
• It can change from good to bad in an instant!
6
Some Additional PQ Observations
• 95% of the PQ problems are on the customer side of the meter.
• 80% of the $$$ losses are caused by the 5% of the problems from the utility side of the meter.
• The vast majority of the problems from the utility are voltage sags.
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4
7
Sources of Power Quality Problems in Order of Frequency of Occurrence• User loads• User electrical distribution and grounding• Weather related...lightning, wind, rain, etc.• Utility distribution.• Utility transmission.• Utility generation.
8
The Cost of Poor Power Quality• Various studies (annual
costs to U.S. business)....– Clemmensen (1993) $25.6
Billion – EPRI (1995) $400 Billion– Swaminathan and Sen
(1998) $150 Billion– Douglas (2000) $50 Billion
• The truth is no one really knows...our cost accounting systems just do not capture the data to provide an accurate indication of the true cost of poor power quality.
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5
9
Air Traffic Control: Lost control at a major airport can cost $15,000-$50,000/minute
DuPont: Saved $75 million/annually by implementing PQ solutions. ($50,000 to $500,000 per event...additionally risk of accident and pollution.)
Compressor manufacturer: Sags and interruptions cost some $1,700,000/year. ($100,000 per event.)
Automotive Industry: Momentary interruptions cost some $10 million/year ($50,000 to $500,000 per event.)
Paper Industry: Billinton study determined cost of 2 second outage to be approximately $30,000
Source: EPRI Power Electronics Applications Center
The Cost of Poor Power Quality
10
Power Interruption Cost Calculator• Disturbance Statistics
– Downtime duration (Hrs.)– Recovery time (Hrs.)– Number of idled personnel – Average hourly rate ($/Hr)– Number of recovery
personnel– Average hourly rate ($/Hr)– Payroll overhead & benefits
($/Hr)– Scrap material (units)– Scrap material unit cost
($/unit)
• Cost of Losses– Other lost material value ($)– Canceled orders– Late delivery / performance
penalty payments– Lost customer confidence
• Recovery Costs– Equipment
repair/replacement costs– Software / restarting costs
(labor & material)
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6
11
Power Quality & Reliability
12
The "9s" of Reliable Power
Standby Generator
Multiple Redundancy UPS, Standby Generators
Mirrored Sites, Multiple Redundancy UPS, Standby Generators
30 MillisecondsOn-line Markets99.9999999%Nine 9s
32 SecondsBanks99.9999%Six 9s
5 MinutesHospitals, Airports99.999%Five 9s
59 MinutesFactories 99.99%Four 9s
9 HoursHomes99.9%Three 9s
Disruption Duration/YearApplicationsReliability
Source: Reliable Power Meters
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)7
13
Failing to "Look" Beyond the Traditional Power Quality Environment
PowerProblem
14
Looking Beyond Traditional Power Quality
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8
15
Why is the Quality of the Environment Important?
Electrical
Environment
Infrastructure
Management
Equipment
Compatibility
Load
Sensitivity
Load
Sensitivity
Equipment
Compatibility
Infrastructure
Management
Electrical
Environment
RELIABILITY
PRODUCTIVITY
PROFITABILITY
16
T&D
Generation
Facility Wiring& Construction
TraditionalLoads
ElectronicLoads
Climatic & Geographic
What Determines Electrical Environment Quality?
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)9
17
U.S. Lightning Flash Density - 1989-98
18
Lightning Activity
• It is not a question of if, but when?
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)10
19
Electrical Loads
• Traditional– Lights– Motors
Electronic
LN
AC
DC
L
N
G
20
Sources of Electrical Problems
• External– Utility sources– Other utility customers– A.O.G.
• Internal– Wiring errors and poor
construction practices– Other loads– EMI / RFI
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)11
21
Evaluating the Changes Over the Past 30-Years• Equipment
characteristics
• Technology
• Environment
22
Equipment Characteristics
• Past...– Inefficient power
supply, voltage regulation generally required.
– Large physical size– Increasing applications– Limited networking
(stand alone systems)
• Present...– Compact, high
efficiency design– More sensitive to high
frequency electrical noise
– Increased temperature sensitivity
– Voltage regulation generally not required
– Increasing networking applications
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)12
23
The Technology
• Past...– Discrete components --
relatively robust, high power logic
– Slow data rates and processor cycle times
• Present...– Increasing IC densities– Increasing processor
speed and data rates– Switch mode & PFC
power supplies– Increasing network
applications– New technology
• Wireless , Cellular, Power line networks...
24
The Environment• Past...
– Engineering, Construction & Maintenance
• Internal (Except for very large jobs or additions)
• Good records• Good infrastructure
management
• Present...– Limited internal engineering,
if any– Out-source most
construction– Deferred maintenance– Little internal control over
electrical environment– Installation by Folklore and
Tradition– Lack of understanding of the
Real World Environment
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)13
25
The Future...
• Increasing complex applications• Component technology continues to evolve• Increasing operating speeds and data rates• Increased networking applications• Power supplies--CE Mark complications /
harmonic limits– Decreased filter capacitors to reduce harmonics also
decreases effective ride-through...voltage regulation???– Application of "choppers" to provide sinusoidal current
draw results in increased low frequency emissions and voltage source interactions
26
Increased Data Rates and Processor Speed
Data Rate (bps) Time Approximate Distance
60 16.7 mS 3100 Miles2400 417 uS 78 Miles1 M 1 uS 982 Feet10 M 100 nS 98 Feet
100 M 10 nS 10 Feet1 G 1 nS 1 Foot
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)14
27
Power Supply Technology
SMALL HF TRANSFORMER
SWITCH MODE D.C. POWER SUPPLY
L
PWM
VoN
LINEAR D.C. POWER SUPPLY
Vo
L
NLINEARREGULATOR
LARGE 60HzTRANSFORMER
N:1
28
The Changing Electrical Environment
• Changing electrical loads (SCRs)– Variable speed drives (ac & dc)– Frequency modulators– Large UPS systems
• Loss of control over the internal electrical environment
• Decreased infrastructure management and control
• Changing residential electrical environment
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)15
29
The Electromagnetic Environment
FacilityLoads
(Harmonics)
ElectricalService
Configuration
ElectricUtility
Reliability
FacilityWiring,
Grounding &Construction
TelcoInterface
& Protection
Mission CriticalEqpt & Sys
NetworkFacilities
Dist & Prot
EMI&
RFI
ElectrostaticDischarge
(ESD)Control
30
The Future of Power Quality
• The Utility• The Mitigation Equipment Supplier• The Consulting Engineer• The Electrical Contractor• The User
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)16
31
The California Experience
32
Electric Utility Deregulation
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)17
33
Electric Utility Deregulation
Generation
Transmission
Distribution
Customer Service
Power Producers(GENCOs or IPPs)
Regional Transmission Network Operators (TRNSCOs)
Bulk Power Trader(POWERCOs)
Distribution System Operators(DISTCOs)
Retail Power Marketers(RETAILCOs)
Energy Service Companies (ESCOs)
Deregulated& Industry
Restructuring
Vertically Integrated Electric Utility
Deregulated Electric Utility Industry
34
Power Quality and the Utility
• Reliability and quality will decrease with deregulation
• Increased monitoring and performance measurement requirements
• Most will offer enhanced and/or contract services (SEFI&O)
• Stability of the utility power industry will be a problem, at least in the short-term
• Displaced workforce as competition and deregulation become a reality
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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35
PQ and the Mitigation/Protection Equipment Supplier• Market segmentation• Suppressors• Filters• UPS equipment• Margins continue to
erode -- commodity pricing
• Push vs. Pull• Direct vs. Indirect• Market channels• Positioning and
product differentiation• Vertical market
segments• F.U.D.
36
Monitoring Equipment Suppliers
• New competitors will continue to enter the market
• More permanently installed monitoring & control systems
• Equipment will evolve slowly providing an opportunity for additional competition
• New low cost monitoring equipment will do well in this market as long as complex programming or setup is not required
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)19
37
PQ and the Consulting Engineer
• Work will become more competitive and less profitable
• Larger firms will dominate• Some will offer PQ services as a method of
maintaining customer/account control• Some will probably have a sales operation
for protection/mitigation products or a relationship with suppliers (additional revenue source)
38
PQ and the Electrical Contractor
• Increased awareness of Power Quality opportunity– TEGG
• Most will have some "bad" experiences with PQ• Some contracting operations (medium size, 10 to
50 employees) will develop PQ capabilities in an effort to– Increase revenue and – Differentiate themselves from the competition
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)20
39
PQ and the User
• Will become more demanding• Will increase reliance on electrical energy• Will have a greater variety of loads• May, in some instances, make Power
Quality a PRIORITY!
You Never Have a Problem...
Until You Plug it IN!
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)1-1
I The Electric Utility System
2
The Consumers View of the Utility
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)1-2
3
Managing the Electric Utility Grid
4
The US National Grid
• Transmission level interconnections
• Evolving mission from backup to power transfer
• Three major interconnections
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)1-3
5
Electric Utility Energy Sources
6
Electric Utility Customers & Usage
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)1-4
7
The Utility
8
Power Quality & Utility Reliability
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)1-5
9
Electrical Conditions that can Disrupt a Process.• Voltage sags, i.e., 90% of nominal for 6-12 cycles• Single phasing, i.e., loss of one of three phase
sources• Voltage interruption of several cycles caused by a
utility reclosure operation• Complete extended power outage• Transients caused by:
– Lightning– Utility grid and capacitor switching– Non-linear loads
10
Std. Nominal System VoltagesVoltage Class 2-wire 3-wire 4-wire
Low Voltage (LV)120* 120/240*
480600
240/120208Y/120480Y/277
Medium Voltage (MV)
2400416048006900
1380023000345004600069000
4160Y/24008320Y/4800
12000Y/693012470Y/720013200Y/762013800Y/7970
24940Y/1440034500Y/19920
High Voltage (HV)115000138000161000230000
Extra High Voltage (EHV)
345000500000765000
1100000
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)1-6
11
Power Quality and the Utility
• Transformers– Transmission &
distribution– Service
• wye• delta• open delta• red-leg (high-leg) delta
OR
12
Service Transformers
• Single phase • Three phase
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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13
Pad mount3-phase pole mount3-phase red-leg delta
Service Transformers
14
Protective apparatus
• Fuses and circuit breakers• Lightning arresters and suppressors• Insulators, conductors and switches
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)1-8
15
Circuit Breakers / Reclosure
• 5 to 6 Cycles for operation after application of the fault condition– Customer experiences a sag during this interval
• Open duration from 20 cycles to 2 to 5 seconds– Actual duration depends on location of fault and local
utility practices• Multiple operations (typically 3) may be
experiences if the fault does not clear during initial operations
16
Reclosure
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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17
Customer Impact of Utility Faults
• Faults on adjacent feeders and circuits generally result in voltage sags
• Faults on serving feeder results in sag followed by interruption
Circuit Breakers
1 3 42
Transmission
Distribution
13.8k
230k
480 V
To HV Transmission &
Power Generation
A B
Customers
Customer
= Single line-to-ground fault (SLGF)
18
Utility Fault Clearing: Reclosure Operation
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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19
Utility Reclosure Operation
• Utility fault on customer feeder
V & I = Source
20
Utility Reclosure Operation
• Fault on adjacent feeder
V & I = Source
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)1-11
21
Utility Reclosure Operation / Lightning
22
Sag Correcting Devices
• SoftswitchingTechnologies
Dip Proofing Technologies, Inc.
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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23
Corrective apparatus
• Voltage regulating equipment• Power factor correction capacitors
24
Power Factor Correction Capacitors
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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25
Power Factor Correction Capacitors
26
Power Factor Capacitor Switching
• Zero Voltage Sensing Control--before & after
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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27
Utility Fault
28
V & I = Source
Utility Transient
Source related transient
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2-1
II Building & Facility Wiring
2
Service Entrance
• Main disconnect and overcurrent protection (circuit breakers).
• Building electrical system earth reference (neutral-to-ground bond).
• Earth grounding system.• Equipment grounding system.• Wiring errors and electrical code violations
(NEC Article 250).
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2-2
3
Building (Facility) Wiring
SUB-PANEL
NPLUG/
RECEPTACLE
BUILDINGSERVICE
TRANSFORMER FEEDERBRANCHCIRCUIT
UTILIZATIONEQUIPMENT
N-GBOND
G
G
MAINELECTRICAL
SERVICEPANEL
N
EARTHGROUNDING
SYSTEM
EQUIPMENT GROUNDINGSYSTEM (GREEN WIRE)GROUND
BUS
EARTHGROUND
NEUTRALBUS
4
Ground Fault Interrupt (GFI)
• Required for all 480V services rated at 1000A or more.
• GFI problems– Excessive current from
voltage sag or load operation.
– Harmonic distortion confuses current summing circuitry.
– Electrical noise (interference) confuses the GFI controller
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2-3
5
Ground Fault Interrupt (GFI) Troubleshooting• Monitor neutral-to-ground bond to determine
if tripping is the result of a fault or wiring errors.
• Monitor for distortion levels.• Monitor service voltage levels.• Have GFI circuitry tested and calibrated.• Do not disable GFI equipment or adjust
threshold limits to their maximum range.
6
Distribution Transformer Uses
• Isolation• Voltage transformation
(step-up/step-down).• Limit neutral-to-ground
voltage differentials.• Limit and control
undesirable neutral return currents (delta-to-wye
Line
Ground
Neutral
Voltage Transformation
Neutral-to-Ground Voltage Differential = Near Zero
ØC
ØB
ØA
Eqpt Grounding Conductor
Neutral
ØA
ØB
ØC
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2-4
7
Other Transformer Considerations
• Separately derived systems must be grounded as outlined in NEC Article 250 or 645.
• Transformers 1000VA and larger must be grounded to the nearest grounding electrode (NEC Article 250).
• Health care facilities have special requirements.
8
Panelboards (sub-panels)
• Configuration– 1-phase, 3-wire– 3-phase, 4-wire
Ampere Ratings of Mains– 12 to 42 pole positions– 100 to 400 Amp typical
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2-5
9
Panelboards (sub-panels)• 1, 2. Incoming Hot wires. There is 240
volts between these wires, or 120 volts between either wire and the neutral line.
• 3. Neutral wire. This is at the same electrical potential as the ground. At the main breaker only, the neutral is connected to ground.
• 4. Ground Bus Bar. This strip of metal has a row of screws for connecting the ground wires of the various circuits.
• 5, 6, 7. Neutral Bus Bars. This panel has 3 short bus bars for neutral wire connections. Some panels have only one long bar.
• 8. Circuit Breakers. Each single-pole breaker connects to one of the two hot bus bars. Each double-pole breaker connects to both of the bus bars (thus providing 240 volts between hot wires).
• 9. The last available space in this panel. Our new breaker will go here.
10
Neutral to Ground Bonds
• Only ONE allowed!• Extra bonds are common through mis-wiring
& equipment problems• Use separate neutral & ground buses• Monitor circuit and ground conductors
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2-6
11
Overcurrent Protection: "Do's & Don'ts"
• Circuit breakers must be ganged for poly-phase circuits.
• Avoid using fuses in feeders as supplemental protection in poly-phase circuits unless phase loss detection is installed.
• Overcurrent devices can only be loaded to 80% of their rated capacity.
12
More: "Do's & Don'ts"
• Inspect panelboards for loose, noisy or excessively hot circuit breakers (IR or Ultra-sonic scans).
• Inrush (nuisance) tripping -- replace older breakers.
• Excessive voltage drop across circuit breaker -- replace (it will be the HOT one).
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2-7
13
Amp AmpMixer
Osc
In Out 5KHz45KHz
40KHz
Ultrasonic Detectors (Translators)
14
Mechanical Connections• Conduit instead of
grounding conductor– Screw thread– Clamp– Compression sleeve– Flexible
• Wiring termination practices– Mixed wires & double-
lugging– Solid vs stranded– Copper vs aluminum
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2-8
15
Feeders & Branch Circuits
• Recommended voltage drops– Feeders 3%– Branch circuits 3%– Overall 5%
• Methods to decrease voltage drop– Increase wire size– Decrease load– Decrease length of circuit
• Shared Neutral Circuits (Feeders)
16
Shared Neutral Facilities
• Multi-wire circuits and non-linear loads• Non-canceling neutral return currents• Symptoms of high impedance (open)
shared neutral conductors– High incidence of power supply failure– Erratic equipment operation– Load interaction
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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17
ABCNG
MediumLoad
HeavyLoad
LightLoad
VOLTAGE PHASE A PHASE B PHASE CL-N 143 73 166L-G 122 122 123N-G 54 54 54
High Impedance Neutral
18
Results of an Open Neutral
• High Impedance Neutral
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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19
Neutral Current - Sinusoidal Loads
• No Imbalance– Phase currents offset
• Phase Imbalance– Imbalance = neutral
20
Neutral Current and Computer Loads
• Current pulses do not offset
• Current in neutral can reach 1.73 times the size of individual phase currents
• Frequency of current is 3x fundamental – 150 Hz for 50 Hz– 180 Hz for 60 Hz
A
B
C
N
G
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)2-11
21
Solutions for Multiwire Problems
• Delta-wye transformers• Eliminate shared facilities / oversize neutral
conductors• Filtering• Equipment redesign• Managing the environment
22
Receptacles (NEMA Notation)
L21-30R
CONTACT TYPE"L" denotes locking type; nothing denotes straight blade.
VOLTAGE TYPE5 = 120V6 = 240V, 208V14 = 240/120V, 208V21 = 208/120V, 3-Phase
TYPE OF CONNECTOR"R" denotes receptacle, or female."P" denotes plug, or male.
CURRENT CAPACITY15 Amps20 Amps30 Amps
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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23
Standard & IG Receptacles
24
IG Receptacle Construction
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2008 by PowerCET Corporation. All rights reserved. (070320)3-1
1
lll Harmonics
2
Harmonics• Harmonics
– Integer multiples of a fundamental -- added to fundamental create distorted sinusoidal or non-sinusoidal waveform
– Harmonics are caused by Non-linear load currents & Non-linear voltage sources
– Measurements of harmonic content does not always indicate the presence of problems
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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3
Effects of Harmonics• Current
– Current flow without work (low power factor)– Transformer & wiring losses– Negative sequence currents that reduce torque in
motors– Excessive neutral current
• Voltage– Peak voltage loss and "ride-through” reduction– Phase voltage imbalance – Motor plugging or cogging– Zero voltage cross distortion and frequency errors
4
Odd Harmonics
• Symmetrical– 90°, 180°, 270°– Leading/trailing edge– Positive/negative cycle
• Single phase loads– 3rd, 5th, 7th, 9th...
• Polyphase loads– Frequency doublets– 5th & 7th, 11th & 13th
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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5
Even Order Harmonics• Asymmetrical
– 90°, 180°, 270°– Can shift the position of the
fundamental causing loss of 120° phase shift between phases
– Can cause dc bias problems in motors and transformers
– Can cause phase control problems for SCR/Triacloads
6
Harmonic Order• Balanced harmonics
– Frequency doublets: 6n +/-1
– 5, 7, 11, 13, 17, 19, 23, 25 ...– Positive & negative
sequence• Zero Sequence Harmonics
– Triplens: 6n-3 (odd multiples of 150/180 Hz)
– Ground referenced (neutral)• Even order harmonics
– Conduction angle differences
– Diode failure– 3 pulse rectifiers -- IEEE519
Harmonic #
Harmonic Sequence
3 Pulse &L/N Loads 6 Pulse 12 Pulse 18 Pulse 24 Pulse
3 0 x5 - x x7 + x x9 0 x
11 - x x x13 + x x x15 0 x17 - x x x19 + x x x21 0 x23 - x x x x25 + x x x x27 0 x29 - x x31 + x x33 0 x35 - x x x x37 + x x x x39 0 x41 - x x43 + x x45 0 x47 - x x x x49 + x x x
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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7
Power FactorDisplacement Distortion
Power Factor• Power Factor (PF)
– PF = Watts / Volt*Ampere• Displacement Factor (f)
– Cosine of angle (E & I)• Distortion Factor (d)
– d = Afund / Arms
8
Distorted Voltage Waveform
• High impedance distribution system– Load currents interact
with impedance – Peak voltage loss and
extended voltage waveform
– Dominant harmonics third, fifth and ninth
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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9
Computer Load Current
• Load current developed by computers
• Dominant harmonic currents:– Third, fifth and ninth
10
Power Calculations• Fundamental and harmonic contributions to power
– Power = E * I * cosine of angle between E & I • Phase angle affects power contribution
– 0° to 90° (+) : 90° (0) : 91° to 180° (-) : 180 (-1)– 181° to 270° (-) : 270° (0) : 271° to 360° (+)
Harmonic Voltage Phase Current Phase Mean PowerFundamental 121.8 87 32.75 103 3,832
3 12.1 48 14.1 306 -355 2.8 264 8.3 167 -39 1.7 52 1.6 0 2
Total 3,796
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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11
Power Factor Determination
• Mean power delivered = 3,796 watts• RMS voltage = 122.6 volts• RMS current = 36.7 amps• Apparent power = 122.6*36.7 = 4,499 VA• Power factor = 3,796/4,499 =0.84• Distortion factor d = 0.89• Displacement PF = cos(ffun) = cos16 = 0.96
12
Single Phase Angle Control Loads
• Light dimmers and heater controls
• Odd order harmonics dominant
• Power factor and THD depend upon phase angle
• Even order harmonics present when firing angle varies
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2008 by PowerCET Corporation. All rights reserved. (070320)3-7
13
Full Wave Power Supply• Computer loads• Harmonics
– Odd orders dominant• 3rd, 5th, 7th, 9th, 11th...• Zero sequence harmonics• Triplens - 3rd, 9th, 15,
21st...
• THD can exceed 100%– Referenced to fundamental
• Power factor typically 0.7
14
Half Wave Power Supply• Half cycle pulsed current
– Asymmetrical current– DC bias
• Power Factor– 0.5 true power factor– Displacement power factor if
load is inductive• Harmonics
– Odds - 3rd, 5th, 7th, 9th...– Evens - 2nd, 4th, 6th, 8th...– Source of zero sequence
harmonics (triplens) - 3rd, 9th, 15, 21st...
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2008 by PowerCET Corporation. All rights reserved. (070320)3-8
15
6 Pulse Voltage Fed Load• Each half cycle
– Double pulsed current – Symmetrical current
• Power Factor– 0.8 true power factor -
typical– No displacement power
factor• Harmonics
– Odd harmonics– Frequency doublets (6n +/-
1)• 5th, 7th; 11th, 13th...
Phase A
Phase B
Phase C
16
6 Pulse Current Fed Load• Pulsed current each half
cycle– Asymmetrical current due to
commutation differences• Power Factor
– 0.6 to 0.8 true power factor– Displacement power factor
due to motor load• Harmonics
– Odd harmonics • Doublets (6n +/- 1)• 5th, 7th; 11th, 13th...
– Even harmonics - limited amounts
Phase A
Phase B
Phase C
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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17
12 Pulse Current (UPS)
• Top trace -- 100kVA UPS - Normal operation
• Bottom trace --100kVA UPS with problems– Input SCRs failed --
even order distortion about 40%
18
Power Monitor & Harmonic Analysis
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2008 by PowerCET Corporation. All rights reserved. (070320)3-10
19
THD Graphical Displays
Vthd
Ithd
Wthd
20
(Blank)
CHA Volts (%FND)
CHA Amps (%FND)
CHA kWatts (%FND)
CHA Volts Phase(Deg)
CHA Amps Phase(Deg)
THD 3.73 29.21 -0.304 0 0FND 0.00 0.00 0.000 90 105H02 0.04 0.27 -0.000 142 9H03 1.32 21.46 0.024 11 286H04 0.00 0.06 0.000 50 98H05 2.69 18.59 -0.319 262 134H06 0.05 0.17 -0.000 55 202H07 1.32 5.18 -0.007 88 352H08 0.09 0.11 0.000 107 190H09 0.23 1.41 -0.002 331 206H10 0.08 0.17 0.000 189 114H11 1.31 3.29 -0.003 271 177H12 0.05 0.11 0.000 312 257H13 0.18 0.39 -0.001 328 158H14 0.20 0.32 0.000 37 336H15 0.31 0.66 -0.000 39 302
Harmonic Flow -- Power Monitor
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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21
Transformer Sizing
• De-rating– ANSI C57.110-1986– Standard ignores harmonic voltages and even orders
• K-factor– Based upon UL1561– K-factor affected by source impedance– Calculated number may be low– Allow for increased transformer impedance– Avoid the “Goldilocks” approach
22
K-Factor Calculations• Low-Impedance Power
Source– K-Factor = 9.43 – Voltage = 117.8 V rms.,
162.2 V pk, 1.38 CF– Current = 4.38 A rms., 11.2
A pk, 2.55 CF• High-Impedance Power
Source– K-Factor = 3.73 – Voltage = 114.1 V rms.,
145.2 V pk, 1.27 CF– Current = 3.83 A rms., 7.9 A
pk, 2.06 CF
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2008 by PowerCET Corporation. All rights reserved. (070320)3-12
23
K-Factor Correction
• Compensation process– Vthd is <2% the K number is OK– Vthd is >2% and <6% then K+1– Vthd is >5% then K+2
• Rule of thumb K rating– Standard K-Factors: 4, 9, 13, 20, 30, 40 & 50.– At service with load diversity
• K = 4 or 9
– At load• K = 13 or 20
24
Power Supply W/O Power Factor Correction
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2008 by PowerCET Corporation. All rights reserved. (070320)3-13
25
Power Supply With Power Factor Correction
26
Neutral Current• Old style switch mode power supplies
– Draw current in unique pulses– Ratio of neutral vs. phase current can reach 1.73:1
• New style supplies with PFC– Power supplies with power factor correction circuitry (PFC) draw
current in a more sinusoidal form.– Concentrations of PFC corrected supplies will offset and not
contribute to neutral current.– Ratio of neutral vs. phase current may be less then 1 : 1.
• The need to double neutral conductor size may decrease with PFC corrected equipment.
• The need to double the neutral conductor size for theaters is a code requirement.
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2008 by PowerCET Corporation. All rights reserved. (070320)3-14
27
Harmonic Propagation• Harmonic effects increase with load/source
interaction• Odd harmonics develop naturally with rectangular
waveforms• Even harmonics develop with asymmetrical
waveforms– Asymmetry results in direct voltages and currents (dc)– DC conditions can adversely affect magnetic devices– Even harmonics often indicate load problems
• Harmonic content normally decreases with increased frequency (1/3 of the third, 1/5 of the fifth...)
28
Harmonic Problems Summary• Overheated, noisy
transformers• Overloaded or burned
(hot) neutrals• Timing errors in logic
controlled equipment• Blown SCRs• Capacitor failure• Variable speed drive
(VSD) dropout
• Drift or hunting in electronic controls
• Rapid motor failure or insufficient torque
• Insufficient distribution capacity
• Power factor or harmonic rate penalties
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2008 by PowerCET Corporation. All rights reserved. (070320)3-15
29
Harmonics and Power Factor• Mitigation methods
– Delta-wye transformers– Eliminate shared
neutrals– Filtering– Phase angle blending
for control of harmonics– Equipment redesign
(linearize)– Management of the
environment
• Displacement Factor = Power Factor– Correction capacitors
should work• Distortion Factor =
Power Factor– Harmonic filters or
phase shifting required• Displacement &
Distortion Present– Proceed with caution
30
IEEE 519
V harmonic
I harmonic
PCC
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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31
IEEE 519 Harmonics Standard• Utility responsibility
– Limit overall voltage distortion
– General limit 5% THD at PCC
– Maximum single harmonic 3% of fundamental
• Voltage distortion reflects– User-injected harmonic
currents– Utility system impedance
• Customer responsibility– Limit current injection into
utility– Limits based on short-circuit
capacity and maximum demand
– Limits based on total demand distortion
– Individual harmonics limited– Even harmonics limited to
25% of odd– No half-wave converters!
32
ISC / IL <11 11 ≤ h < 17 17 ≤ h < 23 23 ≤ h < 35 35 ≤ h TDD<20* 4.0 2.0 1.5 0.6 0.3 5.0
20<50 7.0 3.5 2.5 1.0 0.5 8.050<100 10.0 4.5 4.0 1.5 0.7 12.0
100<1000 12.0 5.5 5.0 2.0 1.0 15.0>1000 15.0 7.0 6.0 2.5 1.4 20.0
Maximum Harmonic Current Distortion in Percent of ILIndividual Harmonic Order (Odd Harmonics)
Even harmonics are limited to 25% of the odd harmonic limits above.Current distortions that result in a dc offset, e.g., half-wave converters, are not allowed.*All power generation equipment is limited to these values of current distortion, regardless of actual Isc / IL .whereIsc = maximum short-circuit current at PCCIL = maximum demand load current (fundamental frequency component) at PCC.
IEEE519 Current Distortion Limits (120V Through 69000V)
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-1
IV Grounding
2
Grounding Considerations• Safety grounding
("earthing")– Low frequency currents– Personnel safety– Reference the power
system ground– Requires low resistance
paths
• Signal & performance grounding– High frequency currents– Equipment
performance– Reference is local
equipment chassis– Low impedance paths
• Low inductance• High capacitance
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-2
3
Grounding System• Earth grounding system
– Grounding electrode conductor
– Grounding electrode(s)• Driven rod(s)• Metal buried water pipe• Structural steel• Concrete encased
electrode (Ufer)• Buried ring or linear
conductor
• Equipment grounding (conductor) system– Grounds exposed metal and
cabinets– Starts at the neutral-to-
ground bond– Must be run in same conduit
as phase/neutral conductors– May use conduit– Connected to electronics dc
& logic reference
4
Earth Grounding System
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-3
5
Facility Grounding• NEC
– 25 Ohms or supplement– NEC 250-56 [2002]
• Health Care– IEEE Std. 602-1996 (White)– Section (10.4.5.2)– No more than 10 ohms– 5 Ohms or less preferred
• Industrial Plants– ANSI/IEEE Std. 141-1986 (R1999)
(RED)– Section 7.5.2– 1 ohm or less for substations– 5 ohms or less for industrial plants
• Sphere of influence– Radius equals length of buried rod
6
Facility Grounding – Ground Rods
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-4
7
Lightning Protection System Grounding
8
Resistance Measurements• 3-Point Fall of
Potential• Single Point
Measurement
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-5
9
Soil Type Average ResistivityOhms per CM
5/8" x 10' Driven Rod Ohms Resistance
Well graded gravel, gravel-sand 60,000 -- 100,000 180 -- 300
Loose gravel, gravel-sand 100,000 -- 250,000 300 -- 750Clayey gravel, sand-clay 20,000 -- 40,000 60 -- 120Silty sands, sand-silts mixtures 10,000 -- 50,000 30 -- 150
Clayey sands, sand-clay mixtures
5,000 -- 20,000 15 -- 60
Silty or clayey fine sands w/plasticity
3,000 -- 8,000 9 -- 24
Fine sandy or silty soils, elastic silts
8,000 -- 30,000 24 -- 90
Gravelly clays, sandy clays, silty clays, lean clays
2,500 -- 6,000 (moisture related) 17 -- 18 (moisture related)
Inorganic clays, high plasticity 1,000 -- 5500 (moisture related) 3 -- 16 (moisture related)
Soil Type vs. Resistivity(IEEE Std. 142-1991Grounding of Industrial and Commercial Power Systems)
10
1020
3040
5060
7080
Temperature in F
10
100
1,000
10,000
Ohm
s
8' Ground Rod Resistance
05
1015
2025
30
% Moisture Content by Weight
10
100
1,000
Ohm
s
8' Ground Rod Resistance
Effects of Soil Moisture & Temperature
• Soil temperature • Moisture content
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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11
Optimal Facility Grounding Means• Building Footer
– Ufer Ground• Ground ring & rods
– Bonded at corners
12
Enhanced Conductivity Concrete
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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13
Grounding Electrode System • Driven Ground• Water Pipe Bond• Structural Steel Bond• Metering
– Must not impede grounding path
– NEC 250-50(a)(1)[1999]• Underground gas pipes
– Not part of GES– NEC 250-51(a) [1999]
• Gas pipes inside facility– Bonding after shutoff valve– NEC 250-104(b)[1999]
14
Floated ServiceResistance GroundingGround Fault Interrupt
Mains Grounding Variations
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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15
Mains Grounding Variations• Floated Delta Service
– Absence of solid ground reference allows ground referenced voltage fluctuations
• Load related fluctuations usually within voltage envelope of service
• Utility related fluctuations reflect primary voltages• Lightning transients create severe dv/dt
• Impedance Grounded Service– 480/277Vac service– No neutral connected loads– Creates ground referenced voltage during faults
16
Safety Grounding System• Equipment grounding conductor
– Grounds exposed metal and cabinets– Starts at the neutral-to-ground bond– Must be run in same conduit as phase/neutral
conductors– May use conduit– Connected to electronics dc & logic reference
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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17
Grounding Issues• Grounding conductor
size– Is bigger better?
• Transformer grounding• Ground loops• "Isolated" grounds
• Conduit instead of grounding conductor– Screw thread– Clamp– Compression sleeve– Flexible
18
Low Frequency Ground Current - 1
LINE
NEUTRAL
GROUND
BUILDINGELECTRICAL
SERVICETRANSFORMER
N-GBOND
GROUND
GROUND
EARTH GROUND(MAIN BUILDING ELECTRICAL GROUND)
SUB-PANEL
SUB-PANEL
BC
A
LEGEND:LOAD CURRENT
NEUTRAL RETURN CURRENT
1
D
2
UTILIZATION
EQUIPMENT
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-10
19
LINE
NEUTRAL
GROUND
BUILDINGELECTRICAL
SERVICETRANSFORMER
GROUND
GROUND
EARTH GROUND(MAIN BUILDING ELECTRICAL GROUND)
SUB-PANEL
SUB-PANEL
A
BC
N-GBOND
LEGEND:LOAD CURRENT
NEUTRAL RETURN CURRENT
D
2
1
UTILIZATION
EQUIPMENT
Low Frequency Ground Current - 2
20
LINE
NEUTRAL
GROUND
BUILDINGELECTRICAL
SERVICETRANSFORMER
N-GBOND
GROUND
GROUND
"ISOLATED" GROUND,GROUND ROD, COLD
WATER PIPE, ETC..
EARTH GROUND(MAIN BUILDING ELECTRICAL GROUND)
SUB-PANEL
SUB-PANEL
A
BC D
E
LEGEND:LOAD CURRENT
NEUTRAL RETURN CURRENT
1
2
F
UTILIZATION
EQUIPMENT
Low Frequency Ground Current - 3
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-11
21
LINE
NEUTRAL
GROUND
BUILDINGELECTRICAL
SERVICETRANSFORMER
N-GBOND
GROUND
GROUND
"ISOLATED" GROUND,GROUND ROD, COLD
WATER PIPE, ETC..
EARTH GROUND(MAIN BUILDING ELECTRICAL GROUND)
SUB-PANEL
SUB-PANEL
A
BC D
E
LEGEND:LOAD CURRENT
NEUTRAL RETURN CURRENT
1
2
F
UTILIZATION
EQUIPMENT
Low Frequency Ground Current - 4
22
High Frequency Ground Current• Sources
– Transients from lightning and switching
– Electromagnetic interference
– Radio frequency interference
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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23
High Frequency Interference Current - 2 (RS-422 Interference)
24
Signal Reference Grid -- EricoA very good reference grid
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-13
25
Safety Ground Vs Reference Grid
26
Connections to Reference Grid• Short flat straps best• Metal braid OK• Bond at opposite
corners of equipment• Bond all equipment
within room
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-14
27
Transient
Arrives here first
Problem of Networked Computers --Differential ground voltage
28
Differential Ground Voltage Solutions• Reference grid (computer rooms)• Fiber optic networks• Twisted pair networks (10baseT)• Ferrite cores• Over-voltage protectors• Grounding Inductance
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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29
High Frequency Interference Measurement
• Signal voltages small and mingled with noise
• Voltage probe insertion may hurt signals• Currents much larger, easier to measure• Couple using high-frequency transformer• Measure using digital storage oscilloscope• Some applications, use spectrum analyzer
30
Controlling Network Interference• OVP Protectors (SAD)• Filters (ferrite cores -- shunt capacitors)
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-16
31
Ferrite Cores• Ferrous metal baked in
ceramic fixture• Functions by creating
high frequency losses• Inductive & resistive
characteristics
32
Filter Pin Connector• Normally use capacitive elements internally• Specify desired level of capacitance• Some designs add series inductance
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-17
33
Data Cable Protectors• Silicon Avalanche
Diodes
• MOV Components
34
5 Pin Protector (Classic)• Gas tube OVP• Sneak current coils• Protects
– Tip to ground– Ring to ground
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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35
5 Pin Telco Protectors (Variations)
36
5 Pin Hybrid Protector• Gas tube• Silicon Avalanche diode & low capacitance diodes• Capacitors
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-19
37
High Frequency Interference Measurement
`
38
High Frequency Monitoring
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-20
39
High Frequency Monitoring / Scatter Plot
40
High Frequency Interference Current (facility ground interference)
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-21
41
Communications Media Sensitivity• Most sensitive: RS- 232, Thinnet & similar
single-ended unbalanced systems• Less sensitive: RS 422 & similar balanced
systems• Better still: Signal transformer or opto-
isolated systems (10 Base-T)• Best: Non-conducting media, fiber-optic
and radio
42
Data Line Shielding• Shields effectively conduct
high frequency current• Shields do not effectively
limit effects of low frequency current
• Must be grounded BOTH ends– Or - ungrounded ends
MUST be protected
• Suppression may also be needed
• Electrical Code Data Line Safety Issues – On entering building:
• Shields require grounding• Listed protectors must be
used– Where there is:
• Exposure to lightning• Exposure to power lines
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-22
43
Shield Grounding• 1kV ESD Pulse --
Shield Grounded (normal conditions)
• 1kV ESD Pulse -- 2" Shield Pigtail (shield drainwire)
44
AC POWER TELCO
CATV
Very Bad!
AC POWER TELCO
CATV
Code compliant,but still bad!
AC POWER
TELCO
CATV
Single point is the preferred application
NEC 2002250.56, 800.40 & 830.40
AC & Communications Grounding
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)4-23
45
Concluding Statements• Current Flows in Paths
– Kirchhoff's Laws Prevail• Ground is a path not a terminus• Understanding the paths is the key to good
grounding• Electrical Codes cannot be compromised by
grounding practices
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-1
V Power Problems
2
"Power Hit"
Surge
Sag
Impulse
Event
Glitch
Swell
Distortion
Outage
Glitch
Transient
Notching
Blink
Anomaly
Confusion???
Terms for Power Problems
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-2
3
Voltage Tolerance Curves
4
Voltage Tolerance Curves
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-3
5
Power Problems
• Events are anomalies– Event recording is dependent on the threshold settings
of the monitoring equipment and the nature of the electrical environment.
• Disturbances are undesirable consequences of events– Correlation establishes the relationship between
EVENTS and equipment DISTURBANCES. Single correlation is not conclusive -- it may be "coincidence!"
• Power Problems are a consequence of disturbances -- a set or class of disturbances.
6
Power Problems Depend On:• Nature and source of event
– External (source)– Internal (load)
• Susceptibility of load to the event– Load does not react...no problem– Load reacts...activity / process interruption
• Effect on process or activity– Stops the activity / process– Easy "work around"
• Cost sensitivity to this effect– BIG $$$ – No real identifiable costs...can not justify $$$ to mitigate problem
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-4
7
Power Problems
• Source – Internal or external– Utility or load
• Coupling– Direct– Induced
• Characteristics– Low Frequency– High Frequency
8
Power Problems - Coupling
• Directly conducted• Electromagnetically coupled or induced
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-5
9
Power Problems: Low Frequency
• Variation of amplitude near power system frequency
• Important Characteristics– Magnitude, Duration
and Source
• Types of event:– Swells (surges)– Sags & brownouts– Dropouts & outages– Frequency variation
10
Power Problems: Frequency
• Not usually a problem with utility - a "stiff" source
• Typical problem sources:– Engine generators– UPS systems– Small, remote or
isolated power systems
• How do power monitors measure frequency?– Cycle-by-cycle– Averaged over a multi-
cycle sample
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-6
11
Typical RMS Voltage Disturbances
12
Power Problems: Utility
• Power factor correction capacitor switching
• Circuit breaker operation and grid switching
• Arcs and line fault clearance
• Lightning and storms
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-7
13
Storm-Related Problems - Lightning
14
Storm Related Event
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-8
15
Facility Exposure to Lightning
16
Power Problems: Facility
• Loose connections• Overloaded circuits
and transformers• Wiring errors• Ground loops (low and
high frequency)
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-9
17
Facility Power Problems
• Breaker trip & fuses blow on motor start-up
18
Facility Power Problems-2
• ATS operation during motor start-up
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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19
Facility Power Problems-3
ATS Re-transfer to preferred source
20
Facility Power Problems-4
Good Start-up!
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-11
21
Facility Power Problems-5
ATS Wiring Error!!!!
22
Power Problems: Equipment
• Equipment turn on/off• Equipment current
distortion• Phase-angle controlled
loads• Low immunity to
disturbances
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-12
23
V & I = Load
Load Related Events - 1
Load related event--load "turn-on"
24
Load Related Events - 2
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-13
25
Load Related Events (Harmonic Eval.)
26
Induction Motor Response to Outage
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-14
27
Equipment Response to Notch
28
Sub-cycle and Other Disturbances
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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29
Transient modes
• Normal mode– AC line to line– AC line to neutral– Telco tip to ring
• Common mode– Any line to local ground
• Differential ground mode– Between physically
separated grounds
• One mode often converts to another through:– Circuit voltage drop– Capacitive coupling– Mutual inductive
coupling
30
Measurement Techniques
Normal Mode Common Mode Longitudinal Mode
Voltage Differential
Line-to Neutral or Phase-to-Phase
Neutral-to-Ground Imbalance between conductors or another reference point
Current Phase or Neutral Current
Line & Neutral Summation or Ground Current
Multiple Conductor Summation
L
N
G
L
N
G
L
N
G
v
v
v
Interference Modes
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-16
31
Power Problems: High Frequency - 1
• Important characteristics– Peak voltage, current &
energy– Rise time (dv/dt, di/dt)– Phase angle– Frequency of
occurrence
32
Transients
• Transient sources include– Lightning– Utility
• Power factor correction capacitors
• Switching
– User• load switching• Equipment operation• ESD
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-17
33
Transient Effects
• Damage– AC power supplies– Data, telephone and
communications interfaces
• Disruption– Data loss– System crash
• Degradation– Minor damage which
surfaces later
34
Transients
• Transient Propagation– Obeys circuit laws– Current flows in circuit– Capacitance may
complete circuit• Transient Protection
Basics– Current block
• Series high impedance– Current divert
• Parallel low impedance
Transient generator Load
Transient generator Load
Block
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-18
35
Meter
20'
6'
Line
Neutral
Placement of Surge Suppressor
36
Let throughAt the suppressorWith 6' of wireWith 20' of wire
6' of Wire
20' of Wire
Surge Suppressor Performance
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)5-19
37
Common Electrical Problems
• Wiring errors– Electrical system– Data,
telecommunications & network
• Overloaded circuits– Lack of power
management– Harmonics
• Ground loops– Leakage– Neutral/ground bonds
• Transients– Switching– Lightning – Electrostatic discharge
38
Electrostatic Discharge
• Causes:– Triboelectric (rubbing) effects– Separation and accumulation of charge
• Results:– High voltages (up to 50 kV)– Spark discharges– High dV/dt and dI/dt
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
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39
ACTIVITY LOW (<20%) HUMIDITY
HIGH (>65%) HUMIDITY
Walking across carpet 35,000 V 1,500 VWalking over vinyl floor 12,000 V 250 V
Worker at bench 6,000 V 100 V
Handling vinyl envelopes 7,000 V 600 V
Picking up poly bags from bench
20,000 V 1,200 V
Movements on urethane padded chair
18,000 V 1,500 V
Electrostatic Voltages
40
Electrostatic Discharge• Avoidance & control:
– High humidity (>50%)– Conductive materials and
flooring– Protective clothing and
straps– Ionizers
• Equipment immunity & hardening– Keyboards, mice & human
interface– Ground, shield & suppress– AC suppression rarely
effective
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-1
VI Power Conditioning
2
Power Conditioning
• Provides improved power quality to load by:– Separating circuits of sensitive loads– Establishing controlled reference grounds– Conditioning power with a treatment device– Providing alternative source of electrical energy
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-2
3
Cascaded Protection
• Uses multiple shunt protectors• Uses blocking impedance
– Power system wiring– Power system transformers– Filter or transformer power conditioners
4
Power Treatment Devices
• Voltage regulators– Ferroresonant– Tap switching
• Surge protective devices– Lightning arresters &
surge suppressors• Filters• Motor generators
• Transformers– Isolation– Low impedance
conditioner– Ferroresonant
• Uninterruptible power sources (UPS)– On-line– Off-line– Line interactive
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-3
5
Surge Protection
• Lightning arresters– Primary and secondary devices – Applied on utility up to PCC (watt-hour meter)
• Surge suppressors– Applied in facility beyond PCC– Service entrance
• Incorrect installation may detract from performance– Distribution system– Point-of-use
6
Arresters & Shunt Suppressors
• Use non-linear shunt elements– Varistor– Spark gap or gas tube– Silicon-controlled
rectifier (SCR)– Suppression diode
stacks
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-4
7
Voltage
Current
System
Clamping
Non-Linear Shunt Elements
• High "off" impedance• Low "on" impedance• Rapid transition
between states• Low to moderate
"headroom"
8
Metal Oxide Varistor
• Best overall modern device
• Strengths:– Good clamping and
headroom– Excellent durability– Sub-nanosecond switching
• Weakness:– Low voltage devices not
effective – High capacitance
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-5
9
Suppression Diodes
• Applications: special power and data protection
• Strengths:– Excellent clamping and
headroom– Moderate to good durability– Sub-nanosecond switching
• Weaknesses:– Low voltage devices most
effective– High capacitance
10
Gas Tubes
• Good choice for special data protection applications
• Strengths:– Excellent clamping– Good to excellent durability– Microsecond switching– Low capacitance
• Weaknesses:– Overshoot on fast
wavefronts– Not auto-resetting
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-6
11
Component Service Life
• Service Component Damage– Caused by thermal
overstress:• Exceeding surge energy
rating• Exceeding rated voltage
– AC overvoltage• Wiring errors• Accidents• Utility problems
• Service Degradation– Varistors & diodes:
• Small change in leakage current
• Not limiting service factor
– Gas Tubes:• Electrode erosion• Rupture
12
120 VOLTS 114 VOLTS
3 VOLTS0 VOLTS
LOAD
UTILITY
HOT
NEUTRAL
GROUND
IR IR
IRIR
ELECTRICALSERVICE
TRANSFORMER
Dedicated Circuit
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-7
13
Surge Suppressor Specs ("Standards")
• Underwriters Laboratories (UL) Std. 1449• Commercial Item Descriptions (CIDs)
– Performance– Endurance (reliability)– Application– Safety– Certification
14
Surge Suppressors (TVSS)
• Nonlinear response to excessive voltage
• Clamping depends upon energy handling
• Device configuration determines protection mode
• Response time based upon MOV or SAD
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-8
15
Filters
• Normally adds LC components to TVSS
• May or may not have sine tracking
• N/G usually weaker performance
• Adds RF attenuation to clamping
16
Isolation Transformers• Isolate common-mode only• Common-mode coupled by
inter-winding capacitance• Capacitance may be reduced by
design• Normal-mode couples
magnetically • Limited normal mode
attenuation– Inductance and load determine
attenuation • Common mode attenuation via
coupling capacitance– Shields or screens improve
attenuation
Line Load
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-9
17
Ferroresonant Voltage Regulators• Transformer operates in
saturated mode• LC filter produces
sinusoidal output voltage• Shielding may improve
common mode performance
PrimaryWinding
OutputWinding
ResonatingWinding
MagneticShunt
Primary Section of Core
Secondary Section of Core
Air Gap
18
Tap Switching Voltage Regulators
• Control of voltage taps– SCR– Triac– Relay
• 0.5 cycle response time
• Continual tap changing
Line
Ground
Electronic ControlTap Selection
Load
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-10
19
Low Impedance Conditioner
• Uses low-impedance isolation transformer
• Varistor suppression on primary
• Filtration on secondary• N-G bond controls
common-mode isolation transformer
• Sine-tracking output filters -- low pass filter
• Ground Impedance
Line Load
Ground
20
Motor-Generator
• Isolates load mechanically
• Provides some dropout ride-through
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-11
21
Uninterruptible Power Supplies
• Provide backup AC power from storage batteries
• Automatically power load on loss of utility source
• May also suppress and condition power
22
UPS
UTILITY
LOAD
Ideal UPS
• Source Input:– Disturbed (transients &
switching)– Discontinuous – Unregulated – < 100% reliable
• UPS Output:– Undisturbed
(suppressed & no switching)
– Continuous – Regulated– 100% reliability
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-12
23
Real UPS
• Reliability <100% (MTBF)• Discontinuous
– Off-line switch output transfer • On-line switch bypass• Non-sinusoidal output• Poor or no regulation• Poor or no suppression
24
PSEUDO-SINE
RECTANGULAR
SINUSOIDAL
UPS Output Waveforms
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-13
25
HOT
NEUTRAL
GROUND
UTILITY LOAD
HOT
NEUTRAL
GROUND
RECTIFIER INVERTER
AC DC DC AC
+-
BYPASS
UPS Modes of Operation - 1• On-line (Static UPS)
– Inverter drives the load, rectifier/charger powered by utility– Load switched to utility bypass on inverter overload– Output usually filtered, conditioned and regulated– Output usually transformer isolated– Bypass possible source of problems
26
HOT
NEUTRAL
GROUND
UTILITY LOAD
HOT
NEUTRAL
GROUND
RECTIFIER INVERTER
AC DC DC AC
+-
TRANSFERSWITCH
UPS Modes of Operation - 2• Off-line (standby)
– Inverter normally off– Utility supplies load– Load source switched when utility lost– Output may be suppressed but not conditioned– Output not usually transformer isolated– Transfer switch possible source of problems
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-14
27
HOT
NEUTRAL
GROUND
UTILITY LOAD
HOT
NEUTRAL
GROUND
+-
INVERTER
DC AC
RECTIFIER
AC DC
TRANSFERSWITCH
UPS Modes of Operation - 3
• Line interactive– Inverter on but unloaded– Output suppressed, conditioned and regulated– Output may be transformer isolated
28
Inertial and Flywheel UPS
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-15
29
Diesel UPS
30
Diesel Generator
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-16
31
UPS Considerations
• Specifications– Input (distortion &
power factor)– Output (waveform &
filtering)– Reliability (MTBF) and
reparability– Holdup time– Suppression &
conditioning– Acceptance testing
• Maintenance– Battery testing,
monitoring & alarm– Battery replacement &
servicing– Management &
supervision
32
Synchronizing Waveforms
• Synchronizing rate -- A / (A-B)– A frequency = utility; B frequency = generator– 3 Hz delta @ 60 Hz = 20 cycles & 18° per cycle– 0.1 Hz delta @ 60 Hz = 600 cycles @ 0.6° per cycle
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-17
33
Make Before Break Transfer
• Sources paralleled and synchronized• Phase offset at moment of transfer - 15°• Preferred offset - 7° or less
34
UPS -- ATS Problems• Site symptoms
– Burned contacts on automatic transfer switch (ATS)
– Blown fuses and tripped breakers at utility
– Synchronizing option added to ATS
– UPS static transfer failed and UPS transfers to bypass
– Problem worst with transfers from generator to utility
– Very large current inrush into UPS
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-18
35
Transfer to Utility - Sync cycle
36
Transfer -- Open Transition
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-19
37
Transfer -- Closing Transition
38
Transfer Complete -- Inrush Current
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)6-20
39
PQ Solutions Do Not Have to be Expensive
• Determine your equipment's sensitivity to various power events and the impact on your operation.
• Is the sensitivity of the equipment associated with the entire unit or just a subsystem.– In many cases it may be possible to add an inexpensive
device to increase the hold-up time for the line relays.– Drop-out or time delay relays can protect 3-phase loads
from single phasing• Understanding the problem that you are trying to
resolve is key to implementing cost effective solutions.
40
CONTROLS
MOTORS
OTHERLOADS
INCREASING COST
1
4
2
3
Feeder orGroup ofMachines
UtilitySource
1 - EquipmentSpecifications
4 - Utility Solutions
3 - Overall Protection Inside Plant
2 - ControlsProtection
Customer Solutions
Source: Electrotek Concepts, Inc.
The Cost of Power Quality Solutions
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)7- 1
VII Safety
2
WARNING #1Performing power quality investigations in and around energized equipment, exposed electrical buss work , and inside confined spaces can be dangerous. Testing and inspection of energized equipment should only be performed by qualified individuals familiar with proper safe work-practices.
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)7- 2
3
WARNING #2• Follow all appropriate safety rules and
procedures– Company– NFPA / NEC– OSHA– Appropriate state and local work rules
4
Potential Safety Hazards• Follow applicable safe
work practices and lockout procedures
• Familiarity with application, installation and operation of various diagnostic equipment
• Use approved clothing and protective equipment
• Ensure that all tools and equipment are in proper working order and condition
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)7- 3
5
Safety Equipment / Apparel• Rubber gloves rated at
600v/20kv• Leather protectors• Hard hat• Hearing protection (when
appropriate)• Safety face or eye protection
(UV rating)• Long-sleeved shirts (Nomex or
Indura flame-resistant clothing) worn while working on or near 0-600 volts
• Specialized safety equipment for high voltage and other hazardous environments
6
Never Assume a Circuit is Dead
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)7- 4
7
Jewelry / Surroundings / Conductor / Neutral
8
Typical Body Current Paths
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)7- 5
9
Applied to skin (Macroshock)6+ Amps: Sustained myocardial contraction followed by normal rhythm. Temporary respiratory paralysis. Burns, if small area of contact.100 - 300 mA: Ventricular fibrillation. Respiratory center intact.50mA: Pail, fainting, exhaustion, mechanical injury. Heart and respiratory function intact.16mA: "Let go" current, muscle contraction1mA: Threshold of perception; tingling.
Applied to Myocardium (Microshock)100uA: Ventricular fibrillation.10uA: Recommended maximum leakage current.
Effects of Electric Shock
10
(Blank)
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 1
VIII Planning & Performing a Power Quality Survey
2
What is a PQ Survey?
• A forensic activity (investigation). • It is much like investigating the scene of a
crime. – Gather evidence– Interview witnesses– Surveillance (monitoring)– Review the evidence and surveillance data– Present your findings– "Arrest the guilty!"
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 2
3
Reasons for a PQ Survey• Normal reason is a loose
forensic activity (problem investigation)
• Estimating effects of electrical changes– New equipment or changes
to the distribution system– Effects of Harmonics
• Governmental regulations• Baseline and maintenance• ISO9000 Compliance
procedures
4
Survey Justification
• Money, Manpower & Test Equipment– Labor required to
perform the survey– Use of expensive
equipment– Disruption of normal
activities
• Survey must provide a ROI– Immediate problem
resolution– Energy management
cost reduction• Management
participation in survey goals
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 3
5
The Six Steps to a Successful PQ Survey
• 1 - Plan / Prepare• 2 - Inspect (Survey)• 3 - Monitor• 4 - Data Analysis• 5 - Key Findings & Recommendations (the
Solution)• 6 - Implementation & Verification
6
Why have a Written Survey Plan?
• Some surveys have continued for months without tangible results because they were not well planned.
• Complex facilities, multiple monitors and data collection systems require a formal plan for the activity to be brought to a successful completion.
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 4
7
When a Written Survey Plan May Not be Needed
Simple uncomplicated monitoring activities may not require a formal written plan, but all the same steps will need to be considered (at least informally) for the activity to reach a satisfactory conclusion.
8
Survey Objectives
• What are the objectives for the activity?– What is to be accomplished?– Is it measurable? (Deliverables)
• Objectives must be clear, well defined and most importantly: accepted by the individual (organization) requesting the survey
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 5
9
Examples of Survey Objectives
• Solve an equipment performance problem• Identify and correct sources of interference• Determine overall electrical environmental
quality• Determine capacity for a facility• Predict the impact of harmonic loads
(IEEE519)• Establish an electrical environment
"baseline" for a facility (ISO9000)
10
Determinants of the Scope of Activities
• Size of the facility• Complexity of electrical
system and equipment• Quantity of monitoring
equipment • Duration of monitoring
program• Quantity and complexity of
monitor data
• Number and length of event logs
• Access to restricted areas or equipment
• Specialized options (RF, current, temperature, humidity, etc.)
• Involvement of staff and administrative support
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 6
11
Power Monitor Placement
• Classic placement– Service Entrance(s)– Transformers – Distribution -- feeders
and panelboards– Point of use -- branch
circuits, equipment
• Multiple monitors– Improves quality of data– Speeds-up the
investigative process.• Service entrance, load
center, utilization equipment
– Additional monitors can be rented for between $500 and $1000 / month.
12
Verify Survey Plan• Is the objective clear and
measurable?• Is the quantity and
placement of monitoring equipment clear?
• Are personnel and responsibilities assigned?
• Is the length of the survey established?
• Is the data collection system (event logs) defined and ready for testing?
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 7
13
Equipment Event Logs
• Things to include in the EVENT LOG– Operator / Location / Activity– Record of normal operating cycles– Record of equipment anomalies– Record of environmental anomalies
• Design log to make the data collection as easy as possible.
• Use alarm relays, control switches to aid in time stamping events.
14
Preparing for the Survey
• Documentation and data collection– Site history– Equipment/activity event log(s)– Service/repair history
• Tools and equipment
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 8
15
Site History
• Has the system or equipment ever worked satisfactorily?– When did the problems start?
• Time of occurrence for recurrent problems– Look for patterns
• Failure symptoms or hardware failures– Someone somewhere knows what parts were replaced
• Electrical service and configuration– wye-wye or delta-wye
16
Site History - 2
• Inventory of major loads in the facility– Operating cycles for major loads in the facility
• Recent equipment changes• Renovations in the facility• Telecommunications/data-network facilities
and equipment– Recent implementation of wireless technology
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 9
17
Monitoring Tools & Equipment• Power quality • Power quantity• High frequency
– DSO– Spectrum analyzer
• ESD meters• Multi-meters (True
RMS)• Thermographic
recorders
• ELF & VLF field strength meters
• Ultrasonic meter• Video camera• Ground resistance
meter• Current probes
– Current transformer– Hall Effect (d-c)
• Circuit tester
18
ESD & ELF Meters
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 10
19
Popular 1Ø Phase Monitoring Instruments
• Fluke 43B– Power quality analyzer
• Fluke 41B– Harmonics & energy
20
Flexible AC Current Probes
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 11
21
3Ø Monitoring Instruments / $2K to $6K
• Ideal Model 805
• Summit Technologies Power Sight 4000
• LEM Analyst 3Q
• AEMC PowerPad 3945
• Fluke 430-Series
• Dranetz-BMI PowerGuide 4400 & PowerVisa 440
22
LEMTopaz 10000
RPM (Fluke)PowerRecorder
Dranetz-BMIPowerXplorerPX5 (PX5-400 for 400Hz apps.)
Hioki 3196
Portable 3Ø Power Quality Monitors / $7K to $15K
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 12
23
PML ION77 Dranetz-BMI Signature System
PowerLogic CM4000T RPM (Fluke) Multipoint Dranetz-BMI Encore
Electro Ind. NEXUS 1250
Permanent Power Monitors / $2K to $4K + Installation & Software
24
Laptop CPU / Controller
e/w HS Modem
Energy Analyzer
High Speed DSO
Power Quality Analyzer
Spectrum Analyzer
Monitoring Systems
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 13
25
Inspecting the Site - Visual/External
• Type of electrical service (underground, aerial, low or high voltage?)
• Utility power factor correction capacitor installations
• Neighboring facilities• Utility substation in the immediate vicinity• Physical location of building (exposure)• Lightning protection system• Building construction
26
Review the Electrical Service
• Service entrance -- single or multiple?• How are the service entrances grounded?• Building Grounding Electrode System?• Transformer isolation?• Ground Fault Interrupt?
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 14
27
Inspecting the Site -- Internal• Review major facility loads
and how they are controlled– Large photocopiers– Variable speed drives– UPS – Elevators / escalators– Lighting systems– Welders– Battery chargers– Air conditioning
compressors, chillers and air handlers
28
Inspecting the Site - 1• Look for obvious problems
– Broken or corroded conduits– Transformers which are hot or noisy – Electrical panels with hot or loose circuit breakers– Loose connections -- EMT without grounding wires– Conduits which are hot and buzzing– Transformers or conduits near CRTs with screen
"wiggle"– Coffee pots plugged in with file servers– Power cord plug/connectors showing signs of excessive
wear -- check for warm spots
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 15
29
Inspecting the Site - 2• Talk with the
equipment/system operators and users– Management's perception of
the problem may be quite different from the people using the equipment.
– Listen! Listen! Listen! • Most people want to tell you
about the problem.• Learn to translate the
information into appropriate terminology.
30
Monitoring
• Power monitoring configurations– Match the configuration of the load– Monitor neutral-to-ground to record "common mode"
events – Use current probes to record phase, neutral or ground
currents.• Use multiple monitors - service entrance,
distribution center, utilization equipment• Monitor threshold settings - sensitive, normal or
tolerant
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 16
31
Identifying Problems - 1
• Review monitor data– Look for events which occurred during periods
of equipment malfunction (event log entries) – Identify severe events.
• Identify events that exceed equipment performance parameters
• Correlate problems found during the physical inspection with equipment symptoms.
32
Identifying Problems - 2
• Review site history and event logs• Plot monitor event summaries
– Look for trends• Compare event summaries to equipment
event logs– Single Event Correlation is not conclusive
• Compare event data to equipment performance specifications
• Select key events
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 17
33
XX
XX
XXEvent Log#2
Event Log#3
Event Log#1 XXX
X
Summary Info w/Event Log Correlation
34
Key Event
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 18
35
Symptom Possible CauseI/O port failure Longitudinal CMIProcessor lockup Software / RF / ESDKeyboard controller failure ESDPower supply failure Surge-transient / ESDSystem crash Surge-transient (voltage)Wavy screen EMFClock/date reset Battery / conducted RFOpen door/cabinet halt Radiated RF
Identifying Problems - 3
36
Writing the Report - Software Tools• AiPower (Kreiss-Johnson
AI based report generator, supports multiple manufacturers)
• Dranetz-BMI Technologies– DranView Versions 4, 5 & 6
• Fluke / RPM– PAS & Scenario w/Report
Writer– EN50160 Report Writer– Flukeview
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 19
37
PQ Survey Report Organization
• Executive Summary– Written last after the main report is completed– Never more than 2-pages
• Overview/Background• Methodology• Key findings• Recommendations• Summary• Appendices
38
PQ Survey Report Content
• Quality information NOT quantity!– The purpose of the report is to identify and present the
significant information, not bury the reader in paper.• Use summary information
– Easier for people to understand• Use waveform data (graphics) sparingly to add
emphasis and support recommendations– Do not include every waveform recorded as it tends to
lessen the value of the data
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 20
39
Be Wary and Watchful
• Never assume a single cause– Peel the onion
• Know your instrumentation• Don't become part of the measurement• Use equipment symptoms as a guide• Never assume the equipment is without guilt
40
Make Solutions A Priority• Inaction is costly• Reaction is costly
– Too little, too late for too much
• Monitor on an ongoing basis
• Be part of the solution• Provide ROI• Manage the facility
infrastructure
ANALYZEDATA
EVALUATESOLUTIONS
GATHERDATA
IMPLEMENTSOLUTIONS
PQ103 - Introduction to Power Quality: Problems, Analysis & Solutions
© 2007 by PowerCET Corporation. All rights reserved. (070320)8- 21
41
Summary
• Apply the TEST OF REASONABLENESS to all data and information.
• Know the limitations of monitoring and test equipment.
• Look for the OBVIOUS.• Don't become the victim of ANALYSIS
PARALYSIS.• Do the simple thing first.
42
If All Fails...Call an Expert!!!
Recommended