© 2007 Ideal Industries 1 of 73 Basics of Power Quality Understanding Power Quality Problems

© 2007 Ideal Industries 2 of 73 Basics of Power Quality Objectives This presentation has been adapted to NJATC Lesson It’s intent is to give the student a basic understanding of Power Quality as describe in this lesson plan. –Describe the nature of several different types of power- related problems. –Identify the causes or source of many power related problems –List steps that can be used with different electrical equipment to minimize the equipment’s contribution to power-related problems.

© 2007 Ideal Industries 3 of 73 Basics of Power Quality What is Power Quality Except for complete failure, most really don’t pay close attention to the power we are supplied. But if we were in the middle of an important document or key manufacturing process it would be more than a simple announce. A knowledge of power quality is necessary to identify and resolve electrical environmental problems

© 2007 Ideal Industries 4 of 73 Basics of Power Quality What is Power Quality With the emergence of the “Electronics Age” there has be a change in the requirement of our electrical distribution systems. Unlike traditional load, like lighting or motors, Sensitive loads are more susceptible to power disturbances. Electronic equipment requires a much more stable power source.

© 2007 Ideal Industries 5 of 73 Basics of Power Quality Importance of Power Quality Consequences of poor Power Quality can result in: –Lost productivity –Lost/corrupt data –Damaged equipment –Poor power efficiency U.S. companies waste an estimated $26 billion on electrical power-related issues each year* * Electrical Contractor Magazine, “Surveying Power Quality Options” March 2000

© 2007 Ideal Industries 6 of 73 Basics of Power Quality Power Quality There is no absolute definition of power quality, but many define it as the degree to which both the utilization and the performance of electric power affects the performance of an electrical distribution system. Organizations such as the IEEE -Institute of Electrical and Electronics Engineer and ANSI -American National Standards Institute are setting Stringent requirements for power Quality. –IEEE Recommended limits on Harmonics –ANSI C84.1 Specification on normal voltage ratings and tolerances

© 2007 Ideal Industries 7 of 73 Basics of Power Quality Key Contributors Power Factor –Measure of how efficiently Power is used Disturbances –Momentary disruptions to the Electrical system Harmonics –Integers of the Fundamental Frequency which have an effect on the electrical systems and loads

© 2007 Ideal Industries 8 of 73 Basics of Power Quality Power Quality The NIST -National Institute of Standards and Technology publication NIST SP768 Shows that power disturbances can be defined in two categories, Steady State or Intermittent. –Steady state disturbances are Noise, Harmonics, long term Overvoltage or Undervoltage conditions. –Intermittent disturbances are Sages, Swells, Impulse, Transients, and interruption,

© 2007 Ideal Industries 9 of 73 Basics of Power Quality ITI (CBEMA) Curve

© 2007 Ideal Industries 10 of 73 Basics of Power Quality Power Factor –Incandescent lighting, heating elements, motors and capacitors –Affect on Electrical source are phase shifts due to capacitive and inductive reactance –Phase shift is measured as Power Factor or PF Most utilities have an additional charge if PF is less than.95 to.90

© 2007 Ideal Industries 11 of 73 Basics of Power Quality Power Factor Apparent Power is the product of Volts times Amps –VA or KVA=V x A Real Power is the time average of instantaneous product of Volts time Amps –W or kW = V x A x cosine theta Time average of instantaneous evaluates phase shift between Volts and Amps Power factor is Watts divide by Apparent Power – PF= W/VA

© 2007 Ideal Industries 12 of 73 Basics of Power Quality Power Factor VAR or Reactive Power is magnetic energy, which causes a phase shift between voltage and current Waveform This overlapping of waveforms delivers less power to the load –VA 2= VAR 2 + W 2 –VAR =

© 2007 Ideal Industries 13 of 73 Basics of Power Quality VAR’s VAR’s or the non- working energy may be thought of as water in a hose. When water is first applied there is a slight delay before water gets to the end of the hose. If we used a storage device, water at the end of the hose would flow immediately.

© 2007 Ideal Industries 14 of 73 Basics of Power Quality Power Disturbances Power disturbances generally fall into one of six categories. –Voltage Sags and Swells –Under-voltage or Over-voltage –Transients spikes, impulses and surges –Outages –Harmonics –Noise

© 2007 Ideal Industries 15 of 73 Basics of Power Quality Power Disturbances Voltage Sag –Momentary decrease in line Voltage –.5 to 30 Cycles (up to.5sec) –Caused by the start of heavy loads or fault occurrence on source. Voltage Swells –Momentary increase in line Voltage –.5 to 30 Cycles (up to.5sec) –Occurs due to sudden load decrease or de-energizing of heavy equipment.

© 2007 Ideal Industries 16 of 73 Basics of Power Quality Power Disturbances Over-Voltage –Abnormally high voltage –>.5sec to a few seconds –Power voltage regulation Under-Voltage –Abnormally low Voltage –>.5sec to a few seconds –Result for clearing of a fault or intentional utility regulation.

© 2007 Ideal Industries 17 of 73 Basics of Power Quality Power Disturbances Transients: –Short duration high amplitude pulses are surges that are superimposed on a normal voltage waveform. –Vary widely from twice the normal voltage to several thousand volts in time from < microsecond to a few hundreds of a second. –Result for loads cycling on and off in a building, utility, or lighting

© 2007 Ideal Industries 18 of 73 Basics of Power Quality Power Disturbances Outages –Outage is a complete loss of power lasting from a few milliseconds to several hours. –Caused by power system failure due to damage to supply lines or equipment failure

© 2007 Ideal Industries 19 of 73 Basics of Power Quality Power Disturbances NOISE: is an unwanted signal or distortion that is superimposed on a normal voltage waveform –Normal Mode noise –Common Mode noise –RFI: Radio Frequency interference –EMI: Electromagnetic interference

© 2007 Ideal Industries 20 of 73 Basics of Power Quality Harmonics Harmonics are multiples of the fundamental frequency of 60 Hz in an electrical system. Most harmonics are generated from Non-linear loads, or solid-state device equipment –Examples are Computers, Copiers, Laser printers, UPS systems, industrial controls, welding machines, Adjustable Speed Drives {ASD} or Variable Speed Drives {VFD}

© 2007 Ideal Industries 21 of 73 Basics of Power Quality Harmonics Non-linear is used to describe the switch mode power supply {smps} found in most microprocessor based equipment and rectified supplies found in industrial loads.

© 2007 Ideal Industries 22 of 73 Basics of Power Quality Harmonics Non-Linear loads –Computers, printer, copiers, electronics lighting –Adjustable speed drives and other microprocessor controlled equipment –Effects on electrical systems or odd harmonics 3 rd, 5 th, 7 th etc.

© 2007 Ideal Industries 23 of 73 Basics of Power Quality Harmonics Total Harmonic Distortion –Expressed as %THD –Percentage of distortion to the sine wave –Should not exceed 5% of line voltage or 20% of current Harmonic FFT’s –Breakdown of the THD to the individual harmonics –Show the amount of harmonic as a percentage of the fundamental. Knowing each harmonic and its effect can help in determines the impact on the system

© 2007 Ideal Industries 24 of 73 Basics of Power Quality Plan, Investigate & Test Where to start –Plan your site survey –Investigate suspected areas –Test or monitor –Analyze results or date Please refer to Table 2 Electrical Distribution Systems Equipment and Grounding Measurement and Considerations

© 2007 Ideal Industries 25 of 73 Basics of Power Quality Plan Make a block diagram of you facility.

© 2007 Ideal Industries 26 of 73 Basics of Power Quality Investigate Investigate suspected areas Try to establish time of occurrence and duration history Equipment usage cycles or new equipment instillation Personnel Interview others- Find out what they have observed

© 2007 Ideal Industries 27 of 73 Basics of Power Quality Impulse Most impulses are generated within a facility when inductive loads are switched on and off Typical causes of impulses include switch contacts and sharp current transitions interacting with source impedance.

© 2007 Ideal Industries 28 of 73 Basics of Power Quality Impulse The origin of an impulses can be determined by reviewing the polarity of the leading edges of the simultaneous voltage and current impulses If the voltage is “+” and current is “+”, or if the voltage is “-” and the current is “-” then the origin is source- related. If the voltage is “+” and the current is “-” then the origin is load related.

© 2007 Ideal Industries 29 of 73 Basics of Power Quality Voltage Sags Voltage sags are sometimes caused by a problem on the utility power supply outside of the facility If current on a circuit being monitored increases during a sag the origin is normal load related. If current decreases or drops to zero during a sag the origin is normal source related.

© 2007 Ideal Industries 30 of 73 Basics of Power Quality Voltage Sags Other causes are, load interaction with wiring, (equipment at start-up) or voltage source impedance

© 2007 Ideal Industries 31 of 73 Basics of Power Quality Voltage Distortion Voltage Distortion can be caused by large harmonic currents from Nonlinear loads or Power sources with no sinusoidal Voltage Characteristic Linear loads have small effects on voltage distortion. Non-Linear loads have a larger effect on voltage distortion Excessive Current drawn as the Voltage waveform reaches Peak can cause Voltage distortion. Referred to as Flat Topping or Clipping.

© 2007 Ideal Industries 32 of 73 Basics of Power Quality Ground to Neutral Events Causes of neutral-to- ground voltage –Return current in neutral conductor –Excessive neutral conductor resistance –Ground current –Excessive ground resistance Ohm’s Law we can derive Voltage between Neutral And the ground. V=I * R, V= 50A *.1 ohm or V=5

© 2007 Ideal Industries 33 of 73 Basics of Power Quality Where to Look Most power quality failures may be tracked down to one of three areas. –Supply- Utilities and its distribution. –Internal Distribution- Feeders and Branches, Grounding, wiring and termination –Internal Loads- load disturbances and Harmonics

© 2007 Ideal Industries 34 of 73 Basics of Power Quality Supply- Utilities disturbance Supply Disturbances and service area –Utility faults, switching transients, regulation –Lighting, Transients, outages –Accidents to Transmission lines outages –Failure of backup sources Outage, under of over voltages

© 2007 Ideal Industries 35 of 73 Basics of Power Quality Internal Distribution Inspect your Electrical distribution entrance service, ensure compliance with NEC. Look for: –Check ground –Corroded connections –Defective conduit –Defective electrical devices –Adequate wiring

© 2007 Ideal Industries 36 of 73 Basics of Power Quality Internal Distribution Inspect all grounding, ensuring compliance with NEC. –Inspect receptacle, sub-panels, Feeder and etc, for proper grounding. –Inspect neutral to ground bonding per NEC compliance Inspect Electrical panels. –Loose electrical connections, improper neutral to ground bonding at sub-panels. –Voltages phase to neutral, phase to ground, and phase to phase –Current in branch and feeders.

© 2007 Ideal Industries 37 of 73 Basics of Power Quality Internal Loads Identify major Loads –Computers –Copiers, Laser printers, and other Large office loads –HVAC Equipment –Industrial equipment, Like ASD’s (Adjustable Speed Drives) –Lighting –UPS systems

© 2007 Ideal Industries 38 of 73 Basics of Power Quality Internal Loads Transient –Inductive loads Sags –Starting of large loads Swells –Large load removed Harmonics –Caused by solid-state electronics

© 2007 Ideal Industries 39 of 73 Basics of Power Quality Effects of Harmonics Commercial Effects of Harmonics –Heating of Transformers –Heating of neutrals –Hot breakers and panels –High Voltage drop or Flat Topping –High Neutral to ground Voltage

© 2007 Ideal Industries 40 of 73 Basics of Power Quality Effects of Harmonics Industrial Effects of Harmonics –Heating of Transformers –Effects on Electromagnetic equipment –Power Factor Capacitors problems

© 2007 Ideal Industries 41 of 73 Basics of Power Quality Transformers Cause of Transformer heating –Harmonic currents cause an increase in copper losses and stray flux losses. –Harmonic voltage cause an increase in iron losses –Combined effect on transformer is heating

© 2007 Ideal Industries 42 of 73 Basics of Power Quality Transformer K-Factor rated transformers were designed to handle the additional heat generated by high harmonics. Recommended Practice for Establishing Transformer Capabilities, –IEEE Standard C , Never use a K-Factor that is higher than needed. It will reduce the transformers ability to withstand power glitches. –K rated transformers have lower impedance. You need some impedance to reduce effects of disturbances.

© 2007 Ideal Industries 43 of 73 Basics of Power Quality De-rating Transformers This method should only be used in de-rating phase to neutral loads. –Measure the True rms current for each phase –Measure the instantaneous peak for each phase –If the I peak and I rms values on each phase are not close, use the average value for each. –THDF= (1.414 x I rms )/ I peak. (a value between 0 and 1.0) –KVA de-rated =KVA nameplate x THDF (avg de-rating of a transformer is in the range of 20% to 40%)

© 2007 Ideal Industries 44 of 73 Basics of Power Quality Hot Neutral Conductors Neutral Conductors can have as much as 150% of triplen harmonics (3 rd, 9 th, 15 th, etc) as any phase conductor. –Triplen harmonics don’t cancel, but add in the neutral conductor. –“Skin Effect”, higher frequencies travel not through the wire, but on the outer surface of the wire. Small gauge wire have less surface so it is a higher resistance to the higher frequencies currents This is one reason that conduit makes such a good ground for noise- the higher frequencies run on the surface of the conduit.

© 2007 Ideal Industries 45 of 73 Basics of Power Quality Hot Neutral Conductors Reducing the effects of hot neutrals –One is to up-size the neutral. In resent years this has been the most popular action. –Triplen harmonic filters could be used at key source panels. This would reduce not only neutral currents but also help reduce phase to neutral load on transformers. –No shared neutrals. In a 240/120 three phase distribution shared neutrals were common, but with so many SMPS being added to the electrical distribution performance wiring practice can reduce effect on power disturbances.

© 2007 Ideal Industries 46 of 73 Basics of Power Quality Branch Circuits Line to Neutral Voltage –Transients, Sags& Swells, Voltage drops, Flat toping Neutral to Ground Voltage –Tripling harmonics, High ground impedance.

© 2007 Ideal Industries 47 of 73 Basics of Power Quality Branch Circuit Test receptacles in sequence along the branch circuit Identify the receptacle where the voltage drop increases significantly Check voltage drop on remaining receptacles –If voltage drop is acceptable in remaining receptacles, then problem is probably localized at receptacle connection –If voltage drop is unacceptable, then problem exists within the hot or neutral conductors

© 2007 Ideal Industries 48 of 73 Basics of Power Quality Integrity of the Branch Circuit If all branch receptacles have unacceptable voltage drops, then the problem is most likely in the circuit between the panel and the first receptacle, or at the panel –Undersized wire for length of run –Possible splices –Poor connections or corroded contacts at panel Breaker, neutral bus, etc. –Most show up as hot spots in the panel

© 2007 Ideal Industries 49 of 73 Basics of Power Quality Integrity of the Branch Circuit Ground to neutral voltage measurement –Indicates feedback on the neutral conductor –Caused by load balance or harmonic Three-phase 208/120V power systems –2 volts or less is acceptable level of voltage –IEEE recommends 0.25 ohms or less for any phase conductor, Ground is not considered a conductor by NEC however it would be a good guideline to consider.

© 2007 Ideal Industries 50 of 73 Basics of Power Quality Integrity of the Ground Identify false grounds –False or “bootleg” grounds are defined as a short between neutral and ground –Accidental short or improper bonding of ground and neutral conductors –Shows up as normally wired condition with receptacle testers Test & Measurement

© 2007 Ideal Industries 51 of 73 Basics of Power Quality Installation of Safety Devices Ground Fault Circuit Interrupters –NEC requires installation of GFCI in bathrooms, kitchens and outside. –Purpose is to protect individuals by detecting ground faults. –Defective or improperly installed GFCI can lead to shock.

© 2007 Ideal Industries 52 of 73 Basics of Power Quality Installation of Safety Devices TVSS Transit voltage surge suppresser –Purpose is to protect equipment. –70% of all surges are generated within a facility –Defective TVSS can lead to lost productivity and damaged equipment.

© 2007 Ideal Industries 53 of 73 Basics of Power Quality Recommend Practices Limit the number of electronic loads on sensitive circuit –Recommendation: limit the number of outlets to 3 to 6, instead of 13 or 14 –Not practical for all wiring installations, but essential in areas with high density of electronic equipment –Place large loads on dedicated circuit –Limits the harmonic distortion on the branch

© 2007 Ideal Industries 54 of 73 Basics of Power Quality Recommend Practices Neutrals, double-sized or larger on 3-phase systems. (Most common 208/120 3 phase/4wire) Phase conductors, upsized to reduce voltage fluctuations Use harmonic rated transformers or de-rate standard transformers

© 2007 Ideal Industries 55 of 73 Basics of Power Quality Recommend Practices Install isolated grounds to protect costly or vital electronic equipment from harmonic distortion –Computers, ATM machines and expensive copiers often require isolated grounds –Important issue in hospital environment Verify isolated ground before installation of electronic equipment Test & Measurement

© 2007 Ideal Industries 56 of 73 Basics of Power Quality Recommend Practices Limit the number of outlets Place larger loads on dedicated circuits Run separate neutrals (no shared neutrals) Isolated Grounds Multiple Circuit – Separate Neutral - Loop Feed (w/Pigtail Connections)

© 2007 Ideal Industries 57 of 73 Basics of Power Quality Industrial Concerns Power Factor –Cause by our inductive loads Sags and Swell; over or under voltage conditions –Cause heavy loads or source variations Phase voltage and current balance –Source or load problems Harmonics and harmonic resonance

© 2007 Ideal Industries 58 of 73 Basics of Power Quality Industrial Concerns Power factor improvement can reduce supply need and cost.

© 2007 Ideal Industries 59 of 73 Basics of Power Quality Industrial Concerns Sags, Swells, over-voltage, under Voltages –Plus or Minus 10% will trip in most drives Voltage Balance –Plus or Minus 2% to 5% can cause problem in most drives Current Balance –Plus or Minus 20%, 10% or less or Adjustable speed drives are more sensitive to Imbalance. Consult with drive or motor manufactures for acceptable imbalance

© 2007 Ideal Industries 60 of 73 Basics of Power Quality Motor Voltage Imbalance First measure the three phase Voltages –V average {Vavg.} Vavg.=V Total/3 –V deviation {Vdev.} Vdev=V max/V avg. –V unbalance(Vub) Vub=Vdev/V avg *100 L1-L2L1-L3L2-L3 460V481V475V

© 2007 Ideal Industries 61 of 73 Basics of Power Quality Motor Current Imbalance First measure the three phase Currents –A average {Aavg.} Aavg.=A Total/3 –A deviation {Adev.} Adev=A max/A avg. –V unbalance(Vub) Vub=Vdev/V avg *100 A phaseB phaseC phase 30 A 35 A28 A

© 2007 Ideal Industries 62 of 73 Basics of Power Quality Industrial Concerns Commonly found in industrial facilities are –Variable Frequency drives {VFD’s} – Variable Speed Drive {VSD’s} –The most common is the pulse width modulation drive {PWM} Harmonic reversal {5 th, 11 th, and etc} Resonance Harmonic migration to Capacitor Banks Transient voltage spikes at motor caused by improper installation of drive

© 2007 Ideal Industries 63 of 73 Basics of Power Quality Reference Material Reference and additional Information –IEEE Emerald book, Recommended Practice for Powering and Grounding of Sensitive Electronic Equipment. –Federal Information Processing standard Pub #94 ie {FIPS-PUB-94] –EC&M Practical Guide to Quality Power for Sensitive Electronics Equipment 2 nd Edition. –Electrical Power Research Institute, Wiring and Grounding for Power Quality –Copper Development Association, A Primer on Power Quality.

© 2007 Ideal Industries 64 of 73 Basics of Power Quality Test and Monitor Test or Monitor, Basic measurement tools –Circuit Analyzer –Multimeter or ClampMeters (True RMS responded) –Receptacle Event Recorder –Power Quality Monitor. –Infrared temperature device Always follow proper Safety precautions Lock-out Tag-out, safety gear like glasses and gloves

© 2007 Ideal Industries 65 of 73 Basics of Power Quality Test and Monitor Most equipment, like circuit Analyzers, meters and clamps are slow responding. –They sample at speeds around 2 or 3 times a second. –OK for steady state problems –To slow for intermittent disturbances. –Intermittent disturbances require equipment which samples at a number of samples per cycle.

© 2007 Ideal Industries 66 of 73 Basics of Power Quality Instrumentation True RMS – Digital Mulitmeters – ClampMeter –Accessories rated with higher Frequency bandwidth. Avg. responding instruments can have an error of as much as 20% to 40% when measuring Non-sinusoid waveforms

© 2007 Ideal Industries 67 of 73 Basics of Power Quality Two Methods of Measuring AC Average responding RMS Calibrated –Meter responds to the average value of a sinusoidal waveform and multiplies it by 1.11 to display the RMS result. –Works well only for “pure sine wave” or “sinusoidal wave form”

© 2007 Ideal Industries 68 of 73 Basics of Power Quality Two Methods of Measuring AC True RMS responding –The Meter calculates the true effective (heating) value of the waveform. –Average sensing meters will not correctly display the effective (heating) value on a “non-sinusoidal waveform.

© 2007 Ideal Industries 69 of 73 Basics of Power Quality Two Methods of Measuring AC In this example, the error of the avg. reading is –35%. Avg. meters used to measure non-sinusoidal wave forms can have an error of +10% to –40% Always use a True RMS instrument whenever you are in an electrical environment with non-liner loads.

© 2007 Ideal Industries 70 of 73 Basics of Power Quality Troubleshooting Equipment 800 Series Power Clamps SureTest Circuit/Harmonics Analyzers 800 Series Power Analyzer

© 2007 Ideal Industries 71 of 73 Basics of Power Quality SureTest Circuit/Harmonics Analyzers Circuit Analysis –Measures voltage drop under full 15 Amp load, ground impedance Power Measurements –Power Factor, kW Harmonic Measurements –%THD, harmonic factorization to 31st harmonic

© 2007 Ideal Industries 72 of 73 Basics of Power Quality 800 Series Power Clamps Power Measurements –True Power (kW) –Power Factor (PF) –Apparent Power (VA) –Reactive Power (kVAR) Dual display to view key measurements simultaneously Calculates power measurements on three- phase systems

© 2007 Ideal Industries 73 of 73 Basics of Power Quality 800 Series Power Analyzer Power measurements –kW, Power Factor, kVA, kVAR Harmonic measurements –%THD, harmonic factorization to 51st harmonic Disturbances –Capture level 2 transients (0.5µs)