Understanding Power Quality Monitoring

Understanding Power Quality Monitoring
Adapted for the NJATC Lesson Plan As a training aid for 4th year students or as a review to journeyman already in the electrical business. Note that any Italic print should be emphasized In many cases this information is noted as an answer to one Of the questions for lesson You will also find reference material in the notes section of the presentations. Basics of Power Quality Monitoring

Basics of Power Quality Monitoring
Objectives What is Power Quality and how do we determine Methods of test. Describe the nature of several different types of power-related problems. Describe the methods for testing for the different types of problems. Basics of Power Quality Monitoring

What is Power Quality Except for complete failure, most really don’t pay close attention to the power we are supplied. 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. Q2 Electronic equipment requires a much more stable power source. With the emerging of the electronics age there has been a change in the electrical environment of the American workplace. Technologies that consume less power are increasingly being used to improve efficiency and cost effectiveness. The microcomputer or microprocessor based equipment are now common place in data processing, communications, security, safety equipment and controls. Unlike our more tradition loads like motors, incandescent lighting, and HVAC load, most modern electronic equipment require a more stable voltage source. These “sensitive” loads are susceptible to power disturbances that originate on either side of the electric meter. Basics of Power Quality Monitoring

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* The consequences of poor power quality problems, impulses, sags and swells can have a negative impact on sensitive electronic equipment. These problems can range from lost productivity, lost or corrupted data, equipment damage or just plan power efficiency problems. It is estimated that poor power quality problems cost US companies an estimated $26 Billion each year. *Electrical Contractor Magazine, “Surveying Power Quality Options” March 2000 Basics of Power Quality Monitoring

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 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. Q3 a&b Organizations such as the Institute of Electrical and Electronics Engineer (IEEE) and the American National Standards Institute (ANSI) are setting Stringent requirements for power Quality. Many of these Organizations set standards for the design or operational tolerances. Example are IEEE Recommended limits on Harmonics, and ANSI C84.1 which set specification on normal voltage ratings and tolerances Basics of Power Quality Monitoring

Power and 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 Basics of Power Quality Monitoring

Power Quality Power And Power Factor
Power is measured in KW or Kilowatts Kilowatt is defined as Volts x Amps x Cos Φ Φ is the phase angle difference between the Voltage and current. Most utilities have an additional charge if PF is less than .95 to .90 Basics of Power Quality Monitoring

Disturbances The NIST -National Institute of Standards and Technology shows that disturbances can be defined in two categories, Steady State or Intermittent. Steady state disturbances are Noise, Harmonics, long term Over-voltage or Under-voltage conditions. Intermittent disturbances are Sages, Swells, Impulse, Transients, and interruption, 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, and long term over voltage or under voltage conditions. Intermittent disturbances are Impulse, Transients, and interruption, Basics of Power Quality Monitoring

Power disturbances Voltage Sags and Swells Under-voltage or Over-voltage Transients spikes, impulses and surges Outages Harmonics Noise Q4 Power disturbances generally fall into one of six categories. Voltage Sags and Swells Transients spikes or impulses and surges Outages Harmonics Noise under or over voltages Basics of Power Quality Monitoring

Voltage Sag Momentary decrease in line Voltage Caused by the start of heavy loads or fault occurrence on source. Voltage Swells Momentary increase in line Voltage Occurs due to sudden load decrease or de-energizing of heavy equipment. Q6 Sages, Swells, and surges generally last .5 to 30 cycles Q9. Explain in your own words the difference between voltage sages and swells. Voltage Sages and Swells are momentary decreases or increases in line voltage that is outside of normal tolerance. Sag is a decrease in RMS voltage of down to 80% of normal voltage with a duration of up to 10 seconds or a sag of up to 70% with a duration of up to .5 seconds This may occur when there is a momentary loss of available energy due to starting of heavy loads or fault condition in the electrical system. Swell is an increase in RMS voltage of up to 120% of normal voltage with a duration of up to .5 seconds This may occur when there is a momentary surge of available energy due to load shift. Basics of Power Quality Monitoring

Over-Voltage Abnormally high voltage Power voltage regulation Under-Voltage Abnormally low Voltage Result for clearing of a fault or intentional utility regulation. Q5 Overvoltage and Undervoltage are often caused by intentional reductions by power utilities. Long term over voltage: is when RMS voltage exceeds 120% of normal voltage form >.5 sec to a duration of more than a few seconds Long term under voltage is when RMS voltage falls to 80% of normal voltage from >.5 sec to a duration of several seconds. Dropout: includes both severe RMS voltage sags and complete interruptions of normal voltage. Interruption may last up to 20 milliseconds. Result from the clearing of a fault in the system, Power voltage regulation and intentional reductions by the utility Basics of Power Quality Monitoring

Impulse (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 Q7 Impulses, or spikes may sometimes have magnitudes up to 6KV Q10 Voltage spikes or impulses or surges are high voltage transients lasting only between a nicrosecond and a milliseconds. Transients: are short duration high amplitude pulses, are surges that are superimposed on a normal voltage waveform. Transient can very widely from twice the normal voltage to several thousand volts in time from < microsecond to a few hundreds of a second. Depending on time in relation to the waveform the transient may add or subtract from the waveform. Cause: is the result of a repaid release of energy stored in an inductive or capacitate source in the electrical system or from an external source release such as lightening. Wave shapes applicable to transients and general test conditions are described in ANSI/IEEE C Basics of Power Quality Monitoring

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 Q11 Outages An outage is a complete loss of power that may lasts for a few milliseconds to several hours. Typical outages are caused by power systems distribution due to line damage in accidents or storms or from the failure of distribution equipment like transformers or generators. Basics of Power Quality Monitoring

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 Q13 distortion It is to be understood that in this presentation “Normal Voltage” refers to an ideal 120V rms sinusoidal waveform at 60Hz Steady-state describes an RMS voltage which is constant with little to no variations. The uncertainty is +/- 10% from nominal voltage. NOISE: is an unwanted signal superimposed on a normal voltage waveform Normal Mode noise is voltage which exists between any two conductors Common Mode noise is voltage which exists between ground and line or between ground and neutral RFI: Radio Frequency interference EMI: Electromagnetic interference Basics of Power Quality Monitoring

Harmonics Harmonics are multiple of the fundamental frequency For us in the USA this is 60 Hz Harmonics in our electrical systems are normally caused by distortion of either our Voltage or Current waveform Major cause of harmonics is electronic loads that draw there currents in short pulses. 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, and long term over voltage or under voltage conditions. Intermittent disturbances are Impulse, Transients, and interruption, Basics of Power Quality Monitoring

Harmonics Non-Linear loads Computers, printer, copiers, electronics lighting Adjustable speed drives and other microprocessor controlled equipment Effects on electrical systems or odd harmonics 3rd, 5th, 7th etc. Non-Linear loads are one in which the current waveform is not proportional with the Voltage waveform. Current is either switched on or pulses through the use of semiconductor devices like diodes, Triacs, and SCR. Because of the deviation of the current to a non-sinusoidal waveform, harmonic frequencies are generated that have negative effect on the Electrical Systems Harmonics are integral multiples of the fundamental frequency. In and Electrical systems 60 Hz is the fundamental frequency where 120 would be the 2nd , 180 the 3rd, and 300 the 5th . In an electrical system, even harmonics tend to cancel out, so the 2nd, 4th …. would typically not be present. With the insurance of the electronic or technology Non-Linear loads (products with switch mode power supplies) are commonly found everywhere. Examples are; computers, printers, copiers, electronics lightings, microprocessor controllers, Adjustable speed drives, and other industrial equipment. Basics of Power Quality Monitoring

Harmonics 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. There are two key terms used when discussing harmonics. The first is total harmonic distortion. This is normally expressed as %THD. It is the percent of distortion to the wave form. The rule of thumb is that the %THD should not exceed 5% of line voltage or 20% of current. The second term is harmonic FFT. This is simply the process of breaking down the distortion to its effective amplitude affect of each individual harmonic . For example, is the distortion on the 2nd harmonic, the third harmonic, etc. This is important when troubleshooting, because the individual harmonic that the distortion resides on determines the impact that it will have on the electrical system. Lets look at a couple of common examples. Knowing each harmonic and its effect can help in determines the impact on the system Basics of Power Quality Monitoring

Power Quality- Standards
ITIC (CBEMA) Curve ITIC, Information Technology Industry Council is just one of may professional or governing agency that have adopted acceptable tolerance for power delivered to our sensitive electronic equipment. The ITI, Information Technology Industry Council (Formal CBEMA, Computer Business Equipment Manufacturers Association) updated the CBEMA Curve to the above. The curve is a susceptibility profile. It is the most referred to data in understanding how sensitive electronics is effected by it’s electrical source. The vertical axis of the graph is percentage of voltage from normal, where the horizontal axis of the graph depicts time from a few microseconds to several seconds. In the center of the graph is the acceptable area or within the tolerance of the equipment. (this can very from manufacture) If the source stays within the acceptable area it is felt that the equipment will operator properly. The curve is applicable to 120V systems derived form 208Y/120V or 120/240 systems Basics of Power Quality Monitoring

Plan, Investigate & Test
Where to start Plan your site survey Investigate suspected areas Test or monitor Analyze results or date So how do we track down our Power Quality problem Analyze results or data Apply corrective actions Basics of Power Quality Monitoring

Plan Plan your site survey Make a block diagram of your facility. Most problems are found at your sensitive loads. You may wish to start there, working your way back through the electrical services Make a block diagram of you facility. Basics of Power Quality Monitoring

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 Investigate suspected areas Try to establish time of occurrence and duration history Equipment usage cycles or new equipment instillation Personnel Interview other- Find out what they have observed Basics of Power Quality Monitoring

Test Power and Power Factor, Inductive or Capacitive reactance, or how efficient we use the power that is delivered. A Power Analyzer is the tool of choose when the measurement of Power usage are efficiency is desired. Disturbances, like Sage Swell and Impulse are normally generated within a facility and affecting our sensitive electronics equipment In the pass Power analyzers my have been used at a main or sub-panel, but were not cost effective for branch circuit monitoring. Today, however we have a small inexpensive tools that can be plug at the device or equipment that is being effected. Q15 Most impulses within a building are generated when loads cycle on and off Basics of Power Quality Monitoring

Testing 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 Most power quality failures may be tracked down to one of three areas. Supply- Utilities and its distribution. Internal Distribution- Gear, Ground, wiring and termination Internal Loads- load disturbances and Harmonics Basics of Power Quality Monitoring

Testing 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 Utility systems are designed to provide us with bulk reliable power, but we know that it may not possible for a utility to provide a constant “clean” power source . Lightning strikes, utility switching, storm or accident damage to utility distribution systems or intermittent disturbances, all can create interruption or disturbances on the utility side. Investigate possible feedback (dumping) from your neighboring facilities. Any one connected to your PCC (point of common coupling) could be the cause. PCC is where one or more utility customer are connected to the power grid. IEEE 519 has set a limit of no greater than 5% THD (Total Harmonic Distortion) at PCC Basics of Power Quality Monitoring

Testing Internal Disturbances Many studies have been conducted and found that 80% of power Quality problems are generated within a facility Of this, 80% of those are related to inadequate wiring or poor grounding. Power and Power reactance. Line to Neutral Voltage Sags& Swells, under-voltage & over-voltage, Impulse, Distortion. Neutral to Ground Voltage High resistance grounds, Load imbalance, Harmonics Internal Distribution- Many major organizations, and agencies, have proven through case studies that the vast majority of power quality problems originate from within a building or facility. They have also found that through closer attention to design, enhanced electrical systems, closer attention to construction or installation technique that may of these incidence can be reduced or eliminated According to the Electric Power Research Institute, 80% of all power quality problems relate to inadequate wiring or grounding. Inspect your Electrical distribution systems, Look for: Corroded connections Defective conduit Defective electrical devices Adequate wiring Proper grounding Hot breakers, neutrals, or transformers. Basics of Power Quality Monitoring

Testing A Hospital is wanting to add new diagnostic equipment. Before the equipment is added to the service they need to determine if the present system can handle the additional load. Basics of Power Quality Monitoring

Testing This is an example of data taking at a hospital in North Carolina. Two observation can be made from this data. First, is a drop in Voltage during Wednesday, not seen in any other days data. Why? Second, is a load imbalance, where phase 2 and 3 are drawing around 40 amps more that phase 1 Basics of Power Quality Monitoring

Testing When we look at the Power of each phase we can also see that Phase 1 average is 4000 Watts less that phase 2 and 3. Both phase 2 and 3 average in the range of 7000 Watts. Basics of Power Quality Monitoring

Testing Branch Circuits Line to Neutral Voltage Transients, Sags& Swells, Voltage drops, Flat toping Neutral to Ground Voltage Tripling harmonics, High ground impedance. Basics of Power Quality Monitoring

Testing Branch Circuits
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 Q18 Voltage Distortion can be caused by large harmonic currents form Nonlinear loads or Power sources with no sinusoidal Voltage Characteristic Excessive Current drawn as the Voltage waveform reaches Peak can cause Voltage distortion. Referred to as Flat Topping or Clipping. Basics of Power Quality Monitoring

Testing Branch Circuits Major loads affected Computers Copiers, Laser printers, and other Large office loads HVAC Equipment Industrial equipment, Like ASD’s (Adjustable Speed Drives) Lighting UPS systems Internal Loads effect on power quality 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 Acceptable input power requirement for critical loads Frequency +/- 5%, Steady State Voltage +/- 8%, Transient Voltage conditions not to exceeded +15% or –18% nominal, with a return to normal voltage <.5 sec Line to Line voltage imbalance not to exceed 2.5% in a 3-phase system Total harmonic voltage distortion not to exceed 5%. Basics of Power Quality Monitoring

Testing Key Points for comparison Only important evens are logged Events are sorted by Time (log) Events are sorted by Type (event) Waveform shape is measured for THD Basics of Power Quality Monitoring

Testing Events Log? Sag – low voltage for brief periods (dips) Swell- high voltage for brief periods (surges) Voltage Transient- impulses (spikes) THD for Total Harmonic Distortion (noise) Basics of Power Quality Monitoring

Testing What cause the event and When ? Amplitude of the event Number of Cycles (duration) Time of event Date of event Basics of Power Quality Monitoring

Test Equipment Test or Monitor , Basic measurement tools
Circuit Analyzer Multimeter or ClampMeters (True RMS responded) Receptacle Event Recorder Power Quality Monitor. Infrared temperature device Test or monitor, The basic tools Circuit Tester Multimeter or ClampMeters (True RMS responded to AC) Receptacle Event Recorder Power Quality Monitor. Infrared temperature device Always follow proper Safety precautions Lock-out Tag-out, safety gear like glasses and gloves Basics of Power Quality Monitoring

Test Equipment 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. Depending on what type of problem you are investigating, will help you determine what type of equipment to use Most equipment like circuit testers, meters and clamps are slow responding. They sample at speed around 2 or 3 times a second. This is OK for steady state problems however much to slow for intermittent disturbances. Basics of Power Quality Monitoring

Test Equipment 160 Series SureTest Circuit Analyzers 830 Voltage Performance Monitor 800 Series Power Analyzer Lets take a look at some of the products to troubleshoot electrical power systems and help us analyze power quality problems. Basics of Power Quality Monitoring

SureTest Circuit Analyzers
Circuit Analysis Measures voltage drop under full 15 Amp load, Neutral to Ground Voltage Ground Impedance Hot and Neutral Conductor Impedance. The SureTest Circuit/Harmonics Analyzer, model ST-1THD, will do all of the circuit analysis done by the , model ST-1D. Basics of Power Quality Monitoring

830 Voltage Performance Monitor
830 Voltage Performance Monitor is great for evaluation clean Power on a branch circuits. Sag Swells Impulses %THD Depth and duration of each event is log with time and date stamp The powerful box with the Power Quality Engineer inside Basics of Power Quality Monitoring

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) The 800 Series power analyzer is the most versatile and complete power analyzer on the market today. It will measure all of the power quality problems we have talked about today, and comes with the PowerVision analysis software for in-depth analysis on your PC. Basics of Power Quality Monitoring

Understanding Power Quality Monitoring

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