© 2007 Ideal Industries 1 of 40 Basics of Power Quality Monitoring Understanding Power Quality Monitoring

Basics of Power Quality Monitoring© 2007 Ideal Industries www.idealindustries.com 1 of 40

Understanding 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.


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.


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


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 519-81 Recommended limits on Harmonics

– ANSI C84.1 Specification on normal voltage ratings and tolerances


Power Quality

• 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


Power Quality

• 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.

Power And Power Factor

Most utilities have an additional charge

if PF is less than .95 to .90


Power Quality

• 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,

Disturbances


Power Quality

– Voltage Sags and Swells– Under-voltage or Over-voltage– Transients spikes, impulses and surges– Outages– Harmonics– Noise

Power disturbances


• 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.

Power Quality


Power Quality

• Over-Voltage– Abnormally high voltage

– Power voltage regulation

• Under-Voltage– Abnormally low Voltage

– Result for clearing of a fault or intentional utility regulation.


Power Quality

• 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


Power Quality

• 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


• 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

Power Quality


Power Quality

• 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.

Harmonics


Power Quality

• 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.

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.

Knowing each harmonic and its effect can help in determines

the impact on the system

Harmonics


Power Quality- Standards

• 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.

ITIC (CBEMA) Curve


Plan, Investigate & Test

• Where to start – Plan your site survey

– Investigate suspected areas

– Test or monitor

– Analyze results or date


Plan

Make a block diagram of you facility.


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


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.


• 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

Testing


Testing

• 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

Supply – Utilities Disturbance


Testing

• 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 Disturbances


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.


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


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.


Testing

• Line to Neutral Voltage– Transients, Sags& Swells,

Voltage drops, Flat toping

• Neutral to Ground Voltage– Tripling harmonics, High

ground impedance.

–

Branch Circuits


Testing

• 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.

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

Branch Circuits

Testing


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


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)


Testing

What cause the event and When ?• Amplitude of the event

• Number of Cycles (duration)

• Time of event

• Date of event


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

Always follow proper Safety precautionsLock-out Tag-out, safety gear like glasses and gloves


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.


Test Equipment

• 160 Series SureTest Circuit Analyzers

• 830 Voltage Performance Monitor

• 800 Series Power Analyzer


SureTest Circuit Analyzers

• Circuit Analysis– Measures voltage drop

under full 15 Amp load,

– Neutral to Ground Voltage

– Ground Impedance

– Hot and Neutral Conductor Impedance.


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


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)

Documents

© 2007 Ideal Industries 1 of 40 Basics of Power Quality Monitoring Understanding Power Quality Monitoring