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Lecture 24
ECE 528 – Understanding Power Quality
Paul Ortmann
[email protected]
208-733-7972 (voice)
208-736-3248 (fax)
http://www.ece.uidaho.edu/ee/power/ECE528/
Lecture 24 2
Today…
- Housekeeping…
- Text errors and homework clarifications
and help
- Conclude Harmonics
- Neutral loading
- Interharmonics
- Standards
Lecture 24 3
Text corrections and HW4 changes
- FPQ page 219 table 6.4:
- Under “type” the second transformer group is
“oil-filled”, not “dry”; see PSQ page 213, table
- HW 4 Question 4 was modified to conform
with the definition of K-factor in FPQ and
IEEE C57.110.
- Magnitude of the load is given:
- Same as the drive in problem 3
- Transformer size is given: 100kVA.
Lecture 24 4
HW4 – a little assistance
- Problem 2: A “B versus H” curve relates
the flux density (B) and the magnetic field
strength (H).
- In a transformer, the transformer’s
magnetizing characteristic curve, which
relates applied voltage to transformer
exciting current (see FPQ pg. 212) has the
same shape as its B versus H curve.
Lecture 24 7
Interharmonics examples:
V ( t)
t
V ( t)
t
Lecture 24 8
Sources of interharmonics
- Power-line-carrier signals
- Frequency converters
- Drives
- Cycloconverters
- Induction furnaces
- Arcing loads
- Load variations
Lecture 24 9
Interharmonics issues
- Analysis
- Power quality instruments may not accurately
measure them
- Impacts
- Same heating and distortion issues as regular
harmonics
- Oscillations in mechanical systems
- Interference with power-line-carrier systems
- Tuned filters may not work because of the variability
of the harmonic spectrum
Lecture 24 10
Interharmonics – data analysis issue
Event #1 at 02/27/2008 11:59:59. Timed
Event Details/Waveforms
11:59:59. 02/27/ Wednesday
11:59:59.85 11:59:59.90 11:59:59.95 12:00:00.
0
10
20
Amps
A I
Sel : 256 samps
Free sel.
Waveform harmonics
%
660.0 Hz
A VHarm A IHarm
Lecture 24 13
Why have harmonic (and other) standards?
- Compatibility between the power system and
end-user equipment
- For utilities
- Provides measurable limits that can be used as the
basis for system design
- For equipment manufacturers
- Describes the electrical environment the equipment
may be expected to operate in
- Helps manufacturers design equipment to operate
acceptably
Lecture 24 14
Harmonic standards
- IEEE 519-
- Recommended Practices and Requirements for
Harmonic Control in Electrical Power Systems
- Requirements
- Limits harmonic current produced by loads
- Limits voltage distortion on the utility system
- Reference material
- Describes harmonic generation by power converters, arc
furnaces, SMPS, etc.
- Covers effects on motors, transformers, capacitors,
conductors, and other equipment
Lecture 24 15
Harmonic standards
- IEEE 519-
- Practices
- Covers analysis methods for –
- System frequency response
- System modeling
- Telephone interference
- And more…
- Covers measurements
- Describes a methodology for evaluating new
harmonic sources
Lecture 24 16
Other harmonic standards
- IEEE -519a or 519.1– “Guide for Applying
Harmonic Limits on Power Systems”
- Provides examples and additional guidance on
the application of IEEE 519-1992.
- Not an official standard yet.
- Not currently available outside the standard
committee.
Lecture 24 19
Other standards and standards-related work
- EN 50160 – “Voltage Characteristics Of
Electricity Supplied By Public Distribution
Systems”
- Voltage at the PCC only
- Addresses harmonics, sags, swells, etc.
- Incorporated in newer power quality
recorders
- Describes 95% conditions
- Operation at minimum requirements is not
likely to be acceptable to customers.
Lecture 24 20
Standards
- Standards are becoming more international –
several IEEE standards reference IEC standards.
- IEEE Power Engineering Society Power Quality
Subcommittee
- Works to coordinate international power quality
standards including harmonic standards
- In some cases identical standards are issued from
multiple organizations now
- ANSI/ISA-61010-1 is practically identical to IEC 61010-1, CSA
C22.2 No. 1010.1, and UL 61010-
