Transcript Project overview presentation

Harmonics Problems in Distribution Systems
Case Study
AEP Texas Central Company
Scott Lee, Reliability Engineer
WHAT’S WRONG WITH MY LIGHTS?!
SYMPTOMS OF A PROBLEM
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Residential customer calls complaining of problems
with electronics: TV, thermostat – AC, motors making
strange noises
Serviceman and Operations Tech troubleshoot and
have transformer replaced because of unusual
humming and arcing sounds from coil
New transformer makes the same sound, customer
still has problems – call the engineer
Tech goes to new pipe plant down the road and finds
2000kVA pad transformer making same noise
THE SOURCE
Houston based company built a pipe coating
and storage plant in George West to better
serve the Eagle Ford Shale area
 Two 1000kW induction furnaces to heat and
coat 2 inch to 24 inch diameter casing with
fusion bonded epoxy
 Two solid state 6-pulse rectifiers and step up
transformers provide variable frequency 4kV
power to induction coils
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For more info . . . see texisle.com and ajaxtocco.com
INSTALLATION
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Previously during the plant planning stages, AEP provided
system, line, and transformer impedances to drive
manufacturer for design. Distance and PQ were discussed.
3 miles of distribution feeder was upgraded with 477MCM
aluminum, with a total length of 6.4 miles
Drive manufacturer wanted two 1500kVA or one 3000kVA
transformer, we supplied one 2000kVA. They were also very
insistent on our transformer meeting their specs. Actual peak
is 1380kW.
A 1000kVA pad was installed for other plant power that peaks
at 600kW
AEP standard for three phase padmounts is wye-wye
IEEE-519 requirements were not discussed, customer did not
tell us the inverter was a 6-pulse drive
Plant *
Residence 
George West Sub
138/12kV 9.4 MVA
Feeder upgraded to 477,
6.4 circuits miles from
sub to customer
AJAX TOCCO, PACER-2 DRIVE
1000kW
 500 Hz
 Variable Frequency
 6-pulse rectifier
 No filtering
 Water cooled
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INDUCTION HEATING LINE
FUSION BONDED EXPOXY COATING
MEASUREMENTS
PMI recorders installed at plant transformer
and at residential customer. Set to record
harmonics and capture waveforms.
 Voltage THD at pipe plant on secodary, 14%
 Voltage THD at residential secondary, 5.1%
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PMI stands for Power Monitors Incorporated, see www.powermonitors.com, iVs-3 and Eagle 440
Unfiltered, running at 1550kVA
5th
7th
3rd
2000 kVA Padmount
6-Pulse Drive
11th 13th
12.4%
THD-Voltage
5th
7th
11th
23.4%
THD-Amps
Unfiltered, 2000kVA Padmount, 6-Pulse Drive
12.4% THD-V
23.4% THD-A
THE FIX
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Met with pipe company and drive manufacturer to request they
install filtering and comply with IEEE-519 (5% THD limit on
voltage)
Move other distribution customers in area to another feeder
Drive manufacturers said they would install passive filters
(reactors and capacitors) but parts would have a 14 week lead
time plus engineering and installation time
I countered to pipe company that this was unacceptable, and
offered three filter manufacturers with on the shelf parts that
offered active filtering and engineering support.
Recomended MTE Matrix Pure Sine active filters, Schaffner
EMC ECOsine active filters, and TCI H5 active filters.
THE FIX cont.
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There was a debate over passive versus active, but
after some research, I pressed the customer to go
with active filters because of the varying load and the
possibility of hitting resonance with a passive unit,
also recommend a 5% line reactor which is standard
for 6 pulse drives
The customer chose a vendor, and we had several
phone conferences about what to install, and what
would be acceptable with AEP
The vendor chosen was Schaffner EMC and the
ECOsine FN3420 filter with additional 5% reactors
For more info . . .
List location or contact for specification (or other related documents)
ACTIVE FILTER
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Schaffner EMC ECOsine
filter injects up to 300
amps of current
Compensates for harmonic
currents
Compensates for reactive
current
Can choose percentage of
overall current dedicated to
each harmonic
Two installed with 5%
reactor ahead of each drive
MEASUREMENT AFTER FILTER INSTALL
Before at 1850 amps of load:
 Voltage THD 12.6% Current THD 23%
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After at 2150 amps of load:
 Voltage THD 5.5%
Current THD 8.8%
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After at 1320 amps of load:
 Voltage THD 7%
Current THD 5%
 Adjacent Transformer Voltage THD 3.5%
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HARMONIC CURRENTS BEFORE/AFTER
Total Load 1800 amps
Harmonic
Amps
5th
427
7th
225
11th
113
13th
60
THD-V from 12.2% to 8.1%
Amps with Filter
49
60
52
59
Testing, filter on and off
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Filter off
2300A rms
5.9% THD-V
9.6% THD-A
8.4% THD-V
24.2% THD-A
Neutral volts and amps
Waveforms showing commutation notching
6.9% THD-voltage
5% THD-current
1300 amps
UG Residence, one mile from pipe plant, plant running at 7% THD-V
3.5% THD-V
3rd, 7th, and 5th
V
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STILL PROGRESS TO BE MADE
Not below 5% THD on voltage at meter
 Filtering has done all it can do
 Work with drive manufacturer to control
commutation notching using saturating
reactors on SCRs to speed gate closing
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IN RETROSPECT
Should have required drive manufacturer to
meet IEEE 519 standard
 Get a written proposal from drive manufacturer
on how they will meet the standard
 Use delta primary transformer to trap Triplen
harmonics, this is 2.7% of total
 Recommend active filtering
 Recommend 12 pulse drives or technology to
reduce commutation notching
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