_renella_blagojevic.pdf
TRANSCRIPT
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Locating Winding Insulation Defects in Large Electrical Machines
Dragana Popovic Renella & Marjan Blagojevic
CWIEME 5th June 2013, Berlin
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Outline
• Magnetic Measurement Instruments
• Current Sensors
• Insulation Defect Locator
• Outlook
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Digital Teslameter / Gaussmeter
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• Integrated 3-axis Hall Probe • Very high resolution: 1ppm • Accuracy: 0.001% • High f-bandwidth • High temperature stability
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Applications
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• Magnetic Field Mapping, e.g. in Particle Accelerators • Characterization of Permanent Magnets
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Application: Monitoring Electrical Machines
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Detecting rotor winding shorted through measurement of: • Main Rotor magnetic field • Stator Reaction magnetic field • Rotor Slot Leakage magnetic field • Air-gap magnetic field
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6/10/2013 6
SENIS’ Teslameter
reso
lutio
n &
acc
urac
y (p
pm)
field (T) *Luca Bottura of CERN; Revised by SENIS 2011
Magnetic Measurement Technologies
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Current Sensing using Magnetic Field
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Application: Current Sensors
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I = 0.2A …10A
B I
I = 200A …3000A
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Application: Clamp-On MicroAmmeter
Key Features ▪ Measurement range ± 100mA (100μT)
▪ Offset Drift IOF,RMS< 10μA (10nT)
▪ Sensitivity 100V/A (100’000V/T)
▪ Withstanding voltage 50kV
▪ Jaw opening Ø50mm
SENIS Hall sensor inside
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Application: Insulation Defect Locator
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IDL – Theoretical background
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Typical current stator slot cross section
IDL – Theoretical background
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Predicted diagram of leakage current based on simplified schematic diagram. Current limit for controllable high voltage source is about 15mA.
IDL – Theoretical background
Control voltagefor HV source
Leakage current of coil
Current of HV source
HV so
urce
ope
rates
like
vol
tage s
ourc
e
HV source operates like current source
Rise time Fall time
Trailing edge
Width time
Leading edge
Current limit
Current Limiter
Stat
or C
oil C
Leakage Resistance
High Voltage Generator
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IDL Consisting Parts
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Measurement diagram for one phase of generator
IDL – Measurement Procedure
Rins
ulat
ion
Hig
h V
olta
ge D
C G
ener
ator Win
ding
und
er te
st
Multifunction DAQ
DC
Clam
p-O
n M
icro
amm
eter
1
DC Clamp-On Microammeter 2
R
#1 #2 #12
CT
CT
CT
CT
1
2
9
10
11
A
B
C
D
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Technical Challenges
Very low magnetic resolution order of nT
=> Minimization of noise and offset fluctuation
Influence of external magnetic field
=> Dual core
Remanet magnetic field
=> Degaussing & material with low Br
High voltage compatibility
=> Fiber-optic transfer data
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Case Story - Twin Lakes Colorado
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Case Story – Grand Coulee
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Case Story – Buffalo Bill G2 Plant
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Case Story – Buffalo Bill G2 Plant
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SENIS’ Current Sensors - Outlook
• Development of a New generation of Clamp-On MicroAmmeters for leakage current detection.
- Objective: Offset fluctuation and drift <3µA over 10min - Deadline: End of 2013 • High-Accuracy Clamp-On DC/AC Current Transducers for Test
and Measurement applications, ranges from 100A to 1000A - Objective: Absolute accuracy better than 0.2% (now the best
on the market: 1%); major improvement of repeatability and immunity to external magnetic fields.
- Time: Mid-2014
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Demonstration
Booth No. 4333, Hall 4.2
Thank you!
www.senis.ch