New Experience in the
Transformer Diagnosis
Michael Krüger, OMICRON Austria
Electrical Measurement Methods I
Measurement Method
Application
Contact problems,
broken or loose
Winding resistance (static)
connections,
broken conductors
Contact problems at the
Winding resistance (dynamic) diverter switch, broken
transition resistors
Leakage reactance (stray
Winding deformation
reactance)
Indicated by
Kind of on-/offTest*
line
High internal temperatures,
e.g. indicated by DGA results
or Buchholz Relay
FRT
off
DGA, Buchholz Relay
FRT
off
High through-fault currents
FRT
off
Frequency Response of the
Stray Losses (FRSL)
Shorted parallel strands
of CTC's
High internal temperatures,
e.g. indicated by DGA results
FT
off
No-load impedance
Core problems, shorted
turns
High internal temperatures,
e.g. indicated by DGA results
FT
off
No-load current
Core problems, shorted
turns
High internal temperatures,
e.g. indicated by DGA results
FT
off
*F=Fingerprint, R=Routine, T=Troubleshooting, S=Special
Annual Convention 2012 – Eilat, Israel
PAGE 2
Electrical Measurement Methods II
Measurement Method
Turns ratio
Frequency Response
Analysis (FRA)
Application
After Buchholz Relay
tripping
Winding deformation,
winding displacement,
core faults, faulty screen
or core connections
Indicated by
Kind of on-/offTest*
line
Buchholz Relay has tripped
T
off
High through-fault currents,
transportation
F(R)T
off
FRT
off
Breakdowns, Buchholz Relay
tripping
Insulation resistance
Insulation problems
Capacitance and Dielectric
Dissipation Factor
Main insulation: ageing,
moisture - Bushings:
DGA
ageing, partial breakdowns
FRT
on/off
Dielectric Response
Measurement (FDS and
PDC)
Main insulation: ageing,
high water content in oil /
moisture - Bushings:
high dielectric losses
ageing, partial breakdowns
FRT
off
Partial Discharge
Insulation problems
T
on/off
DGA
*F=Fingerprint, R=Routine, T=Troubleshooting, S=Special
Annual Convention 2012 – Eilat, Israel
PAGE 3
Content
• Winding Resistance Measurement
• Fault Finding on Transformer Windings with FRA
• Moisture Measurement on Transformers
• Partial Discharge Measurement on Transformers
Annual Convention 2012 – Eilat, Israel
PAGE 4
Winding Resistance Measurement
Annual Convention 2012 – Eilat, Israel
PAGE 5
Diverter Switch Contact of Phase V
Annual Convention 2012 – Eilat, Israel
PAGE 6
Winding Resistance after Repair
Annual Convention 2012 – Eilat, Israel
PAGE 7
Content
• Winding Resistance Measurement
• Fault Finding on Transformer Windings with FRA
• Moisture Measurement on Transformers
• Partial Discharge Measurement on Transformers
Annual Convention 2012 – Eilat, Israel
PAGE 8
Fault on a 115kV /
34.5kV Transformer
• There was a breakdown in
phase B of the 34.5 kV busbar
in the substation
• The differential protection
relay of the faulty transformer
tripped
Annual Convention 2012 – Eilat, Israel
PAGE 9
DGA
Phase 1: Trip out of Service, Differential
Phase 2: DGA
second DGA showed 19ppm C2H2
Annual Convention 2012 – Eilat, Israel
PAGE 10
Transformer Model for FRA
Annual Convention 2012 – Eilat, Israel
PAGE 11
Swept Frequency Response Analysis (SFRA)
5.0
5.0
Transformer
U0*(1-K(f1))
3.0
3.0
1.0
1
N
-1.0 0
0.2
0.4
0.6
0.8
1
1
U
1
V
1.0
1
W
1/f1
-1.0 0
1.2
-3.0
0.2
0.4
0.6
-3.0
complex RLCM-Network
-5.0
0.8
1
1.2
(f1)
-5.0
sine generator
(variable frequency)
(f1)
K(f1)
Phase
Magnitude
transfer function (magnitude)
2.5
2.0
2.0
K(f)
transfer function (phase)
3.0
1.0
1.5
(f)
1.0
0.0
-1.0
0.5
-2.0
0.0
-3.0
0.0
0.2
0.4
0.6 0.8
Frequenz f
frequency f
1.0
1.2
MHz
1.4
0.0
0.2
0.4
0.6 0.8
Frequenz f
1.0
MHz
1.2 1.4
frequency f
Annual Convention 2012 – Eilat, Israel
PAGE 12
FRA LV Winding – Comparison of the 3 Phases
B Phase
Annual Convention 2012 – Eilat, Israel
PAGE 13
Radial Forces
Higher order or
forced Buckling
Buckling with inner
supports
The conductors can bend between the supports all along the circumference
Free mode
or free Buckling
Buckling without inner
supports
Source: Brochure CIGRE WG 12.19 : The Short Circuit Performance of Power Transformers
Annual Convention 2012 – Eilat, Israel
PAGE 14
Radial Failure (Buckling)
Annual Convention 2012 – Eilat, Israel
PAGE 15
Failure Modes due to Radial Forces
B phase with buckling
C phase without buckling
Source: Cigre Brochure 342 “ MECHANICAL-CONDITION ASSESSMENT OF
TRANSFORMER WINDINGS USING FREQUENCY RESPONSE ANALYSIS (FRA)”
Annual Convention 2012 – Eilat, Israel
PAGE 16
Comparison FRA
LV Winding with
Cigre Case Study
of Buckling
Systematic shift of
several resonances
www.e-cigre.org
B Phase
Annual Convention 2012 – Eilat, Israel
PAGE 17
B Phase
Take a closer look
Annual Convention 2012 – Eilat, Israel
PAGE 18
B Phase
Annual Convention 2012 – Eilat, Israel
PAGE 19
Content
• Winding Resistance Measurement
• Fault Finding on Transformer Windings with FRA
• Moisture Measurement on Transformers
• Partial Discharge Measurement on Transformers
Annual Convention 2012 – Eilat, Israel
PAGE 20
Water in the Transformer
Most of the water is contained in the paper!
Mass of the oil:
100,000 kg = 220,000 Lbs
Mass of the solid insulation:
13,000 kg = 20,000 Lbs
Water content at 60 °C:
40 ppm
Water content at 60 °C:
4%
Mass of the water, dissolved in the
oil:
Mass of the water contained in the
paper:
4 kg = 8.8 Lbs
520 kg = 1200 Lbs
Annual Convention 2012 – Eilat, Israel
PAGE 21
Determination of the Water Content in Paper
[Karl Fischer Titration and Equilibrium Curves]
• Curves are only valid
for new oil and new
paper, for aged
oil/paper different
curves are necessary
11
20 °C
[%]
30 °C
40 °C
Water Content in the Paper
9
50 °C
8
7
low
6
60 °C
5
Temperature
4
80 °C
high
3
2
100°C
1
0
0
10
20
30
40
50
60
Water Content in the Oil
70
[ppm]
90
• Oil sampling is critical
(round robin tests)
• Balance between water
content in the paper
and in oil needs
constant temperatures
over a long period
• Only average
measurement
Annual Convention 2012 – Eilat, Israel
PAGE 22
History of Dielectric Diagnostic Methods
•
1960+
U
U(t)
Ur,max
•
Dissipation factor at power frequency
•
Polarization index
•
At that time: No reliable method for onsite moisture diagnostics
•
1991 RVM for water determination
•
Soon questioned by users (Kachler 1996)
tc
1999+ Polarization Depolarization Currents
•
Technical University Zurich Switzerland
•
1999+ Frequency Domain Spectroscopy
•
KTH Stockholm with ABB
•
2007 Combination of PDC and FDS
Annual Convention 2012 – Eilat, Israel
ipol (t)
TC
Uc (t)
idep (t)
Dissipation factor
•
U, I
t
t d t peak
Frequency
PAGE 23
t
Dielektric Response in the Time Domain
Polarisation Depolarisation Current (PDC)
Current = f(t)
Annual Convention 2012 – Eilat, Israel
PAGE 24
Dielektric Response in the
Frequency Domain
Frequency Domain Spectroscopy (FDS) or
Dielectric Frequency Response (DFR)
Annual Convention 2012 – Eilat, Israel
PAGE 25
Dielectric Response Measurement with
Frequency Domain Spectroscopy (FDS) and
Polarisation & Depolarisation Current (PDC)
1
1
Time [s]
1000
0.001
0.1
FDS
1000
Frequency [Hz]
Transformation
Power factor
1
1000
12
100
10
10
8
1
6
0,1
4
0,01
2
0,001
0,0001
0
FDS
Combination of PDC
und FDS reduces
measurement time 0.001
0.001
14
Frequency [Hz]
PDC
DIRANA
1000
Annual Convention 2012 – Eilat, Israel
PAGE 26
Frequency range / Hz
1
Power factor
Current [nA]
PDC
Duration / h
100
Interpretation and Analysis
Dissipation factor
Pressboard:
Water, lmw
Acids
Transition from
Capacitive to
Resistive Voltage
Distribution
Oil: Carbon, Sludge,
hmw Acids
10
1
Pressboard
Overall Response
0.1
1%, 1pS/m, X30, Y15
0.01
0.001
0.0001
0.0001
0.001
0.01
0.1
1.0
10
Annual Convention 2012 – Eilat, Israel
100
1000
f/Hz
PAGE 27
Analysis of the Water Content by
Comparison to Model Results
Measurement
Laboratory Results
Temperature
Oil
Y
XY-Model
Oil
Spacers
Barriers
X
Comparison
Fitting
Tangent Delta
10
Water Content
Oil Conductivity
Source: Weidmann
0,1
0,01
0,0001
0,01 Frequency [Hz] 100
Annual Convention 2012 – Eilat, Israel
PAGE 28
FDS / PDC Measurement on a 130 MVA
Transformer – Situation 2006
• 130 MVA
• 230 / 115 / 48 kV
• Year of manf. 1967
• Rubber membrane
in the expansion
vessel
Annual Convention 2012 – Eilat, Israel
PAGE 29
FDS / PDC Measurement on a 130 MVA
Transformer – Water Content Distribution
Moisture in paper [%]
5
4
3
Tertiary not in
use
2
Average
1
0
FDS HV-LV
FDS
LV- Tertiary
FDS/PDC
FDS
TertiaryTank
Oilsample Oilsample
RH % Karl Fischer
mg/kg
(Oommen
equilibrium)
1mHz-1kHz
Annual Convention 2012 – Eilat, Israel
PAGE 30
130 MVA
Transformer
On-Line Drying
Annual Convention 2012 – Eilat, Israel
PAGE 31
History 2006 – 2008 - 2010
Annual Convention 2012 – Eilat, Israel
PAGE 32
Content
• Winding Resistance Measurement
• Fault Finding on Transformer Windings with FRA
• Moisture Measurement on Transformers
• Partial Discharge Measurement on Transformers
Annual Convention 2012 – Eilat, Israel
PAGE 33
Diagnostic Measurement on a
Cast Resin Type Transformer
Annual Convention 2012 – Eilat, Israel
PAGE 34
Cracks in the Epoxy
Annual Convention 2012 – Eilat, Israel
PAGE 35
PD Measurement Circuit
Annual Convention 2012 – Eilat, Israel
PAGE 36
Test Arangement
CPC100
CP CU1
Compensating
Capacitors
Annual Convention 2012 – Eilat, Israel
PAGE 37
Test Arangement Coupling Capacitor and
MPD600
Annual Convention 2012 – Eilat, Israel
PAGE 38
Separation of PD Sources in 3CFRD
3CFRD
500kHz
500
kHz
2
MHz
8
MHz
2MHz
8 MHz
2 MHz
500 kHz
8MHz
timeframe
1 µs
3CFRD = 3 Center Frequency Relation Diagram
Annual Convention 2012 – Eilat, Israel
PAGE 39
PD Measurement without 3CFRD Filtering
Annual Convention 2012 – Eilat, Israel
PAGE 40
3CFRD Filtering
Annual Convention 2012 – Eilat, Israel
PAGE 41
PD Measurement with 3CFRD Filtering
Annual Convention 2012 – Eilat, Israel
PAGE 42
PD Measurement without 3CFRD Filtering
Annual Convention 2012 – Eilat, Israel
PAGE 43
On-Line PD Measurement on a Transformer
Annual Convention 2012 – Eilat, Israel
PAGE 44
On-Line PD Measurement on a Transformer
GIS - Cable Connection (GIS Side)
3
2
1
Annual Convention 2012 – Eilat, Israel
PAGE 45
Online PD Measurement at the GIS Side
red phase GIS
yellow phase GIS
blue phase GIS
Annual Convention 2012 – Eilat, Israel
PAGE 46
Sensors 1, 2 and 3 at the GIS Side and
Sensor 4 at the Transformer Side
4
100m
Annual Convention 2012 – Eilat, Israel
PAGE 47
PD Measurement at the GIS and the
Transformer Side
blue phase GIS
blue phase Tr
Annual Convention 2012 – Eilat, Israel
PAGE 48
PD Measurement at GIS and TR Side
Trigger = TR Side - Delay on GIS Side
trigger = blue
phase Tr
delayed signal
blue phase GIS
Annual Convention 2012 – Eilat, Israel
PAGE 49
Jumper between Oil/Oil Bushing and
Cable Termination
Annual Convention 2012 – Eilat, Israel
PAGE 50
Jumper between Oil/Oil Bushing and
Cable Termination
Annual Convention 2012 – Eilat, Israel
PAGE 51
michael.krueger@omicron.at
Questions and Remarks?
A last Example:
Fault Investigation on a 220kV Transformer
Annual Convention 2012 – Eilat, Israel
PAGE 53
DGA
Parameter
H2
CH4
C2H6
C2H4
C2H2
CO
CO2
TDCG
DGA 7 Nov 2011
Main Tank
OLTC
1008.8
1183
67
65
54.8
55
668
710
1130
1214
95
107
720
740
3024
3337
Condition 1
≤
100
≤
120
≤
65
≤
50
≤
1
≤
350
≤
2500
≤
720
IEEE C57.104-2008
Condition 2
Condition 3 Condition 4
101 - 700 701 - 1800 >
1800
121 - 400 401 - 1000 >
1000
66 - 100 101 - 150 >
150
51 - 100 101 - 200 >
200
29
10 35 >
35
351 - 570 571 - 1400 >
1400
2501 - 4000 4001 - 10000 > 10000
721 - 1920 1921 - 4630 >
4630
Annual Convention 2012 – Eilat, Israel
PAGE 54
Ratio Measurement HV to LV
Annual Convention 2012 – Eilat, Israel
PAGE 55
Ratio HV to LV Phase A=R
A:
Tap
A 001
A 002
A 003
A 004
A 005
A 006
A 007
A 008
A 009
A 010
A 011
A 012
A 013
A 014
A 015
A 016
A 017
A 018
V prim. Nom. Vsec.Nom. Ratio nom. V prim.
165750.0/√3V
163500.0/√3V
161250.0/√3V
159000.0/√3V
156750.0/√3V
154500.0/√3V
152250.0/√3V
150000.0/√3V
147750.0/√3V
145500.0/√3V
143250.0/√3V
141000.0/√3V
138750.0/√3V
136500.0/√3V
134250.0/√3V
132000.0/√3V
129750.0/√3V
127500.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
8.2875:1
8.175:1
8.0625:1
7.95:1
7.8375:1
7.725:1
7.6125:1
7.5:1
7.3875:1
7.275:1
7.1625:1
7.05:1
6.9375:1
6.825:1
6.7125:1
6.6:1
6.4875:1
6.375:1
1999.5V
1999.57V
1999.39V
1999.35V
1999.5V
1999.42V
1999.58V
1999.74V
1999.5V
1999.42V
1999.4V
1999.43V
1999.54V
1999.49V
1999.49V
1999.5V
1999.43V
1999.56V
Vsec.
0.022947V
0.023128V
0.022972V
0.024964V
0.024298V
0.023854V
0.024173V
0.024195V
0.02426V
0.022962V
0.022158V
0.024335V
0.024313V
0.023602V
0.024304V
0.02426V
0.024024V
0.023816V
Ratio
164.81°
163.61°
164.95°
166.1°
163.59°
162.68°
165.95°
166.09°
163.8°
164.95°
163.12°
164.51°
163.74°
165.97°
165.52°
164.07°
166.21°
166.46°
87143.1684:1
86449.2002:1
87043.535:1
80086.1206:1
82283.9506:1
83815.5523:1
82712.7198:1
82650.9609:1
82419.6208:1
87082.7526:1
90225.6318:1
82162.7286:1
82234.8345:1
84724.1525:1
82266.6118:1
82419.6208:1
83222.8928:1
83962.2087:1
I prim.
1051401.28%
1057382.57%
1079509.74%
1007272.59%
1049774.97%
1084890.97%
1086438.19%
1101912.81%
1115563.23%
1196913.78%
1259594.68%
1165328.77%
1185266.98%
1241279.52%
1225473.36%
1248682.13%
1282719.16%
1316954.25%
0.002665A
0.002657A
0.002673A
0.002634A
0.002631A
0.002637A
0.002651A
0.002648A
0.002632A
0.00267A
0.00267A
0.002629A
0.002629A
0.002663A
0.002641A
0.002625A
0.002654A
0.002636A
77.53°
77.67°
77.14°
77.17°
77.06°
77.55°
76.95°
76.92°
77.03°
77.19°
76.95°
77.23°
77.03°
77.14°
76.95°
77.3°
76.97°
76.95°
2kV on HV -> 23mV on LV on all taps !
Annual Convention 2012 – Eilat, Israel
PAGE 56
Ratio HV to LV Phase B=S
B:
Tap
B 001
B 002
B 003
B 004
B 005
B 006
B 007
B 008
B 009
B 010
B 011
B 012
B 013
B 014
B 015
B 016
B 018
V prim. Nom.
Vsec.Nom.
165750.0/√3V
163500.0/√3V
161250.0/√3V
159000.0/√3V
156750.0/√3V
154500.0/√3V
152250.0/√3V
150000.0/√3V
147750.0/√3V
145500.0/√3V
143250.0/√3V
141000.0/√3V
138750.0/√3V
136500.0/√3V
134250.0/√3V
132000.0/√3V
127500.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
Ratio nom. V prim.
8.2875:1
8.175:1
8.0625:1
7.95:1
7.8375:1
7.725:1
7.6125:1
7.5:1
7.3875:1
7.275:1
7.1625:1
7.05:1
6.9375:1
6.825:1
6.7125:1
6.6:1
6.375:1
999.76V
999.76V
999.81V
999.79V
999.71V
999.83V
999.88V
999.62V
999.78V
999.81V
999.72V
999.87V
999.82V
999.82V
999.84V
999.74V
999.74V
Vsec.
139.451279V
139.450928V
139.457031V
139.454666V
139.442612V
139.460587V
139.466415V
139.43132V
139.453995V
139.453735V
139.43515V
139.456238V
139.448944V
139.449051V
139.452438V
139.436752V
139.438568V
Ratio
-0.04°
-0.03°
-0.03°
-0.03°
-0.03°
-0.03°
-0.02°
-0.02°
-0.03°
-0.03°
-0.03°
-0.03°
-0.03°
-0.04°
-0.04°
-0.02°
-0.03°
7.1692:1
7.1693:1
7.1693:1
7.1693:1
7.1693:1
7.1693:1
7.1693:1
7.1693:1
7.1692:1
7.1695:1
7.1698:1
7.1698:1
7.1698:1
7.1698:1
7.1698:1
7.1698:1
7.1698:1
I prim.
-13.49%
-12.3%
-11.08%
-9.82%
-8.53%
-7.19%
-5.82%
-4.41%
-2.95%
-1.45%
0.1%
1.7%
3.35%
5.05%
6.81%
8.63%
12.47%
0.013008A
0.013062A
0.013101A
0.013075A
0.013093A
0.013151A
0.013023A
0.013017A
0.01313A
0.013136A
0.013087A
0.013013A
0.013118A
0.013131A
0.013061A
0.013088A
0.013088A
-54.74°
-54.89°
-54.94°
-54.92°
-54.7°
-54.94°
-54.64°
-54.79°
-54.97°
-54.96°
-54.67°
-54.65°
-54.87°
-54.94°
-54.9°
-54.71°
-54.73°
All taps have the same ratio 7.2:1 of position 11 !
Annual Convention 2012 – Eilat, Israel
PAGE 57
Ratio HV to LV Phase C=T
C:
Tap
C 001
C 002
C 003
C 004
C 005
C 006
C 007
C 008
C 009
C 010
C 011
C 012
C 013
C 014
C 015
C 016
C 017
V prim. Nom.
Vsec.Nom. Ratio nom. V prim.
165750.0/√3V
163500.0/√3V
161250.0/√3V
159000.0/√3V
156750.0/√3V
154500.0/√3V
152250.0/√3V
150000.0/√3V
147750.0/√3V
145500.0/√3V
143250.0/√3V
141000.0/√3V
138750.0/√3V
136500.0/√3V
134250.0/√3V
132000.0/√3V
129750.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
20000.0/√3V
8.2875:1
8.175:1
8.0625:1
7.95:1
7.8375:1
7.725:1
7.6125:1
7.5:1
7.3875:1
7.275:1
7.1625:1
7.05:1
6.9375:1
6.825:1
6.7125:1
6.6:1
6.4875:1
999.87V
999.78V
999.92V
999.93V
999.74V
999.95V
999.91V
999.68V
999.85V
999.73V
999.69V
999.79V
999.77V
999.67V
999.78V
999.65V
999.85V
Vsec.
139.558258V
139.544296V
139.565689V
139.567307V
139.539001V
139.569595V
139.553513V
139.52594V
139.555328V
139.538071V
139.533554V
139.544205V
139.530441V
139.531235V
139.54483V
139.529968V
139.555405V
Ratio
-0.04°
-0.02°
-0.03°
-0.03°
-0.01°
-0.04°
-0.04°
-0.01°
-0.01°
-0.01°
-0.01°
-0.01°
-0.03°
-0.02°
-0.01°
-0.03°
-0.02°
7.1645:1
7.1646:1
7.1645:1
7.1645:1
7.1646:1
7.1645:1
7.1651:1
7.1648:1
7.1645:1
7.1646:1
7.1645:1
7.1647:1
7.1652:1
7.1645:1
7.1646:1
7.1644:1
7.1645:1
I prim.
-13.55%
-12.36%
-11.14%
-9.88%
-8.59%
-7.26%
-5.88%
-4.47%
-3.02%
-1.52%
0.03%
1.63%
3.28%
4.97%
6.73%
8.55%
10.44%
0.010944A
0.011008A
0.010951A
0.010956A
0.010937A
0.010964A
0.01097A
0.011007A
0.010945A
0.010946A
0.010938A
0.010944A
0.010938A
0.011001A
0.010996A
0.010932A
0.010954A
-47.77°
-47.85°
-47.68°
-47.71°
-47.67°
-47.73°
-47.83°
-47.82°
-47.65°
-47.7°
-47.66°
-47.7°
-47.58°
-47.81°
-47.79°
-47.55°
-47.68°
All taps have the same ratio 7.2:1 of position 11 !
Annual Convention 2012 – Eilat, Israel
PAGE 58
FRA HV
Interruption in phase R, HV side
Annual Convention 2012 – Eilat, Israel
PAGE 59
FRA LV with HV open
Short circuit in phase R, but on LV or HV side ???
Annual Convention 2012 – Eilat, Israel
PAGE 60
FRA LV with HV Open and Shorted
A LV with open loop HV (red line)
B LV with open loop HV (blue solid line)
B LV with shorted
HV (blue dashed line)
Annual Convention 2012 – Eilat, Israel
PAGE 61
Winding Resistance of LV
Phase R LV doesn’t look damaged
Annual Convention 2012 – Eilat, Israel
PAGE 62
Conclusions
• Phase R=A is interrupted on HV side
• The tap changer is broken – in position 11
• The limb R has a shorted winding
• The short circuit in limb R is not on the LV side but on the HV side
Annual Convention 2012 – Eilat, Israel
PAGE 63
Opening of the OLTC Compartment
Annual Convention 2012 – Eilat, Israel
PAGE 64
Opened OLTC Compartment
Interruption in phase R, HV side
Annual Convention 2012 – Eilat, Israel
PAGE 65
Interruption due to Open OLTC Contacts
Annual Convention 2012 – Eilat, Israel
PAGE 66
Removed OLTC – Cables to the Tap Winding
Annual Convention 2012 – Eilat, Israel
PAGE 67
FRA on the Single Tap Winding Segments
Annual Convention 2012 – Eilat, Israel
PAGE 68
FRA on the Single Tap Winding Segments
Segments
11 - 13
9 - 11
8- 9
7- 8
6- 7
5- 6
4- 5
3- 4
2- 3
14 - 2
Annual Convention 2012 – Eilat, Israel
PAGE 69
FRA on the Single Tap Winding Segments
Annual Convention 2012 – Eilat, Israel
PAGE 70
Winding Resistance of the Tap Winding
Segments
4
14mΩ
25mΩ
5
14mΩ
6mΩ
7mΩ
25mΩ
6
The fault was between
tap conductor 4 and 6 !
Annual Convention 2012 – Eilat, Israel
PAGE 71
michael.krueger@omicron.at
Questions and Remarks?