New Experience in the Transformer Diagnosis Michael Krüger, OMICRON Austria
Annual Convention 2012 – Eilat, Israel PAGE 2
Measurement Method Application Indicated by Kind of Test*
on-/off-line
Winding resistance (static)
Contact problems,broken or loose connections,broken conductors
High internal temperatures, e.g. indicated by DGA results or Buchholz Relay
FRT off
Winding resistance (dynamic)Contact problems at the diverter switch, broken transition resistors
DGA, Buchholz Relay FRT off
Leakage reactance (stray reactance) Winding deformation 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
Electrical Measurement Methods I
Annual Convention 2012 – Eilat, Israel
Measurement Method Application Indicated by Kind of Test*
on-/off-line
Turns ratio After Buchholz Relay tripping Buchholz Relay has tripped T off
Frequency Response Analysis (FRA)
Winding deformation, winding displacement, core faults, faulty screen or core connections
High through-fault currents, transportation F(R)T off
Insulation resistance Insulation problems Breakdowns, Buchholz Relay tripping FRT off
Capacitance and Dielectric Dissipation Factor
Main insulation: ageing, moisture - Bushings: ageing, partial breakdowns
DGA FRT on/off
Dielectric Response Measurement (FDS and PDC)
Main insulation: ageing, moisture - Bushings: ageing, partial breakdowns
high water content in oil / high dielectric losses FRT off
Partial Discharge Insulation problems DGA T on/off *F=Fingerprint, R=Routine, T=Troubleshooting, S=Special
Electrical Measurement Methods II
PAGE 3
Annual Convention 2012 – Eilat, Israel
• Winding Resistance Measurement
• Fault Finding on Transformer Windings with FRA
• Moisture Measurement on Transformers
• Partial Discharge Measurement on Transformers
Content
PAGE 4
Annual Convention 2012 – Eilat, Israel
Winding Resistance Measurement
PAGE 5
Annual Convention 2012 – Eilat, Israel
Diverter Switch Contact of Phase V
PAGE 6
Annual Convention 2012 – Eilat, Israel
Winding Resistance after Repair
PAGE 7
Annual Convention 2012 – Eilat, Israel
• Winding Resistance Measurement
• Fault Finding on Transformer Windings with FRA
• Moisture Measurement on Transformers
• Partial Discharge Measurement on Transformers
Content
PAGE 8
Annual Convention 2012 – Eilat, Israel
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
PAGE 9
Annual Convention 2012 – Eilat, Israel
DGA
Phase 1: Trip out of Service, Differential
Phase 2: DGA
second DGA showed 19ppm C2H2
PAGE 10
Annual Convention 2012 – Eilat, Israel PAGE 11
Transformer Model for FRA
Annual Convention 2012 – Eilat, Israel PAGE 12
Swept Frequency Response Analysis (SFRA)
-5.0
-3.0
-1.0
1.0
3.0
5.0
0 0.2 0.4 0.6 0.8 1 1.2
Transformer
1N
1U
1V
1W
complex RLCM-Network -5.0
-3.0
-1.0
1.0
3.0
5.0
0 0.2 0.4 0.6 0.8 1 1.2
(f1)
U0*(1-K(f1))
1/f1
0.0
0.5
1.0
1.5
2.0
2.5
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4Frequenz f
K(f)
MHz
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4Frequenz f
(f)
MHz
sine generator (variable frequency)
transfer function (magnitude) transfer function (phase)
K(f1) (f1)
frequency f frequency f
H1 H2 H2 H3 H3 H1 f/Hz1.000e+002 1.000e+003 1.000e+004 1.000e+005 1.000e+006dB-120-110-100-90-80-70-60-50-40-30-20-10010 H1 H2 H2 H3 H3 H1 f/Hz1.000e+002 1.000e+003 1.000e+004 1.000e+005 1.000e+006°-200-150-100-50050100150Magnitude Phase
Annual Convention 2012 – Eilat, Israel
FRA LV Winding – Comparison of the 3 Phases
B Phase
PAGE 13
Annual Convention 2012 – Eilat, Israel PAGE 14
Buckling without innersupports
Buckling with inner supports
Higher order or forced Buckling
The conductors can bend between the supports all along the circumference
Free modeor free Buckling
Source: Brochure CIGRE WG 12.19 : The Short Circuit Performance of Power Transformers
Radial Forces
Annual Convention 2012 – Eilat, Israel PAGE 15
Radial Failure (Buckling)
Annual Convention 2012 – Eilat, Israel
Failure Modes due to Radial Forces
Source: Cigre Brochure 342 “ MECHANICAL-CONDITION ASSESSMENT OF TRANSFORMER WINDINGS USING FREQUENCY RESPONSE ANALYSIS (FRA)”
B phase with buckling C phase without buckling
PAGE 16
Annual Convention 2012 – Eilat, Israel
Comparison FRA LV Winding with Cigre Case Study of Buckling
B Phase
PAGE 17
www.e-cigre.org
Systematic shift of several resonances
Annual Convention 2012 – Eilat, Israel
B Phase
Take a closer look
PAGE 18
Annual Convention 2012 – Eilat, Israel
B Phase
PAGE 19
Annual Convention 2012 – Eilat, Israel
• Winding Resistance Measurement
• Fault Finding on Transformer Windings with FRA
• Moisture Measurement on Transformers
• Partial Discharge Measurement on Transformers
Content
PAGE 20
Annual Convention 2012 – Eilat, Israel
Water in the Transformer
Most of the water is contained in the paper!
Mass of the oil:100,000 kg = 220,000 Lbs
Water content at 60 °C:40 ppm
Mass of the water, dissolved in the oil:
4 kg = 8.8 Lbs
Mass of the solid insulation:13,000 kg = 20,000 Lbs
Water content at 60 °C:4 %
Mass of the water contained in the paper:
520 kg = 1200 Lbs
PAGE 21
Annual Convention 2012 – Eilat, Israel
Determination of the Water Content in Paper [Karl Fischer Titration and Equilibrium Curves]
0
1
2
3
4
5
6
7
8
9
[%]
11
0 10 20 30 40 50 60 70 [ppm] 90
Wat
er C
onte
nt in
the
Pape
r
Water Content in the Oil
20 °C 30 °C 40 °C
50 °C
60 °C
80 °C
100°C
Temperature
low
high
• Curves are only valid for new oil and new paper, for aged oil/paper different curves are necessary
• 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
PAGE 22
Annual Convention 2012 – Eilat, Israel
History of Dielectric Diagnostic Methods• 1960+• Dissipation factor at power
frequency• Polarization index• At that time: No reliable method for onsite moisture
diagnostics
• 2007 Combination of PDC and FDS
• 1991 RVM for water determination• Soon questioned by users (Kachler 1996)
U(t)
t c
t
U
t peakt d
Ur,max
• 1999+ Polarization Depolarization Currents• Technical University Zurich Switzerland
Uc (t)ipol (t)
idep (t)TC
t
U, I
• 1999+ Frequency Domain Spectroscopy• KTH Stockholm with ABB
Frequency
Dis
sipa
tion
fact
or
PAGE 23
Annual Convention 2012 – Eilat, Israel
Dielektric Response in the Time DomainPolarisation Depolarisation Current (PDC)
Current = f(t)
PAGE 24
Annual Convention 2012 – Eilat, Israel
Dielektric Response in the Frequency DomainFrequency Domain Spectroscopy (FDS) or Dielectric Frequency Response (DFR)
PAGE 25
Annual Convention 2012 – Eilat, Israel
Dielectric Response Measurement with Frequency Domain Spectroscopy (FDS) and Polarisation & Depolarisation Current (PDC)
PDC FDS
Combination of PDC und FDS reduces measurement time
Cur
rent
[nA
]
Time [s]
Trans-formation
Frequency [Hz]
Pow
er fa
ctor
0.0010.001
1
1000
10001
100
1Frequency [Hz]
Pow
er fa
ctor
1000
1
0.001 0.1
024
6
81012
14
PDCFDS DIRANAD
urat
ion
/ h
0,00010,0010,010,1
1101001000
Freq
uenc
y ra
nge
/ Hz
PAGE 26
Annual Convention 2012 – Eilat, Israel
Interpretation and Analysis
f/Hz0.001 0.01 0.1 1.0 10 100
Dis
sipa
tion
fact
or
0.0001
0.001
0.01
0.1
1
10
0.0001
Pressboard
0,51,0 2,0
Öl 1pS/m
Overall Response1%, 1pS/m, X30, Y15
1000
Oil: Carbon, Sludge, hmw Acids
Pressboard: Water, lmw
Acids
Transition from Capacitive to Resistive Voltage Distribution
Pressboard
PAGE 27
Annual Convention 2012 – Eilat, Israel
Analysis of the Water Content by Comparison to Model Results
Measurement Laboratory Results
Temperature
0,0001 0,01 1000,01
0,1
10
Frequency [Hz]
Tang
ent D
elta
Water Content Oil Conductivity
Comparison Fitting
X
Oil XY-ModelOil
Barriers
Spacers
Y
Source: Weidmann
PAGE 28
Annual Convention 2012 – Eilat, Israel
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
PAGE 29
Annual Convention 2012 – Eilat, Israel
FDS / PDC Measurement on a 130 MVA Transformer – Water Content Distribution
0
1
2
3
4
5M
oist
ure
in p
aper
[%]
FDS HV-LV OilsampleKarl Fischermg/kg(Oommenequilibrium)
FDS LV- Tertiary
FDSTertiary-Tank
Tertiary not in use
OilsampleRH %
Average
FDS/PDC1mHz-1kHz
PAGE 30
Annual Convention 2012 – Eilat, Israel
130 MVA Transformer On-Line Drying
PAGE 31
Annual Convention 2012 – Eilat, Israel
History 2006 – 2008 - 2010
PAGE 32
Annual Convention 2012 – Eilat, Israel
• Winding Resistance Measurement
• Fault Finding on Transformer Windings with FRA
• Moisture Measurement on Transformers
• Partial Discharge Measurement on Transformers
Content
PAGE 33
Annual Convention 2012 – Eilat, Israel
Diagnostic Measurement on a Cast Resin Type Transformer
PAGE 34
Annual Convention 2012 – Eilat, Israel
Cracks in the Epoxy
PAGE 35
Annual Convention 2012 – Eilat, Israel
PD Measurement Circuit
PAGE 36
Annual Convention 2012 – Eilat, Israel
Test Arangement
CPC100
CP CU1
Compensating Capacitors
PAGE 37
Annual Convention 2012 – Eilat, Israel
Test Arangement Coupling Capacitor and MPD600
PAGE 38
Annual Convention 2012 – Eilat, Israel
Separation of PD Sources in 3CFRD
2MHz
500kHz
8MHz
500kHz
2 MHz
8 MHz
3CFRD
timeframe 1 µs
500
kHz
2 M
Hz
8 M
Hz
3CFRD = 3 Center Frequency Relation DiagramPAGE 39
Annual Convention 2012 – Eilat, Israel
PD Measurement without 3CFRD Filtering
PAGE 40
Annual Convention 2012 – Eilat, Israel
3CFRD Filtering
PAGE 41
Annual Convention 2012 – Eilat, Israel
PD Measurement with 3CFRD Filtering
PAGE 42
Annual Convention 2012 – Eilat, Israel
PD Measurement without 3CFRD Filtering
PAGE 43
Annual Convention 2012 – Eilat, Israel
On-Line PD Measurement on a Transformer
PAGE 44
Annual Convention 2012 – Eilat, Israel
On-Line PD Measurement on a Transformer GIS - Cable Connection (GIS Side)
21
3
PAGE 45
Annual Convention 2012 – Eilat, Israel
Online PD Measurement at the GIS Side
yellow phase GIS
red phase GIS
blue phase GIS
PAGE 46
Annual Convention 2012 – Eilat, Israel
Sensors 1, 2 and 3 at the GIS Side and Sensor 4 at the Transformer Side
4
100m
PAGE 47
Annual Convention 2012 – Eilat, Israel
PD Measurement at the GIS and the Transformer Side
blue phase GIS
blue phase Tr
PAGE 48
Annual Convention 2012 – Eilat, Israel
PD Measurement at GIS and TR Side Trigger = TR Side - Delay on GIS Side
delayed signal blue phase GIS
trigger = blue phase Tr
PAGE 49
Annual Convention 2012 – Eilat, Israel
Jumper between Oil/Oil Bushing and Cable Termination
PAGE 50
Annual Convention 2012 – Eilat, Israel
Jumper between Oil/Oil Bushing and Cable Termination
PAGE 51
Annual Convention 2012 – Eilat, Israel PAGE 53
A last Example:Fault Investigation on a 220kV Transformer
Annual Convention 2012 – Eilat, Israel PAGE 54
DGA
Main Tank OLTCH2 1008.8 1183 ≤ 100 101 - 700 701 - 1800 > 1800CH4 67 65 ≤ 120 121 - 400 401 - 1000 > 1000C2H6 54.8 55 ≤ 65 66 - 100 101 - 150 > 150C2H4 668 710 ≤ 50 51 - 100 101 - 200 > 200C2H2 1130 1214 ≤ 1 2 - 9 10 - 35 > 35CO 95 107 ≤ 350 351 - 570 571 - 1400 > 1400CO2 720 740 ≤ 2500 2501 - 4000 4001 - 10000 > 10000TDCG 3024 3337 ≤ 720 721 - 1920 1921 - 4630 > 4630
Condition 3 Condition 4IEEE C57.104-2008Parameter DGA 7 Nov 2011
Condition 1 Condition 2
Annual Convention 2012 – Eilat, Israel PAGE 55
Ratio Measurement HV to LV
Annual Convention 2012 – Eilat, Israel
A:Tap V prim. Nom. Vsec.Nom. Ratio nom. V prim. Vsec. Ratio I prim.
A 001 165750.0/√3V 20000.0/√3V 8.2875:1 1999.5V 0.022947V 164.81° 87143.1684:1 1051401.28% 0.002665A 77.53°A 002 163500.0/√3V 20000.0/√3V 8.175:1 1999.57V 0.023128V 163.61° 86449.2002:1 1057382.57% 0.002657A 77.67°A 003 161250.0/√3V 20000.0/√3V 8.0625:1 1999.39V 0.022972V 164.95° 87043.535:1 1079509.74% 0.002673A 77.14°A 004 159000.0/√3V 20000.0/√3V 7.95:1 1999.35V 0.024964V 166.1° 80086.1206:1 1007272.59% 0.002634A 77.17°A 005 156750.0/√3V 20000.0/√3V 7.8375:1 1999.5V 0.024298V 163.59° 82283.9506:1 1049774.97% 0.002631A 77.06°A 006 154500.0/√3V 20000.0/√3V 7.725:1 1999.42V 0.023854V 162.68° 83815.5523:1 1084890.97% 0.002637A 77.55°A 007 152250.0/√3V 20000.0/√3V 7.6125:1 1999.58V 0.024173V 165.95° 82712.7198:1 1086438.19% 0.002651A 76.95°A 008 150000.0/√3V 20000.0/√3V 7.5:1 1999.74V 0.024195V 166.09° 82650.9609:1 1101912.81% 0.002648A 76.92°A 009 147750.0/√3V 20000.0/√3V 7.3875:1 1999.5V 0.02426V 163.8° 82419.6208:1 1115563.23% 0.002632A 77.03°A 010 145500.0/√3V 20000.0/√3V 7.275:1 1999.42V 0.022962V 164.95° 87082.7526:1 1196913.78% 0.00267A 77.19°A 011 143250.0/√3V 20000.0/√3V 7.1625:1 1999.4V 0.022158V 163.12° 90225.6318:1 1259594.68% 0.00267A 76.95°A 012 141000.0/√3V 20000.0/√3V 7.05:1 1999.43V 0.024335V 164.51° 82162.7286:1 1165328.77% 0.002629A 77.23°A 013 138750.0/√3V 20000.0/√3V 6.9375:1 1999.54V 0.024313V 163.74° 82234.8345:1 1185266.98% 0.002629A 77.03°A 014 136500.0/√3V 20000.0/√3V 6.825:1 1999.49V 0.023602V 165.97° 84724.1525:1 1241279.52% 0.002663A 77.14°A 015 134250.0/√3V 20000.0/√3V 6.7125:1 1999.49V 0.024304V 165.52° 82266.6118:1 1225473.36% 0.002641A 76.95°A 016 132000.0/√3V 20000.0/√3V 6.6:1 1999.5V 0.02426V 164.07° 82419.6208:1 1248682.13% 0.002625A 77.3°A 017 129750.0/√3V 20000.0/√3V 6.4875:1 1999.43V 0.024024V 166.21° 83222.8928:1 1282719.16% 0.002654A 76.97°A 018 127500.0/√3V 20000.0/√3V 6.375:1 1999.56V 0.023816V 166.46° 83962.2087:1 1316954.25% 0.002636A 76.95°
PAGE 56
Ratio HV to LV Phase A=R
2kV on HV -> 23mV on LV on all taps !
Annual Convention 2012 – Eilat, Israel PAGE 57
Ratio HV to LV Phase B=S
All taps have the same ratio 7.2:1 of position 11 !
B:Tap V prim. Nom. Vsec.Nom. Ratio nom. V prim. Vsec. Ratio I prim.
B 001 165750.0/√3V 20000.0/√3V 8.2875:1 999.76V 139.451279V -0.04° 7.1692:1 -13.49% 0.013008A -54.74°B 002 163500.0/√3V 20000.0/√3V 8.175:1 999.76V 139.450928V -0.03° 7.1693:1 -12.3% 0.013062A -54.89°B 003 161250.0/√3V 20000.0/√3V 8.0625:1 999.81V 139.457031V -0.03° 7.1693:1 -11.08% 0.013101A -54.94°B 004 159000.0/√3V 20000.0/√3V 7.95:1 999.79V 139.454666V -0.03° 7.1693:1 -9.82% 0.013075A -54.92°B 005 156750.0/√3V 20000.0/√3V 7.8375:1 999.71V 139.442612V -0.03° 7.1693:1 -8.53% 0.013093A -54.7°B 006 154500.0/√3V 20000.0/√3V 7.725:1 999.83V 139.460587V -0.03° 7.1693:1 -7.19% 0.013151A -54.94°B 007 152250.0/√3V 20000.0/√3V 7.6125:1 999.88V 139.466415V -0.02° 7.1693:1 -5.82% 0.013023A -54.64°B 008 150000.0/√3V 20000.0/√3V 7.5:1 999.62V 139.43132V -0.02° 7.1693:1 -4.41% 0.013017A -54.79°B 009 147750.0/√3V 20000.0/√3V 7.3875:1 999.78V 139.453995V -0.03° 7.1692:1 -2.95% 0.01313A -54.97°B 010 145500.0/√3V 20000.0/√3V 7.275:1 999.81V 139.453735V -0.03° 7.1695:1 -1.45% 0.013136A -54.96°B 011 143250.0/√3V 20000.0/√3V 7.1625:1 999.72V 139.43515V -0.03° 7.1698:1 0.1% 0.013087A -54.67°B 012 141000.0/√3V 20000.0/√3V 7.05:1 999.87V 139.456238V -0.03° 7.1698:1 1.7% 0.013013A -54.65°B 013 138750.0/√3V 20000.0/√3V 6.9375:1 999.82V 139.448944V -0.03° 7.1698:1 3.35% 0.013118A -54.87°B 014 136500.0/√3V 20000.0/√3V 6.825:1 999.82V 139.449051V -0.04° 7.1698:1 5.05% 0.013131A -54.94°B 015 134250.0/√3V 20000.0/√3V 6.7125:1 999.84V 139.452438V -0.04° 7.1698:1 6.81% 0.013061A -54.9°B 016 132000.0/√3V 20000.0/√3V 6.6:1 999.74V 139.436752V -0.02° 7.1698:1 8.63% 0.013088A -54.71°B 018 127500.0/√3V 20000.0/√3V 6.375:1 999.74V 139.438568V -0.03° 7.1698:1 12.47% 0.013088A -54.73°
Annual Convention 2012 – Eilat, Israel
C:Tap V prim. Nom. Vsec.Nom. Ratio nom. V prim. Vsec. Ratio I prim.
C 001 165750.0/√3V 20000.0/√3V 8.2875:1 999.87V 139.558258V -0.04° 7.1645:1 -13.55% 0.010944A -47.77°C 002 163500.0/√3V 20000.0/√3V 8.175:1 999.78V 139.544296V -0.02° 7.1646:1 -12.36% 0.011008A -47.85°C 003 161250.0/√3V 20000.0/√3V 8.0625:1 999.92V 139.565689V -0.03° 7.1645:1 -11.14% 0.010951A -47.68°C 004 159000.0/√3V 20000.0/√3V 7.95:1 999.93V 139.567307V -0.03° 7.1645:1 -9.88% 0.010956A -47.71°C 005 156750.0/√3V 20000.0/√3V 7.8375:1 999.74V 139.539001V -0.01° 7.1646:1 -8.59% 0.010937A -47.67°C 006 154500.0/√3V 20000.0/√3V 7.725:1 999.95V 139.569595V -0.04° 7.1645:1 -7.26% 0.010964A -47.73°C 007 152250.0/√3V 20000.0/√3V 7.6125:1 999.91V 139.553513V -0.04° 7.1651:1 -5.88% 0.01097A -47.83°C 008 150000.0/√3V 20000.0/√3V 7.5:1 999.68V 139.52594V -0.01° 7.1648:1 -4.47% 0.011007A -47.82°C 009 147750.0/√3V 20000.0/√3V 7.3875:1 999.85V 139.555328V -0.01° 7.1645:1 -3.02% 0.010945A -47.65°C 010 145500.0/√3V 20000.0/√3V 7.275:1 999.73V 139.538071V -0.01° 7.1646:1 -1.52% 0.010946A -47.7°C 011 143250.0/√3V 20000.0/√3V 7.1625:1 999.69V 139.533554V -0.01° 7.1645:1 0.03% 0.010938A -47.66°C 012 141000.0/√3V 20000.0/√3V 7.05:1 999.79V 139.544205V -0.01° 7.1647:1 1.63% 0.010944A -47.7°C 013 138750.0/√3V 20000.0/√3V 6.9375:1 999.77V 139.530441V -0.03° 7.1652:1 3.28% 0.010938A -47.58°C 014 136500.0/√3V 20000.0/√3V 6.825:1 999.67V 139.531235V -0.02° 7.1645:1 4.97% 0.011001A -47.81°C 015 134250.0/√3V 20000.0/√3V 6.7125:1 999.78V 139.54483V -0.01° 7.1646:1 6.73% 0.010996A -47.79°C 016 132000.0/√3V 20000.0/√3V 6.6:1 999.65V 139.529968V -0.03° 7.1644:1 8.55% 0.010932A -47.55°C 017 129750.0/√3V 20000.0/√3V 6.4875:1 999.85V 139.555405V -0.02° 7.1645:1 10.44% 0.010954A -47.68°
PAGE 58
Ratio HV to LV Phase C=T
All taps have the same ratio 7.2:1 of position 11 !
Annual Convention 2012 – Eilat, Israel PAGE 59
FRA HV
Interruption in phase R, HV side
Annual Convention 2012 – Eilat, Israel PAGE 60
FRA LV with HV open Short circuit in phase R, but on LV or HV side ???
Annual Convention 2012 – Eilat, Israel PAGE 61
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 62
Winding Resistance of LV
Phase R LV doesn’t look damaged
Annual Convention 2012 – Eilat, Israel PAGE 63
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 64
Opening of the OLTC Compartment
Annual Convention 2012 – Eilat, Israel PAGE 65
Opened OLTC Compartment
Interruption in phase R, HV side
Annual Convention 2012 – Eilat, Israel PAGE 66
Interruption due to Open OLTC Contacts
Annual Convention 2012 – Eilat, Israel PAGE 67
Removed OLTC – Cables to the Tap Winding
Annual Convention 2012 – Eilat, Israel PAGE 68
FRA on the Single Tap Winding Segments
Annual Convention 2012 – Eilat, Israel PAGE 69
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 - 314 - 2
Annual Convention 2012 – Eilat, Israel PAGE 70
FRA on the Single Tap Winding Segments
Annual Convention 2012 – Eilat, Israel PAGE 71
Winding Resistance of the Tap Winding Segments
25mΩ
25mΩ
7mΩ
14mΩ
14mΩ
6mΩ
4
6
5
The fault was between tap conductor 4 and 6 !