20200901Avista to Staff PR5 Attach A.pdf

Power Grids Canada Inc.
"© Copyright 2020 ABB Inc.ABB CUSTOMER CONFIDENTIAL.The data and information discussed and identified in this document are
considered ABB Customer Confidential and are not to be reproduced, used or disclosed to third parties without written permission."
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As-Found Condition Report for
CUSTOMER: AVISTA
Siemens Transformer S/N: 4008495
ABB Inc.
Stoney Creek
Transformer
Repair & Testing facility
Stoney Creek, Ontario, Canada
Prepared by:
William Himmen
Senior Transformer Specialist
Mustafa Lahloub
Engineering Manager
Approved by:
Ed teNyenhuis
Technical / Operations Manager
Revision 2
March 10, 2020
Rev 0 November 26, 2019: Initial release.
Rev 1 February 26, 2020: Un-tanking inspection section added.
Rev 2 March 10, 2020: “Phases 2 & 3 HV windings rings…” in page 25 corrected to “Phases 1 & 3 HV windings rings…”.
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TABLE OF CONTENTS
1.0 TRANSFORMER DETAILS .................................................................. 3
2.0 TRANSFORMER RECEPTION ............................................................ 3
3.0 ANALYSIS - RECEIVING INSPECTION ELECTRICAL TESTING ..... 5
3.1 Standard Initial Incoming Electrical Tests Performed by ABB
Stoney Creek .............................................................................. 5
3.2 Conclusions from Initial Incoming Electrical Testing ........... 5
3.3 Additional Incoming Electrical Tests Performed ................... 5
3.4 Conclusions from Additional Initial Incoming Electrical Testing
..................................................................................................... 5
3.5 Incoming High Voltage Electrical Testing ............................... 6
3.6 Triangulation................................................................................ 15
3.7 Gas Sample Results—Before and After Induce/Core
Loss/Triangulation ................................................................... 15
3.8 Conclusions from the High Voltage Electrical Testing and
Triangulation and Gas Results. .............................................. 15
4.0 TRANSFORMER UN-TANKING ......................................................... 25
4.1 Inspection Findings ................................................................. 25
4.2 Conclusion from un-Tanking Inspection ............................... 25
3
1.0 Transformer Details
Manufacturer: Siemens
Manufacture Date: 2004
Type:Power Transformer
Serial Number: 4008495
Construction Type:Core Form
Number of Phases: 3
Frequency:60 Hertz
H-Nominal Rating:213/284/355 MVA
HV Rating:532 kV, Wye
HV BIL:1425 kV
HO BIL:200 kv
DeTC:Plus two and minus two, 2.5% full capacity taps
LV-X Rating: 13.8kV, Delta
LV-Y BIL:110 kV
LV-Y Rating:18 kV, Delta
LV-Y BIL:150 kV
Oil Preservation: Cops tank
Cooling System: ONAN / ONAF / ONAF
Winding Rise: 65°C Average Winding Rise
2.0 Transformer Reception
The transformer was received to the ABB Stoney Creek facility in Sept 2019 for Inspection,
testing, un-tanking and disassembly to determine the source of fault and extent of the fault
damage. The transformer was shipped without oil and there was 1 psi pressure in the
transformer tank at time of receiving. A dew point was taken on the main tank while still under
pressure from the barge/shipment. The dew point indicated the unit was wet however not as
severe as expected from earlier site measurements (over 1% moisture). The transformer was
offloaded and moved as close to the test area as possible so that the unit could be tested and
un-tanked for inspection and disassembly.
A visual external inspection was performed. In general, the transformer was found to be in fair
condition. There was no evidence of deformation on the tank walls or cover. The valves were
found to be in fair condition. Surface oil residue was found on the tank wall as a result of a
leaking rad valve.
There was an oil leak in the core ground box (filled with oil during the vacuum filling process
when preparing for HV testing).
The cover of this unit is welded.
The TV2 CT wires in the turret junction box were found to be burnt and had signs of overheating.
The HV2 CT found to have loosened and moved during shipment. There were no signs of
damage.
4
The initial low voltage tests performed upon receipt of the transformer were all satisfactory
(preformed with no oil).
The unit was placed under vacuum for 11 days and the Dew point was found to be acceptable
and indicated the unit was dry (<0.5% moisture).
After assembly of the unit (installation of bushings, piping, conservator tank) and after vacuum
/ vacuum filling, a repeat of the initial low voltage tests was performed and again were
satisfactory.
The transformer was setup for high voltage testing (Induce/Core loss — 60 cycle):
· Performed induce / core loss to 105%.
· Core loss readings taken to compare to original core loss from OEM.
· Setup for PD measurements during induce/core loss with 60 cycle.
· Triangulation performed for determining source/location of partial discharge.
· Gas samples taken before and after high voltage testing.
A comprehensive list of the observations and tests for this transformer is provided in Section
3.0 below. A scope of work will be completed based on all the recommendations provided and
upon agreement with Avista.
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Transformer as Received
3.0 Analysis - Receiving Inspection Electrical Testing
3.1 Standard Initial Incoming Electrical Tests Performed by ABB Stoney Creek
· Marked tests are applicable to this specific transformer
Ratio Test
Single Phase Excitation Test
Winding Resistance Measurements
Winding Insulation Tests
Core Megger Test
CT Ratio and saturation Test
3.2 Conclusions from Initial Incoming Electrical Testing
· No indications of any internal failures from the low voltage tests performed.
· Proceed with next steps which was to assemble, vacuum/vacuum fill and then repeat
above tests prior to any High voltage testing.
Note: Prior to next steps, vacuum was pulled on the transformer for 11 days to attempt to
improve incoming dew point. The Dew point upon completion of vacuum showed great
improvement which was enough to avoid having to dry the transformer out by other means
prior to next steps.
3.3 Additional Incoming Electrical Tests Performed
Ratio Test
Single Phase Excitation Test
Winding Resistance Measurements
Winding Insulation Tests
Core Megger Test
3.4 Conclusions from Additional Initial Incoming Electrical Testing
· Still No indications of any internal failures from the low voltage tests performed.
· Test results indicate unit is dry.
· Proceed with High Voltage Testing
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3.5 Incoming High Voltage Electrical Testing
Induce/Core loss-No Load Excitation Test---60 cycle
· Performed induce-core loss-no load excitation curve (60 cycle) up to 105% while
monitoring partial discharge.
· Measured core loss and excitation at 50%, 80%, 90%, 95%, 100%, 105%.
· All clean up to/until we hit 105% then partial discharge came in. (7000+) pc.
· Held for approx. 5 minutes and it did not drop out.
· Reduced voltage to 100% and pd dropped out.
· Held at 100% for a few minutes then partial discharge back in. (7000+) pc.
· Reduced voltage to 95% of rated voltage. Partial discharge again dropped out.
· Held for a few more minutes at 95% and again partial discharge came back in.
· Repeated at 90% and 87.5% which is where it seemed to settle with no partial discharge.
· Did not proceed any further.
· Did not want to fail transformer and lose important/beneficial triangulation data.
· All parties agreed to leave until Friday when triangulation engineer would be here to
triangulate.
Note: gas samples taken before and after induce/core loss and triangulation.
7
Title:CORE LOSS & EXCITING CURRENT
CUSTOMER:AVISTA JOB:512-72274
MANUFACTURER:SIEMENS SERIAL:4008495
RATING kVA:213/284/355 VOLTAGE:HV kV:532 LV kV:13.8,TV kV:18
INSTRUMENT:#70036 CALIBRATION DUE:2019 12 19
STATUS:INCOMING - BUSHINGS IN TESTED BY: AW JQ FN DATE:2019 11 21
TEMP.:
30.0
°C
SET UP NOTES:SUPPLY X1, X2, X3 GROUND HO
BASE kVA 213,000
HV TAP
#2 RATED (Volts)13,800
LV TAP
#N/A
RATED
(Amps)8911.3
Supply LV WDGs:13,800 L-L Volts
SUPPLY (Volts)6,900 11,040 12,420 13,110 13,800 14,490 15,180
% Level (Volts)50% 80% 90% 95%100% 105% 110%
PHASE A (Volts)6,898 10,960 12,350 13,040 13,740 14,450
PHASE B (Volts)7,013 11,260 12,640 13,290 14,030 14,680
PHASE C (Volts)6,925 11,020 12,350 13,020 13,740 14,380
FLUX (Volts)6,945 11,080 12,447 13,117 13,837 14,503
PHASE A (Volts)6,880 11,020 12,380 13,030 13,830 14,630
PHASE B (Volts)6,968 11,160 12,530 13,190 13,970 14,740
PHASE C (Volts)6,905 11,040 12,400 13,110 13,890 14,690
RMS (Volts)6,918 11,073 12,437 13,110 13,897 14,687
PHASE A (Amps)5.920 A 9.72 A 11.17 A 12.00 A 13.15 A 15.24 A
PHASE B (Amps)5.463 A 9.28 A 10.30 A 10.74 A 11.33 A 12.97 A
PHASE C (Amps)6.948 A 11.12 A 12.48 A 13.20 A 14.11 A 16.20 A
AVG. MEAS. (Amps)6.110 A 10.04 A 11.32 A 11.98 A 12.86 A 14.80 A
PHASE A (kW)17.46
kW 40.6 kW 51.7 kW 58.8 kW 67.9 kW 80.2 kW
PHASE B (kW)12.21
kW 30.9 kW 40.3 kW 46.0 kW 54.1 kW 63.3 kW
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PHASEB (kW)17.04
kW 40.3 kW 50.3 kW 56.3 kW 62.8 kW 70.3 kW
AVG. MEAS. (kW)46.71 111.8 142.3 161.1 184.8 213.8 kW
% EXCITING AMPS 0.069% 0.113% 0.127% 0.134% 0.144% 0.166%
Triangulation Log
Acoustics Setup #1
Acoustic # Side of Tank
HV / LV
Vertical
Distance From Base of
Tank
Horizontal
Distance From Centre of
“B” Phase
Acoustics /
No Acoustics
1 HV 33” from Bottom Of Tank Centre No Acoustics
2 HV 94” from bottom of tank Centre No Acoustics
3 HV 124” from bottom of tank Centre No Acoustics
4 LV 94” from bottom of tank Centre Acoustics
Acoustics Setup #2
1 HV 94” from bottom of tank Centre No Acoustics
2 LV 124” from bottom of tank Centre Acoustics
3 LV 94” from bottom of tank Centre Acoustics
4 LV 33” from Bottom Of Tank Centre Acoustics
Acoustics Setup #3
1 HV 94” from bottom of tank Centre No Acoustics
2 LV 94” from bottom of tank 3’ to left of centre of “B”
phase when facing LV
side. (towards “A”
phase)
Acoustics-Very
little as you
move away
from the centre
of “B” phase.
3 LV 94” from bottom of tank Centre Acoustics
4 LV 94” from bottom of tank 3’ to right of centre of “B”
phase when facing LV
side. (towards “C”
phase)
Acoustics-But
Not as
prominent as
in centre of “B”
phase.
Notes:
1. Triangulation performed at 100% and 105% rated voltage. (On HV tap position 2).
2. Inception level of acoustics was at approx. 45% rated voltage. Dropped out at 38%
rated voltage.
3. See next slide showing approx. locations of the source of PD from the triangulation.
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10
11
12
13
14
15
3.6 Triangulation
See attached.
a) Acoustics
b) Approximate Location of PD Source (From the Inside)
c) Approximate Location of PD Source (From the outside)
3.7 Gas Sample Results—Before and After Induce/Core Loss/Triangulation
See attached gas results showing an increase in fault gasses from Before to After
performing the induce/core loss/triangulation.
3.8 Conclusions from the High Voltage Electrical Testing and Triangulation
and Gas Results.
· Partial discharge seems to be coming from the LV side of the HV.
· Most prominent level of discharge seems to be in the 94” height level from the bottom of
the tank (Centre of B Phase) which puts it around the 54” height level of the HV coil based
on the diagram.
· Generation of fault gas confirms that an active fault exists
16
17
18
19
20
21
22
23
24
25
4.0 Transformer un-Tanking
The transformer active part (core and windings) was un-tanked on February 12, 2020. Two cranes were
used to lift the core and windings assembly from the tank.See Photos 1-3
The outer wraps of the windings were removed February 12-14, 2020 to expose the conductor of the
outer (HV) windings.
4.1 Inspection Findings
· The core and windings are clean. No burn marks or carbon was seen on the winding
outer wraps or LV side pressboard barriers.See Photo 4
· The cleats and leads, busbars, and tap changer assemblies were all clean.
· When inspecting the transformer tank, it was found that a small area adjacent to one of
the tank wall magnetic shunts on the LV side had carbon.See Photos 5&6
· After removing the LV side pressboard barriers and all the outer barriers around the
windings, Phases 1&3 were found to be clean with no signs of failure or carbon tracking.
See Photos 7&8
· After removing the LV side pressboard barriers and all the outer barriers around the
windings for Phase 2, carbon tracking and area of failure was exposed. The location of
the failure was at the same area measured by the triangulation that was completed
earlier. The carbon tracking was on the static shield (ring) located at the center of the HV
winding (at the 500kV line end). Two points on the ring had visible activity signs.See
Photos 9&10
· This type of static shield (ring) is normally made of a hard pressboard insulation in the
core, tightly covered with a conductive layer, then insulated with crepe paper. The crepe
paper insulation that covers the ring of phase 2, at the area of failure, was removed one
layer at a time to expose the conductive material of the ring. As the paper layers were
removed, the tracking area became more visible. Also, it was noticed that the conductive
wrap around the ring core was loose.See Photos 11-14
· Close inspection of the ring failure area showed that, most probably, the failure happened
at the gap area of the ring. A gap is needed in the conductive wrapping around the ring
to prevent creating a shorted turn around the transformer core.
4.2 Conclusion from un-Tanking Inspection
·The carbon found on the LV side tank wall is most probably due to a magnetic shunt
touching the tank wall at this area. The shunt will need to be removed and the cause of
this touching be fixed. This issue is not related to the main failure in Phase 2 HV winding
ring.
·The core and windings are all clean except for what was found in phase 2 HV winding
ring.
·From what is observed at this point, it appears the failure was limited to this area in the
ring and the HV winding copper conductor was not involved. However, this will be
confirmed with further dismantling of the windings.
· The replacement of the static shield (ring) is not likely possible without replacing the HV
winding but again this will be confirmed during the dismantling of the windings.
· Phases 1 & 3 HV windings rings have the same design. They do have the same loose
conductive wrapping.
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Photo 1: Un-Tanking HV Side View
Photo 2: Un-Tanking Side View
27
Photo 3: Un-Tanking LV Side View
Photo 4: Clean Active part and LV Side Pressboard Barriers
28
Photo 5: Carbon adjacent to One of Tank LV Side Magnetic Shunts
Photo 6: Carbon adjacent to One of Tank LV Side Magnetic Shunts
29
Photo 7: Clean Windings (Phase 1)
Photo 8: Clean Windings (Phase 3)
30
Photo 9: Arcing Activities and Carbon (Phase 2)
Photo 10: Arcing Activities and Carbon (Phase 2)
31
Photo 11: Arcing Activities on Ring (Phase 2)
Photo 12: Arcing Activities on Ring (Phase 2)
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Photo 13: Arcing Activities on Ring (Phase 2)
Photo 14: Arcing Activities on Ring (Phase 2)