Upload
nguyencong
View
231
Download
3
Embed Size (px)
Citation preview
Thomas Prevost – OMICRON electronics USA
IEEE T&D Conference
Chicago, Illinois April 17, 2014
New Techniques for the Monitoring of
Transformer Condition
Agenda
• Monitoring Expectations & Needs
• Bushing Monitoring
– Capacitance
– Power Factor
• Transformer Monitoring
– Partial Discharge
– Voltage Transients
• Summary & Conclusions
Scope of Monitoring – Expectations and Needs
Continuous Diagnostics
Condition based maintenance
Full utilization of life span
Fa
ilure
Ra
te
time / a 0 10 20
Classical
Diagnostics
Temporary
Monitoring
Permanent
Monitoring
5a
3a
Scope of Monitoring – Expectations and Needs
Arguments and user expectations
> Continuous monitoring under service conditions
Reliable measurement data
> Diagnostic of errors before they appear
Condition based maintenance
> Knowledge about historical use
Fully utilize life span of equipment
Agenda
• Monitoring Expectations & Needs
• Bushing Monitoring
– Capacitance
– Power Factor
• Transformer Monitoring
– Partial Discharge
– Voltage Transients
• Summary & Conclusions
• According to the data from various researches and
electric power utilities, bushings failures make 5 to
50 %, or in average, one quarter of the total
number of transformer failures .These failures most
commonly cause transformer fires which may result
in huge collateral damages of switchyard.
Reference [3] indicates that 30 % of generator
step-up transformer failures are caused by a
bushing malfunction, and that they also cause
56 % of failures accompanied by fire.
Failure Mechanisms and Diagnostics
• Partial breakdowns
– Capacitance
– Partial discharges
Voltage
[kV]
No. of
layers
%
change
123 14 7.1
245 30 3.3
420 40 2.5
550 55 1.8
A
Emax= high
Emax= low
A
without
layers
with layers
Failure Mechanisms and Diagnostics
• Voids, cracks
– Partial discharges
– Capacitance
• Ageing by-products, moisture
– Dissipation factor / power factor
0,0
0,2
0,4
0,6
0,8
1,0
Dis
sip
atio
n F
acto
r (%
)
typ: 0,25
OIP
typ: 0,35
IEC60137 max: 0,7 %
RIP 0,0
0,2
0,4
0,6
0,8
1,0
Po
wer
Fac
tor
(%)
typ: 0,25
OIP
typ: 0,35
max: 0,85
RIP
max: 0,5
IEEE C57.19.01
Where Can I Get the Reference from?
• Off-line test: Reference from HQ capacitor
• On-line test: Reference?
u
U X (t) U R (t) Z 1
Z 2
C X, C R
0 (t)
Reference Measurement path
I R I X
Im
j
d
Uo
IX IR
Relative C/DF Measurement
> Sum of the bushing currents
> Three phase vectors are added up
> Bushing-to-bushing comparison
> Vectors of bushings in same phase are
compared
L1
L2 L3
from 2011-02-13 to 2011-02-15
[P. Picher “Integration of New Transformer Monitoring Technologies ...”
TechCon Asia-Pazific 2011]
Systematic error
0.65 %
plus instrument
inaccuracy 0.5 %
Capacitance?
DF impossible!
0,0
0,2
0,4
0,6
0,8
1,0
DF
(%)
typ: 0,25
OIP
typ: 0,35
Systematic error
RIP
•PAGE 12
C/DF Measurement over 1.75 Years
0,0
0,2
0,4
0,6
0,8
1,0
DF
(%)
typ: 0,25
OIP RIP
400
467 +/- 2 pF Measurement
478 pF Warning
500
Cap
acit
ance
(p
F)
0,27 +/- 0,05 % Measurement
0.7 % IEC Warning
Agenda
• Monitoring Expectations & Needs
• Bushing Monitoring
– Capacitance
– Power Factor
• Transformer Monitoring
– Partial Discharge
– Voltage Transients
• Summary & Conclusions
Reasons and Effects of Partial Discharges
Reasons
• Failures of design or during manufacturing process
• Aging of equipment
– Electrical stress
– Thermal stress
– Mechanical stress
Effects of PDs:
• Heating
• Creeping destruction of the insulation material
• Treeing, chain reaction
• Insulation breakdown, short circuit
Treeing in polyethylene
PD Activity
over 4 Days
10
1
0.1
0.01
00:00:00 01:00:00 02:00:00 03:00:00 04:00:00 05:00:00
Q in
nC
t in dd:hh:min
L1L2L3
Combination of the Methods
IEC PD Measurement
Corrected IEC PD Measurement
& UHF PD Measurement
IEC
UHF
PD Risk Assessment
Noise rejection
Source separation
Pattern classification
PD localization
• Galvanic
decoupling
• Gating
• UHF
• RTD
• 3 PARD
• 3 FREQ
• Manual
• Automatic
• Asset
• Phase
• Acoustic
localization
Agenda
• Monitoring Expectations & Needs
• Bushing Monitoring
– Capacitance
– Power Factor
• Transformer Monitoring
– Partial Discharge
– Voltage Transients
• Summary & Conclusions
Switching Transients
0
Vo
lta
ge
in
kV
t in ms 80 40 0
200
-200
24 17 t in ms
0
Vo
lta
ge
in
kV
t in ms 100 50 0
200
-200
29 15 t in ms
G
Grid400 kV
GSU1100 MVA
Generator900 MW
21 kVTransmission line
400 kV6 km
Substation
Transformer 2Transformer 1
ca. 10 m
UMTS
Generator
OMS843- PD- Transients- C/DF
UHF620 + UVS
OMS843- PD- Transients- C/DF
Voltag Transformers
OMS843- C/DF
(Reference)
UHF620 + UVS
PDM600
Case Study: Combined Generator and
Transformer Monitoring
C/DF and PD Couplers
Generator:
Capacitive couplers
Transformer:
Capacitive bushing
adapters and UHF
drain valve sensor
Transformer 2Transformer 1
ca. 10 m
UMTS
Generator
OMS843- PD- Transients- C/DF
UHF620 + UVS
OMS843- PD- Transients- C/DF
Voltage Transformers
OMS843- C/DF
(Reference)
UHF620 + UVS
PDM600
Monitoring Results
20 10 0 t in ms
1
0.1
0.01
QIE
C in
nC
10
20 10 0 t in ms
100
1
0.001
U in µ
V
1000 500 0 f in MHz
P in d
Bm
-120
-100
-60
0,0%
0,2%
0,4%
0,6%
0,8%
1,0%
11-20-2012 11-25-2012 11-30-2012
DF
/ %
U
V
W
Influence of Environmental Conditions
0 5 10 15 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1 d
issip
ation
fa
cto
r in
%
0
5
10
15
20
25
30
35
40
tem
pe
ratu
re in
C°
V-phase
U-phase W-phase
IEC60137 max: 0,7 %
time / days
G
Grid400 kV
GSU1100 MVA
Generator900 MW
21 kVTransmission line
400 kV6 km
Substation
0
Vo
lta
ge
in
kV
18 t in ms 12 6 0
200
-400
400
-200
C Phase
B Phase
A Phase
BAT20
BAT10
0
Vo
lta
ge
in
kV
200
-400
400
-200
Transient Over-Voltages
> Oszillation frequency 10 kHz,
beat frequency 600 Hz
> Several times a day
t in ms 12 6 0
BAT10
18 t in ms 12 6 0
Agenda
• Monitoring Expectations & Needs
• Bushing Monitoring
– Capacitance
– Power Factor
• Transformer Monitoring
– Partial Discharge
– Voltage Transients
• Summary & Conclusions
Summary
• On-line monitoring as
future trend
• C/DF monitoring
– The reference problem
– Solution: VT reference
– Accuracy +/- 2pF
• On-line PD monitoring
– The noise problem
– Possible solutions:
• UHF-gating
• Software separation
• Pattern recognition
• Voltage Transients