Seminario Técnico Pentágono de Duval - Diagnóstico DGA

222
Fault Gas Formation
Note: For faults T3 in paper (C), curve for H2 is a bit higher.
Ref: Duval, TSUG 2013.
2
Material Of Dr. Duval
DO NOT REPRODUCE WITHOUT PERMISSION

333
3
Occurrence of Faults in Service at CIGRE
3

444
Triangle Method
4

555
Triangle 4 (using H2, CH4 and C2H6)
Allows to distinguish between:
-Stray gassing of oil at T < 200°C (in zone S)
-Overheating at T < 250°C (in zone O)
-Possible carbonization of paper at T >
300°C, with a probability of 80%, not 100%
(in zone C)
-Corona partial discharges (in zone PD).
5

666
Triangle 5 (using CH4, C2H4 and C2H6)
Allows to distinguish between:
-Hot spots in oil only at T > 300°C or
700°C (in zones T2 or T3)
-Possible carbonization of paper, with a
probability of 90%, not 100%
-For faults O, S, PD, use rather Triangle 4.
6

777
Use of Triangles 4 and 5
Triangle 4 should be used only for faults identified first with Triangle 1
as faults PD, T1 or T2, or when there is a high level of H2.
Triangle 5 should be used only for faults identified first with Triangle 1 as
thermal faults T2 or T3.
Neither Triangle 4 nor Triangle 5 should be used in case of electrical faults
D1 (including sparking PDs) or D2.
When Triangles 4 and 5 do not agree, this often indicates a mixture of faults.
7

8
8
Duval Pentagon 1 (2014):
-The order of gases at the 5 summits of the pentagon
corresponds to the increasing energy required to produce
these gases, i.e., from H2 to C2H2 counter-clockwise.

9
9
Duval Pentagon 2 (2014):
-Free algorithms for Pentagons 1 and 2 are available from duvalm@ireq.ca.

101010
Detection of Multiple Faults in Transformers:
10
-First clue is if there is a change in gas pattern. Second clue is if
Triangles 1,4, 5 and Pentagons 1, 2 do not provide the same
diagnosis. This may be an indication of multiple faults.
-this is because each graphical representation is more sensitive to
some gases. For instance, Triangle 4 is more sensitive to H2 and
therefore to faults S or PD than even the Pentagons.
-similarly, Triangle 5 is more sensitive to C2H4 and to faults T3 in oil
than Triangle 1 and the Pentagons.

11
11
When to Use the Pentagons and Triangles?
-Ask software to indicate for each set of DGA results the fault indicated by Pentagons
1,2 and Triangles 1,4,5 (following the rules for the use of Triangles 4,5).
Display graphically in Pentagon 1 the evolution of DGA points with time. If some of them
are in thermal fault zones, switch to Pentagon 2.
When DGA points move with time from one fault zone to another, this means a new
fault is appearing. If interested to more precisely identify this new fault, subtract the last
gas formation from the new one and add it as DGA point “Delta”.
When the Pentagons and Triangles do not provide the same fault diagnosis for some
DGA results, this may indicate multiple faults. If interested to identify them more
precisely, display graphically Triangles 1, 4 and/or 5 providing different fault diagnosis
(or all of them), in addition to Pentagon 1 or 2.
See examples 19-19 for the interpretation of intermediate mixtures of faults.

121212
Risk of failure vs. type and location of fault
12

131313
Detection of Low DPs of Paper
-CO2, (> 10,000 ppm), CO2/CO (> 20) and furans 2-FAL (> 1 ppm) are
more sensitive than methanol to detect DPs < 400:
13

1414
Cases of Transformers with Low DPs of Paper

1515
Cases of Transformers with Low DPs of Paper
Note: no cases of mechanical failure of paper at low DPs have been
reported to CIGRE so far.

161616
90% Typical Concentration Values
at IEC, in ppm
(vs. source)
16

171717
90% Condition 1 Concentration Values
at IEEE, in ppm
(vs. kV, MVA, age, %O2)
17

181818
Probability of having a
failure-related event in
service (PFS) in %, vs. the
concentration of all gases
in ppm. T = 90% typical
value; P = pre-failure
value.
CIGRE Gas Concentrations above Typical Values
18

191919
CIGRE Sampling Intervals between Typical
and Prefailure Concentrations, in ppm
(based on revised condition 1 values in the US of 2010 and
pre-failure values of CIGRE)
19

202020
CIGRE Sampling Intervals between Typical
and Prefailure Gassing Rates, in ppm/month
(based on gassing rates for condition 1 in the US and pre-
failure gassing rates of CIGRE)
20

212121
CIGRE Approach Applied to the IEEE
Transformers of 2014
21

222222
22
90% Condition 1 Concentration Values
vs. Type of Thermal Fault at CIGRE:
(ppm)
(ppm)
22

232323
23
Condition 4 Concentration Values
vs. Type of Fault at CIGRE:
(in ppm, using previous adjustment factors)
23

242424
24
Comparison with Cases of High Gas Levels
without Failure at CIGRE:
(in ppm)
24

252525
#2 - Attempt a fault diagnosis
• Compare lab results or monitor readings with in-house
typical values of concentration and gassing rate, or
compare with published values (e.g., from IEEE and
CIGRE)
• If measured DGA values are above typical values, a fault
diagnosis may be attempted
25

262626
#3a - Evaluate the severity of the fault
•The severity of the fault will depend on:
• The rate of gas formation
• The concentration of gases
• The nature of the fault (electrical or thermal)
• The location of the fault (paper or oil only)
26

272727
#4 - Actions on the equipment
-Increase the frequency of oil sampling
• (as values move from typical values to pre-failure values)
-Determine the dependence of gas formation on load
-Consider complementary tests
• (UHF detection of partial discharges, detection of hot spots by infra-red
cameras and acoustic tests)
-For critically located or severely affected equipment, install on-line gas
monitors
-For the most severe cases, plan the replacement of the transformer and/or
its removal from service and inspection
-Ask for advise of DGA experts
27

2828
Concentration Limits for Multi-Gas Monitors

2929
Gassing Rate Limits for Multi-Gas Monitors

3030
Fault Detection with Hydrogen Monitors

313131
31
DGA in LTCs at IEEE:
Triangle 2 for compartment types Triangles 2 for in-tank types
31

323232
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Normal operation zones for in-tank types:
• N or N1 for MR types M and D.
• N or N3 for MR types VR and VV.
• N or N4 for MR types R and V.
• N or N5 for MR types G and UZDs.
• Depending on operating conditions.
• Other DGA examples would be needed for the normal and faulty
operation of these LTCs.
32

333333
Pentagon 3 for FR3
33

Seminario Técnico Pentágono de Duval - Diagnóstico DGA

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Seminario Técnico Pentágono de Duval - Diagnóstico DGA