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Mathieu Guertin
Director of Sales, Europe, Russia, Africa
Morgan Schaffer Inc.
Canada
Standard ASTM tests for
Insulating Oil
Oil Quality Tests Detect incipient faults Detect insulation degradation
Assessing Oil Condition
DescriptionASTM
Number
IEC
Number
ISO
NumberDielectric Strength D877/D-1816 60156
Acidity D-974 60296 6295
Interfacial Tension D-971 60296
Color D-1500 60296-1 2049
Water Content D-1533 60814 R760
Density D-1298 60296 6295
Visual Examination D-1524 60296-1 2049
Power Factor D-924 60247
Inhibitor Content D-4768 60666
Dissolved Gas Analysis D-3612 60567
Furan Analysis D-5837 61198
Accuracy
DGA Understanding process and operations
Sampling
techniques
& location
jar
syringe
Multiple and varied steps
Hard to control variables
Multiples operators along the complet analysis process
Sampling
point Packaging
& handling Transportation Sample
preparation
Gas
extraction
Gas separation
and
measurement
Accuracy
C
Head space analysis
Equilibrium between gas
phase and liquid phase at
known pressure,
temperature and volume,
the gases are then
analyzed by GC
B
Stripping method
Oil is injected directly into the
instrument. Nitrogen is allowed to
bubble through the sample. This
strips the gases from the oil where
they are analyzed by the attached
GC.
A
Vacuum Extraction
Oil sample is exposed to
a vacuum to extract the
gases which are then
collected and analyzed
by GC.
ASTM 3612/IEC 60567: Extraction Methods
All done by
Gas Chromatography (GC)
Accuracy
Gas Chromatography
Accuracy
Precise but… not accurate Precise AND accurate
Precise and accurate data is crucial to
your decision making process…
Precision & Accuracy
Understanding the impact on measurements
Accuracy
Your DGA results: Accurate or not?
Every Laboratory should be able to demonstrate their precision and
accuracy, if this is not possible or by any reason unknown, the below
chart is recommended to use as a guide
Accuracy of IEC/CIGRE laboratories, from round-
robin tests using DGA standards.
Medium gas
concentrations
Low gas
concentrations
Best lab ±3% ±22%
Average ±15% ±30%
Worst Lab ±65% ±64% IEEE August 2005, M. Duval, J. Dukarm, Improving the reliability of transformer in gas-in-oil diagnosis
Accuracy
Your DGA results: Accurate or not? Impact of accuracy on the evolution of fault
« Accuracy » of +/- 20%
Measurement
Accuracy
m1 m10
What is the REAL trend?
Concepts
T1 T10
Example of a monitor with
an Accuracy of +/- 20%
USL
LSL
m2
T2
m3
T3
m4
T4
m5
T5
m6
T6 m7
T7
m8
T8
m9
T9
Accuracy
Your DGA results: Accurate or not? Impact of accuracy on the evolution of fault
m1 m2
What is reality?
T1 T2
Increasing?
If yes, how fast?
is it Stable?
Decreasing?
If yes, what’s the
rate? m2
T2
m3
T3
m4
T4
m5
T5
m6
T6 m7
T7
m8
T8
m9
T9
Accuracy
Your DGA results: Accurate or not? Impact of accuracy on the evolution of fault
With improved accuracy,
What is the trend now?
Accuracy of +/- 5%
m1 m2
With improved accuracy,
What is the trend now?
T1 T2
m2
T2
m3
T3
m4
T4
m5
T5
m6
T6 m7
T7
m8
T8
m9
T9
Not only can the engineer see the macro trends, but even micro
changes can be detected at the onset of the fault
Slower evolving
fault
Accuracy
Your DGA results: Accurate or not? Impact of accuracy on the evolution of fault
With improved accuracy,
What is the trend now?
Accuracy of +/- 5%
With improved accuracy,
What is the trend now?
Not only can the engineer see the macro trends, but even micro
changes can be detected at the onset of the fault
m1 m2
T1 T2
m2
T2
m3
T3
m4
T4
m5
T5
m6
T6 m7
T7
m8
T8
m9
T9
Faster evolving
fault
Accuracy
Your DGA results: Accurate or not?
IEEE August 2005, M. Duval, J. Dukarm, Improving the reliability
of transformer in gas-in-oil diagnosis
Diagnostic reliability is affected by the
accuracy of the DGA measurement results
CIGRE result for Round Robin Test
(RRT) at low concentration levels.
. Results of individual laboratories
x prepared DGA standard value ()
+/- 15% variation limit of
absolute values
Accuracy
Diagnosing transformer
condition
1. What is the current situation of the transformer?
2. What is the nature and severity of the fault?
A reference database is built for all transformers, using
reliable and traceable DGA laboratory results.
Accuracy
Diagnosing transformer
condition
A good rule is: Never make a decision based only on a ratio if either of the
two gases used in a ratio is less than 10 times the amount the gas
chromatograph can detect
FIST 03-30, USA Bureau of reclamation
Accuracy
Diagnosing transformer
condition
TDG (Total Dissolved Gases) expressed in % to 1.000.000ppm, i.e. in the picture TRN1 we see 7%, meaning there is a total of 70.000
ppm of gases (all the gases)
TDCG (Total Dissolved Combustible Gases) all the gases except N2, O2 and CO2, also in % to 1.000.000ppm, that’s why we see 0%
(less than 1ppm, as almost all the gases are N2, O2 and CO2)
THCG (Total Headspace Combustible Gases) are the gases on the headspace at the transformers (especially in sealed transformers
with N2 blanket) as the gases dissolved in the oil are in equilibrium with the headspace, we calculate, based on the Ostwald
coefficient, each gas at the headspace level.
Accuracy
Diagnosing transformer
condition
The Duval Triangle method, like any other DGA diagnostic method, should be
applied only when there is some suspicion of a fault, based on an increase in
combustible gas or some other suspicious symptom. The diagnostic method itself
is not a means of fault detection.
Because of the relative inaccuracy of gas-in-oil concentration measurements at low
concentrations, DGA diagnostic methods, including the Duval Triangle, should not
be applied unless the gas concentrations are well above the detection limit.
If reasonably stable concentrations of the gases were present before the onset of
the suspected fault, it is advisable to subtract out the background concentrations,
provided that the differences are large enough for interpretation. The diagnosis
should be based on recently-formed gas if possible, and including pre-fault gas in
the diagnostic calculations can lead to misleading results2.
1 PPMreport, Morgan Schaffer Myrkos’s operating system 2 http://www.deltaxresearch.com/triangle.htm
1
Accuracy
Diagnosing transformer
condition
Rogers used these relationships and determined that if a certain ratio existed, then a specific temperature
had been reached. By comparing a large number of transformers with similar gas ratios and data found
when the transformers were examined, Rogers could then say that certain faults were present. Like the
Key Gas Analysis above, this method is not a “sure thing” and is only an additional tool to use in analyzing
transformer problems.
FIST 03-30, USA Bureau of reclamation
Accuracy
Ability to Monitor the Evolution of the
Condition = Monitoring Value.
Transformers monitoring:
3 key values
Ability to Detect a change in condition
In ALL cases = Protection Value.
Ability to Diagnose the nature of the
“bad” condition = Diagnostic Value.
Value
no.1
Value
no.2
Value
no.3
Accuracy
Deploying online monitors Maximizing coverage of electrical assets
Critical 2
Critical 1
Sub-station
So when a transformer’s condition
changes abnormally…
Detect
Monitor
Diagnose
New
Accuracy
Deploying online monitors Alarm
Critical 2
Critical 1
Sub-station
1
Evolving fault triggers a signal to
substation for action
Detect
Monitor
Diagnose
New
Accuracy
Deploying online monitors Alarm triggers on-site inspection and Myrkos DGA
Critical 2
Critical 1
Sub-station
1
2
Field team quickly addresses the
alert On-site AND channels the
DGA results.
Communicate with Asset Manager
for DGA-based action plan
<<<< 1 day
to provide results for
diagnostics by Asset manager
Detect
Monitor
Diagnose
New
or Lab DGA
Accuracy
Portable DGA
Un
sta
ble
H2 c
on
dit
ion
?
Alert
On-site visit /
visual inspection
Ton-site/sampling Tpacking/shipping/customs Tlab analysis
1-10 Hours 1-10 Hours 1-5 days 1-5 days
Tresults/condition assessment/decision
Critical early detection in H2 change
X X X
Elimination of time consuming and wasteful steps
Extensive deployment of OLM units to…
… maximize Detect Monitor
Sta
ble
H2
co
nd
itio
n
Early detection of fault gases with OLM and Micro GC
Un
sta
ble
H2 c
on
dit
ion
?
Critical early
detection in H2
change
Alert
On-site visit /
visual inspection
Ton-site/sampling Ton-site DGA/ immediate result
Tlab analysis
1-10 Hours 0.1 Hours 1-5 days
Detect Monitor
Sta
ble
H2
co
nd
itio
n
Early detection of fault gases with OLM and Micro GC
Diagnose
PLUS… with Micro GC you
tremendously increase your
Portable DGA
Accuracy
Portable GC as a Fault Gas Analyzer
Ideal configuration:
1) GC based a) Easy calibration
b) for comparability with historical lab data
2) Analyze 9 gases per ASTM/IEC standards
3) Speed : Provides accurate results in a few minutes
4) Offers transformer asset database management
COST BENEFITS
Operating and capital costs as well as consequential damages can be
avoided by using the Micro GC analyzer regularly:
Instant confirmation of the presence or absence of a fault in the event of an alarm
Reduce unplanned outages
Reduce downtime on false alarms
Optimize your maintenance schedule
Better control load on equipment known to have faults
Prevent equipment failure and production losses
Monitor/diagnose critical equipment during re-energizing or commissioning
Monitor/diagnose less critical equipment at a lower cost
Accuracy
