Transformer Tests

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Transformer Tests

• Oil tests and on-line monitoring can increase
  transformer life expectancy

By William Morse Morgan Schaffer Inc.
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Transformers

• The heart of a substation
• Needed to transmit electricity over long
  distances
• Steps up or steps down voltage

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The Inside View
Ready to work again Ready for
repair
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Oil, the Blood of the Transformer

• Part of the Insulation System
• Excellent dielectric properties
• Cools the transformer
• Excellent heat transfer properties
• Ease of access

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Standard ASTM Tests for Insulating Oil

• Description ASTM Number
• Dielectric Strength D-877/D-1816
• Acidity D-974
• Interfacial tension D-971
• Color D-1500
• Water Content D-1533
• Density D-1298
• Visual examination D-1524
• Power factor D-924
• Dissolved gas analysis D-3612
• Inhibitor content D-4768
• Furan Analysis D-5837
• Metals Analysis ICP

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Dielectric Strength
Acceptable limit for serviced aged oil 25 kV
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Interfacial Tension
Acceptable limit for serviced aged oil
18 dynes/cm
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Water Content
The Past And
The Present
Limit for serviced aged oil 35 ppm
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Dissolved Gas Analysis
The most important test you can perform on your
transformer
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Dissolved Gas Analysis

• High vacuum gas extraction apparatus
• Extracts all dissolved gases found in the oil
  sample
• Determines dissolved water in ppm as well
• Extraction of all gases in less than 2 minutes

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Gas Chromatographic Analysis
CO2
C2H4
CO
CH4
C2H6
C2H2
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Oil Breakdown Products
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Partial Discharge
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Overheating
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Arcing
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Two More Important Tests

• Furan analysis
• Determines the state of the solid insulation
• Metals analysis
• Used to pin point the location of a fault

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Predictive Maintenance

• On-site analyzers
• Increase the frequency of testing
• More data points Better decisions
• On-line monitors
• Needed for critical transformers
• Warn of developing problems between routine
  maintenance

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PHA-1000 Hydrogen Analyzer
Fastest way of screening transformers. Analyzes
Hydrogen - A key gas produced by all fault
types High sensitivity and wide range Simple
operation
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• Accurate H2 readings in 60 seconds
• Analysis of H2 only No cross contamination
• No special training required

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MYRKOS Fault Gas Analyzer
A Full DGA Lab in the field
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Typical Gas Extraction Apparatus

• High vacuum gas extraction apparatus
• Fragile
• Not very portable
• Special training required

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The Shake Test Syringe
Completely portable No special training required
Syringe must be filled so that metering pin is
completely outside of syringe cap.
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An exact amount of oil is measured using a
metering pin located on the syringe piston shaft.
Eject the excess oil by pushing the piston until
the metering pin hits the syringe cap.
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Mixing the oil with CO2 free ambient air
Ambient CO2 free air is pulled into the syringe
which is then vigorously shaken to speed up gas
diffusion from the liquid phase to the gas phase.

• Connect syringe to CO2 trap
• Open syringe and CO2 trap
• Slowly pull syringe piston to the end
• Close syringe and CO2 trap
• Disconnect CO2 trap

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Method accepted by IEC 60567 and ASTM D-3612
Complete DGA in 2 minutes on-site
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Once the test is initiated, automatic sampling
occurs and outputs are obtained from both modules
(A B) simultaneously. Calibration is then
performed at a click of the mouse button.
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On-line Monitors

• Continuously measure gas concentration
• Store data and trigger alarms

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CalistoDissolved Hydrogen and Water Monitor
Intelligent Electronic Device IED Highly Accurate
and Precise Monitors Oil-Filled
Transformers Designed for Extreme
Environments Communicates with the World
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Oil circulation and gas extraction circuits
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Gas Extraction Technology
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H2 detection cell
Specially designed thermal conductivity
detector Specific to Hydrogen No interference
from other gases
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H2 detector port
Gas extraction chamber
Oil circulation pump
Water sensor
Primary Heat exchanger
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Heat Generation and Removal System
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CalistoDissolved Hydrogen and Water Monitor
Continuous Hydrogen measurement Two alarm
levels Data storage and trending software
H2
Why Hydrogen? Hydrogen is produced in all
transformer faults. Calisto will detect the fault
before the Bucholz relay is tripped.
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CalistoDissolved Hydrogen and Water Monitor
Continuous dissolved water measurement Two alarm
levels Data storage and trending
software Reported in ppm or RS at 25C
H2O
Why water? Along with polar compounds and acids
water can adversely affect the dielectric
properties of the solid insulation
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Installation
Salt River Project Phoenix, Arizona, USA GE 20
MVA 69 Kv
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Installation
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Installation
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Installations
MPEB Bhopal, India
DUBAL Dubai, UAE
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Communication
Ethernet RS-232 Modem Fiber Optic Wireless RS-485
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Gas Trending
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Benefits
Easy to install
Maintenance free
Fastest response to developing faults
Accurate reliable measurements
Monitors faults AND insulation integrity
Will integrate to ANY data acquisition system or
LAN using STANDARD protocols
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Case Study 650 MVA GSU Transformer failure and
Repair
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DGA results as of November 11th, 2001
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Table 2 H2 generating rates from May 30th to
Sept. 26th 2002
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Sudden increase in hydrogen generating rate
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Source of incipient fault
Nov. 2001 Initial source of high electrical
resistance (e.g. bad connection)
May 2002 to Sept. 17th 2002 Resistive hot spot of
increasing resistance (H2, CH4, and C2H4)
Between Sept. 17th and Sept. 30th (Sept. 27th
?) Additional energy probably through circulating
currents
Burned high voltage lead
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Overheated Connector
Burnt Lead
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Mirant GSU Update as of February 19th, 2003
Constant H2 level at approx. 30 ppm
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50 MVA NPC Philippines
Loose diverter switch contacts
Inspection
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The Future

• More intelligent monitors
• More gases measured
• Cost and size reduced
• Integration with a full substation monitoring
  system
• Equipment that integrates with diagnostic
  software
• Ease of access through the internet

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Preventive Maintenance It Pays
Thank you