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The current environment of higher loading on aging transformers, deferred capital ex-penditures on new equipment and increased service reliability requirements have driven the industry to investigate the use of innova-tive transformer condition assessment and management tools. Based on the historical installation rates of generator step-up, trans-mission and large distribution transformers, the average transformer age is 40 years.

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Dissolved gas analysis is the single-most

comprehensive tool for transformer

condition assessment.

Transformer GVA addition per year

However, age itself is not a cause of failure. As transformers age, they endure various stresses that can contribute to a variety of failure mechanisms. Appropriate online DGA monitoring and diagnostic tools can help utilities avoid unplanned failures, lower maintenance costs and extend transformer useful life.

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Gas chromatography (GC) has long been the accepted standard for the measurement of dissolved gas levels in transformer oil. The GAS-Guard 8 provides accurate and repeatable measurement of the eight critical fault gases as well as other significant parameters.

The GAS-Guard 8 brings the DGA laboratory to your transformer with its rugged, closed-loop gas chromatograph. The GAS-Guard 8 packs this science into a compact package designed to be mounted on or near the subject transformer.

Key benefits include: Field-based fully automated DGA requires no manual oil sampling or remote lab testing

Accurate and timely DGA results improve ability to protect transformer against fault damage

Data generated by the GAS-Guard 8 can be used to support condition-based maintenance programs

Time-date stamped test results allow correlation between real events and measured conditions.

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Through chromatography, the GAS-Guard 8 generates individual measurements of eight critical fault gases found in transformer oil. Accuracy is commensurate with traditional lab results. The sensor continually collects oil samples as often as every two hours. The GAS-Guard 8 can also measure moisture in the oil, oil temperature and ambient tempera-ture. DGA results and other measurement data are date/time stamped and can thus be correlated to transformer load.

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Gas Accuracy1 Repeatability2 Range3

Hydrogen H2 +/- 5% or +/- 2 ppm <2% 2-3,000 ppm

Oxygen O2 +/- 5% or +30 / - 0 ppm <1% 30-5,000 ppm

Methane CH4 +/- 5% or +/- 10 ppm <1% 10-5,000 ppm

Carbon Monoxide CO +/- 5% or +/- 3 ppm <1% 3-10,000 ppm

Carbon Dioxide CO2 +/- 5% or +/- 5 ppm <1% 5-30,000 ppm

Ethylene C2H4 +/- 5% or +/- 3 ppm <1% 3-5,000 ppm

Ethane C2H6 +/- 5% or +/- 5 ppm <1% 5-5,000 ppm

Acetylene C2H2 +/- 5% or +/- 1 ppm <2% 1-3,000 ppm

NOTES: All specifications are independent of oil temperature and gas pressure level.1 Percent of ppm - whichever is greater2 At gas calibration level3 Gas-in-oil

DGA tolerances of the GAS-Guard 8

Graphical representation of GAS-Guard 8 connected to the transformer tank.

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������������ ����������������������������������The software package included with the GAS-Guard 8 sensor allows the user to graph-ically display continuous gas evolution for each of the eight critical fault gases as well as moisture, load and ambient temperature.

Online diagnostic tools

The software package also allows the user to trace changes in fault severity over time through dynamic plots created using the Duval Triangle and Rogers Ratios analysis tools.

Online DGA data populating diagnostic tools deliver new insights. This displays Rogers Ratios (IEEE PC57.104.D11d) and basic gas ratios (IEC 60599-1999-03).

The Duval Triangle (IEC 60599-199-03) provides a diagnostic outcome for combinations of three fault gases.

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Subject to change without prior notice. The information in this document contains general descriptions of the technical options available, which may not apply in all cases. The required technical options should therefore be specified in the contract.