LumaSense SmartDGA, Hardware Manual

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SmartDGA Hardware Manual System Overview
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proportional to the concentration of the gas of interest. By quantifying the amount of light
transmitted to the detectors with and without the gas of interest, the concentration of gas can be
determined.
2.2.2 Other Gas Measurements
The SmartDGA utilizes various independent sensors and calculations to measure Oxygen (O
2
),
Hydrogen (H
2
), Moisture, and Nitrogen (N
2
). Hydrogen is measured using a metal oxide sensor,
Oxygen is measured with a galvanic cell type sensor, and Moisture is measured in-oil using a
thermoset polymer capacitive sensing element. All sensors are individually calibrated by LumaSense
Technologies for optimal performance and accuracy. Nitrogen gas values are calculated as a residual
based on temperatures, gas pressures, and other gas measurements.
2.2.3 Sampling Sequence
1. All of the oil valves are defaulted to their normally closed state between measurement
cycles.
2. A pressure equalization routine runs continuously between measurement cycles. If the
pressure inside the instrument gets too far away from the oil tank pressure (due to
temperature changes), the routine will open the oil valves and equalize the pressure.
3. When the Real-Time-Clock-Calendar of the EZHub unit reaches the time of the next
measurement cycle, it sets the instrument’s state to “Go”.
4. As a safeguard against the transformer/LTC being degassed when a cycle starts, if the
measured inlet oil pressure is not 2 psi above the measured ambient pressure, the cycle will
abort.
5. The instrument flushes the oil within its oil loops with fresh oil from the transformer/LTC.
This takes approximately 10 minutes.
6. At the end of the flush, the instrument will circulate the fresh oil sample through its inner
oil loop. The oil loop contains approximately 35 mL of oil.
7. As the sample of oil circulates past the membrane gas separator, the gas migrates across the
membrane to establish partial pressure equilibrium with the gas collection volume.
8. While the oil is circulating past the gas separator on the oil side, the gas collection volume is
circulating past the gas separator on the gas side.
9. Gas is allowed to equilibrate for a predetermined period of time.