Case study SMUD. TASA code 2. DRM PERFORMED ON FPE TYPE OLTC. FPE CONTROLS. DGA. Increase in Hydrogen and Methane in 2011 Indicative of hot metal gasses breaking down the oil. TASA Diagnostic Evaluation. DGA Particle count Proprietary algorithms Operating procedure
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TASA code 2
FPE TYPE OLTC
Increase in Hydrogen and Methane in 2011
Indicative of hot metal gasses breaking down the oil
Monitor for increased arcing
Evaluate for worn or damaged components
Indicated: Condition code 2
A slightly abnormal dissipation of energy
Early indication of fault or wear activity
TASA - identifies the wear out of the failure mode and identifies issues
DRM - looks at the functionality timing sequence of the functional steps and identifies the abnormalities
The first static resistance illustrated an issue in Phase 2
Phase 2 – 16L to 16R
We would expect to see symmetry through the reversing switch.
Erratic behavior through the transitions
High resistance through some contacts
FIVE CHARACTERISTIC TRANSITIONS DIRECTION 16R-N
Phase1 (same for Ph.3)
When one complete side shows a problem
Reversal switch is the culprit
Phase 3 – 16L to 16R
Phase 1 - 16R to 16L
The increase in motor current coincides with the squeaking noise heard during the motor operation. This could be an indication of misalignment of mechanical components.
on FPE OLTC
Right After our Findings
Updated diverters, installed shunt straps to all 6 diverters
Replaced all arcing contacts, because of unusual cracking in face of contacts.
Re-aligned face to face mating by bending arms until flush.
Re-tensioned drive chain and drilled new pin
Replaced 2 diverter barriers
Replaced rotor bearings
Replaced stationary contact locking tabs
Replaced rotor contact nuts
R tested from collector rings, to stationary contacts, through rotor (in milliOhms).
Tap changer operates normally in the lower range. Went through Neutral once last December.
Collector rings and contacts showed tarnish, no coking. Resistance after repair milliOhms