Got a pretty decent fault today. Thought ild share.
Background and fault:
Conducting a inspection of a 175kVA gen set. Gen is reasonably old. It has come back from a site where is was run underloaded and not serviced regularly. Has a number of oil leaks and we are considering writing it off. Once we fixed a start fault we heard some ticking. We localised it down to a small arc from the base of the crankshaft pully to the engine block. Arc happens at 2 to 4 second intervals. Quite a strong arc since we could see it clearly even with sunlight. We noticed our RCD had a fluctuating display of .5mA to 1.2mA.
Initial fault finding.
Initially thought that the battery alternator may be screwed so we disconnected it and ran gen off the battery. No change
Thought than maybe the gen alternator may have a fault so tested winding continuity, insulation resistance and earth continuity. No change.
Thought than since the gen is filthy, that the belts may be somehow causing a static charge to develop. Cleaned the gen and arcing disappeared however RCD still indicates a fluctuating earth current.
Still not convinced we had actually fixed the fault, we tested the RCD current transformer. Continuity checked out. Point to note the arrow on the tranny pointed away from the star point on the gen. Turned it around yet no change.
Considered testing the RCD however didnt have any spares and it passed a the RCD test.
Background and fault:
Conducting a inspection of a 175kVA gen set. Gen is reasonably old. It has come back from a site where is was run underloaded and not serviced regularly. Has a number of oil leaks and we are considering writing it off. Once we fixed a start fault we heard some ticking. We localised it down to a small arc from the base of the crankshaft pully to the engine block. Arc happens at 2 to 4 second intervals. Quite a strong arc since we could see it clearly even with sunlight. We noticed our RCD had a fluctuating display of .5mA to 1.2mA.
Initial fault finding.
Initially thought that the battery alternator may be screwed so we disconnected it and ran gen off the battery. No change
Thought than maybe the gen alternator may have a fault so tested winding continuity, insulation resistance and earth continuity. No change.
Thought than since the gen is filthy, that the belts may be somehow causing a static charge to develop. Cleaned the gen and arcing disappeared however RCD still indicates a fluctuating earth current.
Still not convinced we had actually fixed the fault, we tested the RCD current transformer. Continuity checked out. Point to note the arrow on the tranny pointed away from the star point on the gen. Turned it around yet no change.
Considered testing the RCD however didnt have any spares and it passed a the RCD test.