- Dec 15, 2021 5:29 pm GMT
Routine inspection and cleaning of bus areas is key to preventing forced outages in high voltage electrical systems. During a recent customer inspection, an MD&A expert found a situation in an EX2100e static exciter where corrosion of a bus bolt could have led to a significant destructive event. Onsite fabrication of a new bus bar, and thorough cleaning of the area easily remedied the issue which could have taken out the unit and destroyed the exciter.
The customer’s EX2100e static exciter’s bus bolt was heavily corroded and damaged which caused overheating of the bus bar and bolt. The overheating melted nearby materials in the exciter and had already broken the bus connectors. Further damage would have eventually caused an equipment short.
A new busbar was fabricated during the outage and was lightly coated with dielectric grease to impede oxidation, increase current efficiency and reduce temperature rise. Additionally, several other fasteners needed to be retorqued to ensure similar issues did not occur in future.
Our expert also discovered oil and grease in the collector housing which was already causing field ground alarms and, left uncorrected, would have caused damage to the rotor. After cleaning and reenergizing, MD&A experts were able to eliminate the condition in the short term. However, this emphasizes the need for properly functioning auxiliary systems, such as the oil system.
Additionally, the aux contacts on the exciter output contactor were binding when the main contactor was in the closed position. Over time this can break the contact assemblies. Once the aux contact plungers were readjusted, the contacts operated smoothly.
Even with spotless conditions, regular inspections are recommended to deter outage and trip situations. Several actions are recommended for this equipment:
- Periodic thermal imaging inspection of the bus bar and rectifier bridge. The thermal imaging operations should be kept to less than a minute due to airflow over the bridge. Visual inspection of bolt torque marks should also be performed.
- Consistent cleaning of the cabinets of the exciter, linear reactor and the PPT.
- Correction of the oil misting at the collector end of the generator. During future outages, removal, cleaning and remounting of the collector rings may be required if this condition is not corrected.
Thorough inspections are crucial in maintaining high voltage equipment. MD&A experts will conduct these operations resulting in reduction in unplanned outages and increased reliability.
MD&A’s Control Systems Division maintains a staff of OEM experienced field engineers who provide installation, technical support, advanced troubleshooting, training, and consulting services for gas and steam turbine controls, generator excitation, and auxiliary systems. Call MD&A today at +1 (518) 399-3616
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