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High-voltage switchgear is designed for decades of reliable service, but that reliability doesn’t come without proper maintenance. In medium-voltage distribution systems, the difference between a transformer that runs for 30 years and one that fails prematurely often comes down to how well the switchgear is maintained.
Here are five maintenance practices that are frequently overlooked but critically important.
Check all elbow connectors for signs of tracking, corona damage, or moisture ingress. Look for surface discoloration, cracking, or carbonized paths on the EPDM rubber housing. Any suspect connector should be replaced immediately — do not wait for a failure.
Deadbreak apparatus bushings and bolted elbow connectors rely on mechanical pressure for their electrical interface. Over time, thermal cycling can cause connections to loosen. Use a calibrated torque wrench to verify all bolted connections are within specification.
Periodic megohmmeter testing of bushings and insulated connectors can identify degraded insulation before it leads to a fault. Test between each phase and ground, and compare results against factory baseline values. A significant decrease (typically below 1,000MΩ for new equipment) warrants further investigation.
For critical applications, periodic PD testing can detect incipient faults that are not visible to the naked eye. Elevated PD levels indicate material degradation long before a catastrophic failure occurs.
Keep a stock of critical spare parts — particularly Bay-O-Net fuses and elbow arresters — so that emergency replacements can be made without delay. Many utilities and industrial facilities keep a 12-month spare parts inventory for their most critical transformers.
Preventive maintenance of high-voltage switchgear is an investment, not a cost. A well-maintained system delivers higher reliability, fewer unplanned outages, and lower total lifecycle cost.
