Discharge of tubular busbar terminals

Discharge at tubular busbar terminals occurs due to high electric stress, surface defects, or environmental factors, and can be detected using UV, infrared, and ultrasonic testing.

Causes of Discharge

Discharges at tubular busbar terminals, such as corona or partial discharge, typically occur when the local electric field exceeds the dielectric strength of air. Common causes include: Surface defects or roughness on terminal balls, which increase local electric stress and promote corona formation, especially in areas exposed to wind and sand erosion. Aging or deterioration of support insulators, leading to reduced insulation strength and higher likelihood of discharge.

Poor workmanship or improper installation, including loose connections or misaligned terminals. Environmental factors, such as high humidity, pollution, or altitude, which can lower the breakdown voltage of air around the busbar.

Detection Methods

Early detection of discharge is critical to prevent insulation failure and potential blackouts. Key diagnostic methods include: Ultraviolet (UV) Imaging: Detects UV light emitted during corona discharge, allowing precise localization and intensity assessment. Infrared (IR) Thermography: Measures temperature differences to identify overheating or abnormal current paths that may indicate discharge.

Ultrasonic Testing (UT): Detects high-frequency acoustic emissions from partial discharges, useful for identifying internal defects or voids in insulation. Partial Discharge (PD) Testing: Measures discharge in Coulombs across the conductor-insulation interface, revealing inefficiencies or defects in power transfer.

Prevention and Maintenance

To minimize discharge risks at tubular busbar terminals: Regular inspection and maintenance of terminal surfaces and support insulators, replacing aging components as needed. Surface treatment of terminal balls to reduce roughness and prevent corona amplification, particularly in areas prone to wind and sand erosion. Strict adherence to installation standards and torque specifications for bolted or compression connections.

Comprehensive testing combining insulation tests with UV, IR, and ultrasonic diagnostics to detect early-stage or hidden discharges. Environmental considerations in design, including adequate clearances, proper insulation, and protection against pollution or moisture.

Summary

Discharge at tubular busbar terminals is a critical issue in high-voltage substations, caused by electrical stress, surface defects, aging insulators, and environmental factors. Early detection using UV, IR, ultrasonic, and partial discharge testing, combined with proper maintenance and design practices, is essential to prevent insulation failure and ensure reliable power distribution.