Condition Monitoring of Circuit Breakers and Switchgear Olli

Condition Monitoring of Circuit Breakers and Switchgear Olli Vaniala

Condition Monitoring of Circuit Breakers and Switchgear 1. Circuit Breakers 2. Switchgear 3. Failure Modes and Wear 4. Condition Monitoring and Maintenance

1. Circuit Breakers A. Critical part of a power system • Essentially a pair of switchable contacts • Used to prevent electric equipment failure due to short-circuits or overload fault currents • Subject to high electrical and mechanical stress B. Different types of circuit breakers • Pneumatic, Hydraulic or Spring operated • Air, oil or gas (SF 6 or CO 2) isolation • Different failure modes, failure rates and maintenance requirements ABB 550 k. V Circuit Breaker

2. Switchgear A. Combination of circuit breakers, switches and/or fuses • Used to control, isolate and protect electric equipment • Switchgear may be used as an isolator, load-break switch or grounding switch A. Different types of switchgear • Manual or remote controlled • Air, oil or gas (SF 6 or CO 2) isolation

3. Failure Modes

3. Wear L = Low Influence M = Medium Influence H = High Influence

4. Condition Monitoring and Maintenance A. Visual inspection (every 1 -2 years) • • • Signs of damage or leakages Insulation medium level Breaker operations count B. Non-intrusive condition assesment (every 5 -10 years) • • Measurements and testing Cleaning C. Fully detailed overhaul (every 10 -20 years) • Dismantling of mechanism and poles

4. Visual Inspection A. Signs of damage or leakage A. Burn marks, cracks or dents B. No grease or condensation within switchgear casings B. Insulation medium level A. Insulation level, density, concentration C. Breaker operations count A. Compare with mean time between failure(MTBF) B. Manual operation exercise

4. Non-Intrusive Condition Assesment A. B. Measurements and testing A. Contact times, speeds, damping curves, DRM test B. Overcurrent or short-circuit protection testing Lubrication A. Cleaning A. D. Based on measurements, some gears or latches may need lubrication Insulators, main contacts(for low voltage switchgear) Thermal imaging A. Loose bus connections B. Faults in breaker terminals or connectors

4. Fully Detailed Overhaul A. Reconditioning A. Disassembly, cleaning and replacement of damaged or worn parts B. Upgrading equipment A. Expensive