Reliability of Switchgear
Simplicity means fewer components. According to the principle that system reliability equals the product of individual component reliabilities, fewer parts lead to higher reliability.
For PT trolleys in air-insulated switchgear, a simplified drawer-type design is adopted. On the cable compartment side, the PT trolley eliminates the need for a 200mm chassis to rack in and dispenses with blossom contacts. Instead, it uses the PT’s built-in fuse and striker mechanism, making direct contact with the busbar. The secondary plug connects directly, achieving full insulation and sealing—simple, safe, reliable, and easy to maintain. For intelligent switchgear, intelligence does not necessarily require a large display screen.
True intelligence lies in simplified hardware, leveraging software for measurement and protection calculations. The core is protection functionality, which must be prioritized. It must promptly analyze various circuit faults—such as short circuits, ground faults, overvoltage, undervoltage—and issue timely commands to interrupt the circuit for effective protection.Second is power quality monitoring. After ensuring safe and controllable power, the focus shifts to efficiency—timely compensation of reactive power and other parameters, automatic switching, and fine-grained control to ensure efficient energy use.
Equipment health monitoring is largely auxiliary. The primary purpose of monitoring health is to prevent unexpected outages. Continuous monitoring ensures equipment remains in good condition, enabling early intervention and shifting from periodic, reactive maintenance to proactive, targeted repairs.
Why online temperature monitoring? There are many reasons—design, installation, and management. The key concern is vacuum circuit breaker trolley contacts. Since the circuit breaker and switchgear are separate components, misalignment of primary contacts can occur, leading to poor contact and excessive heating. Why not use fixed-mounted circuit breakers with disconnectors? Disconnectors have fixed relative positions of moving and stationary contacts within the same body, which is advantageous for maintaining good contact.
Fixed-mounted circuit breakers are viable only if the breaker itself is highly reliable, maintenance-free, and requires no servicing within its service life, thus ensuring overall system reliability. All these functions rely on sensors and measuring devices, whose installation must not compromise equipment functionality. Adding smart components should not reduce equipment reliability.
Gas-insulated switchgear allows integration of multiple functions. With advances in sealing technology and manufacturing, a single gas compartment can now accommodate multiple bushings for metering PTs, supply PTs, and cable in/out connections. Removable designs allow individual components to be withdrawn for maintenance, but this is often a compromise due to insufficient product quality. If product quality is assured and service life meets expectations, integrated designs are preferable.
We don’t need to aim for 40 years; even achieving 10 years of maintenance-free operation would be a significant improvement. As maintenance personnel point out, while mechanical life of circuit breakers is claimed at 10,000 operations, real-world performance often reaches only 3,000. Rather than spending money on intelligent health monitoring devices, it is better to invest in improving product quality to genuinely extend lifespan and enhance reliability.
Outdoor switchgear should be designed for direct outdoor use—simple and reliable. Placing indoor switchgear inside a separate outdoor enclosure does not make it outdoor switchgear. For outdoor installations without the need for an operating corridor, the switchgear’s side panels can serve directly as the outdoor enclosure, reducing cost, weight, and footprint. The new power system demands local integration, consumption, and isolation of green, clean energy, thus requiring flexible and simple distribution equipment. Self-powered, maintenance-free systems with distribution automation, remote control, measurement, regulation, and signaling are ultimately about convenience, flexibility, and minimal special design.
Control and protection methods should match the application: where a load switch-fuse combination suffices, a circuit breaker is unnecessary.
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