SF6 gas, owing to its superior insulation and arc-quenching properties, serves as the core medium in high-voltage circuit breakers, with its pressure level directly determining the operational safety of the equipment.
Industry-standard pressure parameters are based on an ambient temperature of 20°C (gauge pressure). Temperature variations affect pressure readings, necessitating temperature compensation via density relays to prevent misjudgment.
Pressure standards for circuit breakers across different voltage levels exhibit significant differences, forming a core reference for operational maintenance.
Medium-voltage circuit breakers (7.2-36kV) are widely used, with SF6 rated pressures typically ranging from 0.4 to 0.5 MPa. For instance, 10kV indoor SF6 circuit breakers are often rated at 0.5MPa, while some 40.5kV outdoor models operate at 0.4MPa. The low-pressure lockout threshold is generally set approximately 0.1MPa below the rated pressure, i.e., 0.4MPa (at 20°C).
When the pressure in equipment of this rating falls below the lockout threshold, tripping and closing operations are automatically prohibited to prevent arc extinction failure and component burnout.
High-voltage and ultra-high-voltage circuit breakers (110kV and above) have higher pressure standards. The rated pressure for 110kV GIS circuit breakers is 0.4-0.5MPa, increasing to 0.5-0.6MPa for 220kV models. Ultra-high-voltage 800kV units can reach a rated pressure of 0.6MPa, with a minimum operating pressure not falling below 0.5MPa.
These devices also require differentiation between alarm thresholds and lockout thresholds. For example, a common alarm threshold for 220kV circuit breakers is 0.52MPa, with a lockout threshold of 0.5MPa, enabling proactive mitigation of fault risks.
Two critical points require attention: First, pressure tolerance limits—operating pressure must not fall below 80% of the rated value, and the annual leakage rate must be ≤0.5% (as per national standards). Second, gas replenishment specifications—after leakage, SF6 gas with a purity ≥99.995% must be used for replenishment, with the rate controlled at ≤0.1MPa/min.
After replenishment, allow 24 hours of settling before retesting the pressure. Additionally, in high-altitude regions, pressure must be increased by 8% for every 1000m elevation gain to prevent degradation of insulation and arc-quenching performance.
Xizi Energy is a Barometer manufacturer in China, specializing in precision barometers designed for medium and high voltage switchgear, SF6 load break switches, and gas‑insulated equipment.
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