Paunsa ang Pili sa usa ka High-Voltage Circuit Breaker: Key Parameters & Expert Guide

Ang pagpili og high-voltage circuit breaker usa ka importante nga gawasn nga direkta nga nakaapekto sa seguridad, estabilidad, ug reliable nga operasyon sa mga sistema sa kuryente. Ania ang key technical specifications ug considerations sa pagpili og high-voltage circuit breakers—detailed, comprehensive, ug professional.

Core Selection Process and Key Considerations

I. Basic Parameters Matching System Conditions (The Foundation)

Kini ang fundamental nga requirement—kailangan buhata ang full match sa characteristics sa installation point.

• Rated Voltage (Uₙ)

• Requirement: Ang rated voltage sa breaker kailangan mas dako o equal sa maximum operating voltage sa iyang installation location.

• Example: Sa usa ka 10kV system diin ang maximum operating voltage mao ang 12kV, dapat ipili ang 12kV rated voltage breaker.

• Rated Current (Iₙ)

• Requirement: Ang rated current sa breaker kailangan mas dako o equal sa maximum continuous operating current sa circuit.

• Calculation: Isipon ang normal load current, overload capacity, potential future expansion, ug isama ang safety margin. Iwasan ang "undersized breaker for large load" o excessive investment.

• Rated Frequency (fₙ)

• Kinahanglan magmatch sa power system frequency—50Hz sa China.

II. Critical Short-Circuit Performance Parameters (The Capability Test)

Kini nga mga parameters nagsukol sa interrupting ug closing capabilities sa breaker ug kinahanglan ipili batas sa system short-circuit calculations.

• Rated Short-Circuit Interrupting Current (Iₖ)

• Definition: Ang maximum RMS value sa short-circuit current nga ma-reliably interrupt ang breaker sa rated voltage.

• Requirement: Kini ang most critical parameter. Ang rated interrupting current sa breaker kailangan mas dako o equal sa maximum prospective short-circuit current sa installation point (typical ang three-phase short-circuit current calculated from system studies).

• Note: Isipon ang potential growth sa system short-circuit capacity over the breaker's service life.

• Rated Short-Circuit Making Current (Iₘᶜ)

• Definition: Ang maximum peak short-circuit current nga ma-successfully close onto ang breaker.

• Requirement: Typical 2.5 times the RMS value of the rated interrupting current (standard value). Kini kinahanglan mas dako sa maximum prospective short-circuit current peak aron matagantanan ang enormous electrodynamic forces during closing.

• Rated Short-Time Withstand Current (Iₖ) / Thermal Withstand Current

• Definition: Ang RMS value sa short-circuit current nga makapadayon ang breaker sa specified duration (e.g., 1s, 3s, 4s).

• Requirement: Kinahanglan mas dako o equal sa prospective short-circuit current RMS value sa installation point. Nagsukol kini sa ability sa breaker nga matagantanan ang thermal effects sa short-circuit currents.

• Rated Peak Withstand Current (Iₚₖ) / Dynamic Withstand Current

• Definition: Ang peak value sa first cycle sa short-circuit current nga makapadayon ang breaker.

• Requirement: Kinahanglan mas dako o equal sa prospective short-circuit current peak. Nagsukol kini sa mechanical strength sa breaker under electromagnetic forces during a short circuit.

III. Insulation and Environmental Protection Requirements

• Insulation Medium Type (Core Technology Choice)

• Advantages: Extremely high interrupting capacity, excellent performance.

• Disadvantages: SF₆ is a potent greenhouse gas; requires high sealing integrity; leakage risk; relatively complex maintenance.

• Application: Primarily used in high-voltage, high-capacity systems (≥35kV) or special environments (e.g., extremely cold regions).

• Recommendation: In the 10–35kV range, unless special requirements exist, prefer vacuum breakers for their maturity and environmental benefits.

• Advantages: Strong arc-quenching capability, long service life, compact size, low maintenance, no explosion risk, environmentally friendly. Suitable for frequent switching applications (e.g., arc furnaces, motor switching).

• Application: The mainstream and preferred choice for 10–35kV voltage levels today.

• Vacuum Circuit Breaker (e.g., VS1, ZN63):

• SF₆ (Sulfur Hexafluoride) Circuit Breaker:

• External Insulation

• Creepage Distance: Select bushings and insulators with sufficient creepage distance based on the site’s pollution level (I–IV), to prevent pollution flashover.

• Condensation: For indoor switchgear in high-humidity or large temperature-differential environments prone to condensation, select breakers or switchgear equipped with heaters or anti-condensation devices.

IV. Mechanical Characteristics and Operating Mechanism

• Operating Mechanism Type

• Spring-Operated Mechanism: Most common, mature technology, high reliability, no external power source required. The preferred choice in most cases.

• Permanent Magnet Actuator (PMA): Fewer parts, simpler structure, theoretically higher reliability and faster operation. However, field repair is difficult after failure—usually requires full replacement.

• Electromagnetic Operating Mechanism: Used in older models; requires high-power DC supply and large closing current; gradually being phased out.

• Mechanical and Electrical Endurance

• Mechanical Endurance: Number of open-close operations without current (typically 10,000–30,000+ cycles).

• Electrical Endurance: Number of normal interruptions at rated current (e.g., E2 class: 10,000 operations; C2 class: 100 short-circuit interruptions). For applications requiring frequent switching of capacitor banks, reactors, or motors, select breakers with high electrical endurance.

• Breaking Time and Close-Open Time

• For systems requiring coordination with relay protection or fast auto-reclosing, pay attention to the breaker’s total clearing time (from initiation of trip command to arc extinction).

V. Secondary Control and Auxiliary Functions

• Control Voltage: Must match the substation’s DC power system (commonly DC 110V or DC 220V).

• Auxiliary Contacts: Quantity must meet requirements for measurement, signaling, and interlocking.

• Interlocking Functions: Must include reliable anti-pumping circuits, closing/tripping interlocks, etc., to ensure safety.

• Smart Interface: Modern breakers often include intelligent controllers providing electrical parameter measurement, fault recording, condition monitoring, and support for communication protocols (e.g., IEC 61850), facilitating integration into integrated automation systems.

VI. Installation, Environment, and Brand/Service

• Installation Type: Fixed or withdrawable (drawer-type)? Must match the switchgear model and structure.

• Environmental Conditions: Consider altitude, ambient temperature, humidity. At high altitudes, breaker ratings must be derated.

• Brand and After-Sales Service: Choose reputable brands with proven quality, and consider spare parts availability, technical support, and after-sales service.

VII. Summary: Selection Checklist

• Confirm system parameters: system voltage, frequency, maximum operating current.

• Calculate short-circuit current: obtain prospective RMS and peak short-circuit current at the installation point (provided by power system design).

• Match breaker capabilities: ensure rated interrupting current, making current, and dynamic/thermal withstand currents all exceed calculated values.

• Select type: prefer vacuum breakers for 10–35kV; confirm operating mechanism (spring mechanism preferred).

• Verify external insulation: confirm creepage distance based on pollution level.

• Consider special needs: frequent operation? Smart interface? Special environmental conditions?

• Brand and commissioning: select reliable brands; during acceptance, focus on factory test reports (especially main circuit resistance and mechanical characteristics).

By following these steps, you can select a safe, suitable, and reliable high-voltage circuit breaker for your system. For critical applications, it is strongly recommended to jointly review and finalize the selection with professional electrical engineers or design institutes.