| Vacuum Interrupter | Sealed vacuum bottle with metal contacts; commonly applied in medium-voltage switchgear from 3.6 kV to 40.5 kV. | The vacuum provides a high dielectric-strength medium. After contact separation, the arc is extinguished near the next current zero. | Long electrical life, low contact erosion, compact dimensions, and no oil or insulating gas handling. | Type and routine tests are generally specified under IEC 62271-100 and applicable Chinese GB/T standards. |
| Rated Voltage Classes | Common medium-voltage classes include 12 kV, 24 kV, and 40.5 kV. The actual rating depends on the network and switchgear design. | The interrupter, insulation system, clearances, and creepage distances are coordinated for the selected system voltage. | Supports distribution networks, industrial substations, renewable-energy collection systems, and rail-transit applications. | Rated voltage and insulation levels are selected according to the relevant equipment specification and grid requirements. |
| Rated Frequency | 50 Hz is the normal power-system frequency used in mainland China. | The breaker is designed for the thermal, mechanical, and dielectric stresses associated with the system frequency. | Ensures compatibility with standard Chinese distribution and industrial power networks. | Frequency, current, and temperature-rise tests are included in equipment qualification programs. |
| Spring Operating Mechanism | Stored-energy mechanism using closing and opening springs; manual and motor-charged versions are common. | A motor or manual handle stores mechanical energy. The release system transfers this energy rapidly to the moving contact. | Reliable operation, straightforward maintenance, and suitability for automatic reclosing and remote control. | Mechanical endurance and operating-sequence tests are performed according to the applicable breaker standard. |
| Permanent-Magnet Actuator | Electromagnetic actuator that holds the breaker in an open or closed position without continuously energizing a holding coil. | A magnetic latching system controls the moving contact with electronic or electromagnetic release commands. | Fewer moving parts, low operating noise, reduced auxiliary power consumption, and stable timing performance. | Control-voltage tolerance, operating-time, endurance, and fail-safe tests are normally required. |
| Contact Material and Contact Design | Copper-chromium contact materials are widely used in modern medium-voltage vacuum interrupters. | The contact geometry and material are engineered to control arc behavior, contact erosion, and dielectric recovery. | Improves interruption capability, contact life, and resistance to welding under short-circuit conditions. | Short-circuit interruption, contact-resistance, and electrical-endurance tests verify performance. |
| Embedded-Pole Construction | The vacuum interrupter is molded or sealed into an epoxy-insulated pole assembly. | The solid insulation supports the interrupter and reduces exposure to dust, moisture, and mechanical impact. | Compact structure, improved environmental protection, reduced maintenance, and consistent insulation distances. | Power-frequency withstand, lightning-impulse withstand, partial-discharge, and environmental tests may be applied. |
| Solid Insulation and Epoxy Encapsulation | Cast-resin insulation is commonly used around the interrupter, operating rod, and primary conductive parts. | Epoxy resin provides mechanical support and electrical insulation between energized components and earth. | Useful for compact switchgear and harsh indoor or outdoor operating environments when properly sealed. | Insulation coordination, partial-discharge, thermal-cycling, and aging evaluations are relevant validation methods. |
| Arc-Control Contact Geometry | Axial-magnetic-field or transverse-magnetic-field contact structures may be used depending on the interrupter design. | Magnetic fields distribute the vacuum arc over the contact surface and help limit localized heating. | Supports higher interruption ratings and helps reduce contact wear during fault-current interruption. | Interruption tests are conducted at the specified short-circuit current and transient-recovery-voltage conditions. |
| Electronic Protection and Control | Protection relays, trip coils, undervoltage releases, auxiliary contacts, and remote-control interfaces are commonly integrated. | Protection equipment detects abnormal current or voltage conditions and sends a trip command to the operating mechanism. | Enables overcurrent protection, earth-fault protection, automation, remote monitoring, and interlocking. | Control circuits are checked for insulation, dielectric strength, EMC behavior, trip reliability, and functional logic. |
| Mechanical and Electrical Interlocking | Interlocks may prevent incorrect racking, grounding-switch operation, door opening, or breaker closing. | Mechanical linkages and electrical permissive circuits block unsafe operating sequences. | Reduces the risk of accidental energization, equipment damage, and maintenance-related incidents. | Functional interlock checks are included in factory acceptance and commissioning procedures. |
| Short-Circuit Interruption Capability | Typical medium-voltage ratings vary by product configuration; 16 kA, 25 kA, 31.5 kA, and 40 kA are common rating points. | The interrupter separates contacts and extinguishes the fault arc while withstanding the transient recovery voltage. | Provides fault clearance for distribution feeders, transformers, motors, and industrial bus sections. | Short-circuit type tests must be performed at the declared voltage, current, power factor, and operating sequence. |
| Lightning-Impulse and Power-Frequency Insulation | Insulation levels depend on the rated voltage class and installation conditions. | Insulation coordination ensures that internal clearances and external surfaces withstand temporary and transient overvoltages. | Improves reliability during lightning events, switching surges, and abnormal system conditions. | Power-frequency withstand and lightning-impulse withstand tests are standard insulation checks. |
| Temperature Monitoring | Optional sensors may monitor busbar joints, cable connections, and primary conductive interfaces. | Temperature sensors identify abnormal heating caused by loose connections, overloads, or increased contact resistance. | Supports condition-based maintenance and helps prevent thermal damage before failure occurs. | Sensor accuracy, alarm thresholds, communication functions, and thermal performance should be verified on the final assembly. |
| Environmental and Maintenance Design | Vacuum interruption eliminates oil replacement and reduces the need for arc-medium maintenance. | The sealed interrupter contains the interrupting medium, while the operating mechanism is serviced through mechanical inspections. | Lower routine maintenance workload, cleaner operation, and reduced fire risk compared with oil circuit breakers. | Environmental protection, mechanical endurance, corrosion resistance, and maintenance procedures depend on the final enclosure design. |