| Primary insulation medium | SF₆ gas | Dry air, technical air, nitrogen, or vacuum interruption combined with air insulation | Epoxy or other solid dielectric materials, often combined with vacuum interruption | Depends on the primary switchgear design; digital functions are technology-neutral | Confirm the exact gas or insulating material used and its end-of-life treatment requirements |
| Typical voltage class | 12–24 kV | 12–24 kV | 12–24 kV | 12–36 kV, depending on configuration | Match the rated voltage with the local utility standard and network insulation level |
| Typical continuous current | Up to approximately 630–1,250 A | Up to approximately 630–1,250 A | Up to approximately 630–1,250 A | Up to approximately 630–1,250 A | Verify busbar, switch-disconnector, circuit-breaker, and transformer-feeder ratings separately |
| Typical short-time withstand current | Approximately 12.5–25 kA for 1–3 seconds | Approximately 12.5–25 kA for 1–3 seconds | Approximately 12.5–25 kA for 1–3 seconds | Determined by the underlying switchgear design; commonly 12.5–25 kA | Use the calculated network fault current, not only the nominal equipment rating |
| Load-break switching | Mature | Mature | Mature | Mature | Check duty-cycle compliance and the applicable IEC or regional standard |
| Fault interruption | Gas-insulated load switch or vacuum circuit breaker, depending on design | Typically vacuum circuit breaker for feeder protection | Typically vacuum circuit breaker for feeder protection | Vacuum circuit breaker with electronic protection and remote-control capability | Confirm breaker operating sequence, TRV capability, and relay coordination |
| Greenhouse-gas profile | Contains SF₆, a high-GWP gas | No SF₆ in the primary insulation system | Normally SF₆-free | Depends on the selected primary insulation technology | Request a written declaration covering gas composition, leakage policy, and disposal method |
| Environmental operating range | Commonly around −25°C to +40°C; verify gas-density compensation at low temperature | Commonly around −25°C to +40°C; verify pressure, condensation, and altitude limits | Commonly around −25°C to +40°C; verify thermal ageing and humidity performance | Commonly around −25°C to +40°C; electronic devices may require heaters or climate control | For outdoor or high-altitude sites, request the complete environmental qualification report |
| Altitude capability | Often rated for sites up to 1,000 m without derating; higher altitudes may require correction | Often rated for sites up to 1,000 m without derating; higher altitudes may require correction | Often rated for sites up to 1,000 m without derating; confirm dielectric clearances | Switchgear and communication equipment may have different altitude limits | State the installation altitude in the technical specification before quotation |
| Partial-discharge monitoring | Available through external or integrated sensors | Available through capacitive, HF, UHF, or other sensor arrangements | Useful for detecting insulation deterioration, interfaces, and defects | Strongest when sensors, analytics, and alarms are integrated | Specify detection method, sensitivity, alarm thresholds, and data retention requirements |
| Remote monitoring | Optional; commonly based on auxiliary contacts and RTU integration | Optional to standard, depending on the automation package | Optional to standard, depending on the automation package | Standard design objective; supports status, alarms, measurements, and event logs | Confirm whether remote monitoring is included or priced as an option |
| Automation functions | Remote open/close, interlocking, and protection are available as options | Remote open/close, fault passage indication, and feeder automation are available | Remote open/close, fault passage indication, and feeder automation are available | FLISR, sectionalizing, automatic transfer, and SCADA integration | Define the required operating philosophy, fail-safe behavior, and local override rules |
| Communication protocols | Hardwired I/O, Modbus, IEC 60870-5-101/104, or IEC 61850 depending on package | Modbus, IEC 60870-5-101/104, IEC 61850, or hardwired I/O | Modbus, IEC 60870-5-101/104, IEC 61850, or hardwired I/O | Typically supports multiple protocols, including IEC 61850 and Modbus | Require a protocol map, point list, cybersecurity architecture, and interoperability test |
| Protection functions | Overcurrent and earth-fault protection are common; advanced functions vary | Overcurrent and earth-fault protection are common; arc and directional options may be available | Overcurrent and earth-fault protection are common; advanced functions vary | Overcurrent, earth-fault, directional, sensitive earth-fault, and event recording options | Check relay accuracy, CT/VT technology, coordination curves, and disturbance-recording capability |
| Interlocking | Mechanical and electrical interlocks are widely used | Mechanical and electrical interlocks are widely used | Mechanical and electrical interlocks are widely used | Mechanical interlocks should remain independent of software-based permissions | Require documented prevention of unsafe switching sequences and clear emergency procedures |
| Maintenance profile | Low routine maintenance; SF₆ handling and gas-density checks may be required | Low routine maintenance; vacuum interrupter and mechanism checks remain necessary | Low routine maintenance; inspect mechanisms, interfaces, and condition indicators | Includes switchgear maintenance plus firmware, battery, sensor, and communication checks | Evaluate total maintenance workload rather than only the initial purchase price |
| Space requirement | Compact | Usually larger than SF₆ designs at comparable ratings, depending on insulation approach | Compact to moderate | May require additional low-voltage, RTU, battery, or communication compartments | Confirm footprint, cable-entry direction, rear clearance, and future extension space |
| Operational visibility | Local position indication and mimic diagram are typical | Local position indication and mimic diagram are typical | Local position indication and mimic diagram are typical | Local HMI plus remote status, alarms, measurements, and event history | Require clear local indication even when the communication system is unavailable |
| Cybersecurity requirements | Limited for non-digital configurations; increases with remote access | Limited for non-digital configurations; increases with remote access | Limited for non-digital configurations; increases with remote access | High priority: authentication, segmentation, secure updates, logging, and access control | Include cybersecurity requirements in the purchase specification and factory acceptance test |
| Best-fit applications | Established urban distribution networks, compact substations, and retrofit projects | New distribution networks, green procurement, renewable integration, and environmentally regulated markets | Indoor substations, compact installations, harsh environments, and projects prioritizing SF₆ elimination | Unmanned substations, smart grids, renewable generation, critical facilities, and remote networks |
| Procurement priority | Compactness, installed base, service familiarity, and proven type-test documentation | SF₆-free compliance, dielectric performance, footprint, and local service capability | Material ageing data, partial-discharge performance, repairability, and type-test evidence | Interoperability, automation functionality, cybersecurity, lifecycle support, and data ownership |
