I. Product Overview and Basic Parameters
1. Model Definition
KYN: Refers to metal-clad withdrawable indoor switchgear ("K" stands for clad, "Y" for withdrawable, and "N" for indoor).
28: Design serial number (derived from ABB technology, representing a mainstream center-positioned switchgear).
12: Rated voltage of 12 kV.
2. Core Functions

It is used in 12 kV three-phase AC power systems to undertake tasks such as power distribution, control, protection, and monitoring. It supports ring network power supply and terminal power distribution, meeting the needs of scenarios such as substations, industrial and mining enterprises, and commercial buildings.

II. Structural Design Features
1. Cabinet Layout
Fully Enclosed Metal Cladding: The cabinet body is welded from cold-rolled steel plates, achieving a protection rating of IP2X (protection against solid foreign objects > 12.5 mm). The busbar chamber is independently isolated, reducing the risk of phase-to-phase short circuits.
Modular Units: It adopts a center-positioned design (withdrawable circuit breaker). Core components such as circuit breakers and current transformers can be removed, facilitating maintenance and replacement.
2. Insulation and Arc Extinguishing Technologies
The main circuit can be equipped with either a vacuum arc extinguishing chamber or SF6 gas insulation (KYN28-12 may continue to use SF6, but the recent trend is to replace it with solid insulation).
The insulation medium must meet a power frequency withstand voltage of 42 kV (between phases)/48 kV (at isolation disconnector), and a lightning impulse withstand voltage of 75 kV/85 kV.
3. Operating Mechanism and Interlocking
Spring Energy Storage Mechanism: Supports manual/electric opening and closing, with a mechanical life exceeding 10,000 cycles for the circuit breaker.
"Five-Prevention" Interlocking System: It forcibly prevents accidents such as mis-opening/closing of switches, operation under load, and closing of grounding switches while energized.

Parameter    Value    Basis
Rated Voltage    12 kV    
Rated Current    630 A - 3,150 A (selectable in sections)    
Short-Time Withstand Current (4 s)    20 - 40 kA    
Peak Withstand Current    50 - 100 kA    
Mechanical Life    Circuit breaker ≥ 10,000 cycles; isolating switch ≥ 2,000 cycles    
Protection Rating    IP2X (enclosure)    

IV. Applicable Environment and Settings
Environmental Adaptability:
Temperature: -25°C to +40°C (extendable to -45°C with special design).
Altitude: ≤ 1,000 m (customized for high-altitude models, supporting up to 4,000 m).
Humidity: Daily average ≤ 95%, with no condensation.
Typical Application Scenarios:
Ring network nodes in urban distribution networks, underground substations (e.g., in subways and tunnels), industrial and mining substations with limited space, and integrated box-type substations.

V. Intelligent Control Functions (Optional Expansion)
Intelligent Interfaces:
Reserved sensor installation positions support the addition of:
Wireless temperature measurement devices (to monitor contact/busbar temperatures).
Microcomputer protection devices (for overcurrent, instantaneous, and ground fault protection).
Remote monitoring modules (supporting telemetry, telesignaling, and telecontrol, and integration into SCADA systems).

VI. Selection and Maintenance Recommendations
1. Selection Considerations:
For scenarios with large short-circuit capacities (> 25 kA), prioritize vacuum circuit breaker solutions.
For environments with strict environmental requirements, recommend solid insulation as an alternative to SF6.
2. Maintenance Points:
SF6 cabinets require regular gas pressure checks to prevent insulation performance degradation.
Solid insulation cabinets are maintenance-free but require periodic verification of mechanical interlocking.