ZN28-12 Indoor Vacuum Circuit Breaker for 12kV Switchgear

The ZN28-12 indoor vacuum circuit breaker is a 12kV fixed-type VCB widely used in indoor switchgear for medium-voltage distribution. Featuring a side-mounted contact structure and a reliable vacuum interrupter, it is especially suited for retrofitting or upgrading fixed metal-clad cabinets.

🔧 Product Overview

ZN28-12 adopts a spring-operated mechanism (compatible with CD10/CD17 type), with a compact frame and mechanical interlock system. It provides safe circuit interruption for load currents, short-circuit conditions, and transformer protection within 12kV switchgear systems.

Key Advantages:

Fixed installation type (non-withdrawable)
Side terminal structure for cabinet wiring compatibility
Reliable arc extinction in a vacuum without gas
Long mechanical life, up to 10,000 operations
Conforms to IEC 62271-100 and GB 1984 standards

📐 Technical Specifications

Parameter	Value
Rated Voltage	12 kV
Rated Current	630 A / 1250 A
Rated Short-Circuit Breaking	25 kA / 31.5 kA
Mechanical Life	≥ 10,000 operations
Rated Frequency	50 Hz
Lightning Impulse Withstand	75 kV
Operating Mechanism	Spring-operated (manual or motor)
Installation Type	Fixed panel-mounted

🌍 Typical Applications

Medium-voltage indoor switchgear (fixed type)
Industrial distribution panels
Municipal power stations
Backup circuit breakers in oil/gas/petrochemical sites
Switchgear modernization for older cabinets

📊 Case Study: Retrofitting Petrochemical Plant in Turkey (2022)

In 2022, over 200 ZN28-12 VCBs were installed in a fixed-panel upgrade project at a petrochemical facility in Izmir, Turkey.
Results:

Replaced obsolete air-break units without modifying the cabinet structure
Reduced panel downtime during upgrade
Achieved fault interruption under heavy load with minimal wear

Source: Turkish Petrochemical Engineering Journal, 2022

🛠 Installation Notes

Install directly on the base frame of switchgear with matching screw holes;
Ensure correct terminal busbar alignment (side-out type);
Wire secondary control plug to mechanism (CD10/CD17) for tripping/closing;
Test the mechanical operation before energizing.
Regular maintenance includes checking contact wear and spring lubrication every 2 years.