Centre Post Isolator– Turn & Twist Design (Double Break Type)
In electrical substations, safe isolation, maintenance safety, and operational reliability depend heavily on one critical equipment — the Centre Post Isolator.
Commonly known in the industry as the Turn & Twist Isolator or Center Rotating Isolator, its correct technical name as per standards is:
Double Break Centre Post Isolator
This isolator type is widely used in 33kV, 66kV, 110kV, 132kV, and 220kV substations across transmission and distribution networks.
What is a Centre Post Isolator?
A Centre Post Isolator is a double break, horizontal rotating type isolator where the moving contact rotates on its center post insulator. During operation, the top assembly turns and twists, creating a clear and visible isolation gap on both sides.
This design provides:
- Positive visual isolation
- Smooth mechanical operation
- Balanced contact pressure
- High reliability during switching
- Long service life with minimal maintenance
Why It Is Called “Turn & Twist” Design?
Unlike pantograph or vertical break isolators, the centre post isolator operates with a rotational movement.
• The central post rotates
• The moving blade twists away from the fixed contacts
• Two air gaps are created (Double Break)
• Ensures higher insulation safety
This turning and twisting motion is the reason it is popularly called the Turn & Twist Isolator in substations.
Key Features of Centre Post (Turn & Twist) Isolator
- Double break isolation for enhanced safety
- Uniform contact alignment on both ends
- High short-time withstand current capability
- Suitable for motorized and manual operation
- Ideal for outdoor substations
- Requires less operating space compared to other designs
- Excellent performance in harsh environmental conditions
Voltage Classes Where It Is Commonly Used
Centre Post Isolators are most preferred in:
- 33kV Substations
- 66kV Substations
- 110kV Substations
- 132kV Substations
- 220kV Substations
Importance of Proper Contact Alignment
One of the most critical factors in centre post isolators is perfect alignment between fixed and moving contacts.
Poor alignment can lead to:
This design provides:
- Heating at contact points
- Reduced current carrying capacity
- Contact burning
- Failure during load conditions
At Balaji Isolators, special attention is given to:
Precise fixed and moving contact alignment, ensuring low resistance path and superior current conduction.
Applications in Substations
Centre Post Isolators are installed for:
- Line isolation
- Bus isolation
- Transformer isolation
- Maintenance safety during shutdown
- Interlocking with circuit breakers (Castle Key Interlock)
Why Centre Post Isolator is Preferred Over Other Types?
| Feature | Centre Post Isolator | Other Types |
|---|---|---|
| Space Requirement | Compact | Larger space needed |
| Contact Pressure | Uniform | Uneven in some designs |
| Maintenance | Low | Moderate |
| Mechanical Stability | High | Moderate |
| Visual Isolation | Excellent | Good |
Centre Post Isolator Manufactured by Balaji Engineers Isolators Pvt. Ltd.
Balaji Engineers Isolators Pvt. Ltd. (Balaji Isolators) is one of India’s leading manufacturers and exporters of Centre Post Isolators for substations.
Our isolators are widely used in:
- Transmission Substations
- Distribution Substations
- Solar & Wind Substations
- Hydropower Projects
- Steel Plants & Industrial Power Systems
- Electricity Board Approved Projects & RDSS Tenders
Available Voltage Range
Balaji Isolators manufactures Centre Post Isolators for:
11kV | 22kV | 33kV | 66kV | 110kV | 132kV | 220kV
Watch Our Working Video of Centre Post Isolator (Turn & Twist Design)
To understand the actual turning and twisting operation, watch our detailed working video:
VIDEO LINK 👉 –https://youtu.be/t26_0Ytl7Qs?si=lIquS2NrDsoMtweb
This video clearly demonstrates the double break action and smooth rotational movement of the centre post isolator.
Frequently Searched by people
This blog answers common search queries like:
What is Centre Post Isolator?
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Double Break Isolator working
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Substation isolator types and working
The Centre Post (Turn & Twist) Isolator is one of the most reliable and widely used isolators in substations due to its:
- Double break safety
- Mechanical simplicity
- Excellent contact alignment
- Long operational life
When manufactured with precision and proper alignment, it delivers safe isolation and dependable performance for decades.
For high-quality, precisely aligned Centre Post Isolators, Balaji Isolators stands as a trusted name in the power industry.
