Overview
The BH-0.66B VI protection current transformer is an indoor plastic-case device designed for low-voltage AC systems up to 0.66kV at 50Hz. It delivers a proportional secondary current signal to relay protection systems, monitoring instruments, and low-voltage protective devices during normal, overload, or short-circuit conditions. Unlike metering CTs, this series is engineered specifically for protection applications, ensuring reliable performance under fault-current scenarios.
Featuring a 5P20 accuracy class, the BH-0.66B VI maintains defined composite error limits within its rated accuracy limit factor, enabling precise fault detection and secure relay operation. Its window-type (through-core) structure supports easy installation around busbars or cables in compact switchgear assemblies such as GGD, GCK, and MNS cabinets, making it ideal for industrial and commercial power distribution systems requiring robust protection-class current sensing.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Rated voltage | 0.66kV |
| Rated frequency | 50Hz |
| Protection accuracy class | 5P20 |
| Rated secondary current | 5A or 1A |
| Primary conductor type | Busbar or cable (through-core) |
| Installation environment | Indoor |
| System type | Low-voltage AC |
| Application category | Relay protection, fault detection |
Model Designation
- BH: Indoor enclosed current transformer series
- 0.66: Rated voltage class of 0.66kV
- B: Protection-type / enhanced protection application series
- VI: Design category indicating structural and performance variant
- 50×30, 60×50, 80×60, 100×60: Window aperture dimensions (mm) for busbar or cable routing
Construction
The BH-0.66B VI features an indoor plastic-case design with a through-core (window-type) structure, allowing primary conductors to pass directly through the transformer without electrical connection. The housing is made of flame-retardant, high-insulation thermoplastic material that provides mechanical protection, electrical insulation, and resistance to environmental stress in enclosed switchgear environments. The core is constructed from high-permeability silicon steel laminations optimized for protection-class performance under high overcurrent conditions. Secondary windings are precision-wound and fully encapsulated within the cast-resin insulated assembly, ensuring long-term reliability and dielectric strength suitable for 0.66kV low-voltage systems.
Technical Parameters
Service Conditions
- Installation location: indoor
- System voltage: 0.66kV and below
- Rated frequency: 50Hz
- Ambient temperature: -5°C to +40°C
- Environmental requirements: The installation environment should be free from severe vibration, conductive dust, corrosive gas, explosive medium and heavy pollution.
- Special conditions: For special altitude, humidity, pollution level or cabinet layout requirements, technical confirmation is recommended before ordering.
Technical Parameters
The BH-0.66B VI protection current transformer is designed for low-voltage switchgear applications with standardized electrical ratings and flexible installation options.
Technical Data
| Rated Primary Current (A) |
Rated Secondary Current (A) |
Accuracy Class |
Rated Output (VA) |
|---|---|---|---|
| 200–4000 | 5 / 1 | 5P20 | 10 |
Installation & Wiring
Outline Dimensions
The BH-0.66B VI series features a large-window design for through-core installation on busbars or cables. Key dimensions include window size (a1 × b1), overall width (A), depth (B), height (H), and effective mounting height (h). All dimensions are in millimeters and provided for reference during cabinet layout planning. Final dimensions must be verified against the approved engineering drawing prior to production or bulk ordering.
Wiring Diagram
Connect the secondary terminals according to the polarity markings (typically marked with P1/P2 on the primary side and S1/S2 on the secondary side) and the project-specific wiring diagram. Ensure correct phasing and secure terminal connections. The secondary circuit must never be left open when the primary conductor is energized, as this can generate dangerous high voltages and damage the transformer.
Selection & FAQs
Selection Guide
- Select the 200A–4000A primary ratio from maximum load current and the protection coordination study.
- Choose a 1A or 5A secondary that matches the relay input and secondary cable length.
- Confirm that the 5P20, 10VA specification meets the relay accuracy-limit and total-burden requirements.
- Select the window size from conductor dimensions, insulation clearance, and cabinet layout.
- Verify fault withstand, polarity, mounting, grounding, terminal access, and a safe secondary-shorting arrangement.
Frequently Asked Questions
Q1: Can the BH-0.66B VI current transformer be installed outdoors?
No, it is strictly designed for indoor installation. The environment must be free from severe vibration, conductive dust, and corrosive gases. Please consult our team for alternative solutions.
Q2: Which accuracy class does this low-voltage protection CT feature?
It features a 5P20 accuracy class, ensuring reliable performance during fault conditions. The rated output is 10VA with secondary currents of 5A or 1A.
Q3: Which maximum system voltage is supported by the BH-0.66B model?
The maximum rated system voltage is 0.66kV and below, operating at a rated frequency of 50Hz. It is ideal for low-voltage switchgear protection applications.
Q4: How can we order custom primary current ratings above 4000A?
Standard ratings cover 200A to 4000A. Technical parameters beyond this range can be confirmed through a specific technical agreement between the manufacturer and purchaser.
Q5: What special environmental conditions require technical confirmation before ordering?
Special altitude, humidity, pollution levels, or unique cabinet layout requirements need prior verification. We recommend technical confirmation with our engineering team before placing your order.
Q6: Are there specific applications for the BH-0.66B VI protection transformer?
This low-voltage protection current transformer is specifically designed for indoor switchgear applications. It provides reliable current measurement and protection for systems up to 0.66kV.
Q7: How does the 5P20 accuracy class handle short-circuit currents?
The 5P20 class ensures the transformer maintains accuracy up to 20 times the rated primary current during faults. This guarantees reliable operation for low-voltage protection relays.