BH-0.66B VI Protection Current Transformer, Low Voltage Switchgear

Product Overview

The BH-0.66B VI protection current transformer is an indoor plastic case current transformer designed for low-voltage AC systems with rated voltage up to 0.66kV and rated frequency of 50Hz. It is mainly used in relay protection and current monitoring circuits, providing a proportional small-current signal to protection relays, monitoring instruments, and low-voltage protection devices during normal operation, overload conditions, or short-circuit fault conditions.

Compared with general metering current transformers, the BH-0.66B VI series is designed for protection applications. It supports protection accuracy such as 5P20, helping the transformer maintain the required accuracy within the specified protection range and provide reliable current signal output for fault detection and protection operation.

Product Type

Item	Specification
Product name	Protection Current Transformer
Model series	BH-0.66B VI / BH0.66B(VI)
Product structure	Indoor plastic case, window-type / through-core structure
Rated voltage class	0.66kV and below low-voltage AC system
Rated frequency	50Hz
Protection accuracy class	5P20
Rated secondary current	5A or 1A
Installation location	Indoor
Typical applications	Relay protection, overload protection, short-circuit fault detection, low-voltage switchgear monitoring

Product Display

Product Shows

Main Applications

Low-voltage AC distribution systems rated up to 0.66kV
Relay protection circuits in complete electrical cabinets
Overload and short-circuit current signal acquisition
Low-voltage switchgear such as GGD, GCK, MNS and similar cabinet systems
Power distribution panels, control cabinets and industrial electrical systems
Current monitoring circuits requiring a protection-class current transformer

Key Technical Features

Protection-class design: Designed for relay protection and current monitoring under overload or short-circuit fault conditions.
5P20 accuracy class: Suitable for protection circuits requiring defined composite error performance within the rated accuracy limit factor.
Large-window structure: Available with 50×30, 60×50, 80×60 and 100×60 apertures for different busbar or cable layouts.
Flexible installation: Supports bottom plate fixing, busbar fixing and through-core cable installation inside low-voltage cabinets.
Indoor plastic case: The enclosed housing supports insulation, mechanical protection and compact cabinet assembly.

Working Principle

The BH-0.66B VI current transformer operates according to electromagnetic induction. The primary conductor, busbar or cable passes through the CT window and acts as the primary circuit. When current flows through the primary conductor, magnetic flux is generated in the core, and the secondary winding outputs a proportional current signal to the connected relay or monitoring device.

For protection applications, the transformer must provide a usable current signal under fault-current conditions. The 5P20 protection class indicates that the CT is designed for protection service and can support relay operation within the specified accuracy limit factor under rated conditions.

Model Designation

The model code can be interpreted as follows:

Code	Meaning
BH	Indoor enclosed current transformer series
0.66	Rated voltage class: 0.66kV
B	Protection-type / enhanced protection application series
VI	Design category / product structure series
50×30, 60×50, 80×60, 100×60	Window aperture size for busbar or cable installation

Technical Data

Item	Specification
Rated voltage	0.66kV / 660V
Rated frequency	50Hz
Rated primary current	200A to 4000A according to catalogue data; wider project ratios can be confirmed by technical agreement
Rated secondary current	5A or 1A
Protection accuracy class	5P20
Rated output	10VA
Ambient temperature	-5°C to +40°C
Installation method	Bottom plate fixing, busbar fixing, or through-core cable installation
Applicable standards	GB 1208-2006, IEC 60044-1:2003; project-specific requirements can be confirmed by agreement

Rated Current, Accuracy and Output Reference

Rated Primary Current (A)	Rated Secondary Current (A)	Accuracy Class	Rated Output (VA)
200–4000	5 / 1	5P20	10

Note: Technical parameters beyond the above range can be confirmed through technical agreement between manufacturer and purchaser.

Service Conditions

Installation location: indoor
System voltage: 0.66kV and below
Rated frequency: 50Hz
Ambient temperature: -5°C to +40°C
The installation environment should be free from severe vibration, conductive dust, corrosive gas, explosive medium and heavy pollution.
For special altitude, humidity, pollution level or cabinet layout requirements, technical confirmation is recommended before ordering.

Standards and Compliance

The BH-0.66B VI protection current transformer is designed for low-voltage protection current transformer applications and can be supplied according to GB 1208-2006, IEC 60044-1:2003 and customer-specific technical requirements. For projects requiring updated standards or special testing items, the final requirements should be confirmed in the technical agreement.

Installation and Dimensions

The BH-0.66B VI series uses a large-window structure for busbar or cable through-core installation. The following dimensions are for product selection and cabinet layout reference. Final dimensions should be confirmed according to the approved drawing before production or batch ordering.

Available Window Sizes and Overall Dimensions

Model	a1	b1	A	B	H	h
BH0.66B(VI) 50×30	52	32	111	80	151	135
BH0.66B(VI) 60×50	64	56	129	85	181	165
BH0.66B(VI) 80×60	84	66	164	85	181	170
BH0.66B(VI) 100×60	104	66	189	85	185	170

Unit: mm. Final dimensions are subject to confirmed drawing and selected specification.

Installation and Safety Notes

Confirm the CT model, current ratio, protection class, rated output and aperture size before installation.
Check that the busbar or cable size matches the selected CT window dimensions.
Install the CT using bottom plate fixing, busbar fixing or through-core cable installation according to the cabinet layout.
Connect the secondary terminals according to the polarity marks and project wiring diagram.
The secondary circuit of a current transformer must not be open-circuited when the primary circuit is energized.
Secondary wiring, grounding and terminal protection should comply with the project specification and local electrical regulations.
Installation and maintenance should be performed by qualified electrical personnel.

Ordering Information

Please provide the following information when ordering or requesting a quotation:

Product model: BH-0.66B VI / BH0.66B(VI)
Window size: 50×30, 60×50, 80×60 or 100×60
Rated primary current and rated secondary current
Protection accuracy class, such as 5P20
Rated output / burden in VA
System frequency and installation environment
Installation method: bottom plate, busbar or cable through-core installation
Quantity and cabinet application
Special requirements for terminal layout, labels, drawings, inspection documents, certificates or packaging

Selection Guidelines

Confirm protection purpose: Select BH-0.66B VI when the CT is used for relay protection, overload monitoring or short-circuit fault detection.
Confirm system voltage: The product is suitable for low-voltage AC systems rated up to 0.66kV.
Confirm current ratio: Select the primary current according to the normal operating current and expected fault-current range of the circuit.
Confirm protection class: Use protection accuracy such as 5P20 when the relay circuit requires defined performance under fault conditions.
Confirm rated burden: The total burden of relay, instrument and wiring should not exceed the rated output of the CT.
Confirm aperture and installation method: Match the CT window size and mounting method with the cabinet busbar or cable layout.

FAQs

The BH-0.66B VI current transformer is mainly used for relay protection and current monitoring in low-voltage distribution systems. It provides a secondary current signal to protection devices during normal operation, overload or short-circuit fault conditions.

A metering CT is mainly designed for accurate current measurement under normal load conditions, while a protection CT is designed to provide a reliable signal to protective devices during fault-current conditions and to avoid premature saturation within its specified protection range.

5P20 is a protection accuracy class. It indicates that the current transformer is designed for protection use and maintains the specified composite error performance up to the rated accuracy limit factor under defined conditions.

The BH-0.66B VI series is suitable for low-voltage AC systems rated up to 0.66kV.

The secondary current can be selected as 5A or 1A, depending on the project requirement, relay input specification and secondary circuit wiring distance.

Available window sizes include 50×30, 60×50, 80×60 and 100×60. The final aperture should be selected according to the busbar or cable layout inside the cabinet.

The current ratio should be selected according to the normal operating current, relay setting range and expected fault-current level. For protection circuits, the CT must provide a usable secondary signal under fault conditions without saturating too early.

When the primary circuit is energized, the CT secondary circuit must not be open-circuited. An open secondary circuit may generate high voltage, damage insulation, affect product safety and create risk for maintenance personnel.

This model is designed for indoor installation. Outdoor use requires a current transformer structure suitable for outdoor environmental conditions, including moisture, UV exposure, pollution and temperature variation.

Please provide the model, window size, primary current, secondary current, protection accuracy class, rated output, system frequency, installation method, quantity and any special requirements for terminals, drawings, certificates, labeling or packaging.