Product Overview

The JSJB-6/10G indoor oil-immersed voltage transformer is a three-phase medium-voltage voltage transformer designed for 6kV and 10kV AC power systems. It is used to convert primary system voltage into a standardized 100V secondary voltage signal for voltage measurement, energy metering and relay protection circuits.

This series is designed for three-phase systems with a neutral point that is not directly earthed. It is suitable for indoor installation in medium-voltage distribution rooms, metering panels, power measurement circuits and protection systems where an oil-immersed voltage transformer structure is required.

Application Position

The JSJB-6/10G voltage transformer is normally installed in the voltage measurement and protection circuit of a medium-voltage distribution system. It provides secondary voltage signals to meters, relays, control devices and monitoring instruments.

Main Applications

6kV and 10kV medium-voltage power distribution systems
Voltage measurement and indication circuits
Energy metering and power measurement systems
Relay protection voltage input circuits
Indoor substations and distribution rooms
Three-phase systems with neutral points not directly earthed

Key Specifications

Item	Specification
Model series	JSJB-6 / JSJB-10 / JSJB-6/10G
Product type	Three-phase voltage transformer / potential transformer
Installation	Indoor
Insulation structure	Oil-immersed / oil-filled insulation
System voltage class	6kV and 10kV
Rated primary voltage	6000V or 10000V
Rated secondary voltage	100V
Rated frequency	50Hz or 60Hz
Winding connection group	Y/Y0-12
Service condition	Neutral point not directly earthed system
Main function	Voltage measurement, energy metering and relay protection

Application Fit

Suitable For

Indoor 6kV and 10kV AC distribution systems
Three-phase systems with non-directly-earthed neutral points
Voltage metering and monitoring applications requiring 100V secondary output
Relay protection circuits requiring voltage reference signals
Projects requiring an oil-immersed indoor voltage transformer

Not Recommended For

Outdoor exposed installation without a protective enclosure
Low-voltage systems below the medium-voltage design range
Systems with directly earthed neutral requirements unless technically confirmed
Compact switchgear requiring dry-type or epoxy cast-resin voltage transformers
Projects requiring special connection groups or secondary ratios without confirmation

Technical Structure

Component	Description
Core	CR-type iron core composed of three-phase coil units installed on three posts
Winding	Primary and secondary windings for voltage transformation and secondary signal output
Insulation	Oil-immersed insulation structure for dielectric performance and heat dissipation
Oil tank	Cylindrical oil tank with oil-filled structure
Porcelain bushings	Primary outlet from the tank cover through porcelain bushings
Oil level clearance	Distance from oil surface to tank cover is about 10–15mm according to sample data
Secondary wiring	Secondary winding output for metering instruments and relay protection devices

Model Designation

JSJB-6/10G Indoor Oil-Immersed Three-Phase Voltage Transformer for 6kV 10kV Systems Product Type

The JSJB-6/10G model code can be interpreted as follows:

Code	Meaning
J	Voltage transformer
S	Three-phase structure
J	Oil-filled / oil-immersed insulation type
B	Protection type / protection-related design code
6 / 10	Rated voltage grade: 6kV or 10kV
G	Product variant / design code according to manufacturer specification

Technical Data

The following technical data is based on the JSJB-6 and JSJB-10 product sample information. Final parameters should be confirmed according to the approved technical specification, project requirements and nameplate data.

Type	Rated Voltage (V)		Rated Capacity (VA)			Limit Capacity (VA)	Connection Group	Weight (kg)
Type	Primary Winding	Secondary Winding	0.5	1	3	Limit Capacity (VA)	Connection Group	Weight (kg)
JSJB-6	6000	100	80	150	320	640	Y/Y0-12	48
JSJB-10	10000	100	120	200	480	960	Y/Y0-12	105

Technical notes:

The phase sequence for high-voltage and low-voltage sides should correspond to A-B-C and a-b-c; otherwise, accuracy may be affected.
The product can operate under long-term conditions of 115% rated voltage according to the product sample note.
Service condition: neutral point not directly earthed system.

Service Conditions

Altitude: not over 1000m
Ambient temperature: -25°C to +40°C
Relative humidity: less than 85% at 20°C
The product has passed direct vibration testing with an intensity of 0.4g three-sine waves, equivalent to a high seismic intensity condition according to the product sample statement.
Installation environment should be indoor, clean and suitable for oil-immersed medium-voltage equipment.

Installation and Dimensions

The JSJB-6/10G series should be installed according to the approved project drawing, wiring diagram and foundation layout. Before installation, confirm the tank size, porcelain bushing clearance, secondary terminal position, grounding point and required maintenance space.

Terminal and Wiring Notes

JSJB-6/10G Indoor Oil-Immersed Three-Phase Voltage Transformer for 6kV 10kV Systems Terminal Marking

Primary terminals are arranged through porcelain bushings on the tank cover.
Secondary terminals should be connected according to the approved wiring diagram.
The corresponding phase sequence should be A-B-C on the high-voltage side and a-b-c on the low-voltage side.
The winding connection group is Y/Y0-12 according to the technical data table.
Grounding shall be completed according to project electrical safety rules.

Compliance and Testing

The JSJB-6/10G series is designed for medium-voltage voltage transformer applications. Applicable standards, test requirements and acceptance criteria should be confirmed according to the project specification, local grid requirements and final technical agreement.

Typical Routine Tests

Visual inspection and nameplate verification
Ratio verification
Polarity and terminal marking check
Accuracy test at specified burden
Power-frequency withstand voltage test
Insulation resistance test
Oil level and sealing inspection
Connection group verification when required by the project

Engineering Notes

The secondary circuit should not be short-circuited during normal operation.
Phase sequence must be checked before commissioning to avoid measurement error.
The total secondary burden should not exceed the rated capacity for the selected accuracy grade.
The transformer should not be operated beyond the specified service conditions without technical confirmation.
Check oil level, sealing condition, porcelain bushings and grounding connection during inspection.
Installation and commissioning should be performed by qualified electrical personnel.

Selection Guide

How to Select the Rated Voltage Ratio

Select the transformer according to the primary system voltage. For a 6kV system, JSJB-6 is normally selected with a 6000V primary voltage and 100V secondary voltage. For a 10kV system, JSJB-10 is normally selected with a 10000V primary voltage and 100V secondary voltage.

How to Select the Rated Output

The rated output should be selected according to the connected secondary burden. The secondary burden includes meters, relays, monitoring devices, terminal devices and wiring loss. The total burden should not exceed the rated output under the required accuracy class.

How to Select the Accuracy Class

Accuracy class should be selected according to the circuit function. Class 0.5 is commonly used for higher-accuracy metering circuits, class 1 may be used for general measurement, and class 3 is typically used where lower accuracy is acceptable for indication or protection-related auxiliary functions.

How to Confirm the System Neutral Condition

This series is intended for systems where the neutral point is not directly earthed. Before selection, confirm the system grounding method, wiring diagram, and protection scheme to ensure that the selected voltage transformer matches the electrical design.

Ordering Information

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

Product model: JSJB-6, JSJB-10 or JSJB-6/10G
Rated primary voltage and secondary voltage
Rated frequency: 50Hz or 60Hz
Required accuracy grade and rated output
Connection group requirement, such as Y/Y0-12
System neutral grounding method
Installation site condition: indoor, altitude, ambient temperature and humidity
Quantity
Special requirements for drawings, test reports, certificates, nameplate language, packaging or shipping

FAQs

The JSJB-6/10G voltage transformer is used to convert 6kV or 10kV three-phase primary voltage into a standardized 100V secondary voltage signal for voltage measurement, energy metering and relay protection in medium-voltage power systems.

JSJB-6 is designed for 6kV systems with a 6000V primary winding and 100V secondary winding. JSJB-10 is designed for 10kV systems with a 10000V primary winding and 100V secondary winding. Their rated capacities, limit capacity and weight are also different.

The standard secondary winding voltage is 100V. This secondary signal can be connected to compatible voltage meters, energy metering devices, protection relays and monitoring instruments.

Select the rated capacity according to the total connected secondary burden and the required accuracy grade. The secondary burden includes meters, relays, monitoring devices and wiring loss. The total burden should not exceed the rated capacity for the selected accuracy grade.

Y/Y0-12 indicates the winding connection group of the voltage transformer. When applying this transformer in a metering or protection circuit, the wiring diagram, phase sequence and secondary grounding arrangement should follow the project design and approved connection diagram.

The sample description states that this series is used in systems where the neutral point is not directly earthed. For directly earthed neutral systems or special grounding methods, the application should be technically confirmed before selection.

Check that the altitude is not over 1000m, ambient temperature is within -25°C to +40°C, relative humidity is less than 85% at 20°C, and the installation environment is suitable for indoor oil-immersed medium-voltage equipment.

Typical routine tests include ratio verification, polarity check, accuracy test at specified burden, insulation resistance test, power-frequency withstand voltage test, appearance inspection, nameplate verification, oil level inspection, sealing inspection and connection group verification when required.

Please provide the model, primary voltage, secondary voltage, rated frequency, required accuracy grade, rated capacity, connection group, system neutral grounding method, service conditions, quantity and any requirements for drawings, certificates, test reports, nameplate language or packaging.