Overview
The LZZBJ9-12/150b/2S is an indoor, dry-type, fully enclosed support-type current transformer with epoxy resin cast insulation. It is rated for 10kV, 11kV, and 12kV class medium-voltage AC systems, with a highest system voltage of 12kV and a standard insulation level of 12/42/75kV.
Designed for accurate current measurement, energy metering, feeder monitoring, and relay protection in metal-clad switchgear, this CT complies with IEC standards for 12kV indoor applications. Its compact 150b structure suits space-constrained layouts, while the 2S secondary configuration enables dual-core arrangements for combined metering and protection functions.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV, 11kV, 12kV |
| Highest voltage for equipment | 12kV |
| Insulation level | 12/42/75kV |
| Rated frequency | 50Hz / 60Hz |
| Secondary current | 1A or 5A |
| Phase | Single phase |
| Installation type | Indoor support-type |
| Insulation material | Epoxy cast-resin |
| Structure | Fully enclosed, dry-type |
| Secondary configuration | 2S (two secondary windings) |
| Nominal width code | 150b |
| Application | Metering, measurement, protection |
Model Designation
- L: Current transformer
- Z: Pillar / post type structure
- Z: Epoxy pouring / cast-resin insulation
- B: With protection level
- J: Strengthened design
- 9: Design serial number
- 12: Maximum operating voltage / 12kV class
- 150b: Nominal width / structure dimension code
- 2S: Secondary schematic code / two-secondary configuration
- AS12: Alternative series designation for the same 12kV indoor epoxy cast-resin CT platform
Construction
The LZZBJ9-12/150b/2S features a monolithic epoxy resin casting that fully encapsulates the primary conductor, magnetic core, and secondary windings. This cast-resin construction provides high mechanical strength, stable dielectric performance, and excellent resistance to moisture and contamination in indoor environments. The body is non-hygroscopic and flame-retardant, ensuring long-term reliability under continuous operation in 10kV–12kV switchgear. All live parts are isolated within the solid insulation, eliminating the need for external barriers or oil filling. The support-type mounting base allows secure installation on busbar supports or switchgear frames, with terminals arranged for compatibility with standard indoor panel layouts.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV, 11kV and 12kV class networks
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: -5°C to +40°C
- Installation environment: should be free from severe vibration, conductive dust, corrosive gas, explosive medium, heavy pollution and abnormal condensation.
- Special conditions: For high altitude, humid, coastal, high-pollution or special switchgear conditions, technical confirmation is required before ordering.
Technical Parameters
The LZZBJ9-12/150b/2S is a cast-resin insulated current transformer designed for indoor 10kV–12kV systems, operating at 50/60Hz with an ambient temperature range of -5°C to +40°C. It complies with GB 20840.1-2010, GB 20840.2-2014, and IEC 61869 standards, supporting primary currents from 5A to 400A and dual-secondary configurations for metering and protection applications.
Current Transformer Data
| Item | Specification |
|---|---|
| Rated voltage class |
10kV, 11kV and 12kV class indoor systems |
| Highest voltage for equipment |
12kV class |
| Rated Insulation Level (kV) |
12/42/75kV |
| Rated frequency |
50Hz / 60Hz |
| Rated Primary Current (A) |
5A to 400A reference range in the sample data; other ratios subject to agreement |
| Rated Secondary Current (A) |
5A or 1A |
| Accuracy Class (Protection/ Measurement) |
0.2S/5P, 0.5/5P, 0.2S/10P, 0.5/10P or project-specific metering/protection combinations |
| Rated Output (VA) |
10VA / 15VA / 20VA reference according to accuracy class, ratio and secondary core configuration |
| Ambient temperature |
-5°C to +40°C |
| Insulating medium |
Epoxy resin |
| Installation type |
Indoor support-type / busbar-type installation |
| Applicable standards |
GB 20840.1-2010, GB 20840.2-2014 and special project requirements; IEC 61869 can be used for international projects |
Terminal Configuration
| Terminal Marking |
Function | Application Note |
|---|---|---|
| P1 / P2 | Primary terminals | Primary current direction and busbar connection shall follow the project wiring diagram. |
| 1S1 / 1S2 | First secondary core | Usually used for metering, measurement or the first specified secondary circuit. |
| 2S1 / 2S2 | Second secondary core | Usually used for relay protection or additional monitoring circuit. |
| 2S circuit | Two-secondary schematic | Core function, burden and accuracy class shall be confirmed by nameplate and drawing. |
Selection Table
| Rated Primary Current (A) |
Accuracy Class (Protection/ Measurement) |
Burden (VA) |
Short-Time Thermal Current |
Dynamic Current |
|---|---|---|---|---|
| 5–40 | 0.2S / 5P 0.5 / 5P 0.2S / 10P 0.5 / 10P |
10 / 15 10 / 20 15 / 15 |
150 × I1n | 375 × I1n |
| 50–100 | 0.2S / 5P 0.5 / 5P 0.2S / 10P 0.5 / 10P |
10 / 15 10 / 20 15 / 15 |
200 × I1n | 500 × I1n |
| 150–200 | 0.2S / 5P 0.5 / 5P 0.2S / 10P 0.5 / 10P |
10 / 15 10 / 20 15 / 15 |
31.5kA | 80 |
| 250–300 | 0.2S / 5P 0.5 / 5P 0.2S / 10P 0.5 / 10P |
10 / 15 10 / 20 15 / 15 |
40kA | 100 |
| 400 | 0.2S / 5P 0.5 / 5P 0.2S / 10P 0.5 / 10P |
15 / 20 20 / 20 |
50kA | 125 |
| Special ratio | By agreement | By technical agreement | By agreement | By agreement |
Structure Reference
| Structure | Application Reference |
Selection Note |
|---|---|---|
| 150b | Compact nominal-width support structure | Suitable for switchgear layouts requiring reduced width and compact terminal arrangement. |
| 2S | Two-secondary schematic arrangement | Used for metering/protection or dual-secondary requirements. |
| AS12 | Alternative 12kV series designation | Can be used together with LZZBJ9-12/150b/2S in product naming and selection documents. |
Installation & Wiring
Installation Diagram
The LZZBJ9-12/150b/2S current transformer is installed as an indoor support-type unit within medium-voltage switchgear. It features top-mounted primary terminals and a lower secondary terminal block or terminal box, depending on the approved outline drawing. Mounting is secured through base holes aligned with the switchgear structure, ensuring proper phase clearance, busbar access, and secondary wiring space.
Selection & FAQs
Selection Guide
- Choose the compact 150b/2S platform for 5A–400A indoor feeders where panel width is limited and two independent circuits are sufficient.
- Select the primary ratio from normal current, metering resolution and fault study; obtain technical confirmation for ratios outside the sample range.
- Specify 1A or 5A and pair 0.2S/0.5 metering with 5P or 10P protection, including the required ALF.
- Calculate each secondary burden and select a verified 10/15, 10/20, 15/15, 15/20 or 20/20VA combination.
- Confirm ratio-specific withstand, top-terminal busbar layout, mounting holes, terminal-box access, 12/42/75kV clearances and environment.
Frequently Asked Questions
Q1: Can this 12kV cast-resin current transformer operate in 11kV networks?
Yes, it is designed for 10kV, 11kV, and 12kV class networks. The rated insulation level is 12/42/75kV. Please specify your exact system voltage during ordering.
Q2: What ambient temperature limits apply to this indoor current transformer?
The standard operating range is -5°C to +40°C. Ensure the installation environment is free from severe vibration, conductive dust, and corrosive gases. Contact us for high-altitude adaptations.
Q3: Which secondary winding configuration supports both metering and protection?
This model features a dual-secondary configuration to handle both applications simultaneously. Primary currents range from 5A to 400A. Confirm specific accuracy classes for each core with our engineering team.
Q4: Are international IEC standards met by this current transformer?
Yes, it fully complies with IEC 61869 and GB 20840 standards. Factory test reports are provided to verify compliance. Specify required regional certifications when inquiring.
Q5: How to determine the maximum primary current for short-circuit?
This model supports primary currents from 5A to 400A. Ensure your maximum continuous and short-circuit requirements match the selected ratio. Contact our engineers for exact thermal and dynamic ratings.
Q6: Why is technical confirmation required for coastal installations?
Standard units require clean indoor conditions. For coastal or high-pollution sites, technical confirmation is mandatory. Submit your specific environmental parameters to our sales team for a customized solution.
Q7: Where is this cast-resin indoor current transformer typically applied?
It is primarily applied in indoor medium-voltage switchgear for 10kV to 12kV networks. It operates at 50Hz or 60Hz with cast-resin insulation. Request the latest product catalog for full dimensional drawings.