Overview
The LZZBJ9-12/190b/4S is an indoor epoxy cast-resin, dry-type current transformer designed for 10kV, 11kV, and 12kV medium-voltage AC power systems. It features a fully enclosed support structure with primary and secondary windings and an annular magnetic core embedded in a solid epoxy resin casting, providing reliable insulation and mechanical strength for indoor switchgear applications.
This current transformer supports multiple secondary cores (4S configuration) for combined metering and protection functions. It complies with standard requirements for accuracy class, burden, and short-circuit withstand capability in 50Hz or 60Hz systems. Typical applications include feeder monitoring, energy metering, relay protection, and integration into SCADA or distribution automation systems within metal-clad switchgear.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV / 11kV / 12kV |
| Highest voltage for equipment | 12kV |
| Rated insulation level | 12/42/75kV (per nameplate) |
| Rated frequency | 50Hz / 60Hz |
| Secondary current | 1A or 5A |
| Phase | Single phase |
| Installation type | Indoor support-type |
| Insulation material | Epoxy cast-resin |
| Construction | Dry-type, fully enclosed |
| Applications | Measurement, metering, protection, monitoring |
| Secondary configuration | 4S (multi-core) |
| Structure code | 190b |
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
- 190b: Nominal width / structure dimension code
- 4S: Secondary schematic code / multi-secondary configuration
- AS12: Alternative series designation for the same 12kV indoor epoxy cast-resin CT platform
Construction
The LZZBJ9-12/190b/4S employs a dry-type, fully enclosed construction where the primary winding, secondary winding, and annular magnetic core are integrally cast within a solid epoxy resin body. This cast-resin insulation provides excellent mechanical rigidity, moisture resistance, and stable dielectric performance under indoor medium-voltage operating conditions. The support-type design allows the unit to serve dual roles—providing both current transformation and electrical insulation support within switchgear assemblies. The robust epoxy housing ensures long-term reliability in environments with moderate humidity and dust levels, typical of indoor power distribution installations.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV, 11kV and 12kV class networks
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: -25°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 LZZBJ9-12/190b/4S is an indoor epoxy cast-resin current transformer designed for 10kV, 11kV, and 12kV class systems, with an operating temperature range of -25°C to +40°C. It complies with GB 20840.1-2010 and GB 20840.2-2014 standards and supports primary currents from 10A to 3150A, featuring multi-secondary configurations for combined metering and protection applications.
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) |
Rated Short-Time Thermal Current (kA/1S) |
Rated Dynamic Current (kA) |
|---|---|---|---|---|
| 10~40 | 0.2S/0.5/5P10(10P10)/5P10(10P10) 0.2S/0.5/5P15(10P15)/5P15(10P15) 0.2S/0.5/5P20(10P20)/5P20(10P20) 0.2S/0.5/5P30(10P30)/5P30(10P30) |
15/20/50/50 15/20/30/30 15/20/25/25 15/20/15/15 |
150*I1n(A) | 375*I1n(A) |
| 50~100 | 200*I1n(A) | 500*I1n(A) | ||
| 150~250 | 32 | 80 | ||
| 300~400 | 50 | 125 | ||
| 500~600 | 63 | 160 | ||
| 750~800 | 0.2S/0.5/5P10(10P10)/5P10(10P10) 0.2S/0.5/5P15(10P15)/5P15(10P15) 0.2S/0.5/5P20(10P20)/5P20(10P20) 0.2S/0.5/5P30(10P30)/5P30(10P30) |
20/30/60/60 20/30/40/40 20/30/30/30 20/30/20/20 |
80 | 200 |
| 1000~3150 | 100 | 250 |
Installation & Wiring
Installation Diagram
The LZZBJ9-12/190b/4S, AS12 current transformer is installed as an indoor support-type unit with primary terminals at the top and secondary terminals located at the bottom. Mounting is achieved through base fixing using 4-M10 or 8-M10 bolts, depending on the primary terminal arrangement corresponding to the rated current range. Ensure alignment with switchgear busbar layout and maintain required phase-to-phase and phase-to-ground clearances during installation.
Selection & FAQs
Selection Guide
- Choose the 190b/4S platform when four fully specified circuits need higher protection burden or fault withstand than narrower frames provide.
- Select a 10A–3150A ratio from load, metering range and fault study, then use the standard or enhanced high-current primary layout.
- Assign 0.2S and 0.5 cores to metering/measurement and the third and fourth cores to 5P10, 5P15, 5P20 or 5P30 protection.
- Calculate each circuit burden and select the complete four-value output, such as 15/20/30/30 or 20/30/60/60VA.
- Confirm 7.2kV/12kV equipment class entry, 12/42/75kV nameplate insulation, terminal spacing, 4- or 8-M10 mounting and −25°C service.
Frequently Asked Questions
Q1: Can this 12kV current transformer be installed in 11kV switchgear?
Yes, it is fully compatible. The LZZBJ9-12/190b/4S supports 10kV, 11kV, and 12kV indoor networks. Specify your exact switchgear dimensions for factory verification.
Q2: Which accuracy class combination is best for combined metering and protection?
Select a multi-secondary configuration like 0.2S/0.5/5P10. The 0.2S class handles metering, while 5P10 manages protection relays. Confirm your required rated output in VA during ordering.
Q3: What are the ambient temperature limits for indoor installation?
The operational range is -25°C to +40°C. It must be installed in environments free from conductive dust and abnormal condensation. Request technical confirmation if operating outside these standard conditions.
Q4: How does it handle high short-circuit thermal currents?
It features robust short-time thermal and dynamic current ratings. These ratings scale according to your selected primary current from 10A to 3150A. Provide your exact system fault levels for kA/1s verification.
Q5: What international standards does this epoxy cast-resin CT comply with?
It complies with GB 20840.1-2010 and GB 20840.2-2014 standards. For projects requiring specific IEC or IEEE certifications, documentation is subject to review. Please provide your certification requirements for factory confirmation.
Q6: Can the primary current be customized between 10A and 3150A?
Yes, primary currents are configurable across the 10A to 3150A range. This allows flexible integration into various medium-voltage protection and metering circuits. Submit your exact ratio requirements to our engineering team for custom winding confirmation.
Q7: Where is this indoor current transformer typically applied?
They are applied in indoor medium-voltage switchgear for 10kV to 12kV networks. The epoxy cast-resin design ensures reliable performance in clean, indoor environments. Contact our sales team for specific application drawings and OEM details.