Overview
The LZZBJ9-12/185b/2S is an indoor epoxy cast-resin current transformer designed for 10kV, 11kV and 12kV class medium-voltage AC systems. It features a fully enclosed, support-type structure with epoxy resin insulation, providing reliable performance in indoor switchgear environments.
This dual-secondary CT supports applications including current measurement, energy metering, feeder monitoring and relay protection. It complies with standard insulation coordination levels of 12/42/75kV and operates at 50Hz or 60Hz. The 185b body offers enhanced terminal clearance over compact designs while maintaining compatibility with typical indoor switchgear layouts.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV / 11kV / 12kV |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz / 60Hz |
| Secondary current | 1A or 5A |
| Secondary configuration | 2S (dual-secondary) |
| Insulation material | Epoxy cast-resin |
| Installation type | Indoor support-type |
| Primary current range | Up to 2500A (project-specific) |
| Accuracy classes | Measurement: 0.2, 0.5; Protection: 5P, 10P |
| Short-time thermal current | Per IEC 61869 standards |
| Dynamic current withstand | Per project specification |
| Terminal marking | As per approved outline drawing |
Model Designation
- L: Current transformer
- Z: Indoor type / support structure
- Z: Epoxy resin casting insulation
- B: Protection level available
- J: Strengthened design
- 9: Design serial number
- 12: 12kV class maximum operating voltage
- 185b: Nominal width / structure dimension code
- 2S: Dual-secondary schematic code
Construction
The LZZBJ9-12/185b/2S employs a fully enclosed, support-type construction using epoxy cast-resin insulation. This solid dielectric encapsulation ensures high mechanical strength, stable electrical performance and resistance to indoor environmental factors such as humidity and dust contamination. The primary conductor is integrally molded within the resin body, eliminating air gaps and enhancing partial discharge performance. The 185b structure provides increased internal insulation distance and improved clearance around primary terminals compared to more compact variants, supporting reliable operation under short-circuit conditions. Secondary windings are independently wound on separate magnetic cores and brought out through insulated secondary terminals, facilitating clear separation between measurement and protection circuits.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 12kV class networks
- Rated frequency: 50Hz
- Ambient temperature: -5°C to +40°C
- Installation environment: The installation environment should be free from severe vibration, conductive dust, corrosive gas, explosive medium, heavy pollution and abnormal condensation.
Technical Parameters
The LZZBJ9-12/185b/2S is an indoor epoxy cast-resin current transformer designed for 12kV class systems. It features multiple accuracy class combinations and complies with GB 20840.2-2014 and IEC 61869-2:2012 standards.
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
Short-time thermal current (kA/1s) |
Rated dynamic current (kA) |
|
|---|---|---|---|---|---|
| Class 1 | Class 2 | ||||
| 5 | 0.2/10P10 | 10 | 20 | 1.0 | 2.5 |
| 0.5/10P10 | 10 | 20 | |||
| 0.2/10P15 | 10 | 20 | 0.2 | 1.25 | |
| 0.5/10P15 | 20 | 20 | |||
| 10 | 0.2/10P10 | 10 | 20 | 2.0 | 5.0 |
| 0.5/10P10 | 10 | 20 | |||
| 0.2/10P15 | 10 | 20 | 1.0 | 2.5 | |
| 0.5/10P15 | 20 | 20 | |||
| 20 | 0.2/10P10 | 10 | 20 | 6.0 | 15 |
| 0.5/10P10 | 10 | 20 | |||
| 0.2/10P15 | 10 | 20 | 3.0 | 7.5 | |
| 0.5/10P15 | 20 | 20 | |||
| 30 | 0.2/10P10 | 10 | 20 | 12 | 30 |
| 0.5/10P10 | 10 | 20 | |||
| 0.2/10P15 | 10 | 20 | 4.5 | 11.25 | |
| 0.5/10P15 | 20 | 20 | |||
| 40 | 0.2/10P10 | 10 | 20 | 16 | 40 |
| 0.5/10P10 | 10 | 20 | |||
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
Short-time thermal current (kA/1s) |
Rated dynamic current (kA) |
|
|---|---|---|---|---|---|
| Class 1 | Class 2 | ||||
| 500 | 0.2/10P10 | 10 | 30 | 63 | 130 |
| 0.5/10P10 | 20 | 30 | |||
| 0.2/10P15 | 10 | 20 | |||
| 0.5/10P15 | 20 | 20 | |||
| 600 | 0.2/10P10 | 10 | 30 | 80 | 160 |
| 0.5/10P10 | 20 | 30 | |||
| 0.2/10P15 | 10 | 20 | |||
| 0.5/10P15 | 20 | 20 | |||
| 800 | 0.2/10P10 | 15 | 30 | 80 | 160 |
| 0.5/10P10 | 30 | 30 | |||
| 0.2/10P15 | 15 | 20 | |||
| 0.5/10P15 | 30 | 20 | |||
| 1000 | 0.2/10P10 | 15 | 30 | 80 | 160 |
| 0.5/10P10 | 30 | 30 | |||
| 0.2/10P15 | 15 | 20 | |||
| 0.5/10P15 | 30 | 20 | |||
| 1200,1250 | 0.2/10P10 | 15 | 30 | 100 | 160 |
| 0.5/10P10 | 30 | 30 | |||
| 0.2/10P15 | 15 | 20 | |||
| 0.5/10P15 | 30 | 20 | |||
| 1500,2500 | 0.2/10P10 | 30 | 30 | 100 | 160 |
| 0.5/10P10 | 60 | 30 | |||
| 0.2/10P15 | 30 | 30 | |||
| 0.5/10P15 | 60 | 30 | |||
| 3000,3150 | 0.2/10P10 | 30 | 30 | 100 | 160 |
| 0.5/10P10 | 60 | 30 | |||
| 0.2/10P15 | 30 | 30 | |||
| 0.5/10P15 | 60 | 30 | |||
Installation & Wiring
Installation Diagram
The LZZBJ9-12/185b/2S is installed as an indoor support-type current transformer with the primary terminals located at the top and secondary terminals arranged at the bottom. Installation requires verification of cabinet dimensions, including primary terminal spacing, busbar routing, base mounting holes, and access to secondary terminals. Always refer to the approved outline drawing before proceeding with switchgear assembly or replacement.
Selection & FAQs
Selection Guide
- Confirm a 10kV–12kV indoor application, 12/42/75kV insulation and whether the 185b body’s additional terminal clearance is required.
- Select a 5A–2500A ratio from normal load, metering range and system fault duty, not from maximum load alone.
- Assign the first and second 1A/5A cores to measurement and protection, specifying 0.2S/0.2/0.5 and the required 10P15/10P20 class.
- Calculate the burden of each independent circuit and select a matching 10/20, 10/30, 15/20, 20/20 or 20/30VA combination.
- Verify ratio-specific thermal/dynamic current, P1/P2 direction, busbar routing, mounting holes, secondary access, shorting and grounding.
Frequently Asked Questions
Q1: Which accuracy class combination is suitable for protection relays?
The 10P10 or 10P15 classes are designed for protection applications. They ensure reliable operation during fault conditions up to 10 or 15 times rated current. Contact us to specify your exact relay burden.
Q2: Can this cast-resin CT be installed outdoors?
No, it is strictly designed for indoor medium-voltage switchgear. The environment must be free from severe vibration, conductive dust, and corrosive gases. Standard packaging ensures safe transit to your facility.
Q3: What is the short-time thermal current for 5A primary?
The rated short-time thermal current is 1.0 kA/1s for standard classes, or 0.2 kA/1s for 10P15 classes. The dynamic current is 2.5 kA or 1.25 kA respectively. Verify your system fault levels with our engineering team.
Q4: Are the IEC 61869-2 standards met for this transformer?
Yes, the LZZBJ9-12/185b/2S fully complies with IEC 61869-2:2012 and GB 20840.2-2014 standards. Factory test reports and type test certificates are available upon request. Please specify your required documentation during the inquiry.
Q5: How can we customize the rated output for our project?
Standard rated outputs are 10 VA or 20 VA depending on the accuracy class. Custom burden requirements are subject to factory confirmation. Contact our sales team with your technical specifications for a tailored quotation.
Q6: When should we select this 12kV indoor current transformer?
Select this indoor cast-resin current transformer for current measurement and protection in 12kV class networks. It integrates seamlessly into medium-voltage switchgear operating at a rated frequency of 50Hz.
Q7: Why must the installation environment be free from conductive dust?
Conductive dust and corrosive gases can compromise the epoxy resin insulation. The transformer requires a clean indoor environment with ambient temperatures between -5°C and +40°C.