Overview
The LZJC-12G / LZJC-12Q is an indoor single-phase epoxy cast-resin current transformer designed for 11kV and 12kV class medium-voltage switchgear. It features a fully enclosed support-type structure with primary and secondary windings and the magnetic core encapsulated in epoxy resin, providing robust insulation and mechanical stability.
Suitable for IEC-based 12kV systems, it supports metering accuracy classes of 0.2S, 0.2, and 0.5, and protection classes such as 10P10 and 10P15. The CT is used in current measurement, energy metering, relay protection, feeder monitoring, and SCADA signal input within indoor AC power systems operating at 50Hz or 60Hz.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 11kV / 12kV |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz (60Hz on request) |
| Rated secondary current | 5A or 1A |
| Rated primary current | 5A to 1000A |
| Metering accuracy | 0.2S, 0.2, 0.5 |
| Protection accuracy | 10P10, 10P15 |
| Insulation material | Epoxy cast-resin |
| Construction type | Support-type, fully enclosed |
| Application environment | Indoor, humid or polluted conditions |
| Core configuration | Metering, protection, or combined |
| Typical use | Switchgear, metering cabinets, feeder panels |
Model Designation
- L: Current transformer
- Z: Indoor support / pillar type structure
- J: Reinforced design or enhanced structural reference
- C: Cast-resin insulated, fully enclosed structure
- 12: 12kV voltage class for 11kV and 12kV class indoor systems
- G: Structural / installation variant code; final meaning follows factory drawing
- Q: Reinforced / installation variant code; final meaning follows factory drawing
Construction
The LZJC-12G / LZJC-12Q features a compact, fully enclosed support-type body made of epoxy cast-resin. The annular magnetic core, along with both primary and secondary windings, is completely embedded within the resin matrix, ensuring excellent dielectric strength and long-term operational stability. An external groove design enhances surface creepage distance, improving insulation performance in humid or contaminated indoor environments. Primary terminals are located on the upper side for direct busbar or bolted connection, while secondary terminals are arranged on the lower or side area depending on the specific variant and project drawing. This construction delivers high mechanical strength, clear terminal access, and reliable isolation between medium-voltage primary and low-voltage secondary 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: should be free from severe vibration, conductive dust, corrosive gas, explosive medium, heavy pollution and abnormal condensation.
Technical Parameters
The LZJC-12G/LZJC-12Q is an indoor cast-resin current transformer designed for 12kV class systems. It features epoxy resin insulation and complies with IEC and GB standards. Primary current ranges from 5A to 1000A.
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
Short-time thermal current (kA/1s) |
Rated dynamic current (kA) |
|||
|---|---|---|---|---|---|---|---|
| 0.2S | 0.2/0.5 | 5P | 10P | ||||
| 5~400 | 0.2/10P 0.2S/10P 0.5/10P |
10 | 10 | 15 | 15 | 60×I1n | 150×I1n |
| 600 | 50×I1n | 120×I1n | |||||
| 800 | 50×I1n | 100×I1n | |||||
| 1000 | 45×I1n | 90×I1n | |||||
Installation & Wiring
Outline Dimensions
The outline dimensions define the physical envelope, primary terminal spacing, base mounting hole positions, and secondary terminal layout for both LZJC-12G and LZJC-12Q variants. These dimensions must be verified against the switchgear cabinet layout to ensure proper fit, clearance, and accessibility.
Selection & FAQs
Selection Guide
- Select LZJC-12G or LZJC-12Q from the switchgear mounting, terminal orientation and approved outline; the suffix is structural, not an electrical rating.
- Choose a 5A–1000A primary ratio from load, metering range and protection study, with custom ratios by technical agreement.
- Specify 1A or 5A and pair 0.2S/0.2/0.5 metering with 10P10 or 10P15 protection, including any third core.
- Calculate each burden at cosφ 0.8 where applicable and verify 10VA–20VA output plus ratio-specific Ith/Idyn.
- Confirm 12/42/75kV insulation, grooved creepage, ≤1000m altitude, +55°C duty, P1/P2 terminals, mounting and one-point grounding.
Frequently Asked Questions
Q1: What are the installation environment requirements for this cast-resin current transformer?
Install only indoors free from severe vibration, conductive dust, and corrosive gases. The ambient temperature must remain between -5°C and +40°C. Contact us for abnormal environment solutions.
Q2: Which accuracy class combination is suitable for protective relaying and metering?
Select the 0.2S/10P or 0.5/10P combinations for dual measurement and protection. The 10P class provides a 15 VA rated output for protection circuits. Confirm specific burden requirements with our engineers.
Q3: How does the short-time thermal current scale with higher primary ratings?
Thermal capacity decreases as primary current increases to maintain physical dimensions. For 1000A models, the short-time thermal current is 45×I1n kA/1s, while 5-400A models support 60×I1n. This ensures safe operation during fault conditions.
Q4: What international standards does the LZJC-12G indoor current transformer comply with?
The transformer fully complies with IEC and GB standards for 12kV class networks. It features robust epoxy resin insulation for indoor medium-voltage switchgear. Request the specific type test report during procurement.
Q5: Can the primary current be customized beyond the standard 1000A maximum?
Standard models cover primary currents from 5A to 1000A. Custom ratios beyond this range are subject to factory confirmation and engineering review. Lead times for non-standard ratios vary based on production schedules.
Q6: What is the primary application for the LZJC-12Q epoxy resin transformer?
It is designed specifically for indoor medium-voltage switchgear in 12kV distribution networks. The cast-resin construction ensures reliable current measurement and protection in 50Hz systems. Check our catalog for similar 12kV instrument transformers.
Q7: Is this 12kV current transformer compatible with 60Hz power systems?
The standard rated frequency is strictly 50Hz. Using it in 60Hz networks requires technical evaluation for core saturation and thermal limits. Standard models are not recommended for 60Hz applications without modification.