Overview
The LZZB6-12 and LZZB6J-12 are indoor epoxy cast-resin current transformers rated for 10kV, 11kV, and 12kV medium-voltage switchgear. They feature a fully enclosed cast-resin body with a hollow busbar or cable-through primary conductor, eliminating the need for a wound primary coil. The LZZB6J-12 variant includes a reinforced housing for enhanced mechanical strength and insulation performance.
These CTs support secondary outputs of 5A or 1A and offer accuracy classes including 0.2S, 0.5, and protection classes up to 5P30. They are suitable for current measurement, energy metering, feeder monitoring, and relay protection in 50Hz/60Hz AC systems. The design complies with IEC61869-2 and GB20840 standards, ensuring reliability in indoor switchgear applications.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV / 11kV / 12kV |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz / 60Hz |
| Primary current range | 1500A – 5000A |
| Secondary current | 5A or 1A |
| Metering accuracy | 0.2S, 0.5 |
| Protection class | 5P10 to 5P30 |
| Construction | Epoxy cast-resin, fully enclosed |
| Installation type | Busbar/cable-through |
| Standards | IEC61869-2, GB20840 |
Model Designation
- L: Current transformer (CT)
- Z: Cast-resin insulated
- Z: Indoor type
- B: Busbar-through primary
- 6: Design series number
- -12: Rated voltage class (12kV)
- J: Reinforced housing variant (LZZB6J-12 only)
Construction
The LZZB6-12 / LZZB6J-12 features a monolithic epoxy cast-resin body that fully encapsulates the magnetic cores and secondary windings, providing excellent electrical insulation, moisture resistance, and mechanical stability. The primary conductor path is a hollow aperture designed for direct insertion of busbars or power cables, marked with P1 for polarity reference. The LZZB6J-12 model incorporates a reinforced resin housing with improved dielectric strength and higher short-time thermal withstand capability. Secondary terminals (1S1/1S2 and 2S1/2S2) are accessible via an external terminal box for safe connection to meters or relays. Four integrated mounting holes allow secure installation in metal-enclosed switchgear such as XGN-10 type panels. Equipotential bonding is achieved through conductive paths connected to the switchgear frame via fenestrae around the primary aperture.
Technical Parameters
Service Conditions
- Ambient Temperature: -5°C to +40°C
- Altitude: Not exceeding 1000 m above sea level
- Relative Humidity: Daily average not more than 95%, monthly average not more than 90%
- Installation Environment: Indoor, non-corrosive, free from explosive or conductive dust, and without severe vibration or shock
- Pollution Degree: Class II
- Atmospheric Conditions: No frequent condensation or significant temperature fluctuations causing dew formation
Technical Parameters
The LZZB6-12 / LZZB6J-12 is a 12 kV indoor epoxy cast-resin current transformer with primary insulation made of high-quality epoxy resin. It operates within an ambient temperature range of -5°C to +40°C and is rated for installation up to 1000 m altitude. Compliant with IEC 61869 standards, it supports a wide range of primary current ratings from 10 A to 3000 A.
Model Variants
| Type (Ratio) |
Rated Voltage (kV) |
Rated Primary Current (A) |
Rated Secondary Current (A) |
Accuracy Class (Protection/ Measurement) |
Burden (VA) |
Rated Output (VA) |
Short-Time Thermal Current |
Dynamic Current |
|---|---|---|---|---|---|---|---|---|
| LZZB6-12 | 12 | 10–3000 | 1 or 5 | 0.2 / 0.5 / 1 / 3 /
5P10 / 5P15 / 5P20 |
2.5–30 | 10–30 | 40×In/1s | 100×In |
| LZZB6J-12 |
Current Transformer Data
| Rated Current Ratio (A) |
Rated Insulation Level (kV) |
Current Range |
Accuracy Class (Protection/ Measurement) |
Burden (VA) |
Short-Time Thermal Current |
Dynamic Current |
|---|---|---|---|---|---|---|
| 10/1, 10/5 | 12/70/170 | 10–3000 | 0.2 / 0.5 / 1 / 3 /
5P10 / 5P15 / 5P20 |
2.5–30 | 40×In/1s | 100×In |
| 15/1, 15/5 | ||||||
| 20/1, 20/5 | ||||||
| 25/1, 25/5 | ||||||
| 30/1, 30/5 | ||||||
| 40/1, 40/5 | ||||||
| 50/1, 50/5 | ||||||
| 60/1, 60/5 | ||||||
| 75/1, 75/5 | ||||||
| 80/1, 80/5 | ||||||
| 100/1, 100/5 | ||||||
| 150/1, 150/5 | ||||||
| 200/1, 200/5 | ||||||
| 300/1, 300/5 | ||||||
| 400/1, 400/5 | ||||||
| 600/1, 600/5 | ||||||
| 800/1, 800/5 | ||||||
| 1000/1, 1000/5 | ||||||
| 1200/1, 1200/5 | ||||||
| 1500/1, 1500/5 | ||||||
| 2000/1, 2000/5 | ||||||
| 2500/1, 2500/5 | ||||||
| 3000/1, 3000/5 |
Installation & Wiring
Installation
Selection & FAQs
Selection Guide
- Resolve the source conflicts before selection: primary range is stated as both 10–3000A and 1500–5000A, while insulation is listed as 12/42/75 and 12/70/170kV.
- Select LZZB6-12 or reinforced LZZB6J-12 from the mechanical support, aperture, switchgear structure and approved drawing.
- Choose the exact primary ratio, 1A/5A secondary and required 0.2/0.5 measurement or 5P10–5P20 protection cores.
- Calculate each burden and verify the 10VA–30VA output, accuracy-limit factor and actual ratio-specific fault withstand.
- Confirm busbar/cable fit, centered passage, four-hole mounting, equipotential bonding, ≤1000m altitude, Class II pollution and test certificate.
Frequently Asked Questions
Q1: Can this indoor cast-resin current transformer be installed in high humidity environments?
Yes, it handles daily average humidity up to 95% and monthly averages up to 90%. Ensure no frequent condensation occurs. Contact us for specific environmental assessments.
Q2: What primary current ratings are available for the LZZB6-12 model?
The LZZB6-12 supports primary current ratings ranging from 10 A to 3000 A. Select your exact ratio based on load requirements. Please specify the required ratio when ordering.
Q3: Which accuracy classes are supported for measurement and protection?
It supports multiple accuracy classes for both measurement and protection applications per IEC 61869 standards. Confirm your required accuracy class and burden rating with our engineering team.
Q4: How can we customize the secondary current output for our panels?
Secondary current customization is subject to confirmation based on your specific panel requirements. We can tailor ratios and burden specifications to match your switchgear design. Submit your technical inquiry for factory details.
Q5: Are routine factory tests performed before shipping the LZZB6J-12?
Routine testing protocols and specific certification documents are subject to confirmation based on your order. Please contact our sales team to request the exact factory test reports and compliance certificates.
Q6: What is the maximum rated voltage for this indoor current transformer?
The LZZB6-12 and LZZB6J-12 models are rated for a maximum system voltage of 12 kV. They are designed specifically for indoor switchgear and distribution panels.
Q7: Can this 12kV epoxy resin CT operate at high altitudes?
Standard models are rated for altitudes not exceeding 1000 m above sea level. For installations above this elevation, derating or special factory customization is required.