Overview
The LZZBJ9-35/250-II / LZZB8-35 is an indoor epoxy cast-resin current transformer designed for 35kV, 36kV, and 40.5kV medium-voltage AC systems operating at 50Hz or 60Hz. It features a fully enclosed support-type structure with primary and secondary windings and magnetic core sealed within a solid epoxy resin insulation body, ensuring high dielectric strength, moisture resistance, and mechanical stability.
This CT supports dual applications in energy metering (with accuracy classes such as 0.2S) and relay protection (e.g., 5P20), making it suitable for air-insulated switchgear, indoor distribution cabinets, and power measurement panels. It complies with standard insulation levels of 40.5/95/185kV and can be deployed in indoor environments up to 3000m altitude when insulation coordination is verified during design.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System Voltage Class | 35kV / 36kV / 40.5kV |
| Rated Insulation Level | 40.5/95/185kV |
| Rated Frequency | 50Hz or 60Hz |
| Rated Secondary Current | 5A or 1A |
| Metering Accuracy Class | 0.2S, 0.5, etc. (as per configuration) |
| Protection Accuracy Class | 5P10, 5P20, etc. (as per configuration) |
| Short-Time Thermal Current | As specified per project (e.g., 25kA/1s) |
| Dynamic Withstand Current | As specified per project (e.g., 63kA peak) |
| Burden Rating | Typically up to 50VA per winding |
| Installation Environment | Indoor only |
| Altitude Limit | Up to 3000m (with design verification) |
| Insulation Material | Epoxy cast-resin |
Model Designation
- L: Current transformer.
- Z: Support-type / pillar-type structure.
- Z: Epoxy resin casting insulation.
- B: Series with metering and protection winding options.
- J: Reinforced or enhanced structural design for protection applications.
- 9: Design sequence or platform code.
- 35: 35kV-class platform, applicable to 35kV, 36kV, and 40.5kV systems.
- 250: Epoxy casting body width of 250mm.
- II: Structure version code.
Construction
The LZZBJ9-35/250-II / LZZB8-35 current transformer employs a fully enclosed support-type construction with all active components—primary winding, secondary winding, and magnetic core—embedded and sealed within a solid epoxy cast-resin body. This monolithic insulation system provides excellent electrical integrity, resistance to humidity, and long-term mechanical robustness under indoor operating conditions. The primary terminals are labeled P1 and P2, while secondary terminals follow standard marking conventions such as 1S1/1S2 and 2S1/2S2 for separate metering and protection windings; double-ratio variants may include additional taps like 1S3 or 2S3. The 250mm-wide resin housing is engineered for precise integration into indoor switchgear, requiring careful coordination of cabinet dimensions, conductor routing, terminal clearances, and mounting provisions during system design.
Technical Parameters
Service Conditions
- Ambient temperature: -15°C to +40°C reference; daily average not more than +30°C
- Altitude: Not exceeding 3000m reference for high-altitude indoor service
- Humidity condition: 24h average relative humidity not exceeding 95% reference
- Contamination severity: Class II reference for indoor service condition
- Installation: Indoor installation for 35kV / 36kV / 40.5kV switchgear and distribution systems
Technical Parameters
The LZZBJ9-35/250-II and LZZQB8-35 are indoor epoxy cast-resin current transformers rated for 35kV–40.5kV systems, featuring a 250mm cast body width and compliance with IEC 61869 and GB/T 20840 standards. They operate within an ambient temperature range of -15°C to +40°C at altitudes up to 3000m, supporting primary currents from 50A to 2500A with secondary outputs of 1A or 5A.
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) |
Rated Short-Time Thermal Current (kA/1s) |
Rated Dynamic Current (kA) |
|---|---|---|---|---|
| 10 | 0.2, 0.5, 0.2S 0.5/10P10 |
10, 15 10/15, 15/15 |
6 | 15 |
| 20 | 0.2 0.5 0.2S 0.2/10P10 |
10, 15, 20 10, 15, 20 10, 15, 20 15/15 |
10 | 25 |
| 25 | 0.2 0.5 0.2S 0.2/0.5 0.2/0.5 |
10, 15 10, 15 10, 15 10, 15 10/15, 15/15 |
10 | 25 |
| 30 | 0.2 0.5 0.2S 0.2/0.2 0.2S/0.5 0.2/10P10 0.5/10P10 0.5/10P15 |
10, 15, 20 10, 15, 20 10, 15, 20 10/10, 10/15 10/10, 10/15 10/10, 10/15, 15/15 10/10, 10/15, 15/15 10/10, 15/15 |
10 | 25 |
| 40 | 0.2 0.2S 0.2/0.2 0.2S/0.5 0.2/10P10, 0.5/10P10 0.5/10P15, 0.5/10P20 |
10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/10, 15/15, 20/20 10/10, 15/15, 20/20 10/10, 15/15 |
10 | 25 |
| 0.5 | 10, 15, 20, 30 | 20 | 50 | |
| 50, 60 | 0.2 0.2S 0.2/0.2, 0.2S/0.2 0.2/0.5, 0.2S/0.5 0.2/10P10, 0.5/10P10 |
10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/15, 15/15, 20/20 10/15, 15/15, 20/20 |
20 | 50 |
| 0.5 | 10, 15, 20, 30 | 25 | 63 | |
| 0.2/10P15, 0.5/10P15 0.2/10P20, 0.5/10P20 0.2/0.5/10P10 |
10/10, 15/15, 20/20 10/10, 15/15, 20/20 15/15/15, 30/30/30 |
10 | 25 | |
| 75 | 0.2 0.5 0.2S 0.2/0.2, 0.2S/0.2 0.2/0.5, 0.2S/0.5 0.2/10P10, 0.5/10P10 |
10, 15, 20, 30 10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/15, 15/15, 20/20 10/15, 15/15, 20/20 |
31.5 | 80 |
| 0.2/10P15, 0.5/10P15 | 10/10, 15/15, 20/20 | 25 | 63 | |
| 0.2/10P20, 0.5/10P20 0.2/0.5/10P10 |
10/10, 15/15, 20/20 15/15/15, 30/30/30 |
15 | 38 | |
| 100 | 0.2 0.5 0.2S 0.2/0.2, 0.2S/0.2 0.2/0.5, 0.2S/0.5 0.2/10P10, 0.5/10P10 |
10, 15, 20, 30 10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/15, 15/15, 20/20 10/15, 15/15, 20/20 |
40 | 100 |
| 0.2/10P15, 0.5/10P15 0.2/10P20, 0.5/10P20 0.2/0.5/10P10 0.5/10P10/10P20 |
10/10, 15/15, 20/20 10/10, 15/15, 20/20 15/15/15, 30/30/30 15/15/15, 15/15/20 |
20 | 50 | |
| 125 | 0.2, 0.2S, 0.5 0.2/10P10, 0.5/10P10 |
10, 15 15/15 |
40 | 100 |
| 0.2/10P20, 0.5/10P20 | 15/15 | 20 | 50 | |
| 150 | 0.2 0.5 0.2S 0.2/0.2, 0.2S/0.2 0.2/0.5, 0.2S/0.5 0.2/10P10, 0.5/10P10 0.2/10P15, 0.5/10P15 |
10, 15, 20, 30 10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/15, 15/15, 20/20 10/15, 15/15, 20/20 10/10, 15/15, 20/20 |
50 | 125 |
| 0.2/10P20, 0.5/10P20 0.2/0.5/10P10 0.5/10P10/10P20 |
10/10, 15/15, 20/20 15/15/15, 30/30/30 15/15/15, 15/15/20 |
25 | 63 | |
| 200, 250 | 0.2 0.5 0.2S 0.2/0.2, 0.2S/0.2 0.2/0.5, 0.2S/0.5 0.2/10P10, 0.5/10P10 |
10, 15, 20, 30 10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/15, 15/15, 20/20 10/15, 15/15, 20/20 |
50 | 125 |
| 0.2/10P15, 0.5/10P15 0.2/10P20, 0.5/10P20 0.2/0.5/10P10 0.5/10P10/10P20 |
10/10, 15/15, 20/20 10/10, 15/15, 20/20 15/15/15, 30/30/30 15/15/15, 15/15/20 |
31.5 | 80 | |
| 300, 400 | 0.2 0.5 0.2S 0.2/0.2, 0.2S/0.2 0.2/0.5, 0.2S/0.5 0.2/10P10, 0.5/10P10 |
10, 15, 20, 30 10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/15, 15/15, 20/20 10/15, 15/15, 20/20 |
63 | 160 |
| 0.2/10P15, 0.5/10P15 0.2/10P20, 0.5/10P20 0.2/0.5/10P10 0.5/10P10/10P20 |
10/10, 15/15, 20/20 10/10, 15/15, 20/20 15/15/15, 30/30/30 15/15/15, 15/15/30 |
40 | 100 | |
| 500, 600, 630 | 0.2 0.5 0.2S 0.2/0.2, 0.2S/0.2 0.2/0.5, 0.2S/0.5 0.2/10P10, 0.5/10P10 0.2/10P15, 0.5/10P15 0.2/10P20, 0.5/10P20 0.2/0.5/10P10 0.2/0.5/10P20 0.5/10P10/10P20 0.2/0.5/10P20/10P20 |
10, 15, 20, 30 10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/15, 15/15, 20/20 10/15, 15/15, 15/20, 30/30 10/10, 15/15, 30/30 10/10, 15/15, 30/30 15/15/15, 30/30/30 15/15/15, 30/30/30 15/15/15, 30/30/30 15/15/15/15 |
63 | 160 |
| 750, 800 | 0.2 0.5 0.2S 0.2/0.2, 0.2S/0.2 0.2/0.5, 0.2S/0.5 0.2/10P10, 0.5/10P10 0.2/10P15, 0.5/10P15 0.2/10P20, 0.5/10P20 0.2/0.5/10P10 0.2/0.5/10P20 0.5/10P10/10P20 0.2/0.5/10P20/10P20 |
10, 15, 20, 30 10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/15, 15/15, 20/20 10/15, 15/15, 15/20, 30/30 10/10, 15/15, 30/30 10/10, 15/15, 30/30 15/15/15, 30/30/30 15/15/15, 30/30/30 15/15/15, 30/30/30 15/15/20/20 |
80 | 200 |
| 1000, 1200, 1250, 1500–2500 |
0.2 0.5 0.2S 0.2/0.2, 0.2S/0.2 0.2/0.5, 0.2S/0.5 0.2/10P10, 0.5/10P10 0.2/10P15, 0.5/10P15 0.2/10P20, 0.5/10P20 0.2/0.5/10P10 0.2/0.5/10P20 0.5/10P10/10P20 0.2/0.5/10P20/10P20 |
10, 15, 20, 30 10, 15, 20, 30 10, 15, 20, 30 10/10, 15/15, 20/20 10/15, 15/15, 20/20 10/15, 15/15, 15/20, 30/30 10/10, 15/15, 30/30 10/10, 15/15, 30/30 15/15/15, 30/30/30 15/15/15, 30/30/30 15/15/15, 30/30/30 15/15/30/30 |
100 | 250 |
Installation & Wiring
Outline Dimensions
The outline drawing provides critical mechanical dimensions for cabinet integration, including the 250mm cast-resin body width, mounting base layout, primary terminal positions, and secondary terminal box location. Verify all clearances and interface points against the approved outline drawing before installation.
Wiring Diagram
The wiring diagram illustrates terminal markings and internal connections. Primary terminals are labeled P1 and P2, defining current direction and polarity. Secondary windings are marked as 1S1/1S2 (typically for metering) and 2S1/2S2 (typically for protection). Double-current-ratio variants may include extended terminals such as 1S3 or 2S3—refer to the approved terminal diagram for correct configuration. One point of the secondary circuit must be grounded per project grounding requirements.
Selection & FAQs
Selection Guide
- Confirm the exact companion model name. The title uses LZZQB8-35 while the content alternates with LZZB8-35; verify the full designation, II structure and 250mm body on the nameplate drawing.
- Select a 50A–2500A ratio and winding arrangement. For double ratio, state both ratios and confirm the S2/S3 tap diagram, accuracy, burden and unused-terminal treatment.
- Define each secondary core. Options include dual measurement, measurement plus 5P20, selected three-core 0.2/0.5/5P20 or 0.2S/0.5/5P20, and 5P20/5P20 at higher currents.
- Validate high-altitude insulation. Although 3000m service is referenced, confirm external clearances, creepage, dielectric correction and actual 40.5/95/185kV performance at the project altitude.
- Verify ratio-specific fault and mechanical data. Obtain RMS duration, peak current, especially for 2500A “by agreement,” plus terminal forces, base layout, cabinet clearances, partial discharge and approved IEC 61869 tests.
Frequently Asked Questions
Q1: Can these epoxy cast-resin transformers be used in 40.5kV switchgear?
Yes, they are specifically designed for 35kV, 36kV, and 40.5kV indoor distribution systems. They comply with IEC 61869 and GB/T 20840 standards. Please confirm your exact system voltage during ordering.
Q2: Which short-circuit ratings apply to the 20A primary current model?
The 20A model features a rated short-time thermal current of 10kA/1s and a rated dynamic current of 25kA. These parameters ensure reliable performance during fault conditions in 35kV systems.
Q3: What are the environmental limits for indoor installation of this equipment?
They operate in ambient temperatures from -15°C to +40°C and altitudes up to 3000m. The 24-hour average relative humidity must not exceed 95% with Class II contamination severity.
Q4: How do I select the correct accuracy class for measurement cores?
Available measurement classes include 0.2, 0.5, and 0.2S, with rated outputs from 10VA to 20VA. Choose 0.2S for high-precision metering across varying load currents. Specify your required burden and class when requesting a quote.
Q5: Are these current transformers compliant with international IEC standards?
Yes, the LZZBJ9-35/250-II and LZZQB8-35 models fully comply with IEC 61869 and GB/T 20840 standards. They are certified for indoor 35kV to 40.5kV applications. Request the specific type test reports for your project documentation.
Q6: Do you offer custom primary current ratings above 2500A?
Standard models support primary currents from 50A up to 2500A with 1A or 5A secondary outputs. Custom ratings beyond 2500A are subject to factory engineering confirmation. Please provide your exact primary current requirements for feasibility assessment.
Q7: Where are these 35kV epoxy resin transformers typically applied?
They are primarily used in 35kV to 40.5kV indoor switchgear and power distribution systems. The 250mm cast body width ensures compatibility with standard metal-clad switchgear compartments. Contact our sales team for application-specific technical support.