Overview
The LZZBJ9-36 / LZZBJ9-35/300F is an indoor epoxy resin cast current transformer designed for 35kV, 36kV, and 40.5kV medium-voltage AC systems operating at 50Hz or 60Hz. It features a fully enclosed pillar-type structure with primary and secondary windings and magnetic core sealed in cast-resin insulation, ensuring high mechanical strength, moisture resistance, and stable dielectric performance.
This CT supports both metering (accuracy classes 0.2S/0.5) and protection (5P/10P) applications, making it suitable for energy metering, current measurement, and relay protection in 36kV air-insulated switchgear, high-current feeder cabinets, and substation panels. It complies with standard insulation levels of 40.5/95/185kV and accommodates primary currents from 20A to 3150A with secondary outputs of 5A or 1A.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System voltage class | 35kV / 36kV / 40.5kV |
| Insulation level (Um/Us/Ud) | 40.5/95/185kV |
| Rated frequency | 50Hz or 60Hz |
| Rated secondary current | 5A or 1A |
| Primary current range | 20A – 3150A |
| Metering accuracy classes | 0.2S, 0.5 |
| Protection accuracy classes | 5P, 10P |
| Short-time thermal current (Ith) | Up to 100kA (1s) |
| Dynamic withstand current (Idyn) | Up to 250kA |
| Installation environment | Indoor |
| Insulation material | Epoxy resin cast |
| Construction type | Fully enclosed pillar-type |
Model Designation
- L: Current transformer.
- Z: Pillar-type / support-type structure.
- Z: Epoxy resin casting insulation.
- B: Series with both measurement and protection windings.
- J: Reinforced design for protection applications.
- 9: Design sequence or platform code.
- 36: International 36kV equipment class (corresponds to 40.5kV maximum system voltage).
- 300F: 300F-class structural platform for high-current indoor switchgear applications.
Construction
The LZZBJ9-36 / LZZBJ9-35/300F features a robust, fully enclosed epoxy resin cast body with a wide ribbed external profile for enhanced creepage and insulation coordination at 40.5kV system voltage. The entire magnetic core assembly and all windings are hermetically sealed within the cast-resin matrix, eliminating exposure to humidity and contaminants. The upper section houses the primary conductor terminals, configured in two distinct layouts: a compact arrangement for 10–1000A ratings and a reinforced, wider terminal block for 1200–3150A applications. The lower base integrates a protected terminal compartment for secondary connections, facilitating secure and accessible wiring for metering and protection circuits. This construction ensures high short-circuit withstand capability, long-term dimensional stability, and compatibility with indoor switchgear mounting requirements.
Technical Parameters
Service Conditions
- Installation: Indoor installation for 35kV / 36kV / 40.5kV switchgear and distribution systems.
- Rated frequency: 50Hz or 60Hz.
- Ambient temperature: -25°C to +40°C.
- Site condition: No severe vibration, shock or mechanical impact at the installation site.
- Air quality: Ambient air should not be seriously polluted by dust, smoke, corrosive gases, vapours or salt.
- Humidity: Indoor service without severe condensation; special requirements should be confirmed by project agreement.
- Maintenance: Keep the epoxy resin surface clean and dry to maintain insulation performance.
- Installation check: Confirm the correct terminal layout according to the selected primary current range.
Technical Parameters
The LZZBJ9-36 and LZZBJ9-35/300F are indoor epoxy-resin cast current transformers designed for 35kV / 36kV / 40.5kV systems, with a rated insulation level of 40.5/95/185kV. They operate within an ambient temperature range of -25°C to +40°C, comply with IEC 61869-1/-2 and GB/T 20840.1/.2 standards, and support primary current ranges from 20A to 3150A.
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) |
Rated Short-Time Thermal Current (kA/1S) |
Rated Dynamic Current (kA) |
|---|---|---|---|---|
| 20~40 | 0.2S/0.5/5P10(10P10)/5P15(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) 0.2S/0.5/5P40(10P40)/5P40(10P40) |
30/30/100/100 30/30/80/80 30/30/60/60 30/30/40/40 30/30/30/30 |
150*I1n(A) | 375*I1n(A) |
| 50~100 | 200*I1n(A) | 500*I1n(A) | ||
| 150~250 | 31.5 | 100 | ||
| 300~400 | 45 | 112.5 | ||
| 500~600 | 63 | 160 | ||
| 750~800 | 80 | 200 | ||
| 1000~3150 | 100 | 250 |
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) |
Rated Short-Time Thermal Current (kA/1S) |
Rated Dynamic Current (kA) |
|---|---|---|---|---|
| 20~40 | 0.2S/0.5/5P10(10P10)/5P10(10P10)/5P10(10P10) 0.2S/0.5/5P15(10P15)/5P15(10P15)/5P15(10P15) 0.2S/0.5/5P20(10P20)/5P20(10P20)/5P20(10P20) 0.2S/0.5/5P30(10P30)/5P30(10P30)/5P30(10P30) 0.2S/0.5/5P40(10P40)/5P40(10P40)/5P10(10P40) |
30/30/80/80/80 30/30/50/50/50 30/30/40/40/40 30/30/20/20/20 20/20/15/15/15 |
150*I1n(A) | 375*I1n(A) |
| 50~100 | 200*I1n(A) | 500*I1n(A) | ||
| 150~250 | 31.5 | 100 | ||
| 300~400 | 45 | 112.5 | ||
| 500~600 | 63 | 160 | ||
| 750~800 | 80 | 200 | ||
| 1000~3150 | 100 | 250 |
Installation & Wiring
Installation Diagram
The LZZBJ9-36 / LZZBJ9-35/300F current transformer is designed for indoor installation within 36kV-class air-insulated switchgear or distribution cabinets. It features a cast-resin insulated body with a side width of approximately 300mm and high-current primary terminals. Installation must follow the approved project outline drawing to ensure proper fit, electrical clearance, and terminal accessibility.
Selection & FAQs
Selection Guide
- Choose 300F for high-current or multi-core requirements. Confirm the approximately 300mm platform, wider 1200A–3150A primary terminal arrangement, base interface and 40.5kV cabinet clearances.
- Select the 20A–3150A ratio from load and fault studies. Match 1A or 5A secondary, continuous current, temperature rise and the ratio-specific thermal and dynamic withstand.
- Define every physical secondary winding. Standard configurations show 0.2S, 0.5 and two 5P cores; alternative tables mix 5P and 10P duties and require an approved core/terminal schedule.
- Match protection ALF and VA together. Options extend from P10 to P40, while output decreases across several higher-current groups; calculate each relay-and-lead burden independently.
- Resolve incomplete high-current data. For 1000A–3150A, obtain the exact per-core output, winding count, excitation or limiting data, partial discharge, terminal forces, fault duration and IEC 61869 test commitment.
Frequently Asked Questions
Q1: Can this 35kV current transformer be used in 40.5kV switchgear?
Yes, it is designed for 35kV, 36kV, and 40.5kV indoor distribution systems. The rated insulation level is 40.5/95/185kV. Please confirm your specific system voltage with our engineering team before ordering.
Q2: What are the ambient temperature and humidity requirements for installation?
The ambient temperature must remain between -25°C and +40°C without severe condensation. Keep the epoxy resin surface clean and dry to maintain insulation performance. Special humidity requirements are subject to project agreement.
Q3: Which primary current ranges are available for this epoxy-resin model?
Primary current ranges span from 20A to 3150A. Verify the correct terminal layout according to your selected primary current range during installation. Contact us for specific accuracy class combinations.
Q4: Are IEC and GB standards met by this indoor current transformer?
Yes, it fully complies with IEC 61869-1/-2 and GB/T 20840.1/.2 standards. Factory test reports are provided upon shipment. Request specific certification documents during the procurement phase.
Q5: How do I specify the rated frequency for regional grids?
The transformer supports both 50Hz and 60Hz rated frequencies. Specify your regional grid frequency requirement in the purchase order. Factory configuration is subject to confirmation prior to production.
Q6: When is special humidity confirmation required for this current transformer?
Special humidity confirmation is required when severe condensation is expected at the indoor site. Ensure the installation area remains free from severe vibration or corrosive gases. Contact our team for customized project agreements.