Overview
The LZZB1-35W / LZZBW1-35Q is a fully enclosed, pillar-type outdoor current transformer designed for 33kV, 35kV and 40.5kV AC power systems operating at 50Hz or 60Hz. It uses outdoor-grade epoxy resin cast insulation to encapsulate the primary winding, secondary winding and magnetic core into a single weather-resistant, mechanically robust structure.
This dry-type CT supports standard accuracy combinations such as 0.2S/0.2S, 0.2S/0.5S, 0.5S/0.5S, 0.2S/5P and 0.5S/5P, making it suitable for both precision energy metering and reliable relay protection. It is commonly deployed in outdoor substations, utility feeders, pole-mounted equipment, compact substations and industrial distribution networks that require oil-free, low-maintenance instrument transformers with high insulation performance.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System voltage class | 33kV / 35kV / 40.5kV |
| Rated insulation level | 40.5/95/185kV |
| Rated frequency | 50Hz or 60Hz |
| Rated secondary current | 5A or 1A |
| Insulation type | Outdoor epoxy resin cast |
| Pollution class | IV |
| Construction | Fully enclosed pillar-type |
| Installation | Outdoor |
| Primary terminals | Top-mounted (P1, P2) |
| Secondary terminals | Sealed lower terminal box (S1, S2) |
| Overvoltage withstand | High (suitable for lightning and switching surges) |
| Partial discharge | Low |
Model Designation
- L: Current transformer.
- Z: Pillar-type (post-type) structure.
- Z: Epoxy resin cast insulation.
- B: Series with combined metering and protection windings.
- 1: Design sequence or structural platform code.
- 35: 35kV-class platform, applicable to 33kV, 35kV and 40.5kV systems.
- W: Outdoor type.
- 5A or 1A: Rated secondary current option.
- Accuracy combination: Configurable metering/protection pairs (e.g., 0.2S/5P) per project requirements.
Construction
The LZZB1-35W / LZZBW1-35Q features a monolithic, fully enclosed pillar construction where the primary winding, secondary winding and magnetic core are completely embedded within a single cast-resin body. The insulation material is a specially formulated outdoor-grade epoxy resin that provides arc resistance, UV resistance, aging resistance and long-term mechanical stability under harsh environmental conditions. The top of the unit houses the primary terminals (P1 and P2), while the secondary terminals (S1 and S2) are routed through a sealed, weatherproof terminal box at the base. This design ensures high creepage distance, low partial discharge, and reliable operation in pollution class IV environments without the need for oil or gas insulation.
Technical Parameters
Service Conditions
- Installation: Outdoor installation for 33kV / 35kV / 40.5kV distribution systems.
- Ambient temperature: -25°C to +40°C.
- Rated frequency: 50Hz or 60Hz.
- Pollution level: Class IV reference for outdoor service.
- Site environment: No severe corrosive gas, explosive atmosphere or abnormal mechanical impact beyond the product design limits.
Technical Parameters
The LZZB1-35W and LZZBW1-35Q are outdoor epoxy resin cast current transformers rated for 33kV / 35kV / 40.5kV systems, with an ambient operating temperature range of -25°C to +40°C and standard service altitude per project requirements. They comply with IEC 61869-1/2 and GB/T 20840.1/2 standards and support primary current ratings from 10A to 1500A.
| Rated Primary Current (A) |
1s Thermal Current (kA) |
Dynamic Stability Current (kA) |
Accuracy Classes Combination (1S/2S) |
Rated Secondary Output (VA) |
|---|---|---|---|---|
| 10 | 2 | 5 | 0.2(S)/0.2(S) 0.2(S)/0.5(S) 0.5(S)/0.5(S) 0.2(S)/5P 0.5(S)/5P |
0.2s: 10 0.5s: 10 0.2: 15 0.5: 30 5P10: 50 5P15: 30 5P20: 20 |
| 15 | 2.7 | 6.75 | ||
| 20, 25 | 4 | 10 | ||
| 30 | 6.3 | 15.7 | ||
| 40 | 8.1 | 20.2 | ||
| 50 | 10.8 | 27 | ||
| 75 | 16.2 | 40.5 | ||
| 100 | 21.6 | 51.5 | ||
| 150 | 37.8 | 94.5 | ||
| 200, 250 | 37.8 | 94.5 | ||
| 300, 400 | 54 | 110 | ||
| 500, 600 | 68.4 | 136 | ||
| 700, 800 | 95.5 | 190 | ||
| 1000 | 95.5 | 190 | ||
| 1200–1500 | 140 | 200 |
Installation & Wiring
Installation Diagram
The LZZB1-35W / LZZBW1-35Q outdoor current transformer is mounted vertically on a stable steel bracket, mounting plate, pole-mounted structure, or substation foundation. The primary terminals (P1/P2) are located at the top for connection to the main conductor, while the sealed secondary terminal box is positioned at the bottom for easy access during wiring and maintenance.
Selection & FAQs
Selection Guide
- Choose LZZB1-35W or LZZBW1-35Q from its dedicated drawing. The page does not define their mechanical or terminal differences, so do not assume direct equivalence.
- Select the 10A–1500A ratio and secondary current. Match load, 1A or 5A instruments and the ratio-specific short-time/peak withstand.
- Coordinate protection ALF with burden. Published output falls from 50VA at 5P10 to 30VA at 5P15 and 20VA at 5P20; calculate the total relay circuit.
- Validate Class IV outdoor insulation. Obtain the actual minimum creepage, pollution test basis, IP rating, UV, rain, condensation, tracking, salt-fog and altitude performance.
- Check high-current fault data. The 1200A–1500A 140kA thermal/200kA dynamic pair has an unusual relationship and must be confirmed with duration and peak definitions.
Frequently Asked Questions
Q1: Can these 35kV current transformers be installed in severe pollution areas?
Yes, they are designed for Class IV outdoor pollution levels. They feature epoxy resin casting suitable for 33kV to 40.5kV systems. Confirm specific site conditions with our engineering team.
Q2: Which accuracy class combination is best for protection and metering?
Select 0.2S/5P or 0.5S/5P combinations for dual metering and protection. The 5P class ensures reliable performance during fault conditions. Specify your exact secondary output VA requirements during ordering.
Q3: What is the short-circuit thermal current rating for a 20A primary?
The 1-second thermal current is 4kA, with a dynamic stability current of 10kA for 20A primary ratings. These parameters ensure robust short-circuit withstand capability. Verify higher primary current ratings in the technical datasheet.
Q4: Are these outdoor current transformers compliant with international IEC standards?
Yes, both models fully comply with IEC 61869-1/2 and GB/T 20840.1/2 standards. Factory test certificates are provided with every shipment. Request specific certification formats during the inquiry stage.
Q5: How can we request custom primary current ratings above 1500A?
Standard ratings cover 10A to 1500A. Custom ratios or specific factory acceptance tests are subject to engineering confirmation. Contact our sales team with your detailed technical specifications for evaluation.
Q6: Where are these epoxy resin cast current transformers typically applied?
They are specifically engineered for outdoor 33kV, 35kV, and 40.5kV AC distribution systems. Operating frequencies include both 50Hz and 60Hz networks. Check our catalog for other voltage class options.