Product Overview
The LZZB1-35W / LZZBW1-35Q outdoor epoxy resin cast current transformer is a fully enclosed, pillar-type dry current transformer designed for 33kV, 35kV and 40.5kV outdoor power systems. It is used for current measurement, energy metering and relay protection in AC networks with rated frequency of 50Hz or 60Hz. The product uses outdoor-grade epoxy resin casting insulation, with the primary winding, secondary winding and magnetic core sealed inside the resin body to form a mechanically strong and weather-resistant insulation structure.
This model is positioned as a 40.5kV-class outdoor dry-type CT for utility feeders, outdoor substations, pole-mounted equipment, compact substations and industrial distribution systems. Compared with oil-immersed outdoor CTs, the LZZB1-35W / LZZBW1-35Q is oil-free, easier to maintain and reduces leakage-related risks. Compared with 24kV outdoor epoxy CTs, it is built for a higher insulation level of 40.5/95/185kV, larger creepage distance, stronger overvoltage withstand capability and outdoor pollution service up to pollution class IV.
Product Type
| Item | Specification |
|---|---|
| Product name | Outdoor Epoxy Resin Cast Current Transformer |
| Model | LZZB1-35W / LZZBW1-35Q |
| Installation condition | Outdoor |
| Structure | Fully enclosed pillar-type structure |
| Application | Current measurement, energy metering and relay protection |
| 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 material | Outdoor epoxy resin, arc-resistant, UV-resistant and aging-resistant |
Model Explanation
- L: Current transformer.
- Z: Pillar-type / post-type current transformer structure.
- Z: Epoxy resin cast insulation.
- B: Current transformer series with metering and protection winding options.
- 1: Design sequence / structural platform code.
- 35: 35kV class product platform, suitable for 33kV, 35kV and 40.5kV systems.
- W: Outdoor type.
- 5A or 1A: Rated secondary current option.
- Accuracy combination: Metering and protection combinations such as 0.2S/0.2S, 0.2S/0.5S, 0.5S/0.5S, 0.2S/5P and 0.5S/5P according to project requirements.
Product Positioning
The LZZB1-35W / LZZBW1-35Q should be written as a 35kV outdoor dry-type epoxy current transformer for high-insulation distribution metering and protection. Its main value is not only the current ratio range, but also the outdoor insulation system: arc-resistant epoxy resin, UV resistance, large creepage distance, low partial discharge level, strong overvoltage capability and pollution class IV service suitability.
| Positioning Point | Technical Meaning | Website Expression |
|---|---|---|
| 40.5kV insulation platform | Suitable for 33kV / 35kV / 40.5kV systems | Outdoor CT for 35kV-class distribution networks |
| Outdoor epoxy resin insulation | Dry-type, oil-free insulation body | Oil-free outdoor CT with reduced leakage and maintenance risk |
| Pollution class IV | Designed for harsher outdoor pollution environments | Suitable for exposed outdoor distribution and substation applications |
| Low partial discharge | Improved insulation reliability under medium-voltage stress | Reliable 40.5kV-class insulation performance |
| Top primary terminals | P1 and P2 are led out from the top of the CT | Clear primary connection for outdoor conductors |
| Sealed secondary terminal box | S1 and S2 are led out from the lower sealed outlet box | Safer secondary wiring and easier maintenance inspection |
Applications
- 33kV, 35kV and 40.5kV outdoor distribution systems
- Outdoor substations and utility feeder metering points
- Current measurement for medium-voltage overhead and distribution feeders
- Energy metering for utility, industrial and commercial power supply systems
- Relay protection for incoming and outgoing feeder circuits
- Compact substations, pole-mounted equipment and outdoor switching stations
- Renewable energy grid connection systems, including solar and wind farm collection networks
- Outdoor projects requiring oil-free instrument transformers with high creepage distance
Features
- Fully enclosed pillar structure: The primary winding, secondary winding and core are sealed inside the epoxy resin casting body.
- Outdoor-grade epoxy resin: Designed with arc resistance, UV resistance, aging resistance and long service life.
- High insulation level: Rated insulation level of 40.5/95/185kV for 35kV-class systems.
- Large creepage distance: Supports outdoor insulation reliability, especially in polluted service environments.
- Low partial discharge: Helps improve long-term insulation stability under medium-voltage operating stress.
- Strong overvoltage withstand capability: Suitable for outdoor distribution systems exposed to switching and lightning overvoltage conditions.
- Metering and protection functions: Supports energy metering, current measurement and relay protection in one CT platform.
- Safe terminal arrangement: Primary terminals P1 / P2 are led out from the top, and secondary terminals S1 / S2 are led out from the sealed lower terminal box.
Operating Principle
The LZZB1-35W / LZZBW1-35Q current transformer converts the primary current of a 33kV / 35kV / 40.5kV circuit into a standardized secondary current signal. The secondary signal is supplied to energy meters, measuring instruments, protection relays or monitoring devices. This allows safe measurement and protection without direct electrical connection to the high-voltage primary circuit.
For metering applications, the selected metering winding should maintain its accuracy class within the rated burden. For protection applications, the protection winding must provide sufficient secondary output under fault current conditions. The current ratio, rated secondary current, accuracy class combination, rated output, short-time thermal current and dynamic current should be selected together according to the system load and fault level.
Technical Data
| Parameter | Specification |
|---|---|
| Model | LZZB1-35W / LZZBW1-35Q |
| Product type | Outdoor epoxy resin cast current transformer |
| 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 |
| Rated primary current | 10A to 1500A reference range according to supplied catalogue data |
| Accuracy class combination | 0.2S/0.2S, 0.2S/0.5S, 0.5S/0.5S, 0.2S/5P, 0.5S/5P and related combinations |
| Rated secondary output | 10VA, 15VA, 20VA, 30VA, 50VA and related values depending on accuracy class and winding function |
| Ambient temperature | -25°C to +40°C |
| Pollution level | Class IV |
| Partial discharge level | Complies with GB1208-1997 / related CT standard requirements |
| Applicable standards | IEC 61869-1, IEC 61869-2, GB/T 20840.1, GB/T 20840.2; legacy IEC 60044-1 / IEC185 and GB1208 references by agreement |
Selection Table
The following selection table is reorganized from the supplied catalogue information and optimized for website display. Long headings and accuracy-class cells are split into multiple lines to improve responsive layout.
| Rated Primary Current (A) |
Short-Time Thermal Current Ith / 1s |
Rated Dynamic Current Idyn |
Accuracy Class Combination |
Rated Secondary Output (VA) |
|---|---|---|---|---|
| 10 | 2kA | 5kA | 0.2S / 0.2S 0.2S / 0.5S 0.5S / 0.5S 0.2S / 5P 0.5S / 5P |
0.2S: 10VA 0.5S: 10VA 0.2: 15VA 0.5: 30VA 5P10: 50VA 5P15: 30VA 5P20: 20VA |
| 15 | 2.7kA | 6.75kA | ||
| 20, 25 | 4kA | 10kA | ||
| 30 | 6.3kA | 15.7kA | ||
| 40 | 8.1kA | 20.2kA | ||
| 50 | 10.8kA | 27kA | ||
| 75 | 16.2kA | 40.5kA | ||
| 100 | 21.6kA | 51.5kA | ||
| 150 | 37.8kA | 94.5kA | ||
| 200, 250 | 37.8kA | 94.5kA | ||
| 300, 400 | 54kA | 110kA | ||
| 500, 600 | 68.4kA | 136kA | ||
| 700, 800 | 95.5kA | 190kA | Project-specific combination | By agreement |
| 1000 | 95.5kA | 190kA | Project-specific combination | By agreement |
| 1200–1500 | 140kA | 200kA | Project-specific combination | By agreement |
Note: The table is for preliminary selection. If the required data is beyond the above range, it can be confirmed by technical agreement between manufacturer and purchaser. Final values shall follow the nameplate, approved drawing and factory test report.
Operating 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.
- Altitude: Standard service altitude according to project specification; high-altitude applications should be confirmed separately.
- Site environment: No severe corrosive gas, explosive atmosphere or abnormal mechanical impact beyond the product design limits.
- Outdoor insulation: Designed for UV exposure, humidity, aging resistance, large creepage distance and low partial discharge performance.
Installation and Dimensions
The LZZB1-35W / LZZBW1-35Q is installed outdoors on a stable steel bracket, mounting plate, pole-mounted structure or substation foundation. The product adopts top primary terminals and a lower sealed secondary terminal box. The mounting structure must provide sufficient mechanical support and electrical clearance for the selected current range and conductor layout.
| Installation Item | Recommended Check Point |
|---|---|
| Mounting base | Confirm base dimensions, four mounting points, bracket strength and foundation stability before installation. |
| Primary terminals | Check P1 / P2 terminal direction, conductor connection method and phase-to-ground clearance. |
| Secondary terminal box | Reserve access space for wiring, inspection, sealing and testing. |
| Grounding | Connect the CT base and one point of the secondary circuit to the station grounding system. |
| Outdoor insulation clearance | Confirm creepage distance, pollution level, lightning impulse requirement and site insulation coordination. |
| Drawing confirmation | Use the approved outline drawing for the selected current ratio and terminal arrangement. |
Windings & Terminal Marking
The primary terminals P1 and P2 are led out from the top of the product. The secondary terminals S1 and S2 are led out from the lower sealed terminal box. For products with multiple secondary windings, terminal groups should be marked according to the approved wiring diagram before shipment.
| Terminal | Function | Application Note |
|---|---|---|
| P1 / P2 | Primary terminals | Used for primary current direction and polarity reference. |
| S1 / S2 | Secondary terminals | Used for one secondary output to meter, relay or monitoring device. |
| 1S1 / 1S2 | First secondary winding | Usually assigned to metering or current measurement when multiple windings are specified. |
| 2S1 / 2S2 | Second secondary winding | Usually assigned to relay protection when multiple windings are specified. |
| Grounding point | Secondary / base grounding reference | One point of the secondary circuit and the CT base should be grounded according to project practice. |
Standards and Compliance
For updated international documentation, the LZZB1-35W / LZZBW1-35Q should be specified according to IEC 61869-1 and IEC 61869-2. The supplied catalogue also references IEC 60044-1:2003, IEC185, GB1208-2006 and GB1208-1997. For modern project documents, IEC 61869 and GB/T 20840 series should be used as the preferred reference, while older standards can be retained for catalogue comparison or tender compatibility.
Safety Notes
- Confirm voltage class, insulation level, current ratio, secondary current, accuracy class and rated output before installation.
- Check that the selected CT matches the system fault level, including short-time thermal current and dynamic current requirements.
- Verify P1 / P2 polarity and secondary terminal marking before connecting meters, relays or test equipment.
- Ensure the outdoor mounting bracket is strong enough for the CT weight and wind load at the installation site.
- Ground the CT base and one point of the secondary circuit according to the station grounding design.
- The CT secondary circuit must not be open-circuited while primary current is flowing.
- Before disconnecting meters, relays or test devices, short-circuit the secondary circuit with an approved shorting device.
- Seal the secondary terminal box after wiring to reduce moisture ingress and maintain outdoor reliability.
- Do not install the CT in an environment with severe chemical corrosion, explosive gas or abnormal vibration beyond the product design limits.
- Installation, testing and commissioning shall be performed by qualified medium-voltage electrical personnel.
Selection Guide
- Confirm voltage level: Use LZZB1-35W / LZZBW1-35Q for 33kV, 35kV and 40.5kV outdoor systems.
- Confirm insulation level: Use 40.5/95/185kV as the main insulation level for the 35kV-class platform.
- Select current ratio: Choose the primary current according to feeder load, metering range and protection setting.
- Choose secondary current: Use 5A for conventional meters and relays; use 1A for long secondary wiring or lower burden applications.
- Define accuracy class: Use 0.2S / 0.2 / 0.5S / 0.5 for metering and 5P / 10P classes for protection.
- Check rated output: Match CT burden with connected meters, relays, terminal blocks and secondary cable length.
- Check short-circuit withstand: Confirm Ith and Idyn according to the fault current level at the installation point.
- Confirm outdoor environment: Review altitude, pollution class, UV exposure, humidity, creepage distance and site insulation coordination.
- Approve drawings: Confirm outline drawing, terminal marking, mounting holes and secondary terminal box direction before production.