Product Overview
The LZZBJ9-35/250F-L pillar-type epoxy resin cast current transformer is an indoor medium-voltage current transformer designed for 35kV / 36kV / 40.5kV power systems. It adopts a fully enclosed epoxy resin casting structure and is used for current measurement, energy metering and relay protection in AC systems with rated frequency of 50Hz or 60Hz. The product is suitable for air-insulated switchgear, indoor distribution cabinets and metering panels where high insulation strength and stable protection output are required.
This model should be positioned as a heavy-duty pillar-type epoxy cast CT with a 250F-L large-current structure platform. Compared with compact 35kV single-phase CTs, the LZZBJ9-35/250F-L has a wider upper body, larger base footprint and separate terminal structures for different primary current ranges. It is suitable for projects requiring 15A to 2500A primary current coverage, high thermal stability, and multi-core metering/protection combinations.
Product Type
| Item | Specification |
|---|---|
| Product name | Pillar-Type Epoxy Resin Cast Current Transformer |
| Model | LZZBJ9-35/250F-L |
| Installation condition | Indoor |
| Structure | Fully enclosed pillar-type epoxy resin cast structure |
| Structure platform | 250F-L large-current support-type platform |
| Application | Current measurement, energy metering and relay protection |
| 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 |
| Primary current range | 15A to 2500A reference range according to catalogue table |
| Typical installation | 35kV air-insulated switchgear, indoor distribution cabinet and metering/protection panel |
Model Explanation
- L: Current transformer.
- Z: Pillar-type / support-type structure.
- Z: Epoxy resin casting insulation.
- B: Current transformer series with measurement and protection winding options.
- J: Reinforced / protection-capable design reference.
- 9: Design sequence / product platform code.
- 35: 35kV-class product, suitable for 35kV, 36kV and 40.5kV systems.
- 250F: 250mm-class cast-resin body platform with a large-current structural layout.
Applications
- 35kV, 36kV and 40.5kV indoor medium-voltage AC power systems
- Air-insulated switchgear and indoor distribution cabinets
- High-current feeder measurement and protection circuits
- Energy metering and power measurement panels
- Relay protection for transformers, feeders and bus sections
- Industrial substations and utility distribution rooms
- Projects requiring 15A to 2500A primary current coverage
- Switchgear layouts requiring a wide upper body and large-current terminal structure
Features
- Large-current 250F-L platform: Designed for wider current coverage up to 2500A, with different terminal structures for low/medium and high-current ranges.
- 35kV / 40.5kV insulation platform: Rated insulation level of 40.5/95/185kV for international 35kV-class indoor systems.
- Fully enclosed epoxy casting: The winding and magnetic core assembly is sealed inside the cast-resin body to improve dielectric stability.
- Pillar-type mechanical support: The structure provides stable support inside switchgear while maintaining required insulation clearance.
- Metering and protection combinations: Supports combinations such as 0.2S / 5P15, 0.2S / 5P20, 0.5 / 5P30 and 0.5 / 5P40 depending on current ratio and burden.
- High thermal and dynamic withstand capability: Catalogue data includes rated short-time thermal current up to 100kA and rated dynamic current up to 250kA for selected ranges.
- Separated current-range terminal layouts: Different terminal arrangements are used for 15A-1250A and above 1250A to 2500A current ranges.
- Project-customizable output: Rated outputs such as 30/60/60VA, 30/40/40VA and 30/25/25VA can be configured according to winding function and burden requirements.
Structure Overview
The LZZBJ9-35/250F-L is a support-type epoxy resin cast current transformer with a fully enclosed insulation body. The upper cast body is wide and ribbed to increase creepage path and improve insulation performance in 35kV-class indoor switchgear. The lower metal base provides mechanical support and mounting stability, while the secondary terminal area is arranged for wiring, testing and inspection.
The primary terminal structure changes according to the rated primary current range. For 15A ≤ I1n ≤ 1250A, the catalogue drawing shows one terminal layout, while for 1250A < I1n ≤ 2500A, a larger terminal structure is used. This makes the model suitable for both medium-current and high-current switchgear feeders while keeping the same 35kV-class insulation platform.
Operating Principle
The current transformer converts high primary current in a 35kV / 36kV / 40.5kV circuit into a standardized secondary current, normally 5A or 1A. The secondary current is supplied to meters, protection relays and monitoring equipment, allowing safe measurement and protection control without direct electrical connection to the high-voltage primary circuit.
Technical Data
| Parameter | Specification |
|---|---|
| Model | LZZBJ9-35/250F-L |
| Product type | Indoor pillar-type epoxy resin cast current transformer |
| 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 |
| Primary current range | 15A to 2500A reference range |
| Accuracy combinations | 0.2S/5P15, 0.2S/5P20, 0.2S/5P30, 0.2S/5P40, 0.5/5P15, 0.5/5P20, 0.5/5P30, 0.5/5P40 and related combinations |
| Rated output | 30/60/60VA, 30/40/40VA, 30/25/25VA, 30/15/15VA, 30/30/80/80VA and project-specific combinations |
| Rated short-time thermal current | 150 x I1n, 200 x I1n, 31.5kA, 45kA, 63kA, 80kA or 100kA according to primary current range |
| Rated dynamic current | 375 x I1n, 500 x I1n, 100kA, 112.5kA, 160kA, 200kA or 250kA according to primary current range |
| Ambient temperature | -25°C to +40°C |
| Applicable standards | IEC 61869-1, IEC 61869-2, GB/T 20840.1, GB/T 20840.2; legacy GB20840.1-2010 reference by agreement |
Selection Table
| Rated Primary Current (A) |
Accuracy Class Combination |
Rated Output (VA) |
Rated Short-Time Thermal Current |
Rated Dynamic Current |
|---|---|---|---|---|
| 15-40 | 0.2S / 5P15 / 5P15 0.2S / 5P20 / 5P20 0.2S / 5P30 / 5P30 0.5 / 5P10 / 5P15 0.5 / 5P20 / 5P20 0.5 / 5P30 / 5P30 0.5 / 5P40 / 5P40 |
30 / 60 / 60 | 150 x I1n | 375 x I1n |
| 50-100 | 30 / 60 / 60 30 / 40 / 40 |
200 x I1n | 500 x I1n | |
| 150-250 | 30 / 25 / 25 | 31.5kA | 100kA | |
| 300-400 | 30 / 15 / 15 | 45kA | 112.5kA | |
| 500-600 | 30 / 40 / 40 | 63kA | 160kA | |
| 750-800 | 30 / 25 / 25 | 80kA | 200kA | |
| 1000-2500 | 30 / 15 / 15 | 100kA | 250kA |
Alternative Output Configuration
| Rated Primary Current (A) |
Accuracy Class Combination |
Rated Output (VA) |
Rated Short-Time Thermal Current |
Rated Dynamic Current |
|---|---|---|---|---|
| 15-40 | 0.2S / 0.5 / 5P10 / 5P10 0.2S / 0.5 / 5P15 / 5P15 0.2S / 0.5 / 5P20 / 5P20 0.2S / 0.5 / 5P30 / 5P30 0.2S / 0.5 / 5P40 / 5P40 |
30 / 30 / 80 / 80 | 150 x I1n | 375 x I1n |
| 50-100 | 30 / 30 / 80 / 80 | 200 x I1n | 500 x I1n | |
| 150-250 | 30 / 30 / 50 / 50 | 31.5kA | 100kA | |
| 300-400 | 30 / 30 / 40 / 40 | 45kA | 112.5kA | |
| 500-600 | 30 / 30 / 20 / 20 | 63kA | 160kA | |
| 750-800 | 30 / 30 / 10 / 10 | 80kA | 200kA | |
| 1000-2500 | 30 / 30 / 10 / 10 | 100kA | 250kA |
Note: If the required parameters exceed the above reference range, they can be confirmed by technical agreement between manufacturer and purchaser.
Operating 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 terminal structure according to the selected primary current range before assembly.
Installation and Dimensions
The LZZBJ9-35/250F-L is mounted inside 35kV-class air-insulated switchgear or indoor distribution cabinets. The catalogue drawing shows an overall height of approximately 746 ± 3mm, a body height reference of 416 ± 3mm, an upper body width of approximately 450mm, a base width of approximately 470mm, and a side width of approximately 250mm. The final project drawing shall always be used for manufacturing and installation.
| Installation Item | Recommended Check Point |
|---|---|
| Switchgear space | Confirm overall height, body width, base width and terminal access space. |
| Current range layout | Use the correct terminal structure for 15A-1250A or 1250A-2500A ranges. |
| Primary terminals | Check P1 / P2 direction, conductor connection method and insulation clearance. |
| Secondary terminal area | Reserve wiring, testing and inspection access for secondary circuits. |
| Mounting base | Confirm fixing hole arrangement, base support and grounding position. |
| Electrical clearance | Confirm phase-to-ground and phase-to-phase clearance for 40.5kV equipment class. |
| Drawing confirmation | Use the approved outline drawing and wiring diagram for final production. |
Windings & Terminal Marking
The primary terminals are identified as P1 and P2. Secondary terminals are arranged according to the number of metering and protection windings. Multi-core configurations may include one metering winding and two or more protection windings, depending on the accuracy-class combination.
| Terminal | Function | Application Note |
|---|---|---|
| P1 / P2 | Primary terminals | Used for primary current direction and polarity reference. |
| 1S1 / 1S2 | First secondary winding | Usually assigned to metering or measurement circuit. |
| 2S1 / 2S2 | Second secondary winding | Usually assigned to relay protection circuit. |
| 3S1 / 3S2 | Additional protection winding | Used when multiple protection outputs are required. |
| Grounding point | Secondary circuit grounding reference | One point of the secondary circuit should be grounded according to project practice. |
Standards and Compliance
For international product pages, the LZZBJ9-35/250F-L should be specified according to IEC 61869-1 and IEC 61869-2. GB-based documentation can refer to GB/T 20840.1 and GB/T 20840.2. Legacy catalogue references such as GB20840.1-2010 may be retained for tender compatibility, but modern technical pages should use IEC 61869 and GB/T 20840 series as the preferred standard language.
Safety Notes
- Confirm voltage class, rated insulation level, current ratio, secondary current, accuracy class and rated output before installation.
- Confirm that the selected terminal structure matches the primary current range.
- Check that the CT matches switchgear space, insulation clearance and system short-circuit level.
- Verify P1 / P2 polarity and secondary terminal marking before connecting meters, relays or test equipment.
- Ensure the CT is firmly fixed in the cabinet and that all primary conductor connections are tightened according to project requirements.
- Ground one point of the secondary circuit according to the switchgear 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 active secondary circuit with an approved shorting device.
- Keep the epoxy resin surface clean and dry to reduce tracking and insulation risk.
- Do not use the CT in environments with severe condensation, corrosive gas, explosive atmosphere or abnormal vibration beyond design limits.
- Installation, testing and commissioning shall be performed by qualified medium-voltage electrical personnel.