Overview
The LZZB8 / LZZBJ9-35/250(III) is an indoor epoxy cast-resin current transformer designed for 35kV / 40.5kV medium-voltage AC power systems operating at 50Hz or 60Hz. It features a fully enclosed pillar-type structure with primary and secondary windings, along with the magnetic core, sealed within a solid epoxy resin casting to ensure high insulation strength, moisture resistance, and mechanical stability.
This CT supports combined metering and protection functions, commonly configured with accuracy classes such as 0.2S for metering and 5P20 for protection, with burdens up to 50VA. It is suitable for use in 35kV switchgear, distribution cabinets, and indoor substations where precise current measurement, energy metering, and reliable relay protection are required under controlled installation conditions.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System voltage class | 35kV / 40.5kV |
| Rated insulation level | 40.5/95/185kV |
| Rated frequency | 50Hz or 60Hz |
| Rated secondary current | 5A or 1A |
| Primary current range | Up to 2500A (project-specific) |
| Metering accuracy | 0.2S, 0.2, 0.5 |
| Protection accuracy | 5P20 |
| Typical burden | 15VA, 25VA, 30VA, 50VA |
| Installation condition | Indoor |
| Insulation material | Epoxy cast-resin |
| Structure type | Pillar-type, fully enclosed |
| Cast body width | 250mm |
Construction
The LZZB8 / LZZBJ9-35/250(III) employs a fully enclosed pillar-type construction with all active components—primary winding, secondary winding, and magnetic core—permanently encapsulated in a solid epoxy cast-resin body. This monolithic insulation system provides excellent dielectric strength, tracking resistance, and environmental protection against humidity and contamination. The 250mm cast body width is a key dimensional parameter that governs cabinet integration, phase-to-phase clearance, and secondary terminal placement. Primary terminals are labeled P1 and P2, while secondary terminals (e.g., 1S1/1S2, 2S1/2S2) are arranged according to the number of windings and project-specific wiring diagrams. The design ensures long-term mechanical rigidity and thermal stability under continuous and short-circuit operating conditions typical in indoor 35kV switchgear applications.
Technical Parameters
Service Conditions
- Ambient temperature: -15°C to +40°C reference for high-altitude version; daily average not more than +30°C.
- Altitude: Does not exceed 3000m for high-altitude design reference; confirm insulation correction for special projects.
- Humidity: 24h average relative humidity not exceeding 95% reference.
- Pollution severity: Class II reference for indoor service condition.
- Installation: Indoor installation for 35kV / 40.5kV switchgear and distribution systems.
Technical Parameters
The LZZB8 and LZZBJ9-35/250(III) are indoor cast-resin current transformers rated for 35kV / 40.5kV systems with epoxy insulation, designed for operation between -15°C and +40°C at altitudes up to 3000m. They comply with IEC 61869-1/-2 and GB/T 20840.1/.2 standards and support primary current ratings 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 | 10,15 | 6 | 15 |
| 0.5/10P10 | 10/15,15/15 | 6 | 15 | |
| 20 | 0.2 | 10,15,20 | 10 | 25 |
| 0.5 | 10,15,20 | 10 | 25 | |
| 0.2S | 10,15,20 | 10 | 25 | |
| 0.2/10P10 | 15/15 | 10 | 25 | |
| 25 | 0.2 | 10,15 | 10 | 25 |
| 0.5 | 10,15 | 10 | 25 | |
| 0.2S | 10,15 | 10 | 25 | |
| 0.2/0.5 | 10,15 | 10 | 25 | |
| 0.2/0.5 | 10/15,15/15 | 10 | 25 | |
| 30 | 0.2 | 10,15,20 | 10 | 25 |
| 0.5 | 10,15,20 | 10 | 25 | |
| 0.2S | 10,15,20 | 10 | 25 | |
| 0.2/0.2 | 10/10,10/15 | 10 | 25 | |
| 0.2S/0.5 | 10/10,10/15 | 10 | 25 | |
| 0.2/10P10 | 10/10,10/15,15/15 | 10 | 25 | |
| 0.5/10P10 | 10/10,10/15,15/15 | 10 | 25 | |
| 0.5/10P15 | 10/10,15/15 | 10 | 25 | |
| 40 | 0.2 | 10,15,20,30 | 10 | 25 |
| 0.5 | 10,15,20,30 | 20 | 50 | |
| 0.2S | 10,15,20,30 | 10 | 25 | |
| 0.2/0.2 | 10/10,15/15,20/20 | 10 | 25 | |
| 0.2S/0.5 | 10/10,15/15,20/20 | 10 | 25 | |
| 0.2/10P10,0.5/10P10 | 10/10,15/15,20/20 | 10 | 25 | |
| 0.5/10P15,0.5/10P20 | 10/10,15/15 | 10 | 25 | |
| 50,60 | 0.2 | 10,15,20,30 | 20 | 50 |
| 0.5 | 10,15,20,30 | 25 | 63 | |
| 0.2S | 10,15,20,30 | 20 | 50 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 20 | 50 | |
| 0.2/0.5,0.2S/0.5 | 10/10,15/15,20/20 | 20 | 50 | |
| 0.2/10P10,0.5/10P10 | 10/10,15/15,20/20 | 20 | 50 | |
| 0.2/10P15,0.5/10P15 | 10/10,15/15,20/20 | 10 | 25 | |
| 0.2/10P20,0.5/10P20 | 10/10,15/15,20/20 | 10 | 25 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 10 | 25 | |
| 75 | 0.2 | 10,15,20,30 | 31.5 | 80 |
| 0.5 | 10,15,20,30 | 31.5 | 80 | |
| 0.2S | 10,15,20,30 | 31.5 | 80 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 31.5 | 80 | |
| 0.2/0.5,0.2S/0.5 | 10/15,15/15,20/20 | 31.5 | 80 | |
| 0.2/10P10,0.5/10P10 | 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 | 10/10,15/15,20/20 | 15 | 38 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 15 | 38 | |
| 100 | 0.2 | 10,15,20,30 | 40 | 100 |
| 0.5 | 10,15,20,30 | 40 | 100 | |
| 0.2S | 10,15,20,30 | 40 | 100 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 40 | 100 | |
| 0.2/0.5,0.2S/0.5 | 10/15,15/15,20/20 | 40 | 100 | |
| 0.2/10P10,0.5/10P10 | 10/15,15/15,20/20 | 40 | 100 | |
| 0.2/10P15,0.5/10P15 | 10/10,15/15,20/20 | 20 | 50 | |
| 0.2/10P20,0.5/10P20 | 10/10,15/15,20/20 | 20 | 50 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 20 | 50 | |
| 0.5/10P10/10P20 | 15/15/15,15/15/20 | 20 | 50 | |
| 125 | 0.2,0.2S,0.5 | 10,15 | 40 | 100 |
| 0.2/10P10,0.5/10P10 | 15/15 | 40 | 100 | |
| 0.2/10P20,0.5/10P20 | 15/15 | 20 | 50 | |
| 150 | 0.2 | 10,15,20,30 | 50 | 125 |
| 0.5 | 10,15,20,30 | 50 | 125 | |
| 0.2S | 10,15,20,30 | 50 | 125 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 50 | 125 | |
| 0.2/0.5,0.2S/0.5 | 10/15,15/15,20/20 | 50 | 125 | |
| 0.2/10P10,0.5/10P10 | 10/15,15/15,20/20 | 50 | 125 | |
| 0.2/10P15,0.5/10P15 | 10/10,15/15,20/20 | 50 | 125 | |
| 0.2/10P20,0.5/10P20 | 10/10,15/15,20/20 | 25 | 63 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 25 | 63 | |
| 0.5/10P10/10P20 | 15/15/15,15/15/20 | 25 | 63 | |
| 200,250 | 0.2 | 10,15,20,30 | 50 | 125 |
| 0.5 | 10,15,20,30 | 50 | 125 | |
| 0.2S | 10,15,20,30 | 50 | 125 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 50 | 125 | |
| 0.2/0.5,0.2S/0.5 | 10/15,15/15,20/20 | 50 | 125 | |
| 0.2/10P10,0.5/10P10 | 10/15,15/15,20/20 | 50 | 125 | |
| 0.2/10P15,0.5/10P15 | 10/10,15/15,20/20 | 31.5 | 80 | |
| 0.2/10P20,0.5/10P20 | 10/10,15/15,20/20 | 31.5 | 80 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 31.5 | 80 | |
| 0.5/10P10/10P20 | 15/15/15,15/15/20 | 31.5 | 80 | |
| 300,400 | 0.2 | 10,15,20,30 | 63 | 160 |
| 0.5 | 10,15,20,30 | 63 | 160 | |
| 0.2S | 10,15,20,30 | 63 | 160 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 63 | 160 | |
| 0.2/0.5,0.2S/0.5 | 10/15,15/15,20/20 | 63 | 160 | |
| 0.2/10P10,0.5/10P10 | 10/15,15/15,20/20 | 63 | 160 | |
| 0.2/10P15,0.5/10P15 | 10/10,15/15,20/20 | 40 | 100 | |
| 0.2/10P20,0.5/10P20 | 10/10,15/15,20/20 | 40 | 100 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 40 | 100 | |
| 0.5/10P10/10P20 | 15/15/15,15/15/30 | 40 | 100 | |
| 500,600,630 | 0.2 | 10,15,20,30 | 63 | 160 |
| 0.5 | 10,15,20,30 | 63 | 160 | |
| 0.2S | 10,15,20,30 | 63 | 160 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 63 | 160 | |
| 0.2/0.5,0.2S/0.5 | 10/15,15/15,20/20 | 63 | 160 | |
| 0.2/10P10,0.5/10P10 | 10/15,15/15,15/20,30/30 | 63 | 160 | |
| 0.2/10P15,0.5/10P15 | 10/10,15/15,30/30 | 63 | 160 | |
| 0.2/10P20,0.5/10P20 | 10/10,15/15,30/30 | 63 | 160 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 63 | 160 | |
| 0.2/0.5/10P20 | 15/15/15,30/30/30 | 63 | 160 | |
| 0.5/10P10/10P20 | 15/15/15,30/30/30 | 63 | 160 | |
| 0.2/0.5/10P20/10P20 | 15/15/15/15 | 63 | 160 | |
| 750,800 | 0.2 | 10,15,20,30 | 80 | 200 |
| 0.5 | 10,15,20,30 | 80 | 200 | |
| 0.2S | 10,15,20,30 | 80 | 200 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 80 | 200 | |
| 0.2/0.5,0.2S/0.5 | 10/15,15/15,20/20 | 80 | 200 | |
| 0.2/10P10,0.5/10P10 | 10/15,15/15,15/20,30/30 | 80 | 200 | |
| 0.2/10P15,0.5/10P15 | 10/10,15/15,30/30 | 80 | 200 | |
| 0.2/10P20,0.5/10P20 | 10/10,15/15,30/30 | 80 | 200 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 80 | 200 | |
| 0.2/0.5/10P20 | 15/15/15,30/30/30 | 80 | 200 | |
| 0.5/10P10/10P20 | 15/15/15,30/30/30 | 80 | 200 | |
| 0.2/0.5/10P20/10P20 | 15/15/20/20 | 80 | 200 | |
| 1000,1200,1250 | 0.2 | 10,15,20,30 | 100 | 250 |
| 0.5 | 10,15,20,30 | 100 | 250 | |
| 0.2S | 10,15,20,30 | 100 | 250 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 100 | 250 | |
| 0.2/0.5,0.2S/0.5 | 10/15,15/15,20/20 | 100 | 250 | |
| 0.2/10P10,0.5/10P10 | 10/15,15/15,15/20,30/30 | 100 | 250 | |
| 0.2/10P15,0.5/10P15 | 10/10,15/15,30/30 | 100 | 250 | |
| 0.2/10P20,0.5/10P20 | 10/10,15/15,30/30 | 100 | 250 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 100 | 250 | |
| 0.2/0.5/10P20 | 15/15/15,30/30/30 | 100 | 250 | |
| 0.5/10P10/10P20 | 15/15/15,30/30/30 | 100 | 250 | |
| 0.2/0.5/10P20/10P20 | 15/15/30/30 | 100 | 250 | |
| 1500-2500 | 0.2 | 10,15,20,30 | 100 | 250 |
| 0.5 | 10,15,20,30 | 100 | 250 | |
| 0.2S | 10,15,20,30 | 100 | 250 | |
| 0.2/0.2,0.2S/0.2 | 10/10,15/15,20/20 | 100 | 250 | |
| 0.2/0.5,0.2S/0.5 | 10/15,15/15,20/20 | 100 | 250 | |
| 0.2/10P10,0.5/10P10 | 10/15,15/15,15/20,30/30 | 100 | 250 | |
| 0.2/10P15,0.5/10P15 | 10/10,15/15,30/30 | 100 | 250 | |
| 0.2/10P20,0.5/10P20 | 10/10,15/15,30/30 | 100 | 250 | |
| 0.2/0.5/10P10 | 15/15/15,30/30/30 | 100 | 250 | |
| 0.2/0.5/10P20 | 15/15/15,30/30/30 | 100 | 250 | |
| 0.5/10P10/10P20 | 15/15/15,30/30/30 | 100 | 250 | |
| 0.2/0.5/10P20/10P20 | 15/15/30/30 | 100 | 250 |
Installation & Wiring
Installation Diagram
The LZZB8 / LZZBJ9-35/250(III) current transformer is designed for indoor installation within 35kV-class switchgear or distribution cabinets. Proper alignment of the 250mm-wide cast-resin body, primary terminal orientation (P1/P2), and accessible secondary terminal box must be verified against the approved outline drawing prior to mounting.
Selection & FAQs
Selection Guide
- Select III when three secondary cores are required. Compare the exact 250(III) outline and terminal box with I and II versions; the same body-width code does not guarantee interchangeability.
- Choose the ratio from 50A–2500A. Confirm the unusual 315A row and its fault values before ordering, as its table position and rating progression warrant verification.
- Define all three core functions. At 300A–1600A, specify dual measurement plus protection, measurement plus dual protection, or triple 5P20 protection with per-core terminals.
- Engineer altitude and insulation together. For 3000m versions, confirm 40.5/95/185kV performance, clearances, creepage, temperature rise and partial discharge.
- Verify high-current fault and mounting data. The 2500A row is by agreement; obtain RMS duration, peak current, busbar interface, base, terminal forces and test reports.
Frequently Asked Questions
Q1: Can this 35kV current transformer be installed outdoors?
No, it is strictly designed for indoor installation. It suits 35kV/40.5kV switchgear under Class II pollution conditions. Please contact us for outdoor-rated alternatives.
Q2: What is the rated short-time thermal current for the 10A primary version?
The 10A primary rating offers a 6kA/1s short-time thermal current and 15kA dynamic current. Verify your specific system fault levels with our engineering team before ordering.
Q3: Which accuracy class combination is best for protection and measurement?
Select the 0.5/10P10 combination for dual measurement and protection. It provides 10VA or 15VA rated output per IEC 61869 standards. Confirm exact burden requirements during inquiry.
Q4: How does high altitude affect the operating temperature limits?
The high-altitude design operates up to 3000m with an ambient temperature range of -15°C to +40°C. Ensure daily averages do not exceed +30°C and request insulation correction for special projects.
Q5: Are these current transformers compliant with international IEC standards?
Yes, they fully comply with IEC 61869-1/-2 and GB/T 20840.1/.2 standards. We provide standard factory test reports with every shipment. Request specific certification documents during procurement.
Q6: Can the secondary current output be customized for specific relay panels?
Yes, standard secondary outputs are 1A or 5A to match your relay panel requirements. Custom accuracy classes and output ratings are subject to factory confirmation. Contact sales for tailored specifications.
Q7: What switchgear applications suit this cast-resin current transformer?
It is ideal for 35kV and 40.5kV indoor distribution systems and metal-clad switchgear. The epoxy cast-resin insulation ensures reliable performance in standard indoor environments. Check our catalog for more medium-voltage solutions.