Overview
The LZZBJ9-35/250-I and LZZB8-35Q are indoor support-type current transformers with a fully enclosed epoxy cast-resin insulation structure, designed for 35kV / 36kV / 40.5kV medium-voltage AC systems operating at 50Hz or 60Hz.
These transformers provide accurate current measurement, energy metering, and relay protection functions in air-insulated switchgear, distribution cabinets, and power metering panels. They comply with international standards for indoor medium-voltage applications and feature a standardized 250mm cast-resin body width for consistent cabinet integration and insulation coordination.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| 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 | Customizable per project |
| Accuracy class (metering) | 0.2, 0.5, 1.0 (as specified) |
| Accuracy class (protection) | 5P, 10P (as specified) |
| Rated output (burden) | Per IEC/ANSI standards |
| Short-time thermal current | As per system requirements |
| Dynamic withstand current | As per system requirements |
| Installation condition | Indoor |
| Insulation material | Epoxy cast-resin |
Construction
The LZZBJ9-35/250-I and LZZB8-35Q current transformers feature a fully enclosed pillar-type construction, with primary and secondary windings and magnetic core completely embedded within an epoxy cast-resin insulation body. This monolithic structure ensures high dielectric strength, excellent moisture resistance, and long-term mechanical stability under indoor operating conditions. The 250mm-wide resin body provides a defined reference for switchgear layout and electrical clearance coordination. Primary terminals are labeled P1 and P2, while secondary terminals (e.g., 1S1, 1S2, 2S1, 2S2) are arranged according to the specified winding configuration and appear on the product nameplate and approved wiring diagram.
Technical Parameters
Service Conditions
- Ambient temperature: -5°C to +40°C reference; special high-altitude version may use -15°C to +40°C by project agreement
- Altitude: Standard indoor service; high-altitude applications can be confirmed by technical agreement
- Humidity: Indoor environment without severe condensation; humidity limits shall follow project requirements
- Installation: Indoor installation for 35kV / 36kV / 40.5kV switchgear and distribution systems
- Air quality: Ambient air should not be significantly polluted by dust, smoke, corrosive gases, vapours or salt
Technical Parameters
The LZZBJ9-35/250 and LZZB8-35Q are indoor epoxy cast-resin support-type current transformers rated for 35kV–40.5kV systems, with a standard ambient temperature range of -5°C to +40°C and suitability for standard indoor altitudes (high-altitude versions available by agreement). They comply with IEC 61869-1/-2 and GB/T 20840.1/.2 standards and support primary current ranges from 30A to 2500A.
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) |
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
Outline Dimensions
The outline drawing shows critical mechanical dimensions including the 250mm cast-resin body width, mounting base layout, primary terminal positions (P1/P2), and secondary terminal access area. Ensure cabinet internal space accommodates these dimensions with adequate clearance for insulation and maintenance.
Wiring Diagram
The wiring diagram illustrates terminal markings and connections for the LZZBJ9-35/250-I / LZZB8-35Q current transformer. Primary terminals are labeled P1 and P2 to indicate current direction and polarity. Secondary windings are marked as 1S1/1S2 for the first winding (typically used for metering or measurement) and 2S1/2S2 for the second winding (typically used for protection). Additional secondary terminal groups may be provided for supplementary circuits as per project requirements. One point of the secondary circuit must be grounded in accordance with the project grounding design.
Selection & FAQs
Selection Guide
- Select structural version I from the approved outline. Do not assume interchangeability with 250-II; compare primary terminals, mounting base, body profile and secondary terminal groups.
- Choose the 30A–2500A ratio and 1A or 5A secondary. Match normal loading, instrument range and cable burden, with special attention to temperature rise above 1600A.
- Define measurement and 5P20 cores separately. Options include dual measurement, measurement/protection, dual protection and selected three-core combinations at 1000A–1600A.
- Obtain an unambiguous VA schedule. The page lists 15VA, 25VA and 50VA by group without consistently mapping them to each physical core.
- Confirm special-site and fault data. High altitude is by agreement, and 2000A–2500A fault ratings are unspecified; verify insulation correction, partial discharge, RMS duration, peak current and IEC tests.
Frequently Asked Questions
Q1: Which medium voltage systems support this 35kV epoxy current transformer?
These models are designed for 35kV, 36kV, and 40.5kV indoor switchgear and distribution systems. Ensure installation environments meet standard indoor humidity and air quality limits. Contact us for specific project compatibility.
Q2: How do ambient temperature limits affect the LZZBJ9-35 installation?
Standard indoor installation requires an ambient temperature between -5°C and +40°C. For colder environments down to -15°C, a special high-altitude version is available by project agreement. Confirm your site conditions during ordering.
Q3: Can a charged display device be added to this CT?
Yes, it can be added since the secondary winding supports up to 3 cores. Specify the exact core configuration and display requirements in your technical inquiry.
Q4: What international standards does the LZZB8-35Q current transformer comply with?
It fully complies with IEC 61869-1/-2 and GB/T 20840.1/.2 standards. Request the specific type test and routine test certificates from our sales team for your project documentation.
Q5: Are custom primary current ratios available for this support-type CT?
Yes, standard primary current ranges cover 30A to 2500A. For ratios outside this range or specific accuracy class combinations, submit your detailed specifications for factory confirmation.
Q6: When selecting this model, what determines the short-time thermal current?
The short-time thermal and dynamic current ratings vary based on the specific model and core configuration. Provide your system fault levels to our engineering team for precise parameter selection.
Q7: Why choose an epoxy cast-resin design for indoor 35kV applications?
Epoxy cast-resin provides high dielectric strength and moisture resistance for indoor switchgear. It eliminates oil maintenance requirements while ensuring stable performance in standard indoor environments.