LZZBJ9-12/150B/3s fully-enclosed epoxy resin current transformer

LZZBJ9-12/150B/3s fully-enclosed epoxy resin current transformer

12kV indoor epoxy-cast current transformer for accurate metering, protection

  • Cast resin pillar-type construction: Fully-enclosed epoxy for superior insulation
  • 0.2S/0.5/10P10 accuracy cores: Multi-core metering and protection support
  • 12/42/75kV insulation level: Moisture and pollution class II resistance
  • Tested Ith/Idyn performance: Verified short-circuit fault capability

Product Overview

Functional Definition

The LZZBJ9-12/150B/3s series fully-enclosed epoxy resin current transformer is a fully-enclosed post-type instrument transformer designed for accurate current measurement, energy metering, and relay protection applications in medium-voltage AC power systems. Suitable for 10kV and below voltage classes with operating frequency of 50Hz or 60Hz, the product is specifically engineered for installation within switchgear, ring main units, and other compact indoor environments. The transformer provides reliable performance in high humidity and contaminated environments with superior moisture resistance and pollution resistance capabilities.

Key Ratings

Item Specification (per order / nameplate)
System voltage class 12 kV class (indoor switchgear and distribution applications)
Rated frequency 50 Hz (60 Hz available upon request)
Rated secondary current 1 A or 5 A
Accuracy classes Metering and/or protection cores as specified (e.g., 0.2S / 0.5, 10P10)
Primary current range 20 A to 3000 A
Insulation level 12 / 42 / 75 kV
Rated burden Per core/winding as specified (VA)
Burden power factor cosφ = 0.8 (lagging) unless otherwise specified
Short-circuit withstand Ith (1 s) and Idyn (peak) as specified
Applicable standards GB 1208-1997; IEC 61869-1 / IEC 61869-2; GB/T 20840.1 / 20840.2

Product Shows

LZZBJ9 12pics

Working Principle

Operating on Faraday’s law of electromagnetic induction, the transformer features a toroidal magnetic core with primary conductor passing through the aperture and secondary windings wound around the core. The magnetic flux generated by primary current induces proportional voltage in the secondary winding, delivering standardized output current through connected burden. The fully-enclosed epoxy resin construction ensures stable magnetic characteristics and superior insulation performance throughout the service life.

System Application Position

  • Medium Voltage Distribution: 10-12kV switchgear and distribution panels
  • Energy Metering: Revenue-grade electricity measurement systems
  • Protection Circuits: Overcurrent, differential, and distance protection schemes
  • Ring Main Units: Compact RMU installations requiring space-saving solutions
  • SCADA Integration: Supervisory control and data acquisition systems

Structural Overview

Epoxy resin cast construction with fully-enclosed design ensures superior insulation performance, moisture resistance, and mechanical strength. The post-type mounting configuration provides compact installation in constrained switchgear environments while maintaining excellent electrical clearance and creepage distances. The ring-type magnetic core design optimizes measurement accuracy and thermal stability.

Model Designation

lzzbj9 12 Types

Model Code Explanation

  • L — Current transformer (CT)
  • Z — Indoor support (pillar) type
  • Z — Cast-resin (epoxy) insulated, fully enclosed structure
  • B — Protection configuration available (metering/protection application)
  • J — Reinforced design
  • 9 — Design code (platform/iteration)
  • 12 — Voltage class (kV)
  • 150B/2s, 150B/3s— Mechanical variant code (installation/structure differences)

Variant Differences

LZZBJ9-12/150B/3s , LZZBJ9-12/150B/2s are electrically equivalent when specified with the same ratio, accuracy classes, burdens, and Ith/Idyn. The differences between150B/3s and 150B/2s variants are primarily mechanical and installation-related to match different switchgear layouts and mounting constraints.

Service Conditions

The LZZBJ9-12/150B series current transformers are designed for indoor operation under normal service conditions in medium-voltage power systems.

  • Installation environment: Indoor installation only
  • Altitude: Not exceeding 1000 m above sea level (higher altitude shall be specified for engineering confirmation)
  • Ambient temperature: −5 °C to +40 °C
  • Relative humidity: Daily average ≤ 95%, monthly average ≤ 90% (at +20 °C reference)
  • Environmental conditions: Free from corrosive gases or vapors; free from explosive or flammable media; no severe vibration, mechanical shock, or impact
  • Pollution class: Class II per IEC 60815
Engineering Note: The installation location shall comply with applicable electrical safety regulations and provide stable operating conditions throughout the transformer’s service life.

Construction

Construction Design

  • Structure: Support (post) type for indoor switchgear
  • Insulation: Fully enclosed epoxy resin cast insulation
  • Core: High-strength toroidal ring-type magnetic core design
  • System: Integrated primary and secondary insulation system

The epoxy resin casting provides stable insulation properties and resistance to moisture, contamination, and aging for long-term indoor service. The fully-enclosed design ensures superior protection against environmental contaminants and maintains performance even in pollution degree II environments.

Windings & Terminal Marking

LZZBJ9 10 Primary terminals

  • Primary terminals: P1 / P2
  • Secondary terminals (Group 1): 1S1 / 1S2
  • Secondary terminals (Group 2): 2S1 / 2S2

Terminal markings follow standard CT polarity conventions. Under normal operating conditions, the reference current direction is defined from P1 to P2. Correct terminal identification shall be observed to ensure metering and protection performance.

Safety Warning: Never open-circuit the secondary terminals when primary current is flowing. High voltage may appear across open secondary terminals, creating serious safety hazards. Always short-circuit and ground the secondary before performing any maintenance work.

Technical Data

This section provides selection-oriented technical data for the LZZBJ9-12/150B/2S,  LZZBJ9-12/150B/3S series indoor, cast-resin current transformer used in 12 kV class AC systems (50 Hz). Data shown below is intended for preliminary selection of accuracy class combinations, rated burdens, and short-circuit withstand capability.

Definitions: Accuracy class combination indicates available metering/protection cores in one CT (multi-core configuration may apply). Rated output (VA) is specified per secondary core. Ith is the rated short-time thermal current (typically 1 s). Idyn is the rated dynamic current (peak).

Notation: Ith/Idyn may be expressed as kA or as multiples of rated primary current (×In) depending on configuration; acceptance shall be based on nameplate values and the factory test report.

Data Reference

Rated
Primary
Current (A)		 Accuracy Class
Combination		 Rated
Output (VA)		 Short-time
Thermal
Current (Ith)		 Dynamic
Current
(Idyn)
20~100 0.2S/10P10 10/15 150I1n 375I1n
150~200 0.2S/0.5/10P10 10/15/15 21.5 kA 55.4 kA
300~400 0.5/10P10 10/15 31.5 kA 80 kA
500~600 0.2/10P10 10/15 45 kA 112.5 kA
800 0.2S/10P10 10/15 63 kA 130 kA
0.2S/0.5/10P10 10/15/15
0.5/10P10 10/10
0.2/10P10 10/15
1000 0.2S/10P10 10/15 80 kA 160 kA
0.2S/0.5/10P10 10/15/15
0.5/10P10 10/10
0.2/10P10 10/15
1500 0.2/10P10 10/15 100 kA 160 kA
2000 0.2/10P10 10/15 100 kA 160 kA
Application Engineering Support: Application-specific recommendations may include burden calculation, accuracy assessment, terminal allocation, and switchgear integration guidance based on project specification.

Standards & Normative References

Standard Title Application
GB 1208-1997 Current Transformers Primary national standard for CT requirements
IEC 61869-1 Instrument Transformers – Part 1: General Requirements General requirements
IEC 61869-2 Instrument Transformers – Part 2: Additional Requirements for Current Transformers CT-specific requirements
GB/T 20840.1 Instrument Transformers – Part 1: General Requirements National standard (aligned with IEC 61869 framework)
GB/T 20840.2 Instrument Transformers – Part 2: Current Transformers National CT requirements (aligned with IEC 61869-2)
IEC 60815 Selection and Dimensioning of High-Voltage Insulators for Polluted Conditions Pollution class determination

Factory Test Compliance

  • Routine tests per applicable GB/IEC requirements (including polarity/marking, ratio verification, and accuracy verification per specified class and burden)
  • Dielectric tests per insulation coordination requirements and applicable standard
  • Partial discharge test where specified by the project requirement
  • Visual and dimensional inspection including marking and workmanship conformity
  • Type and special tests as required by the project specification
Compliance Note: All units maintain full compliance with listed standards. Factory test certificates provided for each manufactured unit with traceability to accredited laboratories. Test reports include ratio error, phase displacement, burden verification, and dielectric withstand results.

Installation & Dimensions

Outline

LZZBJ9 12 150B 2s Current Transformers

LZZBJ9-12/150B/2s Current Transformer Outline

LZZBJ9 12 150B 3s Current Transformers

LZZBJ9-12/150B/3s Current Transformer Outline

  • Outline dimensions and mounting details are provided in the dimensional drawings
  • The transformer shall be securely mounted using the designated fixing holes with appropriate torque specifications
  • Primary conductor connection may be made via busbar or bolted terminals
  • Adequate clearance shall be maintained for insulation, heat dissipation, and maintenance access
  • Secondary wiring shall use appropriate cable size to minimize burden contribution
Safety Notice: Secondary circuits must never be left open when energized. Before maintenance, short-circuit and reliably ground the secondary in accordance with local electrical safety regulations. One point of the secondary circuit shall be permanently grounded per applicable safety standards.
  • Secondary circuit must never be left open when the transformer is energized, as dangerous high voltage may appear across the secondary terminals
  • During inspection or maintenance, the secondary circuit shall be short-circuited before disconnecting any instruments
  • One point of the secondary circuit should be reliably grounded in accordance with IEC 61869-1 and local standards
  • All installation and maintenance work shall comply with local electrical safety regulations and qualified personnel requirements
  • Verify correct polarity before connecting to metering or protection devices

When placing an order, the required configuration shall be specified according to the local grid requirements, applicable standards, and project technical specification. The following parameters shall be clearly stated for technical confirmation and production release:

  • Rated primary current / transformation ratio (e.g., 400/5A, 800/1A)
  • Rated secondary current (1 A or 5 A)
  • Application and accuracy requirements (metering and/or protection accuracy class combination)
  • Rated burden (VA) for each secondary core/winding
  • Short-circuit withstand requirements: Ith (1 s) and Idyn (peak)
  • Installation variant (if specific mounting requirements exist)

Selection Guide

  1. Determine rated primary current (Ip) based on feeder/load rating and expected operating range (typically 20-120% of nominal load)
  2. Select metering and/or protection accuracy requirements (e.g., 0.2S / 0.5 for metering; 10P10 for protection per protection coordination study)
  3. Confirm rated burden (VA) for each secondary circuit based on connected meters/relays and wiring losses (include cable resistance calculation)
  4. Verify short-circuit withstand capability (Ith/Idyn) against the switchgear fault level per system short-circuit study
  5. Specify any special requirements including insulation level, partial discharge limits, terminal arrangement, mounting constraints, or certification requirements

If local utility or project requirements apply (e.g., specific insulation level, partial discharge limit, terminal arrangement, mounting constraints, documentation language, or required certificates), specify them at the ordering stage. Special configurations shall be confirmed by technical agreement and final data sheet prior to production.

FAQs

Select CT ratio / rated primary current (Ip) from feeder continuous load and required measurement range, then verify against 12 kV switchgear design and protection coordination.

Specify separate secondary cores for metering and protection, each with its own accuracy class and rated burden (VA) per IEC 61869-2 and GB 1208-1997.

Rated burden (VA) shall cover total connected load (meter/relay + wiring loss) for 1A or 5A secondary current and shall be confirmed during engineering design.

Ith (1 s) and Idyn (peak) shall meet or exceed the system prospective short-circuit current; acceptance is by nameplate and factory test report.

Yes. With identical ratio/accuracy/burden/Ith/Idyn, A/B/C variants are electrically equivalent; selection is based on mounting and switchgear integration.