LZZBJ9-12/185b/4S, AS12/185b/4S Epoxy Cast-Resin Current Transformer

Product Overview

The LZZBJ9-12/185b/4S current transformer, also supplied as AS12/185b/4S, is an indoor epoxy cast-resin, fully enclosed support-type current transformer for medium-voltage switchgear. It is designed for current measurement, revenue metering, feeder monitoring, relay protection and multi-circuit secondary signal distribution in 10kV, 11kV and 12kV class indoor AC power systems.

This model uses a 185b support body with a 4S multi-secondary configuration. Compared with the 185b/2S version, the 185b/4S design is intended for switchgear projects where the CT must provide more independent secondary circuits in one body. It is suitable for panels that require separate cores for metering, indication, protection and backup protection.

The primary conductor, secondary windings and magnetic cores are encapsulated inside the epoxy resin casting body. This dry-type construction provides mechanical strength, stable insulation performance and resistance to indoor humidity and contamination. Each secondary core should be defined separately by function, accuracy class, rated output, terminal marking and burden requirement.

Product Type

Product Display

Applications

• Indoor 10kV, 11kV and 12kV class medium-voltage switchgear
• Incoming and outgoing feeder panels requiring multiple secondary CT outputs
• Revenue metering systems requiring a dedicated metering core
• Protection relay systems requiring independent protection and backup protection cores
• Power monitoring, SCADA, automation and feeder supervision systems
• Switchgear projects requiring 185b support body clearance with 4S secondary terminal arrangement

Features

• 185b support platform: Provides more terminal and busbar clearance than compact 150b models, suitable for higher wiring density and larger switchgear layouts.
• 4S multi-secondary design: Multiple secondary circuits allow separate functions for metering, measurement, protection and backup protection.
• Epoxy cast-resin insulation: Fully enclosed resin insulation supports stable dielectric performance, mechanical protection and indoor environmental resistance.
• International voltage application: Suitable for common 10kV, 11kV and 12kV class networks with 12/42/75kV insulation coordination.
• Flexible accuracy combinations: Typical accuracy options include 0.2S, 0.2, 0.5, 10P, 10P15 and 10P20 according to metering or protection requirements.
• Clear secondary separation: Each secondary circuit can be defined with its own function, burden and terminal marking to reduce wiring errors in complex panels.

Principle

The LZZBJ9-12/185b/4S current transformer converts primary current into standard secondary current by electromagnetic induction. Primary current generates magnetic flux in the CT core, and the secondary windings deliver proportional current signals to meters, relays and monitoring devices. The epoxy resin casting body forms the insulation barrier between the medium-voltage primary side and the low-voltage secondary circuits.

In a 4S configuration, the CT should not be selected as one general output device. Each core should be treated as an independent engineering circuit. Metering cores should be checked for ratio error, phase displacement and burden. Protection cores should be checked for accuracy limit factor, relay burden, short-time thermal current and dynamic withstand level.

Model Designation

Technical Data

Terminals

The 4S schematic structure indicates a multi-secondary arrangement. Typical terminal markings include P1 / P2 for the primary side and 1S1 / 1S2, 2S1 / 2S2, 3S1 / 3S2 and 4S1 / 4S2 for secondary circuits. Final terminal identification shall follow the approved drawing, wiring diagram and nameplate.

Selection Table

The following table summarizes typical 185b/4S ratio ranges and multi-secondary technical selection data. Long accuracy and rated-output values are wrapped into multiple lines for website readability.

Note: The above values are for technical selection reference. If project requirements exceed the listed scope, final parameters shall be confirmed by agreement between manufacturer and purchaser. Nameplate data, approved drawings and factory test reports shall prevail.

Structure Reference

Service Conditions

• Installation location: indoor medium-voltage switchgear
• System voltage: 10kV, 11kV and 12kV class networks
• Rated frequency: 50Hz / 60Hz
• Ambient temperature: -5°C to +40°C
• The installation environment should be free from severe vibration, conductive dust, corrosive gas, explosive medium, heavy pollution and abnormal condensation.
• For high altitude, humid, coastal, high-pollution or special switchgear conditions, technical confirmation is required before ordering.

Standards and Compliance

The LZZBJ9-12/185b/4S current transformer can be supplied according to GB 20840.2-2014, IEC 61869-3:2011 and special project requirements. For IEC-oriented international projects, it can be positioned as a 12kV class indoor epoxy cast-resin CT with 12/42/75kV insulation coordination. Routine tests normally include ratio test, polarity verification, accuracy test, dielectric withstand test and appearance inspection.

Installation and Dimensions

The product adopts an indoor support-type structure with top primary terminals and lower secondary terminal arrangement. Compared with the 185b/2S model, the 4S version requires more attention to secondary terminal space, cable routing and shorting terminal arrangement. The approved outline drawing shall be used before switchgear production or replacement.

Dimensions

Safety Notes

• Confirm model, current ratio, secondary current, accuracy combination, rated output and insulation level before installation.
• Check primary terminal clearance, secondary terminal quantity, cable routing and shorting terminal location before assembly.
• Mark each secondary core clearly according to its function before wiring.
• Connect P1/P2 and secondary terminals according to polarity markings and the project wiring diagram.
• The secondary circuit of a current transformer must not be open-circuited when the primary circuit is energized.
• Before disconnecting instruments or relays, short-circuit the corresponding secondary circuit through an approved shorting terminal block.
• Installation and maintenance shall be performed by qualified medium-voltage electrical personnel.

Ordering Info

• Product model: LZZBJ9-12/185b/4S or AS12/185b/4S
• Rated primary current and rated secondary current
• Function assignment for each secondary core
• Accuracy class combination and rated output for each secondary circuit
• Rated insulation level and applicable IEC / GB standard
• Required short-time thermal current and dynamic current
• Secondary terminal marking and 4S schematic requirement
• Switchgear layout, mounting dimensions and primary terminal direction
• Quantity, certificates, routine test reports, labeling and packaging requirements

Selection Guide

1. Confirm model designation: Use LZZBJ9-12/185b/4S or AS12/185b/4S according to project documents and nameplate requirements.
2. Define secondary functions: Assign each of the four secondary circuits to metering, measurement, protection, backup protection or monitoring.
3. Select current ratio: Choose the rated primary current based on feeder load, metering range and relay setting.
4. Check each burden: Calculate meter burden, relay burden and secondary cable resistance for every core.
5. Verify protection performance: Confirm protection class, accuracy limit requirement and short-circuit withstand values.
6. Review cabinet wiring: Reserve enough terminal and cable space for the 4S configuration.
7. Approve drawings: Confirm outline drawing, terminal diagram, mounting holes and nameplate before production.

FAQs