Product Overview
The LMZ-6 / LMZ-10 / LM-6 / LM-10 current transformer is an indoor, single-phase, epoxy resin cast, through-hole current transformer designed for air-insulated medium-voltage switchgear. It is used for current measurement, electric energy metering, feeder monitoring, and relay protection in 6kV, 10kV, 11kV, and 12kV class power systems with rated frequency of 50Hz or 60Hz.
This series is a busbar or conductor-through type current transformer. The primary conductor passes through the central window, while the secondary winding and magnetic core are encapsulated in epoxy resin casting insulation. The structure is compact and suitable for installation in air-insulated switchgear, ring main units, load switch panels, metering cabinets, and other indoor MV distribution equipment. The product can be supplied for measurement-only, protection-only, or combined measuring/protection applications according to project requirements.
Product Type
| Item | Specification |
|---|---|
| Product name | Indoor Through-Hole Epoxy Resin Cast Current Transformer |
| Model series | LMZ-6 / LMZ-10 / LM-6 / LM-10 |
| Product structure | Indoor single-phase, through-hole, epoxy resin cast current transformer |
| Voltage class | 6kV, 10kV, 11kV, and 12kV medium-voltage systems |
| Rated insulation level | 7.2/32/60kV for 6kV class; 12/42/75kV for 10kV-12kV class |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A according to project requirement |
| Rated primary current | 50A to 630A reference range; customized ratios available by technical agreement |
| Application type | Current measurement, energy metering, relay protection, and switchgear monitoring |
| Installation location | Indoor air-insulated switchgear, RMU panels, metering cabinets, and distribution equipment |
| Applicable standard | IEC 61869-1 / IEC 61869-2; IEC 60044-1 can be referenced for legacy projects |
Product Display
Applications
- 6kV, 10kV, 11kV, and 12kV indoor medium-voltage distribution systems
- Air-insulated switchgear, load switch cabinets, and ring main units
- Current measurement and electric energy metering circuits
- Relay protection and feeder monitoring circuits
- Compact switchgear where the primary conductor passes through the CT window
- MV metering assemblies requiring combined metering and protection secondary outputs
Features
- Through-hole structure: The primary conductor or busbar passes through the central window, simplifying primary wiring and reducing primary winding complexity.
- Epoxy resin casting: The magnetic core and secondary winding are encapsulated in cast resin to improve insulation strength, mechanical stability, and moisture resistance.
- 6kV and 10kV versions: LMZ-6 / LM-6 are used for 6kV class systems, while LMZ-10 / LM-10 are used for 10kV, 11kV, and 12kV class switchgear applications.
- Metering and protection outputs: The CT can be configured with 0.5 / 1 / 3 measuring classes and 10P protection output according to project requirements.
- Compact circular body: The round through-hole body supports easy installation around busbars, conductors, or insulated primary parts in MV panels.
- Customizable configurations: Non-standard current ratios, secondary current, burden, terminal layout, and winding configuration can be confirmed by technical agreement.
Working Principle
The LMZ / LM series current transformer operates according to electromagnetic induction. The primary conductor passing through the central window generates magnetic flux in the magnetic core. The secondary winding outputs a proportional current signal to measuring instruments, energy meters, protection relays, or monitoring devices. The epoxy resin casting provides insulation and mechanical protection for the secondary winding and core.
For metering applications, the transformer should maintain the required accuracy within the rated burden. For relay protection applications, the protection winding should provide a reliable secondary current signal under fault conditions and coordinate with the relay setting, rated burden, and system short-circuit requirement.
Model Designation
The model designation identifies the current transformer type, indoor structure, cast-resin insulation, and voltage class.
| Code | Meaning |
|---|---|
| L | Current transformer |
| M | Busbar / through-hole type structure |
| Z | Cast-resin insulated structure |
| 6 | 6kV class version, normally using 7.2/32/60kV insulation level |
| 10 | 10kV class version, applicable to 10kV, 11kV, and 12kV systems with 12/42/75kV insulation level |
Model coverage: This product page covers LMZ-6, LMZ-10, LM-6, and LM-10. Final selection should be confirmed according to system voltage, current ratio, accuracy class, rated output, insulation level, installation window, and switchgear drawing.
Technical Data
| Item | LMZ-6 / LM-6 | LMZ-10 / LM-10 |
|---|---|---|
| Voltage class | 6kV class | 10kV, 11kV, and 12kV class |
| Rated insulation level | 7.2/32/60kV | 12/42/75kV |
| Rated frequency | 50Hz / 60Hz | 50Hz / 60Hz |
| Rated primary current | 50A to 630A reference range | 50A to 630A reference range |
| Rated secondary current | 5A or 1A | 5A or 1A |
| Accuracy class | 0.5 / 1 / 3; 10P protection available | 0.5 / 1 / 3; 10P protection available |
| Rated output | 3.75VA for measuring reference; 5VA for 10P reference | 3.75VA for measuring reference; 5VA for 10P reference |
| Surface creepage distance | 134mm reference | 175mm reference |
| Weight | Approx. 4kg | Approx. 5kg |
| Insulation medium | Epoxy resin casting insulation | Epoxy resin casting insulation |
| Installation method | Indoor through-hole conductor installation | Indoor through-hole conductor installation |
Terminal Marking
The LMZ / LM series can be supplied with single-core or multi-core secondary winding configurations. The wiring diagram may include single secondary output, dual secondary output, tapped secondary output, or multiple secondary groups according to the required metering and protection circuits.
| Terminal Marking | Function | Application Note |
|---|---|---|
| P1 / P2 | Primary direction marking | The reference primary current direction is normally defined from P1 to P2 through the CT window. |
| S1 / S2 | Single secondary winding | Used for single measuring, metering, or protection output. |
| 1S1 / 1S2 | First secondary group | Usually used for metering or measurement circuit. |
| 2S1 / 2S2 | Second secondary group | Usually used for relay protection or additional monitoring circuit. |
| S1 / S2 / S3 | Tapped secondary winding | Used when a tapped secondary ratio or special wiring arrangement is required. |
Terminal markings follow standard CT polarity conventions. Correct terminal identification shall be observed to ensure metering accuracy, relay protection performance, and safe maintenance. The secondary circuit must not be open-circuited when the primary circuit is energized.
Selection Table
| Model | Rated
Current Ratio |
Accuracy
Class & Rated Output |
10P
Rated Output |
Rated
Insulation Level |
Creepage
Distance |
Weight |
|---|---|---|---|---|---|---|
| LMZ-6 / LM-6 | 50-630A / 5A or 1A | 0.5 / 1 / 3: 3.75VA | 10P: 5VA | 7.2/32/60kV | 134mm | Approx. 4kg |
| LMZ-10 / LM-10 | 12/42/75kV | 175mm | Approx. 5kg |
Note: The table is for preliminary engineering selection. If the required current ratio, accuracy class, burden, secondary current, creepage distance, insulation level, or terminal arrangement exceeds the listed range, final parameters shall be confirmed by technical agreement, approved drawing, nameplate, and factory test report.
Wiring Diagram
The LMZ / LM series can support different secondary wiring arrangements according to metering and protection requirements. Typical configurations include one secondary winding, two independent secondary groups, tapped secondary outputs, and multi-core metering/protection outputs.
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 6kV, 10kV, 11kV, or 12kV class
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: -5°C to +40°C reference range
- Suitable for air-insulated switchgear with controlled humidity and pollution level
- The installation site should be free from severe vibration, corrosive gas, explosive medium, heavy conductive dust, and abnormal condensation.
- For high altitude, high humidity, coastal, high-pollution, or compact switchgear conditions, technical confirmation is recommended before ordering.
Standards and Compliance
The LMZ-6 / LMZ-10 / LM-6 / LM-10 current transformer can be supplied according to IEC 61869-1 and IEC 61869-2. IEC 60044-1 may be referenced for legacy project specifications. Routine tests, dielectric tests, polarity verification, ratio test, accuracy test, insulation resistance, and partial discharge requirements should be confirmed according to the final technical agreement.
Installation and Dimensions
The LMZ / LM series is designed for indoor through-hole installation. The central window, primary conductor size, secondary terminal box, mounting holes, creepage distance, and electrical clearances shall be confirmed according to the approved outline drawing before switchgear design or batch production.
Outline Data
| Item | Selection Note |
|---|---|
| Mechanical structure | Indoor through-hole epoxy resin cast current transformer |
| Primary conductor | Primary conductor, busbar, or insulated conductor passes through the central window |
| Secondary terminals | Terminal block arrangement according to selected winding configuration |
| Mounting method | Switchgear-mounted installation according to outline drawing |
| Drawing confirmation | Final window size, outline, terminal direction, and mounting dimensions shall be confirmed before production |
Safety Notes
- Confirm the model, voltage class, current ratio, secondary current, accuracy class, rated output, insulation level, and wiring arrangement before installation.
- Check the primary conductor diameter, busbar clearance, phase-to-ground clearance, and switchgear layout against the approved drawing.
- Connect secondary terminals according to terminal markings and the project wiring diagram.
- The secondary circuit of a current transformer must not be left open when the primary circuit is energized.
- During meter or relay maintenance, short-circuit the CT secondary circuit before disconnecting any secondary wiring.
- Secondary grounding shall follow the project specification and local electrical safety requirements.
- Installation and maintenance shall be performed by qualified medium-voltage electrical personnel.
Ordering Info
Please provide the following information when ordering or requesting a quotation:
- Product model: LMZ-6, LMZ-10, LM-6, or LM-10
- System voltage: 6kV, 10kV, 11kV, or 12kV
- Rated primary current / current transformation ratio
- Rated secondary current: 1A or 5A
- Accuracy class and rated output requirement
- Protection class requirement, if 10P output is needed
- Primary conductor diameter, busbar size, or through-hole size requirement
- Wiring diagram requirement: single secondary, dual secondary, tapped secondary, or multi-core output
- Insulation level and applicable IEC standard
- Switchgear type, installation layout, terminal direction, and required outline drawing
- Quantity, labeling, certificates, routine test reports, and packaging requirements
Selection Tips
- Confirm voltage class: Select LMZ-6 / LM-6 for 6kV systems and LMZ-10 / LM-10 for 10kV, 11kV, and 12kV systems.
- Check insulation level: Use 7.2/32/60kV for 6kV class and 12/42/75kV for 10kV-12kV class applications.
- Confirm primary conductor size: The conductor or busbar must match the CT window and the switchgear clearance requirement.
- Select secondary current: Choose 5A or 1A according to meter, relay, cable length, and burden calculation.
- Define accuracy requirement: Use 0.5 / 1 / 3 for measurement or metering and 10P for relay protection circuits.
- Confirm wiring diagram: Verify whether the project requires single secondary, dual secondary, tapped secondary, or multi-core output.
- Confirm drawings: Check outline dimensions, terminal direction, and installation space before production.