Product Overview
The LA-10Q / LFZ-10Q / LFZB1-10Q current transformer is an indoor wall-through epoxy resin cast current transformer designed for medium-voltage AC power systems. It is used for current measurement, electric energy metering, feeder monitoring, and relay protection in indoor switchgear and distribution equipment. The product is designed for 10kV class systems and can be positioned for 10kV, 11kV and 12kV class international indoor applications when insulation coordination, service condition, and project standards are confirmed.
This product family is defined by two construction ranges. The 5-200/5A ratios use a semi-enclosed cast-resin structure, which is suitable for lower-current circuits and compact switchgear installation. The 300-1500/5A ratios use a fully enclosed cast-resin structure, providing stronger external insulation and better suitability for higher-current circuits. This makes the series suitable for all-condition indoor applications, including humid, polluted, condensation-prone, and tropical environments.
Product Type
| Item | Specification |
|---|---|
| Product name | Indoor Semi-Enclosed and Fully Enclosed Wall-Through Cast Resin Current Transformer |
| Model series | LA-10Q / LFZ-10Q / LFZB1-10Q |
| Product structure | Wall-through type, epoxy resin casting insulation, reinforced Q-type structure |
| Structure range | 5-200/5A: semi-enclosed type; 300-1500/5A: fully enclosed type |
| Voltage class | 10kV class; applicable to 10kV, 11kV and 12kV class indoor systems by project confirmation |
| Rated insulation level | 11.5/42/75kV |
| Rated secondary current | 5A |
| Applications | Current measurement, energy metering, relay protection, switchgear instrumentation |
Product Display
The catalogue identifies this series as LA-10Q, with corresponding designations LFZ-10Q and LFZB1-10Q. The selection shall be made according to current ratio, structure type, accuracy class, rated output, and confirmed outline drawing.
Applications
- 10kV, 11kV and 12kV class indoor medium-voltage switchgear
- Incoming and outgoing feeder panels in distribution rooms
- Current measurement and electric energy metering circuits
- Relay protection circuits requiring 10P10 performance
- Indoor environments with humidity, condensation, surface dew point, or pollution requirements
- Retrofit projects where older wall-through CT structures require dimensional and electrical review
Features
- Two construction ranges: 5-200/5A adopts semi-enclosed casting, while 300-1500/5A adopts fully enclosed casting.
- All-condition insulation design: The resin casting structure is suitable for indoor applications with humidity, surface condensation, or pollution considerations.
- Wall-through installation: The product is designed for through-panel mounting in indoor switchgear and cabinet structures.
- Reinforced Q-type structure: The stiffened construction improves mechanical support and external insulation performance.
- Metering and protection classes: Accuracy classes include 0.2, 0.5, 1 and 10P10 for measurement and relay protection.
- Current-ratio based selection: The current ratio directly affects structure type, outline dimensions, rated output, and short-circuit withstand data.
Principle
The LA-10Q / LFZ-10Q / LFZB1-10Q current transformer operates according to electromagnetic induction. Current flowing through the primary conductor generates magnetic flux in the core, and the secondary winding outputs a proportional 5A current signal to meters, relays, or monitoring devices. The resin casting insulation separates the medium-voltage primary circuit from the low-voltage secondary circuit.
For metering circuits, the selected accuracy class and VA output must match the connected meter and wiring burden. For protection circuits, the 10P10 core must maintain the required accuracy limit performance under fault-current conditions. Relay burden, cable resistance, and the required protection accuracy limit factor should be checked together.
Model Designation
The model code can be interpreted as follows:
| Code | Meaning |
|---|---|
| L | Current transformer |
| A | Wall-through type |
| 10 | Rated voltage class: 10kV class |
| Q | Stiffening / reinforced type |
| LFZ-10Q | Corresponding wall-through cast-resin CT designation |
| LFZB1-10Q | Corresponding reinforced or fully enclosed wall-through cast-resin CT designation |
Technical Data
| Item | Specification |
|---|---|
| Rated insulation level | 11.5/42/75kV |
| Rated frequency | 50Hz |
| Rated secondary current | 5A |
| Primary current range | 5/5A to 1500/5A |
| Structure by ratio | 5-200/5A semi-enclosed; 300-1500/5A fully enclosed |
| Accuracy class | 0.2, 0.5, 1 and 10P10 |
| Burden power factor | 0.8, lagging |
| Artificial pollution class | Class 2 |
| Partial discharge | Apparent partial discharge not more than 50pC according to GB5583-85 and IEC44-4 reference |
| Installation type | Indoor wall-through mounting |
Selection Table
The following table uses current ratio as the main selection basis. The structure column clearly separates the semi-enclosed and fully enclosed ranges, so the product can be selected according to both electrical rating and cabinet installation requirement.
| Current Ratio
Rated Primary Current |
Structure
Type |
Accuracy
0.2 Output |
Accuracy
0.5 Output |
Class 1
Output |
10P10
Output |
1s Thermal
Current Ith |
Dynamic
Current Idyn |
|---|---|---|---|---|---|---|---|
| 5/5, 10/5, 15/5, 20/5, 30/5, 40/5, 50/5, 75/5, 100/5, 150/5, 200/5 | Semi-enclosed resin casting type |
5-10VA | 10VA | 10VA | 15VA | 90 x In | 160 x In |
| 300/5, 400/5 | Fully enclosed resin casting type |
15VA | 25VA | 25VA | 15VA | 75 x In | 135 x In |
| 500/5 | Fully enclosed resin casting type |
15VA | 25VA | 25VA | 15VA | 60 x In | 110 x In |
| 600/5, 800/5, 1000/5, 1500/5 | Fully enclosed resin casting type |
25VA | 25VA | 25VA | 20VA | 50 x In | 90 x In |
Note: The selection data is based on the catalogue table. Final current ratio, accuracy class, rated output, outline dimension, short-time withstand data, and partial discharge requirement shall be confirmed according to the approved drawing, nameplate, and factory test report.
Structure Range
| Current Range | Structure | Engineering Meaning |
|---|---|---|
| 5-200/5A | Semi-enclosed resin casting | Suitable for lower-current circuits where compact size, metering accuracy, and normal indoor insulation conditions are the main requirements. |
| 300-1500/5A | Fully enclosed resin casting | Suitable for higher-current circuits requiring stronger external insulation, improved environmental resistance, and higher short-circuit withstand capability. |
Protection Curve
The catalogue provides an accuracy limit factor curve for class 10P. For protection applications, relay burden, secondary cable resistance, and the required protection accuracy limit factor should be evaluated together. A larger secondary burden may reduce the available accuracy limit factor, so the selected CT output should be checked against the actual relay circuit burden.
Service Conditions
- Installation location: indoor medium-voltage switchgear
- Rated frequency: 50Hz
- System voltage: 10kV class, with 10kV, 11kV and 12kV class project application subject to insulation confirmation
- Suitable for indoor environments where condensation, surface dew point, or tropical humidity may need to be considered
- Artificial pollution class: Class 2 reference
- The installation environment should be free from severe vibration, explosive medium, corrosive gas, heavy conductive dust, and abnormal mechanical stress.
Standards and Compliance
The LA-10Q / LFZ-10Q / LFZB1-10Q current transformer catalogue references GB5583-85 and IEC44-4 for partial discharge related requirements, with apparent partial discharge not more than 50pC. For international projects, the applicable IEC / GB standard combination, routine test items, insulation requirements, and acceptance criteria should be confirmed in the technical agreement.
Installation and Dimensions
The product uses wall-through installation and includes different hole and overall dimension groups according to current range. The 5-200/5A and 300-1500/5A structures should not be treated as the same mechanical layout. Before switchgear production, the selected current ratio, structure type, mounting hole, terminal direction, conductor path, and clearance shall be checked with the approved outline drawing.
Dimensions
| Current Range | Dimension Group | Installation Note |
|---|---|---|
| 5-200/5A | Semi-enclosed structure drawing group | Use the lower-current hole dimension and overall dimension reference shown for the semi-enclosed version. |
| 300-1500/5A | Fully enclosed structure drawing group | Use the higher-current outline drawing and confirm the L dimension according to current range. |
| 300-400A | L = 340mm reference | Confirm against final drawing before cabinet drilling. |
| 500-600A | L = 410mm reference | Confirm against final drawing before cabinet drilling. |
| 800-1500A | L = 370mm reference | Confirm against final drawing before cabinet drilling. |
Safety Notes
- Confirm current ratio, structure type, accuracy class, rated output, and short-circuit withstand data before installation.
- Use the correct semi-enclosed or fully enclosed outline drawing according to the selected current ratio.
- Check cabinet cut-out, conductor clearance, mounting holes, terminal direction, and maintenance access before production.
- The CT secondary circuit must not be open-circuited when the primary circuit is energized.
- Before disconnecting instruments or protection relays, short-circuit the secondary circuit using a suitable shorting terminal.
- Installation and maintenance shall be carried out by qualified medium-voltage electrical personnel.
Ordering Info
Please specify the following information when ordering:
- Product model: LA-10Q / LFZ-10Q / LFZB1-10Q
- Current ratio and rated secondary current
- Structure type if required: semi-enclosed or fully enclosed
- Accuracy class and rated output
- Short-time thermal current and dynamic current requirements
- Insulation level, pollution class, and service condition
- Cabinet opening, mounting layout, terminal direction, and outline drawing requirement
- Quantity, certificates, test reports, labeling, and packaging requirements
Selection Guide
- Confirm voltage class: Use this product for indoor 10kV class systems and international 11kV or 12kV class projects after insulation verification.
- Choose current ratio: Select the ratio according to feeder current, metering range, and protection settings.
- Select structure: Use semi-enclosed structure for 5-200/5A and fully enclosed structure for 300-1500/5A.
- Define core function: Select 0.2, 0.5, or 1 for metering/measurement, and 10P10 for protection circuits.
- Check burden: Confirm that the connected meter, relay, and cable burden do not exceed the selected VA output.
- Verify fault withstand: Match Ith and Idyn with the switchgear short-circuit level.
- Confirm drawing: Select the correct outline dimension group before drilling or cabinet fabrication.