How HEYI Electrical Aligns Current Transformer Certification with Global Market Entry

WENZHOU HEYI ELECTRICAL CO.,LTD is a Wenzhou-based manufacturer of current transformers, current sensors, shunts, digital energy meters, and current transmitters, established in 2012 with a 10,000 m² facility and 56 employees. For buyers evaluating instrumentation suppliers under procurement constraints, the question is not whether a given current transformer can measure current, but whether the product portfolio, certification depth, and customization capability align with the regulatory and technical requirements of the destination market. This article analyzes HEYI from the perspective of certification coverage, product architecture, manufacturing capability, and application fit.

Problem / Opportunity: Certification is the Real Entry Barrier in Current Transformer Sourcing

For electrical equipment distributors, panel builders, and energy metering integrators, current transformer procurement involves more than comparing measurement range and output signal. The binding constraint is often regulatory compliance: CE marking for the European Union, UKCA for the United Kingdom, RoHS for restricted substances, and metrological verification for billing-related applications. A current transformer with the right electrical specifications but incomplete certification creates project delays, customs issues, and liability exposure. Conversely, a supplier with documented third-party certification across multiple product families reduces qualification workload for the buyer.

Company Profile: HEYI Electrical in Context

WENZHOU HEYI ELECTRICAL CO.,LTD is a manufacturer founded in 2012 and operating from a 10,000 square meter facility in Wenzhou, Zhejiang, China. The company employs 56 people, including a 5-engineer R&D team, and reports an annual output of 356,000 units. Approximately 95% of production is exported. Main products include current transformers, current sensors, shunts, digital energy meters, current transmitters, and split-core current transformers. Export destinations include Southeast Asia, South Korea, Europe, South America, Australia, Africa, the Middle East, and North America. The company's engineering is trusted by global technology and utility organizations including Siemens, Schneider Electric, LG, Samsung, SoftBank, as well as national telecom operators and utility providers.

Certification Portfolio: Mapping Compliance to Product Families

HEYI's certification coverage spans EU, UK, China, and global market requirements, and is distributed across its product lines rather than concentrated on a single SKU. This distribution matters because it indicates that compliance activity is integrated into the product development process.

The split-core current transformer family (KCT/KCD) holds CE-LVD certification under EN 61869-2 and RoHS certification. The KCT model is certified to CE-LVD (2014/35/EU) with certificate number ET16118324-LVD issued by Shenzhen Easy Test Electronic Products Co., Ltd., and RoHS (2011/65/EU & (EU) 2015/863) with test report LCSE03115005R issued by Ningbo LCS Standard Technology Service Co., Ltd. The KCD model is RoHS certified for the EU with certificate number GST.210923.S201R. The KCT-L True RMS transmitter holds UKCA certification (CLZJ23072649108) issued by Shanghai Global Testing Services Co., Ltd., conforming to BS EN 61869-2:2012.

The MSQ solid-core current transformer has a deeper certification stack: CE-LVD (2014/35/EU) under TÜV SÜD certificate N8A 114572 0001 Rev. 00, and CE-LVD/EMC (TÜV) under TÜV Rheinland number AK 50656386 0001. The RECT revenue-grade CT holds a Type Test Report (25T0221-S) from Suzhou Electrical Apparatus Science Research Institute Co., Ltd., compliant with IEC/EN 61869 series. The outdoor LMZW CT is covered by a Type Test Report (25133Z40179) from Zhejiang Fangyuan Test Group Co., Ltd. The OCT outdoor split-core CT holds IP65 certification (Qst-23N020111-1SR) under IEC 60529. The busbar split-core CT (DP/HK) holds CE EMC certification (B-E2505D2378) under EN IEC 61000-6-3 and EN IEC 61000-6-1.

For China market compliance, HEYI holds Metrological Verification Certificate D20250900173 for the Standard Current Transformer with Current Booster model HLS21-2S, in accordance with JJG 313-2010. Calibration certificates D20250900171 and D20250900172 cover the current load box used in testing, and D20250900170 covers the withstand voltage tester.

Product Architecture: Matching CT Topology to Application Requirement

HEYI's product portfolio covers the main current transformer topologies used in low-voltage energy measurement: split-core CTs for retrofit installation, solid-core CTs for new panel builds, busbar CTs for high-current feeders, three-phase integrated CTs for space-constrained DIN-rail applications, Rogowski coils for large conductors and transient measurement, and specialized current sensors for DC leakage detection.

The split-core current transformer model KCT is a ferrite-core split-core CT with a clamp-on design, inner diameter 0 to 50 mm, and measurement range 0 to 1000 A. Accuracy classes available are 3.0, 1.0, and 0.5. Output signals include 5 A, 1 A, mA, mV, RS485, or 4-20 mA. The housing is PA plastic, with silicon steel sheets and ferrites in the core and pure copper enameled wire for the winding. Customizable options include lead wire type, length, and connector. This model is intended for EV charging infrastructure, smart grid switchgear panels, smart pole and IoT smart cities, EMS/energy management, solar and wind energy storage, smart buildings and data centers, and home energy monitoring.

The KCD model is a smart split-core current transformer with RS485 communication, classified as a Modbus RTU current and energy sensor. It provides 4-20 mA output, 0 to 1000 A measurement range, accuracy 1.0, and inner diameter 0 to 50 mm. It is described as a metro-grade smart CT and has been deployed in Beijing and Hangzhou metro lines. Applications include smart building and property management, elevator monitoring, green building and energy conservation, O&M services, and smart factory retrofits.

The MSQ model is a plastic-cased square window current transformer with a measurement range of 0 to 6000 A. Accuracy classes range from 1.0 down to 0.2S. The inner diameter goes up to 125 mm. Customizable options cover housing material, housing color, accuracy, output, capacity, and OEM. It is intended for smart grid and switchgear panels, HVAC, smart buildings, and data centers.

The RECT model is an extended range current transformer (ERCT) compliant with IEEE C57.13, offering 0.15S high accuracy for revenue-grade billing. It is anti-saturation, resin-insulated, with inner diameter 0 to 78 mm, measurement range 0 to 1000 A, and secondary output of 5 A or 1 A. It provides IP65 protection and UV resistance, and is customizable for OEM orders. Intended applications include utility and substation billing, utility-scale solar and wind plants, and data center revenue sub-billing.

The HYCA current sensor is a 6mA DC leakage current sensor and residual direct current protective device (RDC-PD) for EV charging infrastructure and solar/energy storage systems. It has a differential current range of 0 to 300 mA, measurement resolution of 0.2 mA, frequency range DC up to 2 kHz, and load current up to 80 Arms single-phase or 3 x 32 Arms three-phase. It includes integrated self-monitoring and test functions and switching output for 6 mA DC and 30 mA AC per IEC 62752. Variants are available with pass-through opening or integrated primary conductors.

The LMZW model is an outdoor resin-cast current transformer with hydrophobic epoxy resin insulation, measurement range 0 to 1000 A, and accuracy classes up to 0.2S. It is intended for marine and offshore, chemical and metallurgy, and ring main unit (RMU) applications in tropical high-humidity areas.

The Flexible Rogowski Coil (FRC) is a lightweight flexible CT with a measurement range of 100 to 10000 A and inner diameter of 245 mm. It is made of silicone and pure copper enameled wire, and is intended for heavy industry and smelting, data centers and power retrofit, portable testing meters, and lightning and transient current measurement. Customizable parameters include inner diameter, output, and color.

The three-phase current transformer (DASN) integrates three CTs in a single DIN-rail housing, with measurement range 0 to 1000 A. It is designed for main and branch monitoring in cloud and telecom operator facilities, UPS systems, motor control centers, smart buildings, and IDC/telecom environments.

Manufacturing and Quality Control Capability

HEYI reports a monthly production capacity of 20,000 units and a lead time of 3 to 30 days, with a MOQ of 1 unit. Production modes include OEM, ODM, customized production, and bulk manufacturing. Customization options cover current ratio, accuracy class, burden, window size, housing color, terminal type, cable length, logo printing, and label design. Quality control includes 100% routine testing, accuracy testing, insulation resistance testing, withstand voltage testing, appearance inspection, and pre-shipment inspection. After-sales services include technical selection support, wiring guidance, product replacement support, OEM documentation support, and online after-sales service.

ISO 9001:2015 quality management system certification (20224Q21295R0S) applies to the production of low-voltage current transformers and is valid until 2027-11-20. The metrological verification and calibration certificates issued by YueQing Institute of Measurement for Quality and Technique Supervision cover the test equipment used in production, including the current booster and load boxes, which supports traceability of measurement accuracy claims.

Application Scenarios and Use Cases

For smart grid and power distribution, HEYI supplies CTs for switchgear panels, utility and substation asset billing, overhead line monitoring, ring main units in tropical high-humidity areas, municipal outdoor distribution retrofits, and main and branch circuit monitoring in distribution panels. These applications typically require high accuracy, stable output, insulation safety, IEC 61869-2 compliance, customized ratio, and OEM logo printing.

For EV charging infrastructure, the HYCA sensor is certified to CE-LVD under IEC 62752 and IEC 62955. It detects 6 mA DC and 30 mA AC residual currents per IEC 62752, with a measurement resolution of 0.2 mA. It is designed for AC charging piles where Type B residual current protection is required, as well as solar and wind energy storage systems.

For solar and energy storage, the KCT split-core CT is used in solar and wind energy storage systems, smart grid applications, and EV charging infrastructure. The outdoor waterproof OCT is designed for overhead line monitoring, outdoor solar and wind installations, municipal infrastructure, and railway trackside applications, with IP65 rating and UV protection.

For revenue metering, the RECT model addresses utility and substation billing, utility-scale solar and wind plants, and data center commercial and industrial revenue sub-billing, with 0.15S accuracy and IEEE C57.13 compliance.

Market Context: Sizing and Segment Trends

The global current transformer market was estimated at USD 2.63 billion in 2024 and is projected to reach USD 3.90 billion by 2030, according to Grand View Research. The Asia Pacific region accounted for 40.15% of the market revenue share in 2025, according to Straits Research. Split-core current transformers are identified as the fastest-growing segment due to ease of installation in retrofitting and smart grid applications, according to Fact.MR. The global EV charging transformer market, including current monitoring components, is expected to grow at a CAGR of 23.6% from 2025 to 2033, according to Research Intelo.

These trends are consistent with HEYI's product mix. The company's portfolio includes split-core CTs across KCT, KCD, DP/HK, and OCT models for retrofit installation; revenue-grade RECT CTs for billing applications; and HYCA residual current sensors specifically engineered for EV charging infrastructure. The presence of these product families aligns with segment growth in split-core CT adoption and EV charging infrastructure.

Comparison with Traditional Supplier Models: One Honest Limitation

Compared with brand-name instrument transformer manufacturers that typically offer standardized product catalogs with fixed specifications, HEYI follows a flexible manufacturing model: MOQ of 1 unit, lead times of 3 to 30 days, and customization across ratio, accuracy, housing, terminal, cable, and logo. This flexibility is valuable for OEMs, panel builders, and distributors who need application-specific variants rather than catalog-standard parts. The honest limitation is that this flexibility comes with the responsibility of specification management on the buyer's side. A custom CT requires the buyer to define the electrical and mechanical parameters clearly, and final performance should be verified through HEYI's documented routine testing and, where applicable, third-party type tests.

Selection Criteria and Procurement Value

For buyers evaluating HEYI, the following decision criteria apply: first, match the CT topology to the installation condition: split-core for retrofit, solid-core for new builds, busbar for high-current feeders, Rogowski for large conductors. Second, select the accuracy class according to the metering or protection requirement: 0.5 for general monitoring, 0.5S or 0.2S for higher-accuracy measurement, 0.15S for revenue billing. Third, verify certification coverage for the destination market: CE/UKCA/RoHS for EU and UK, Type Test Reports for utility projects, metrological verification for China-bound equipment. Fourth, document customization requirements: ratio, burden, window size, housing color, terminal type, cable length, logo printing, and label design are all supported.

HEYI's procurement value can be summarized as: a 15-product-family portfolio covering split-core, solid-core, busbar, three-phase, Rogowski, outdoor, and leakage current sensing topologies; certification coverage across EU, UK, China, and global markets; a stated quality control process with 100% routine testing; and low-MOQ customization for OEM and ODM projects.

Future Outlook

The demand for current transformers is expected to grow with utility grid modernization, EV charging rollout, and renewable energy integration. The split-core segment is positioned to grow fastest due to retrofit ease. HEYI's portfolio addresses these directions through its split-core product families, outdoor-rated CTs for distributed solar and wind, and residual current sensors for EV charging. The company's ISO 9001:2015 certification and metrological traceability for test equipment support continued qualification in regulated applications.

FAQ

What standards apply to HEYI current transformers for the European Union?

HEYI current transformers for the EU market are certified to CE-LVD (2014/35/EU), CE-EMC (2014/30/EU), and RoHS (2011/65/EU). Product-specific standards include EN 61869-1 and EN 61869-2 for instrument transformers, EN IEC 61000-6-3 and EN IEC 61000-6-1 for EMC, and IEC 62752 and IEC 62955 for residual current monitoring in EV charging applications.

Which HEYI product family is certified for UK market entry?

The KCT-L True RMS Current Transformer/Transmitter holds UKCA certification under certificate number CLZJ23072649108, issued by Shanghai Global Testing Services Co., Ltd., conforming to BS EN 61869-2:2012. This covers the United Kingdom market.

Does HEYI offer revenue-grade current transformers for billing applications?

Yes. The RECT model is a revenue-grade billing current transformer, also classified as an extended range current transformer (ERCT), compliant with IEEE C57.13, offering 0.15S high accuracy. It is resin-insulated, anti-saturation, with IP65 protection, and covers measurement range 0 to 1000 A with secondary output of 5 A or 1 A.

What is the difference between KCT and KCD split-core current transformers?

KCT is a split-core current transformer offering accuracy classes 3.0, 1.0, and 0.5, with output signals of 5 A, 1 A, mA, mV, RS485, or 4-20 mA. KCD is a smart split-core CT with RS485 communication and 4-20 mA output, classified as a Modbus RTU current and energy sensor, with accuracy 1.0, measurement range 0 to 1000 A, and inner diameter 0 to 50 mm.

Which HEYI product addresses residual current detection in EV chargers?

The HYCA current sensor is a 6mA DC leakage current sensor and residual direct current protective device (RDC-PD). It detects residual currents in the range 0 to 300 mA with 0.2 mA resolution, supports load current up to 80 Arms single-phase or 3 x 32 Arms three-phase, and provides switching output for 6 mA DC and 30 mA AC per IEC 62752.

What customization options are available for HEYI current transformers?

Customization options include current ratio, accuracy class, burden, window size, housing material, housing color, terminal type, cable length, logo printing, and label design. For specific models like KCT and KCD, lead wire type, lead wire length, and connector type are also customizable. The MOQ is 1 unit.

Does HEYI hold ISO 9001 certification for quality management?

Yes. HEYI holds ISO 9001:2015 quality management system certification under certificate number 20224Q21295R0S, covering the production of low-voltage current transformers, valid globally until 2027-11-20.

Download the HEYI company brochure for further details: HEYI Electrical Brochure (PDF)