Huanghua Group Co., Ltd. 
Sheet-Metal Processing
Company cabinet-part processing resource shown in About Us.
HEI-24 SF6-Free Gas Insulated Ring Main Unit
HEI-24 is an SF6-free gas insulated ring main unit for 24kV distribution. The source describes nitrogen or dry-air insulation, vacuum interruption and extensible or non-extensible arrangements. Select the circuit functions, current, fault duty and gas specification for the project.
- Rated voltage
- 24 kV
- Published frequency (Hz)
- 50 / 60
- Insulation options
- Nitrogen / Dry air
Select the configuration against your project specification and model-specific data.
PRODUCT OVERVIEW
HEI-24 SF6-Free Ring Main Unit for 24kV Distribution
The HEI-24 ring main unit uses an SF6-free gas-insulated arrangement described with nitrogen or dry air. Its published data separates breaker and load-break duties, cabinet arrangements and selected options. A quotation should identify the supplied gas, circuit configuration and required electrical and installation documents together.
- Rated voltage
- 24 kV
- Published frequency (Hz)
- 50 / 60
- Insulation options
- Nitrogen / Dry air
- Assembly arrangements
- Extensible / Non-extensible
The gas choice, circuit ratings and extension arrangement need selected-model confirmation. Tank test temperatures do not establish the ambient range for the entire assembly. The original pressure basis and report availability require clarification; environmental claims do not establish destination approval.
Product Overview
The HEI-24 is Huanghua Group’s next-generation eco-gas insulated metal-enclosed ring main unit (SF₆-free RMU) for 24 kV medium-voltage distribution networks. Nitrogen (N₂) or dry air replaces conventional SF₆ as the insulating medium, with a global warming potential (GWP) below 1, eliminating SF₆ emissions and end-of-life recovery obligations. It fully complies with the EU F-Gas Regulation (EU 517/2014 as revised in 2019/2024) for SF₆-free new MV switchgear. Rated voltage 24 kV, rated current 630 A / 1,250 A, internal arc classification IAC A FLR 25 kA 1 s, gas tank protection IP67, annual leakage rate ≤0.1% — ideal for urban distribution grids, renewable stations, rail transit, data centres and ESG-driven EPC projects.
Type Designation
Key Highlights
| Highlight | Description |
| Zero SF₆ · GWP < 1 | Nitrogen (N₂) / dry air insulation with GWP < 1, no PFCs and no SF₆, removing F-Gas reporting, recovery and carbon-accounting obligations. |
| EU F-Gas Regulation Compliant | Meets EU 517/2014 (as revised 2019/2024) SF₆-free requirements for new MV switchgear, qualifying for EU public tenders mandating SF₆-free equipment from 2026. |
| Sealed Stainless Tank, IP67 | 304L laser-welded stainless steel tank, IP67 main tank protection, ≤0.1% annual leakage, ≥30-year sealing life; immune to humidity, dust, condensation and pollution. |
| Internal Arc Class IAC A FLR | Internal arc classification IAC A FLR 25 kA 1 s, with a non-rupturable pressure-relief diaphragm and top-vented duct, providing verified protection for personnel at the front, sides and rear. |
| Insulation Level 65 kV / 125 kV | Rated power-frequency withstand 65 kV and lightning impulse withstand 125 kV (BIL), complying with IEC 62271-1 for 24 kV equipment and coordinated with 24 kV transformer insulation levels. |
| VCB-Centric V-Module Design | VCB module breaking capacity 25 kA / 31.5 kA, making current 63 kA / 80 kA, mechanical endurance 10,000 operations (C2). As N₂ has weaker arc-quenching than SF₆, the V-module (VCB) is recommended for transformer protection. |
| Compact 600 mm Footprint | Only 600 mm wide (incomer / outgoing / sectionalising / disconnector), 1,500 mm deep and 2,400 mm high — a major space saving for urban underground substations and compact substation retrofits. |
| Extensible & Maintenance-Free | Extensible via silver-plated finger contacts with bellows sealing — field extension without de-gassing adjacent bays; hermetically sealed tank requires essentially no maintenance over its service life. |
Scope of Application
Suitable for urban ring and terminal distribution networks, renewable (PV / wind / BESS) collection and step-up, industrial plants and campuses, hospitals and data centres, rail transit and municipal works, as well as EU public procurement and ESG-driven packaged substation projects.
Product Features
| Feature | Detailed Description |
| N₂ Insulation · Zero SF₆ | Nitrogen (N₂) or dry air serves as the primary dielectric with GWP < 1 and negligible greenhouse effect; free of PFCs and SF₆, with no F-Gas reporting, annual leakage auditing or end-of-life recovery obligations. |
| Laser-Welded Stainless Gas Tank | The tank is laser-welded from 304L stainless steel on longitudinal and circumferential seams, with helium mass-spectrometer leak testing on every unit; welds are ground and NDT-inspected to guarantee ≥30-year sealing life. |
| Gas Density Monitoring | A temperature-compensated gas density monitor alarms at low pressure and blocks operation on further decline. Since N₂ dielectric strength is directly density-dependent, monitoring is even more critical than on SF₆ units. |
| Non-Rupturable Pressure Relief | A non-rupturable relief diaphragm vents hot, high-pressure gas from an internal arc through a dedicated duct to the cabinet top, preventing secondary injury to personnel and adjacent equipment. |
| Three-Position Load Break Switch | Close – Open – Earth is achieved with a single operating handle and mandatory mechanical interlocking, preventing energising onto an earthed circuit and earthing a live circuit; mechanical endurance 5,000 operations (M2). |
| Vacuum Circuit Breaker Module | The V-module uses a vacuum circuit breaker with 25 kA / 31.5 kA breaking, 63 kA / 80 kA making, rated operating sequence O-0.3 s-CO-180 s-CO and 10,000-operation mechanical endurance (C2). |
| Fully Insulated & Fully Sealed | All live HV parts — busbars, LBS and VCB — are sealed inside the stainless tank, immune to condensation, pollution, salt mist and vermin; suitable for basements, coastal and high-humidity sites. |
| Extensible Modular Design | Plug-in silver-plated finger contacts with bellows sealing enable common-busbar extension; bays can be added or removed on site without de-gassing adjacent units. Flexible V / De module combinations. |
| Compact Enclosure & Installation | Standard units are 600 mm wide (metering panel 800 mm), 1,500 mm deep and 2,400 mm high; front operation with bottom cable entry and generous termination space — ideal for space-constrained switchrooms and compact substations. |
| Smart Distribution Interface | The LV control compartment accommodates numerical protection relays, energy meters, live-line indicators and SCADA interfaces, supporting telemetry, remote signalling and control for distribution automation and unattended operation. |
| Lifecycle Green Compliance | LCA (Life Cycle Assessment) declaration and a GWP < 1 certificate are available on request, supporting ESG bids, carbon-footprint accounting and green-procurement scoring; no special SF₆ disposal process at end of life. |
Technical Parameters
1.RMU Assembly Parameters
| Parameter | Unit | Data |
| Product type | — | Eco-gas insulated metal-enclosed RMU (SF₆-free) |
| Rated voltage (Ur) | kV | 24 |
| Rated frequency | Hz | 50 / 60 |
| Rated insulation level | kV | PF 65；BIL 125 |
| Rated short-duration power-frequency withstand voltage | kV | 65 |
| Rated lightning impulse withstand voltage | kV | 125 |
| Internal arc classification | — | IAC A FLR 25kA 1s |
| Type of insulating gas | — | N₂/ Dry air |
| Global warming potential (GWP) | — | ＜1 |
| Insulation gas pressure (absolute, at 20 °C) | MPa | 0.02 |
| Annual gas leakage rate | %/per year | ≤0.1 |
| Sealing life | years | ≥30 |
| Degree of protection — main tank body | — | IP67 |
| Degree of protection — operation mechanism & LV control cubicle | — | IP4X |
| Creepage distance | mm | ≥720 |
| Gas tank material & process | — | 304L stainless steel, laser-welded |
| Cabinet enclosure material | — | Galvanised steel, powder-coated RAL 7035 |
| Pressure relief | — | Non-rupturable diaphragm, vented to cabinet top |
| Gas monitoring | — | Temperature-compensated density monitor, alarm + lockout |
| Extensibility | — | Extensible / non-extensible |
| Cable entry | — | Bottom entry |
| Operating temperature — gas tank | ℃ | -40 ~ +70 |
2.AC Load Break Switch Parameters
| Parameter | Unit | Data |
| Rated voltage | kV | 24 |
| Rated current / rated busbar current | A | 630 |
| Rated frequency | Hz | 50 / 60 |
| Rated short-time withstand current (4 s) | kA | 25 / 31.5 |
| Rated short-circuit making current | kA | 63 / 80 |
| Rated mainly active load-breaking current | A | 630 |
| Mechanical endurance class | ops | 5000（M2） |
| Positions | — | Close – Open – Earth |
3.AC Circuit Breaker (VCB Module) Parameters
| Parameter | Unit | Data |
| Rated voltage | kV | 24 |
| Max. rated continuous current | A | 630 / 1250 |
| Rated frequency | Hz | 50 / 60 |
| Rated short-circuit breaking current | kA | 25 / 31.5 |
| Rated short-circuit making current | kA | 63 / 80 |
| Rated short-time withstand current (4 s) | kA | 25 / 31.5 |
| Rated operating sequence | — | O-0.3s-CO-180s-CO |
| Mechanical endurance class | ops | 10000（C2） |
| Operating mechanism | — | Spring mechanism |
4.Dimensions (24 kV, Main Busbar Current up to 1250 A)
| Panel Type | Width (mm) | Depth (mm) | Height (mm) |
| Incoming, Segmented, Disconnect, Outgoing | 600 | 1500 | 2400 |
| PT panel | 600 | 1500 | 2400 |
| Measurement (metering) panel | 800 | 1500 | 2400 |
5.Applicable Standards & Eco Compliance
| Standard / Regulation | Code | Scope |
| Gas-insulated metal-enclosed switchgear with alternative gases | IEC 62271-214 | Primary standard for 24 kV eco-gas RMU |
| High-voltage alternating-current circuit breakers | IEC 62271-100 | VCB in the V-module |
| High-voltage alternating-current load break switches | IEC 62271-103 | Three-position LBS |
| Internal arc test method | IEC 62271-200 | IAC A FLR verification |
| Common specifications for HV switchgear | IEC 62271-1 | Ratings and insulation co-ordination |
| Degrees of protection provided by enclosures | IEC 60529 | IP67 / IP4X verification |
| EU F-Gas Regulation | EU 517/2014（2019 / 2024 修订） | SF₆-free compliance |
| GWP & carbon footprint | GWP ＜ 1；LCA | ESG bid support |
| Quality management system | ISO 9001 | Manufacturing & inspection |
6.Type Tests & Routine Tests
| Test Item | Type | Test Condition | Remark |
| Dielectric test | Type | Power-frequency 65 kV / 1 min; lightning impulse 125 kV (peak) | Applied to earth, between phases and across the open break as required by the standard |
| Short-circuit making and breaking test | Type | VCB 25 kA / 31.5 kA breaking; LBS+fuse combination 31.5 kA making (symmetrical) | IEC 62271-100 / 62271-103； Carried out with the rated operating sequence O-0.3 s-CO-180 s-CO |
| Short-time and peak withstand current test | Type | 25 kA / 31.5 kA for 4 s (busbars and joints inside the tank) | Verifies dynamic (peak) and thermal withstand of main and earthing circuits |
| Temperature-rise test | Type | Full-load cyclic duty; temperature rise at contacts and joints ≤65 K | Confirms continuous current-carrying capability with stable contact resistance |
| Mechanical endurance (mechanical operation) test | Type | LBS 5,000 operations (M2); VCB 10,000 operations (C2) | IEC 62271-103 / 62271-100 |
| Internal arc test | Type (on request) | IAC A FLR, 25 kA / 1 s | IEC 62271-200 Annex AA; assesses accessibility type for front, lateral and rear |
| Gas tightness test (helium leak detection) | Type | Helium mass-spectrometer leak test, ≤0.1% / year | N₂ leakage causes an immediate dielectric drop — more critical than on SF₆ units |
| Verification of the degree of protection (IP code) | Type | Main tank IP67; mechanism and LV compartment IP4X | IEC 60529 |
| Gas composition stability test | Type | Thermal cycling -40 °C → +70 °C; no condensation, no decomposition products | Unlike SF₆, N₂ produces no toxic SOF₂ / SO₂ decomposition under arcing |
| Helium leak check (per tank) | Routine | Sniffer helium test on every tank | Performed on every unit; stricter than the SF₆ equivalent |
| Power-frequency withstand voltage test (tank-internal) | Routine | As specified in the product specification, 1 min | Performed on every cubicle before delivery |
| Measurement of the resistance of main and earthing circuits | Routine | DC voltage-drop method; measured value not exceeding the design limit | Verifies contacts and joints |
| VCB timing and travel test | Routine | Opening / closing times, pole synchronism, travel and clearance | Performed on every cubicle; characteristic curves retained |
| Three-position switch and interlock function check | Routine | Close – Open – Earth positions; door and earthing-switch interlocks | Includes five-prevention interlock verification |
| Calibration of the gas density monitor | Routine | Calibration of alarm and lockout thresholds | Performed on every cubicle before delivery |
| Cable terminator torque and visual inspection | Routine | Tightening torque, phase identification and overall finish | Performed on every cubicle before delivery |
SELECTION GUIDE
Specify HEI-24 for Your Project
Circuit schedule and fault duty
Provide the 24kV system specification, frequency, circuit functions and continuous currents. State the prospective fault current and required duration so breaker and load-break duties can be selected separately.
Gas and assembly configuration
Identify nitrogen or dry air and whether extension is required. Request the selected gas specification, pressure basis, monitoring arrangement and supplied assembly drawing for confirmation.
Cable, control and room layout
Send cable interfaces, cabinet lineup, access requirements, control supply and indication signals. Include metering, protection and any remote functions explicitly in the quotation scope.
Acceptance and destination documents
Provide the site conditions and required technical standards. Agree the model-specific test records, internal-arc scope where requested, inspection and destination document package before order approval.
MANUFACTURING AND PROJECT EXPERIENCE
Project Support from Huanghua Group
Huanghua Group manufactures power transmission and distribution equipment under the CNHK brand. Its published company resources include sheet-metal processing, switchgear assembly and electrical testing. Project support covers selection, drawings, documentation, inspection arrangements and after-sales coordination.
Switchgear Assembly
Company switchgear assembly workshop shown in About Us.
Wiring and Commissioning
Company wiring and commissioning activity shown in About Us.
Power Distribution Project Experience
Company resources and project references do not establish a test certificate for the selected equipment model.
Huanghua Group’s Greece PV Substation Project describes substation and distribution equipment, coordinated protection and site documentation. Review it as a company project reference; the published case does not identify the selected equipment model.
PROJECT SUPPORT
Service and Technical Documents
Technical Service and Documentation
Share the electrical requirements, selected configuration and destination standard. Huanghua Group coordinates technical questions, drawings, document requirements, inspection arrangements and after-sales follow-up against the confirmed product and order scope.
OEM and Project Integration
CNHK’s published OEM and ODM programme covers distribution transformers and power distribution equipment. Discuss equipment configuration, integration, labels, packing and project documents. Confirm the equipment-specific OEM scope, branding and customization requests before they become part of the order.
Documents to Confirm with Your Enquiry
- Selected-model data sheet and outline drawing
- Electrical interfaces and connection requirements
- Agreed inspection records and available certificates
- Manuals, packing list and shipment documents
The document package follows the selected configuration, destination requirements and confirmed order.
Define the SF6-Free RMU Configuration
Review the range, then request the selected gas specification, circuit duties, extension arrangement and available reports.
Related Products
TECHNICAL FAQ
HEI-24 Questions and Answers
SF6-Free Insulation and Confirmed Assembly Scope
HEI-24 explicitly describes an SF6-free design, while the HRM6 base products describe SF6 insulation. Gas choice alone does not settle circuit ratings, extension, enclosure or test coverage. Compare the complete selected assembly and its documents.
Switchgear and RMU rangeWhich insulation gases are described for HEI-24?
The source describes nitrogen or dry air for this SF6-free gas-insulated product. Confirm the selected gas specification, pressure basis and monitoring arrangement in the supplied model documents.
Are all HEI-24 circuits rated the same?
No. The original data separates vacuum-breaker and load-break functions and lists configuration-dependent currents and short-circuit duties. Send the circuit schedule so each required function can be matched to the selected rating.
Is every cabinet prepared for later extension?
The source describes both extensible and non-extensible arrangements. Specify the required future lineup and bus interface when requesting the quotation; extension should not be assumed from the family name.
Do the tank test temperatures define the cabinet ambient range?
No. The source describes a gas-tank temperature-cycle test. That statement does not establish the ambient operating range of the complete assembly, controls and accessories. Provide the site conditions for selected-design review.
Does SF6-free establish all required approvals?
The gas description does not by itself prove a selected assembly’s test coverage or destination acceptance. Request the applicable model-specific reports, agreed inspection scope and project documentation instead of relying on a general environmental label.
PROJECT ENQUIRY
Send Inquiry
Send your HEI-24 configuration, quantity and destination.
Huanghua Group will review your requirements for a quotation.
Your Project Requirements
- Gas and circuit configuration
- Gas specification, circuit schedule, current, fault duty, extension, cable interfaces, controls and site requirements.
- Quantity and destination
- Order quantity, destination market and requested delivery date for review.
- Drawings and documents
- Site drawings, electrical interfaces and the required document or inspection list.