Neutral Earthing Resistor

Product Function

The Neutral Earthing Resistor from RST Electric plays an indispensable role in modern medium-voltage power systems. In solidly earthed or unearthed networks, single-phase-to-ground faults can generate destructive currents that damage transformers, cables, and rotating machinery while creating dangerous step and touch potentials. This Power System Resistor addresses these risks by inserting a precisely calculated resistance between the system neutral point and earth, limiting ground fault current to a manageable level – typically between 10A and 2000A – while still allowing sufficient current for sensitive earth fault relays to detect and isolate the affected circuit.

Product Performance

The engineering philosophy behind this Neutral Earthing Resistor emphasizes longevity and performance under extreme conditions. The resistive element employs a grid-type configuration fabricated from high-grade stainless steel alloys (SUS430 and SUS304), chosen for their exceptional corrosion resistance, stable temperature coefficient of resistance, and ability to withstand repeated thermal cycling during fault events without mechanical degradation. These elements are mounted within robust enclosures available in multiple material options: SUS304 stainless steel for standard outdoor use, SUS316 for marine and offshore environments requiring superior salt-spray resistance, or painted galvanized steel for cost-effective indoor installations.

Electrical performance is verified through comprehensive testing protocols. Insulation resistance exceeds 100MΩ, while dielectric withstand testing is conducted at levels from 32kV to 95kV for one minute depending on system voltage. Basic Impulse Level (BIL) ratings range from 60kV to 170kV, ensuring the resistor can survive lightning strikes and switching transients without insulation failure. Time ratings from 5 to 60 seconds accommodate various protection schemes, with the resistor designed to absorb full fault energy while remaining within temperature limits. As a trusted Neutral Earthing Resistor manufacturer in China, RST Electric combines over 10 years of power resistor engineering expertise with deep understanding of global earthing practices to deliver components that meet the stringent requirements of utilities, industrial facilities, and renewable energy developers worldwide.

Technical Specification

Product Features

1.High Temperature Withstand – Stainless steel grid elements engineered to withstand the extreme thermal stress of fault current conditions without distortion, sagging, or significant resistance change.

2.Stable Resistance Characteristics – Low TCR alloy ensures resistance remains within tight tolerances during fault cycles, maintaining accurate current limitation.

3.Robust Mechanical Construction – Heavy-duty stainless steel grids with reinforced supports resist vibration, shock, and magnetic forces during faults.

4.Integrated Monitoring Options – Optional current transformers for remote current measurement, thermal sensors for overtemperature protection, and alarm contacts for SCADA integration.

5.IEEE32 & IEC Compliance – Designed and tested to meet international standards for neutral earthing devices, ensuring reliable performance and operator safety.

6.Wide Application Coverage – Suitable for systems from 6.3kV to 35kV with fault currents from 10A to 2000A, accommodating diverse protection philosophies.

7.Flexible Time Ratings – Available from 5 seconds to 60 seconds to match specific relay coordination and fault clearing requirements.

8.Corrosion-Resistant Enclosures – Choice of materials including SUS304, SUS316, and painted galvanized steel for optimal durability in any environment.

9.High Insulation & Impulse Levels – BIL ratings to 170kV and power frequency withstand to 95kV ensure survival of lightning strikes and switching surges.

10.Custom Engineering Capability – Special voltage ratings, resistance values, enclosure configurations, and monitoring packages available for unique applications.

Product Applications

Drawing and dimensions

Spec L(mm) W(mm) H(mm) Weight(KG)

6.3&10kv-10~200A 800 800 2200 300

10kv-400A 1000 1000 1800 400

10kv-800A 1200 1200 1800 600

10kv-1000A 1200 1200 2200 700

21KV-300A 1000 1000 1800 500

35KV-200A 1600 2400 2200 1200

35KV-400A 1800 1500 2300 1300

Package and shipment

RST Electric implements rigorous packaging protocols for every Neutral Earthing Resistor:

● Export-Worthy Crating: Each NER is securely mounted on a heavy-duty steel skid and enclosed in a custom-built, fumigation-free plywood crate compliant with ISPM 15 standards for international shipping.

● Moisture Protection: Units are wrapped in VCI (Vapor Corrosion Inhibitor) film with desiccant packs to prevent condensation damage during sea freight.

● Lifting & Handling: Clear labeling of center of gravity and lifting points; shipping brackets and spreader bars provided for safe crane handling.

● Bushing Protection: Porcelain bushings are protected with weather-resistant caps and foam padding to prevent damage.

● Documentation: Comprehensive shipping documentation includes packing lists, certified factory test reports, material certificates, and customs clearance support.

● Freight Options: We partner with experienced heavy-lift freight forwarders for FCL sea freight, project cargo, breakbulk, or air freight as required.

All units undergo full factory acceptance testing (FAT) witnessed by customer representatives when required, including resistance measurement, insulation resistance, dielectric withstand, and visual inspection.

FAQ

Q: What core manufacturing capabilities does RST Electric possess?

A: RST Electric is a fully licensed and certified manufacturer in China, specializing in the design and production of Neutral Earthing Resistor for over 10 years. It has a complete vertical integration production capacity, covering from grid component manufacturing, shell production, finished product assembly to inspection and acceptance, all of which are independently controlled throughout the process to ensure stable and traceable product quality, and to eliminate quality risks caused by outsourcing at each stage. We have an ISO 9001-certified factory, equipped with dedicated production lines for stainless steel grid resistors and medium-voltage components. Every grounding resistor will undergo 100% routine testing before leaving the factory, covering core indicators such as resistance value, insulation resistance, and power frequency withstand voltage. At the same time, type tests such as lightning impulse (BIL), temperature rise verification, and short-term current capacity will also be conducted to comprehensively ensure that the product performance meets the standards. In addition, our engineering team is highly experienced and focuses on grounding system design, application of IEEE32/IEC standards, and protection coordination. They can fully control the product's compatibility from design to production.

Q: What customization parameters are supported by the neutral grounding resistance?

A: RST Electric offers comprehensive customization services. The parameters can be flexibly adjusted according to the actual application scenarios of the customers to meet various personalized needs. The system voltage typically covers 6.3kV to 35kV, and higher voltages can be achieved through customized design. The fault current supports 10A to 2000A, and special rated values can be developed as needed. The time rating is 5 to 60 seconds, and the specific duration can be customized. The resistance value can be calculated based on the application scenario, ranging from 1Ω to 9999Ω. In addition, the shell material can be selected from SUS304, SUS316 stainless steel, painted steel or custom alloys. The protection level can be adjusted from IP23 to IP65 according to the on-site environment. At the same time, current transformers (CTs), thermal sensors, alarm contacts and remote monitoring interfaces can be equipped to fully meet the grounding protection requirements of different industries.

Q: Does your company have global supply experience?

A: RST Electric has extensive global supply experience. It is a trusted supplier for EPC contractors, power companies, industrial operators, and renewable energy developers across five continents. Our products have been exported to 40+ countries and regions, covering major markets such as the UK, Germany, the United Arab Emirates, Saudi Arabia, Australia, Singapore, and South Africa. We have accumulated profound industry experience in the application of Neutral Earthing Resistors and are familiar with different national and international standards. We can precisely meet the compliance requirements of various customers, whether it's for power systems, industrial plants, or renewable energy projects. We can provide highly adaptable and reliable neutral grounding resistance solutions to help customers achieve safe grounding protection for their systems.

Q: What is the delivery time? What are the supporting materials and after-sales guarantees?

A: RST Electric has a stable production capacity and can efficiently respond to customer order demands. For the standard neutral grounding resistance with regular specifications, the delivery time is 30-45 working days; for customized products, the delivery time is 45-60 working days, ensuring that it does not affect the project progress of the customers. Each batch of products will be accompanied by complete technical documents, including test reports, material certificates, IEEE32 compliance statement, IEC statement and operation and maintenance manual, which is convenient for customers to accept, compliance review and later use. We provide a 24-month warranty service. Relying on the global spare parts network, we can provide remote fault diagnosis and rapid delivery of spare parts. At the same time, we can also provide value-added services such as on-site debugging support according to customer needs, and provide full protection for the customer's project throughout the process.

Q: What advantages does choosing RST Electric have in terms of procurement cost and value for money?

A: We adhere to the factory direct supply model, without any middle-level price hikes. The pricing is completely transparent, allowing customers to purchase high-quality Neutral Earthing Resistor at a more reasonable cost, significantly improving the procurement value for money. At the same time, our products are produced through the entire process of independent production and undergo strict inspections, ensuring stable quality and long service life, which can effectively reduce the maintenance and replacement costs in the future. Moreover, our engineering team can optimize the product design based on the customer's project requirements, while ensuring the performance meets the standards, providing customers with more cost-effective solutions that balance product quality, compliance, and procurement costs, enabling customers to achieve low-cost and high-security system grounding protection.