Electricity and Control September 2025

Cover article

Local development of 11 kV 360 A NEC/R units for export

I n early 2025, ArmCoil Afrika (Pty) Ltd, a leading manufacturer of transformers and related substation equipment in South Africa, was approached with a highly technical export-oriented project. The request came from a well-respected South African consulting engineer and business owner who had secured an international contract requiring two custom-designed Neutral Earthing Compensator with Resistor (NEC/R) units. While this may seem routine at first glance, the project specifications revealed its complexity. Several other local manufacturers declined to quote, citing design challenges and the extensive IEC type testing required. ArmCoil saw the request as an opportunity to demonstrate its engineering depth, manufacturing capability, and ambition to compete on a global scale. The challenge The project involved the design, manufacture, test and delivery of two NEC/R units, each rated at 11 kV, 360 A, for use in sensitive European networks. The units had to meet strict West-Central European IEC standards, particularly around: - Type testing in accordance with IEC 60076 standards - Special protection and monitoring schemes - Use of environmentally friendly insulating materials - Highly corrosion-resistant outdoor enclosures - Zero-compromise reliability under fault conditions. The client’s specifications also required a zigzag winding configuration, tailored to deliver a low impedance path for zero sequence fault current, enabling e•ective protection coordination without disrupting sensitive network stability. Additionally, the client requested full pre-export verification and certification, meaning the units would need to undergo factory testing, laboratory performance tests, and third-party IEC-compliant type testing – all prior to acceptance and delivery. In short, ArmCoil needed to design and build world-class fully type tested, high-performance NEC/R equipment without the benefit of local benchmarks or reference units. ArmCoil’s engineering response True to its innovation-first approach, ArmCoil accepted the challenge and deployed a multidisciplinary team comprising design engineers, protection specialists, manufacturing technicians, and quality assurance experts. The team worked in close collaboration with the client’s appointed electrical engineer to: 1.Design the NEC/R units from first principles, including mechanical, thermal, and magnetic simulations 2. Source and validate high-grade materials, suitable for IEC compliance and extreme environmental resilience 3. Integrate smart monitoring systems that o•er real-time data acquisition, fault recording, and thermal profiling. Each NEC/R unit comprised the following key components: - 360 A Neutral Earthing Compensator (NEC) - 11 kV Neutral Earthing Resistor (NER) - Two line BCTs (for overcurrent and fault detection) - Two neutral BCTs (for sensitive earth fault protection) - KNAN synthetic ester oil, chosen for its high fire point and bio

degradability

- Zigzag

core-winding

configuration

(50 Hz) - 3CR12 stainless steel enclosure, provid ing long-term corrosion protection - Advanced smart relays and remote mon itoring Instruments - Protection features including overtemperature alarms, restricted earth fault inputs, and SCADA-ready interfaces. The units were designed for performance and safety as well as serviceability and ease of integration in foreign electrical grids. Testing and certification ArmCoil committed to a multi-phase zero-compromise testing and certification programme to meet IEC compliance and client assurance requirements. This involved: - Internal Factory Acceptance Testing (FAT) - High-voltage performance testing, performed at accredited high-voltage laboratories - Type testing in accordance with IEC 60076, performed at the South African Bureau of Standards (SABS). ArmCoil’s NEC/R units are believed to be the first in South Africa to be type tested to the level required under the IEC standard. The two units were delivered fully certified within the project’s tight deadline, successfully exported and commissioned, with positive feedback from the engineering client and end-user site engineers abroad. The impact of this project extends beyond a single order: it validates ArmCoil’s IEC type testing capabilities, demonstrates its ability to deliver customised, turnkey export solutions in the substation equipment space, reinforces confidence in South African manufacturing for international high-spec markets, and establishes new internal quality and design benchmarks that will benefit future projects.

ArmCoil custom-engineered, manufactured, tested and delivered the two NEC/R units to order, for a project in Europe.

For more information contact ArmCoil. Tel: +27 (0)11 763 2351 Email: sales@armcoil.co.za Visit: www.armcoil.co.za

3 SEPTEMBER 2025 Electricity + Control