In early 2025, ArmCoil Afrika (Pty) Ltd, a leading manufacturer of transformers and related substation equipment in South Africa, was approached with a highly technical and 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 (NECR) units.
While this may seem routine at a glance, the project specifications quickly revealed the complexity of the undertaking. Several other local manufacturers declined to quote, citing excessive design challenges and the extensive IEC Type Testing required. In contrast, ArmCoil saw this as a valuable opportunity to demonstrate its engineering depth, manufacturing capability, and ambition to compete on a global scale.
THE CHALLENGE
The request involved the design, manufacture, test and delivery of two
NECR units, each rated at 11kV, 360A, for use in sensitive European style networks. These 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 effective protection coordination without disrupting sensitive network stability. Additionally, the client requested full pre-export verification and certification, meaning the units would 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:
- Design the NECR Units from First Principles, including mechanical, thermal, and magnetic simulations.
- Source and validate high-grade materials, suitable for both IEC compliance and extreme environmental resilience.
- Integrate smart monitoring systems that offer real-time data acquisition, fault recording, and thermal profiling.
Each NEC/R unit comprised the following key components:
- 360A Neutral Earthing Compensator (NEC)
- 11kV 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 biodegradability
- ZigZag Core-Winding Configuration (50Hz)
- 3CR12 Stainless Steel Enclosure, providing long-term corrosion protection
- Advanced Smart Relays & Remote Monitoring Instruments
- Protection features including overtemperature alarms, restricted earth fault inputs, and SCADA ready interfaces
The units were designed not only for performance and safety but also for serviceability and ease of integration in foreign electrical grids.
TESTING & CERTIFICATION PROCESS
ArmCoil committed to a multi-phase, zero-compromise testing and certification program to meet IEC compliance and client assurance requirements.
- Internal Factory Acceptance Testing (FAT)
All components underwent full mechanical and electrical inspection, including winding resistance, turns ratio, insulation resistance, and vector group verification. - High-Voltage Performance Testing
Performed at accredited high-voltage laboratories, including:
– Lightning Impulse Testing (1.2/50µs)
– Chopped Wave Testing
– Partial Discharge (PD) Testing completed at rated voltage, ensuring PD levels within allowable thresholds for long-term insulation reliability - Type Testing in Accordance with IEC 60076
The NECR units were submitted to the South African Bureau of Standards (SABS), where they underwent:
– Impulse Testing
– Thermal Rise Testing – Successfully completed at ArmCoil
– Dielectric Type Tests – Successfully completed at ArmCoil
– Verification of Temperature Monitoring and Control Equipment – Successfully completed at ArmCoil
– Functionality Testing of Integrated Smart Relays and Instrumentation – Successfully completed at ArmCoil
Notably, ArmCoil’s NECR units are believed to be the first in South Africa to be Type Tested to this level under the IEC standard, with no prior reference designs or local precedent.
RESULTS AND PROJECT IMPACT
ArmCoil delivered the two fully certified NEC/R units within the project’s tight deadline, passing all internal and third-party testing with full compliance. The equipment was successfully exported and commissioned, with positive feedback from both the engineering client and end-user site engineers abroad.
The impact of this project extends well beyond a single order:
- Validation of ArmCoil’s IEC Type Testing Capabilities
- Proven ability to deliver turnkey export solutions in the substation equipment space
- Reinforced confidence in South African manufacturing for international high-spec markets
- New internal quality and design benchmarks that benefit all future projects
This case solidifies ArmCoil’s position not only as a trusted domestic supplier but as a serious international contender in high-specification, engineered-to-order transformer and earthing solutions.
