Power protection solutions provider Swedish Neutral will exhibit its Ground Fault Neutraliser (GFN) earth fault protection system at this year’s POWER-GEN & DistribuTECH Africa, taking the opportunity to highlight the protection benefits that the system can offer power grids with an unreliable supply in Africa.

Consisting of three components – an arc suppression coil, a residual current compensator and a control cabinet – Swedish Neutral sales coordinator Viacheslav Levashov highlights that the GFN system provides complete protection for all parts of interconnected power grids.

He explains that earth faults – single phase to ground faults – are the most common type of fault in an electrical network. Installed in the substation, the GFN can provide rapid grid protection during transient and sustained earth faults by influencing the fault current and its inception time through one point, which is the transformer neutral.

Instead of tripping the faulty feeder, the GFN brings the fault current down to almost zero by injecting a phase-opposite current into the neutral and effectively cancelling out the fault current. This provides a fast interception that has no impact on the conveyance of payload over the faulty feeder, making it possible to maintain safe grid operation without interrupting the power supply. With a total response time of less than 60 m/s, the GFN is substantially faster than traditional protection systems, regardless of the fault’s location.

The GFN also includes fast, reliable and highly sensitive algorithms for earth faults detection, and a fault detection system that locates the fault site for further inspection and repair. The GFN Fault Passing Indicator (FPI), which works with access to the Internet, can detect more sensitively than traditional FPIs. Levashov further points out that this is an important advancement, as many of the line faults in overhead grids are high-impedance, midspan faults with poor ground contact, making them high risk for fire ignition.

The GFN FPI can be combined with any type of sectionalising equipment, and all fault confirmation and sectionalising controls are available at the central GFN control cabinet, or can be transmitted to a dispatch centre or hand-held field monitor.

“By using the inherent zero sequence properties of the three-phase electric power system – used globally by electric grids to transfer power – the GFN elevates grid protection to new levels of performance by achieving all the benchmarks of good protection; this includes speed, selectivity and detection sensitivity. Customers can, thus, achieve the safest and most reliable power supply in the market and ensure the highest possible gain to end-consumers.”

Combined with online partial discharge measurement, the GFN, moreover, offers a new powerful tool for grid insulation monitoring and prefault protection, allowing for the systematic forechecking strategies for the early detection of defective components.

The GFN enhanced monitoring works on all type of plants, including rotating machines, transformers, switchgears and cable feeders. The method can also be used before, during and after the commissioning of a new plant to verify the quality of workmanship on cable joints and terminations.

“Distribution network owners and operators looking for new and cost-efficient means to monitor the condition of their ageing cable grids may benefit from this novel tool to support their ongoing condition-based maintenance activities.”

Meanwhile, the GFN harmonic monitor and compensation element will enable users to maintain adequate power quality in a high-voltage network by monitoring the harmonic content and compensating for the harmonic current, in addition to the fundamental current. The harmonic monitor measures and records harmonic components up to and including the seventh harmonic. Real-time results are presented in the terminal software.

“The harmonic compensation compensates for the harmonic content during an earth fault. A harmonic-free network imposes much less strain on equipment and lengthens its life span, which means lower maintenance cost and replacement costs.”

Swedish Neutral will exhibit the GFN at POWER-GEN & DistribuTECH Africa at the Sandton Convention Centre in Johannesburg from July 18 to 20.