What is Ground or Earth Potential Rise?

Ground Potential Rise (GPR) or Earth Potential Rise (EPR) is a phenomenon that occurs when large amounts of voltage and current enter the earth.

It is generally caused when lightning strikes at electrical power equipment or when there is an electrical fault in the electrical equipment such as transformer or switchgear. When currents of large magnitude enter the earth from a grounding system, not only will the grounding system rise in electrical potential, but so will the surrounding soil as well.

The voltages produced by a Ground Potential Rise or Earth Potential Rise event can be very hazardous to the personnel working in the vicinity.

Is Ground or Earth Potential Rise Study Required?

Safety is the utmost factor in any working environment. In the event of ground potential rise, personnel may face a risk of electrocution due the difference in potential (Voltage), which in turn current will flow into the human body.

Fibrillation current is the amount of electricity needed to cause cardiac arrest, from which recovery will not spontaneously occur, in a person and is a value based on statistics.

IEEE Std 80-2013 provides a method to determine the value of fibrillation current for a safety study, along with a good explanation of how it is derived.

Hence, for human safety, 2 things are required to know

1. Maximum permissible TOUCH VOLTAGE
2. Maximum permissible STEP VOLTAGE

GPR Study using XGSLab Software

XGSLab (or shortly XGS) is one of the most powerful software of electromagnetic simulation for power, grounding and lightning protection systems and the only software on the market that takes into account International (IEC/TS 60479-1:2005), European (EN 50522:2010) and American (IEEE Std 80-2000 and IEEE Std 80-2013) Standards in grounding system analysis

GSA module from XGSLab is based on a PEEC static numerical model and to the equipotential condition of the electrodes and can analyse the low frequency performance of grounding systems composed by many distinct electrodes of any shape but with a limited size into a uniform or multilayer soil model.

Honeycomb Electrical Services uses GSA and GSA_FD modules for calculations and simulations based on client’s requirements.

GSA can take input data in the form of either graphical (from “dxf” files or from the integrated CAD) or numerical and render powerful graphical facilities via it’s optimised and validated computation algorithms, thus making it an indispensable tool for grounding system design and verification.

GSA includes the module SRA to calculate uniform or multilayer soil model parameters starting from measured soil resistivity data.

GSA is essentially a low frequency tool but in several practical cases (with little electrodes), it can be also useful to calculate the impulse impedance of electrodes under lighting currents with an accuracy level adequate for many engineering applications.

Summary of GSA features

• Calculation model based on PEEC method in static conditions
• Possibility to consider International (IEC/TS 60479-1:2005), European (EN 50522:2010) and American (IEEE Std 80-2013) standards
• Possibility to import grid layout from “dxf” files
• Automatic debug of data before calculation
• Analysis of grounding systems of any shape, with choice of the total number of elementary sources
• Possibility to analyse up to 999 distinct electrodes on the same calculation, including for instance return electrodes, transmission line grounding systems or floating potential underground electrodes
• Characterization of soil with a uniform or multilayer model. Beyond this a superficial thin layer can be added
• Possibility to analyse electrodes partially insulated or encased in concrete or buried in treated soil to lower resistivity
• Libraries with typical properties of soil, soils covering, concrete and backfill materials
• Possibility to export layout data and results in .dxf file