Fault current distribution analysis and modelling

Fault current distribution and analysis, output files

Electrical earthing systems are concerned with the behaviour of electrical current beneath the surface of the ground. Only in rare instances can electricity be seen by the naked eye and as such it should be considered that the hunt for electrical voltage in an earthing system is looking for something which is invisible that inhabits deep within the ground beneath your feet. It is unsurprising that methods for determining the likely activity of electricity within the ground have been thoroughly researched and parties with expertise in this field are understandably prized. Fault current distribution analysis is undertaken to determine the volume and share of fault current that an area may experience. Knowing how electrical current will behave enables designers of electrical earthing systems, along with DNOs and other interfacing parties to make astute decisions about the performance attributes.


Acquisition of relevant design criteria

Like any of the design decisions or computational processes required in electrical earthing systems, the quality of the input data is essential. Once the relevant governing standard has been determined it is important for designers to know the variety of cable between the primary and secondary substation in a given system. They next will want to clarify the length of the cable along with the cross sectional area. With these data assets in hand the Earthing Services electrical earthing system design engineer will seek to learn the earth mat resistance at both the primary and secondary substations. It would be impossible to proceed with any meaningful fault current distribution analysis without being in possession of the phase to earth fault level, and for this to be processed a knowledge of the average soil resistivity for the area will need to be achieved.

Computing with formulas from governing standards

Earthing Services electrical earthing design engineers reference governing standards whenever undertaking fault current distribution analysis. By using a combination of specialist software and the formulas obtained from electrical earthing standards the engineers are able to determine the likely distribution of fault current.

Determining percentage split

It is imperative that the correct percentage of fault current to the secondary substation is determined as this will ultimately form the basis for design within the CDEGS software used by Earthing Services electrical earthing design engineers. If an inappropriate percentage or inaccurate volume of electrical current is specified then it is highly likely to result in an overspecified electrical earthing system, which will increase costs.

Site classification

Once a site’s electrical earthing performance has been ascertained it is possible for Earthing Services electrical earthing designers to define whether the site classification should be “hot” or “cold”. In the event that a site is cold then no further actions are likely to be required.

Pursuit of “cold site” status

If the electrical earth system is notionally hot then additional design work is required to ensure every opportunity has been taken to reduce the earth system resistance at the secondary substation and hopefully achieve cold site status. In the event that every avenue has been exhausted and a site remains hot all relevant parties must be contacted so that other precautions can be undertaken. Earthing Services engineers will continually pursue a cold site classification and that is one of the many reasons customers recurrently find their way to the company.