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Sourav tells us that:
Our Client is asking for an insulated copper conductor for the ground grid at a depth of 2’ from the grade level instead of bare copper due to corrosion issues. We are trying to model and analuze the grounding system using SKM Ground Grid software which does not differenciate between insulated & bare conductors. Per IEE Std. 80-2000, grounding grids must be bare copper conductor (refer to clause # 3.16 & 9.4.c of IEEE Std. 80-2000). Please let us know if insulated copper conductor can be issued for ground grid.
Hi Milind,
Thank you for your question regarding the design of earth mats at high voltage substation switch yards, it is our pleasure to help.
These high-voltage substations are very dangerous places for personnel to work in. There are numerous electrical hazards to be concerned about, including Arc-Flash hazards, Step & Touch Voltage hazards, and more. The grounding grid is an important part of not only providing a safe working environment, but also in providing an effective electrical system. Continue reading
Hi K. M.,
Thank you for your question regarding ohm-meter to ohm-cm, it is our pleasure to help.
The answer is actually very easy, simply multiply the ohm-meters by x100 and you get ohm-centimeters. Continue reading
Justin tells us:
I have recently encountered in a new building installation, lightning protection down leads coming from the roof air terminals, and running through the ceiling sleeved in PVC until it is cadwelded on to the building steel structure, I was called in to answer the question is this to code. My first answer was no due to the plastic of the PVC being in a plenum ceiling. but the question is if the PVC is taken out, what is the rules for re-supporting the wire that is left hanging? I was under the impression that the wire is not allowed to hang on or touch anything else in the ceiling space, becuase the lightning could spread, but I cannot find a code that states this. Please advise. thank you.
Hi Janarthanan,
Thank you for your question regarding earth pit loads, it is our pleasure to help.
One of the more common aspects of electrical grounding that people tend to overlook is in regards to electrical loading. That is, how much electrical energy (in amps) can a given grounding electrode handle before the thermal load causes it to burn open like a fuse? Continue reading
Hi Chander,
Thank you for your question regarding GPR and GPD acceptable limits. It is our pleasure to help.
There are actually no specified limits to either of these electrical phenomena’s, as they are simply indicative factors for other specifications. Let us explain:
The Ground Potential Rise (GPR) is a factor that describes the maximum voltage that will be seen during an electrical fault on a give grounding system. You can imagine that as fault currents enter a grounding grid, the voltage will rise at some gradient across the system. The actual voltage that the system rises is not the primary concern, it’s the current or amperage that can flow across people or equipment that is our concern. So, like a bird landing on a power line which may have high voltage, the bird will be safe as long as no current flows through the bird itself. If your building rises to 500 volts or 50,000 volts, it can be either good or bad, depending on the current flow at critical points. Here is some more information on GPRs: Continue reading
Hi Leyreu,
Thank you for your questions regarding grounding electrodes, it is our pleasure to help.
First of all, you may NOT have isolated grounding electrodes under any circumstance. This is a violation of the National Electrical Code and every other known electrical standard. While it is fine and possibly even advisable to have a dedicated electrode for your electrical room, it must be bonded back to all the other grounding electrodes, including any lightning protection system that you may be installing. Continue reading
Hi Syam,
Thank you for your questions regarding seismic waves and electrode spacing, it is our pleasure to help.
In regards to testing the earth resistivity, we are not aware of any terminology associated with DSR & TSR. However, Geologists do use the terms DSR &TSR when dealing with seismic wave analysis when they calculate the velocity of a wave during a Seismic Refraction Survey. DSR stands for “Distance from Source to Receiver” and TSR stands for “Time from Source to Receiver”. By setting up at least two receivers at a known distance, the time differential of when the wave strikes the receivers can be used to calculate the velocity of the wave. Some more information on this subject can be found here: Continue reading
Hi Fahad,
Thank you for your question regarding computer room grounding, it is our pleasure to help.
There are often many questions regarding the various grounding and bonding systems found within a computer data center, and this mostly has to do with the difference between the low-impedance ground fault path required by the National Electrical Code (NEC), and the grounding systems required by computer manufacturers. Remember that the grounding systems required by the NEC are only to ensure that Over Current Protection Devices (OCPD) such as circuit breakers and fuses will function properly. These systems require that a low-impedance ground fault path exists so as to enable a massive flow of current to temporarily pass through the OCPD, tripping the breaker and/or blowing the fuse. This grounding system is not designed to eliminate transient currents, stray voltages, or to reduce differences in potential that could harm sensitive electronic equipment. Continue reading
Hi Benjamin,
Thank you for your questions regarding lightning protection and grounding resistances, it is our pleasure to help.
There are two (2) classes of material requirements found in NFPA 780, the Standard for the Installation of Lightning Protection Systems. Class I materials are required for structure less than 75-ft in height, and Class II Materials are required for buildings greater than 75-ft in height. The down conductor is properly listed in the standard as a “Main Conductor Cable”. Continue reading
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