AEMC® - Understanding Ground Resistance Testing (3640 Discontinued Replaced by 6424)

Understanding Ground Resistance Testing
A grounding system is a conducting connection by which an electrical circuit or equipment is connected to earth. This connection is used to establish and maintain as closely as possible the potential of the earth on the circuit or equipment connected to it. This connection to the earth provides a low impedance path for electrical currents to travel under fault conditions. The system ground can be a simple metal rod driven into the ground, a grid consisting of multiple electrodes, or another type of grounding system.
When these disruptions of normal electrical operation do occur, it's very important for the grounding system to operate efficiently. For this to be possible, the grounding circuit must have a low resistance connection to the surrounding earth. And a grounding system will only perform properly if it is designed and installed with local soil conditions taken into consideration.
This video is an introduction to grounding systems. Our goal is to provide you with a good basic understanding of why grounding is important, the environmental factors to consider when designing a grounding system, and the testing required to ensure your grounding is properly installed and performing to specifications.

[@SillyPutty3700]

This video is pretty good at explaining how to test grounding electrodes and electrode systems. It does however muddle the differences between BONDING and Grounding. The grounding electrode system has little to do with clearing a fault (protecting equipment from faults 2:48). Think about that for a moment, apply 120v to a 25 ohm rod (NEC suggested target) will the resulting current flow cause a breaker to trip? 120/25= 4.8a that is not going to cause a 20a or 15a breaker to trip. Even if we lower the resistance to 5 ohms which is a common engineering standard we would only cause a 26a breaker or fuse to open thus clearing a fault. In a commercial building where breakers are often rated at 100a -1000a that could not realistically be relied on to clear a fault. Fault current for tripping breakers is dependent on a low resistance path NOT to earth as suggested here but to the center tap of the transformer or transformer neutral terminal which is a function of BONDING. The NEC in article 250.4(A)(1) states that grounded electrical systems “shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.” Simply stated a grounding electrode system at a service entrance is for power quality not clearing faults. That is not to say it is not an essential part of your electrical system and the rest of this video does a great job explaining how that works.

[@tfun101]

True for the commercial and residential jobs..but for the utility multiple grounds are used which can assist with clearing the faults.

[@robvandijen8481]

A professor from Siemens Germany came over for a complicated malfunction of a machine control. He did not allow us to talk about earthing. After all, planes and ships have no earth either. Equipotential bonding was the right word.😁

[@mernokallat645]

Ships are literally grounded. The seawater is at ground potential.

[@eugenepohjola258]

Howdy. 1. Power lines. Low grounding impedances provide a parallel path to the neutral + earth wire. It hepls to uphold the voltage symmetry along the line during unsymmetrical loading. Some degree of limiting of avalanche voltages is also provided caused by lighting bolts. 2. Consumer service panels. Low grounding impedances increase fault currents and speed up triggering of circuit breakers. However, more important is the potential equalizing of the environment of utilization. Therefore. The service gronding should be a copper wire in the ground that encircles the house. Regards.

[@ganesanmuthiganesanmuthi5356]

Low impedance so thst the fault current flows, travels fast to earth without affecting others and surroundings.

[@kemusindi1577]

Best tutorial for grounding ever, much appreciated

[@andysummersthxcinemaandmyc7748]

26 dislikes wasn't grounded. Informative video.

[@spelunkerd]

Well explained, I wish I found this a few years ago.

[@djmaidjmai6120]

شكرا لك يا احسن استاذ ياغالي والعزيز في قلوبنا. شكرا شكرا شكرا

[@MM10-us1rv]

Hi! Thank you for the video, how do we find the standard deviation of the results after testing has completed using the Wenner method on the 6471? Thanks!

[@AEMCInstruments]

Here is an online standard deviation calculator: www.calculator.net/standard-deviation-calculator.html Just plug your numbers in and hit "Calculate"

[@MM10-us1rv]

@@AEMCInstruments Thanks! Is there a way to show the standard deviation numbers on the screen of a 6471 ground tester machine?

[@AEMCInstruments]

Unfortunately, no. Any standard deviation calculations will need to be done externally from the 6471. The calculator linked above can be useful if you wish.

[@ravindraf2462]

INFORMATIVE VIDEO TO ELECTRICAL COMMUNITY-THANKS AEMC

[@AEMCInstruments]

You are welcome!

[@npcasp5279]

buena explicación, tengo una duda, porque en los manuales la distancia "A" debe ser mayor a 80 metros ?, no será un error y es 80´to 100`,gracias

[@AEMCInstruments]

Hola, la distancia A sugerida es entre 8 y 10 veces la profundidad de la pica de puesta a tierra con el fin de evitar que se empalmen las áreas de resistencia efectiva de la pica Z(H) y del sistema de puesta a tierra bajo prueba. Asumiendo que la pica de puesta a tierra está enterrada 8 m, la distancia A sugerida sería de 80 m. Aún con 80 m de distancia, es necesario realizar tres mediciones posicionando la pica Y(S) a 52%, 62% y 72% de la distancia de A con el fin de verificar la validez de los resultados. Si tiene más preguntas, no dude en contactarnos en techsupport @ aemc.com.

[@fikaarsyad]

is it possible to measure on the transmission tower? if the Z electrode is placed 80 feet from the ground rod. Or can we use clamp on tester on transmission tower?thanks

[@AEMCInstruments]

We sell a 6474 Tower Testing Kit for tower testing. Here's a video describing the process: kzbin.info/www/bejne/iJDIqYegedibg5Y

[@BYENZER]

In residential, with a 200 Amp service, what is the MAX AMPS allowed to RETURN back to the utility, VIA the UFER?

[@djhatton6858]

There is a problem with this video incorrectly describing ground fault current traveling "thru" the ground...doesn't happen/won't happen to trip a breaker. The service neutral wire performs the effective fault current path. Earth cannot be used as an effective fault current path. NEC 250.4(A)(5)

[@ellwalenndhejunny3229]

the best explanation sir! thank you

[@SundayOwens]

great video, may I know if aluminum can be used for earthing? if there is no copper rod.

[@AEMCInstruments]

Bare aluminum is not recommended as a grounding electrode in contact with the dirt/earth. Bare aluminum will likely corrode quickly when in contact with the dirt and the ground system will become ineffective.

[@lucyelec]

Good vedio. Deserve for likes and sharing

[@AEMCInstruments]

Thank you so much!

[@thejunkbox]

Thank you very much for very elaborateing explanation

[@AEMCInstruments]

You are welcome! Glad it was helpful.

[@rakamuhammadyusuf44]

this video really helps me to understand how to measure the grounding ressitance, and I have a question about it. is it possible to only use a voltmeter, ammeters, and current sources(current genertor) to measure ground resistance using the fall-of-potential method? Thank You

[@AEMCInstruments]

Yes, it is possible but not practical. A tuned voltmeter would be needed to reject all other frequencies than the source test frequency. Our meters use various frequencies to test and the voltmeter is tuned to that frequency for the most accurate readings, rejecting surrounding noise and interference. Also, the stack-up of tolerances from all the meters you described would need to be added together to determine the accuracy of the readings you took. With our meters, there is only one accuracy spec for the reading. Our multi-function meters also store the distances (in meters or feet) of each measurement needed to graph a full Fall of Potential plot. A minimum of 9 measurements are needed for a valid Fall of Potential plot. This plot is critical in proofing your measurements to know if they are valid. Good luck if you try this method!

[@surendrakverma555]

Very good. Thanks 🙏🙏🙏🙏

[@AEMCInstruments]

Most welcome.

[@markdejong1984]

Great video, helped resolve issue at work! Thanks.

[@electroumit]

Thank you.

[@AEMCInstruments]

You're welcome!

[@nazrinrahman94]

During the survey, you mentioned that the electrodes were planted 6 inches deep (5:50). May I know if there are any effects of different electrode depth? As far as I know, the injected current is regarded as a point source located at the air-ground boundary, regardless of the electrode depth planted.

[@AEMCInstruments]

At that moment in the video, the electrodes were placed 10-feet apart performing a Wenner Soil Resistivity Test method. To use the simplified formula for the Wenner method, AEMC recommends no more than 1/20th of the spacing for the depth of the electrodes. 1/20th of a 10-foot spacing is 0.5-ft (6-inches) There’s no concern when you are at, or shallower than, these depths and using the simplified formula. Our meter assumes you are using the simplified formula method and therefore calculates the Rho based upon the simplified formula and the 1/20th depth-to-spacing guideline. If you push the electrodes deeper than recommended by us, the simplified formula is no longer valid and the long formula must be used. Our instrument does not perform the long formula calculations automatically. These calculations must be done manually. Please contact AEMC Tech Support (techsupport @ aemc . com) for more information.

[@saifahmed6131]

How ground resistance test will be performed for Hull floating on water

[@shazogutu6091]

The best explanation. Thank you Sir

[@AEMCInstruments]

You are most welcome. Thank you!

[@hamzalag2006]

Thanks

[@cameronrampersadh889]

Hey, can you please explain why the resistance of an earthing system (ie in a power substation) has to be sufficiently low?

[@AEMCInstruments]

A grounding system should provide a low-impedance path for fault currents and lightning-strike currents to enter the earth/dirt. This ensures maximum safety from electrical system faults and lightning. The low impedance ground protects equipment and buildings from being damaged by directing this dangerous energy to the earth/dirt. More importantly, this provides a level of safety for people and any living animal nearby.

[@cameronrampersadh889]

@@AEMCInstruments great thank you so much

[@zog0017]

@@AEMCInstruments I like the video, it is very informative. I don't like your wording about "a grounding system should provide a low-impedance path for fault currents and lightning strike currents to enter the earth/dirt". These are very different situations; one requires a 25 ohm impedance and one does not. They should be looked at separately.

[@mc.esteban653]

Nice video!! tanks

[@AEMCInstruments]

Glad you liked it!

[@dhadumia]

Awesome video. Thank you!

[@nbkk771]

Explained very well

[@AEMCInstruments]

Thank you

[@djhatton6858]

The explanation of fault current from a ground rod (and as not explained to create the circuit to the service transformer) is an incorrect understanding/explanation of effective ground-fault current path. The NEC does not allow earth as an effective fault current path as the resistance is too high to allow the fault current to flow of sufficient magnitude to trip source breaker. Suggest redoing this part of the video as the information is not being correctly discussed. NEC 250.4(A)(5) "the earth shall not be considered as an effective ground-fault currrent path".

[@EDGEHILLBBKE]

very informative

[@AEMCInstruments]

Glad you liked it!

[@bienlaborte4583]

Too Awesome video. Thank you

[@baobaoyang1840]

Can this product test larger metals underground? For example, gold and silver buried by wealthy people in the past.

[@AEMCInstruments]

Doubtful. It is true that gold and silver is very conductive and will help lower the overall soil resistivity readings. The problem is that measuring low readings does not automatically indicate lode or placer gold and silver deposits below. For example; subsurface water, ashes, cinder and brine will also lower the readings significantly. Prospecting for gold and silver would be a frustrating trial and error operation using this method. Good luck!

[@mightyhandengineeringmight6289]

Why was 3711 discontinued?

[@AEMCInstruments]

To introduce the next generation of handheld ground testers, the 6416 and 6417. As of December 2020, we still calibrate, repair and service the 3711.

[@mightyhandengineeringmight6289]

@@AEMCInstruments thank you

[@livingfortomorrow.]

nice video

[@AEMCInstruments]

Thanks!

[@vinothy3858]

Boss I want some doubt

[@johngreen6421]

I really like earth grounding resistance meter. I have it on my wish list. Do you need a electrical salesman in Northern California. I love to market your product.

[@AEMCInstruments]

Thank you for your kind feedback! We currently have a sales representative in the Bay Area who's very good. Send an email to techsupport @ aemc . com and I can get you in touch with them about any opportunities in CA.

[@copepaste]

Thank you

[@AEMCInstruments]

You're welcome!

[@sandipnshinde6504]

My observation that when we give earthing then electricity meter revel fast and bill increase why it happened please reply must

[@AEMCInstruments]

I am unclear. Did you say that when you add earthing to your system, your electricity bill increases? This is unusual and should not happen. Please give more detail. Thank you

[@James_Bowie]

I don't understand your question, however one interpretation may be that your earth current is too high, which can be an indication of a lost/bad neutral connection which is a HIGHLY dangerous situation and needs to be checked by a qualified electrician.

[@luisalejandrocardozogutier9365]

por favor este vídeo se podrá ver en español gracias

[@AEMCInstruments]

Por ahora no tenemos la versión en español de este video. Por favor consulte la versión en español del libro de trabajo Entendiendo las Pruebas de Resistencia de Tierra, en el siguiente enlace: www.aemc.com/userfiles/files/resources/workbooks/950-WKBK-GROUND-SP.pdf Este video está basado en el contenido de este libro de trabajo.

[@thakurarvindsingh5239]

hello i need help regarding earthing issue,

[@AEMCInstruments]

Please contact our Tech Support Hotline at 1-800-343-1391 x351 or email us at techsupport @ aemc . com

[@cesarelicano3679]

Your explanation is too broad but non substantial for me, what we need is the actual testing at site not like people working construction on their desk or table only.

[@AEMCInstruments]

Understood. Thanks for your valuable feedback.

[@nancyhulan8106]

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