Forgot Password? New Posts. Today's Posts. Community Member List. Forum Actions Mark Forums Read. Quick Links View Forum Leaders. Typical resistance between ground and neutral at electrical outlet? Thread Tools. Should I be reading resistance at my electrical outlets between ground and neutral wires? Since they're bonded in my service panel, I wouldn't think so.Learn about the basics of grounds, grounding, and ground symbols.
Not all grounds are created equal. In this article, we'll discuss earth ground, common ground, analog ground, and digital ground. In electronics and electrical engineering, it is by convention we define a point in a circuit as a reference point. This reference point is known as ground or GND and carries a voltage of 0V. Voltage measurements are relative measurements. That is, a voltage measurement must be compared to another point in the circuit.
If it is not, the measurement is meaningless. The ground reference point is often, but not always—more on this later—represented by a standard ground symbol. See Figure 1. Typically, this reference point is the base for all other voltage measurements within the circuit. However, not all voltage measurements are taken from this reference point. For instance, if you were to measure the voltage across the upper resistor in a resistive voltage divider, your reference point would not be ground.
See Figure 2.
A true earth ground, as defined by the National Electrical Code NECconsists of a conductive pipe, or rod, physically driven into the earth to a minimum depth of 8 feet.
The earth provides an electrically neutral body, and due to the earth's virtually infinite state of neutrality, it is immune to electrical wavering. It should be noted, however, that "earth being immune to electrical wavering" is, in fact, a generalization. In reality, earth ground is quite the complex subject given all variables and materials that make up the earth. And, earth's electrical potential does indeed experience some isolated areas of varying due to events such as lightning hits, as an example.
Power poles, those that are strung throughout neighborhoods, are also connected to ground. Figure 3 shows an earth grounding wire attached to a power pole. This outlet connection to earth ground provides a means for, as an example, test equipment to be connected to earth ground—the ground green wire from a power cord is connected to the equipment's internal frame or chassis.
And when connecting various pieces of test equipment to earth ground, they are all connected to a common grounding point, and, therefore, have a common reference. You can verify this point by measuring the resistance between the ground terminals of any two pieces of test equipment. This common reference is brought out, to the user, as a ground lead terminal. Side note: your desktop computer's chassis is also connected to earth ground.
For instance, the earth ground symbol is also used as a common ground symbol or a 0V reference. This is a bit misleading because a 0V reference is not actually connected to earth ground. Digital circuits generate spikes of current when the digital signals change states.
Although there are multiple techniques for proper grounding, when it comes to mixed-signal grounding it's of most importance—regardless of which grounding technique is adopted—to separate the "more-noisy" digital return currents from the "less-noisy" analog return currents. Such ground currents—think of them as changing currents—when applied to ground return paths, create voltage variations recall Ohm's Law called noise.
You may have heard the term "a noisy ground.
Grounding has always been a major obstacle for design, system, and test engineers.Why don't fictional characters say "goodbye" when they hang up a phone?
If we can't tunnel through the Earth, how do we know what's at its center? What is the difference between neutral earthing resistance and solid earth? All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply. Hottest Questions. Previously Viewed.
An Introduction to Ground: Earth Ground, Common Ground, Analog Ground, and Digital Ground
Unanswered Questions. Electrical Engineering. Wiki User The impedance may be a resistor or an inductorchoke depending on the nature of the earth return. In general, if the earth resistance is low, then resistive earthing is used; if the earth resistance is high, then inductive earthing is used. The tank is then filled with water, and it is the resistance of the water that provides the required resistance to earth.
The actual resistance of the water is modified to the desired value by dissolving sodium carbonate into the water while measuring its resistance. The solution has a negative temperature coefficient of resistance, which means that, in the event of an earth fault, as the fault current increases, the increasing temperature causes the resistance of the water to decrease, thus accelerating the response time of the protective system.
Related Questions Asked in Electrical Engineering, Electrical Wiring What is the difference between earthing transformer and neutral grounding transformer? First of all, there is no difference between "earthing" and "grounding", since "earthing" is being used in Europe, whereas "grounding" is more common in the USA.
An earthing or grounding transformer is a transformer which is used in a substation in order to derive the substation LowVoltageAC supply from the main power transformer. If you use an earthing or grounding transformer in order to provide an artificial neutral in a network without a neutral where for various reasons, only delta windings are used at a particular voltage levelyou refer to such a transformer as a neutral earthing or neutral grounding transformer. Asked in Electrical Engineering Why is neutral of step up transformer grounded?
This serves various purposes like to drain away unwanted currents, to provide a reference voltage for circuits needing one, to lead lightning away from delicate equipment. Earthing and Grounding both is refer to zero potential but the system connected to zero potential is differ than Equipment connected to zero potential.To understand the difference between Neutral, Ground and Earth, we must understand the need of these things first. Neutral is return path for an AC circuit which is supposed to carry current in normal condition.
This current may be because of many reasons, primarily because of phase current imbalance and some time because 3rd and 5th harmonics also. There may be others reasons too but the magnitude of this current is in fraction of phase current and in few case it can be even double of phase current. So Neutral wire is always assumed to be charged in active circuit. This neutral wire is given to ground by grounding to make the second terminal of neutral wire at zero potential.
Earth or Ground is for safety concerns against leakage or residual currents on the system via least resistance path. This current is not directly coming from live or phase wire, but is from secondary links which was not in touch with live system in normal condition. This current is usually much lesser than main line current or phase current and mostly is in order of mA. But this leakage current is good enough to kill someone or may risk fire.
Continuity between live and earth wires in ceiling light
Such current are being provided a low resistance path and sent to earth via earth wire. Because of the difference in application we never mix grounding of neutral and earth.
However both are made grounded of-course the process may be different. If both will be mixed then the earth wire which is not supposed to carry any current in normal conditionmay have some charges across and will become hazardous. Good to Know:.
Typical resistance between ground and neutral at electrical outlet?
There is no difference between Earthing and Grounding but these are the same terms used for Earthing or Grounding. In simple words, Earthing and Grounding are synonyms. Both are similar words used for the same thing. You may also read:. Raise in continuous temperature, of wire effects directly to its life, and hence domestic wires are Class 2, having less conductor resistance, and higher current carrying capacity.
Whereas class 5 Max no of strands, less Diais having high resistance than class 5, and limited cirrent carrying capacity than class 2. Dear sir, How r u, sir i want to know that i used the generator kva on three phase.
The problem is, the nuetral side of the generator show ampere. So how would i free my generator nuetral from current. Means what i do that my nuetral show 0 amp. Your graphic representation is very poor. Also the power supply to motor should show PE Protective Earth conductor.
Earthing of the motor frame is there only to avoid excessive touch voltages and not a positive return path for fault current. Where Neutral and Protective conductors are combined into one or are separated. You are so many thanks to developed this website. This website is very helpful me. Again thanks to developer and other assistant.
Unfortunately, I cannot find that article any-more. Anyway, IEEE makes an important distinction between ground and earth. At least, this is what I have understood.
Now i am found a good place that easily helps me, to learn about my subjects. Dear sir, i want to know about the solar panel 25 kw,sir if are solar supply fail than,i ant that it automatically to cames to main supply and in the same way if main supply is failed than its come to generator supply. Basic diagram of star wound generator and distribution system.Unfortunately, there is not one standard ground resistance threshold recognized by all certifying agencies.
In facilities with sensitive equipment it should be 5ohms or less. The telecommunications industry has often used 5 ohms or less as their value for grounding and bonding while electric utilities construct their ground systems so that the resistance at a large station will be no more than a few tenths of one ohm. There is no NEC NEC In my company, a telecommunication giant in Nigeria, the standard earth resistance value ranges from 2.
Please let me know, the standard earth resistance value ranges from 2.Grounding and Bonding
But the inverter was still destroyed by thunder. This made me to to run a test on the earthing and was discovered it was 27ohms. How come it was only the inverter that was affected and not the house appliances as well.
Because inverter has an isolation transformer and surge circuit inside to avoid cascading the fault current goes. Avoid to use any mineral who can Damager or Corrosion your Metal Later. Please I want to do earthing as my thesis for my 2nd degree project so can you give me some PDF on earthing?
The highly recommended value of ground resistance for a residential and commercial area is less than or equal to 1 ohm. You need to use more earth electrode to achieve this value. You guys are doing a great job!
Very educative. This is electrical engineering made easy and real. Thank you. Hey man thats a brief and very informative article.This article focus on explaining the similarities and dissimilarities between neutral and earth ground.
Understanding the difference between the neutral and earth may be difficult in the beginning. A Lot of safety and protection related aspects need to be carefully studied for a better understanding of the difference between them.
Neutral acts as a return conductor for current flow in a single-phase, two-wire L-N AC circuit.
It completes an AC circuit. It is centre tap point of a Wye connected transformer. Hence it carries the return current back to the transformer source. Normally this point is earthed for various reasons. In an ideal AC system, neutral and earth should be at the same potential, which means the voltage measured between the neutral and the earth should be zero. An Earth or ground is a safety connection to protect personnel from electric shock.
When a bare conductor inside a piece of equipment touches its metal body or in case of insulation failures, there is a risk of electric shock to the person who operates or touches the equipment.
Earth conductors provide a low resistance path for the leakage currents to discharge, hence protecting the equipment and the personnel.
Normally conductor used for grounding a piece of equipment is sized just to carry fault current discharged on the equipment body. Well-grounded equipment avoids the risk of electric shock the person using it. Normally the neutral point is earthed at the distribution transformer Delta — Wye connected transformers.
Under certain conditions, a conductor used to connect to a system neutral is also used for grounding earthing of equipment and structures. Current carried on a grounding conductor can result in objectionable or dangerous voltages appearing on equipment enclosuresso the installation of grounding conductors and neutral conductors is carefully defined in electrical regulations.
Where a neutral conductor is used also to connect equipment enclosures to earth, care must be taken that the neutral conductor never rises to a high voltage with respect to local ground. Ground or earth in a mains AC power electrical wiring system is a conductor that provides a low- impedance path to the earth to prevent hazardous voltages from appearing on equipment high voltage spikes. Under normal conditions, a grounding conductor does not carry current.
Grounding is also an integral path for home wiring because it causes circuit breakers to trip more quickly ie, GFIwhich is safer. Adding new grounds requires a qualified electrician with knowledge particular to a power distribution region. Neutral is a circuit conductor that normally completes the circuit back to the source.
Neutral is usually connected to ground earth at the main electrical panel, street drop, or meter, and also at the final step-down transformer of the supply. That is for simple single panel installations; for multiple panels the situation is more complex.
In a polyphase usually three-phase AC systemthe neutral conductor is intended to have similar voltages to each of the other circuit conductors, but may carry very little current if the phases are balanced. All neutral wires of the same earthed grounded electrical system should have the same electrical potential, because they are all connected through the system ground.
Neutral conductors are usually insulated for the same voltage as the line conductors, with interesting exceptions.
Neutral wires are usually connected at a neutral bus within panelboards or switchboards, and are "bonded" to earth ground at either the electrical service entrance, or at transformers within the system. For electrical installations with split-phase three-wire single-phase servicethe neutral point of the system is at the center-tap on the secondary side of the service transformer.
Other arrangements of polyphase transformers may result in no neutral point, and no neutral conductors. The IEC standard IEC codifies methods of installing neutral and ground conductors in a building, where these earthing systems are designated with letter symbols. The differences are that the conductors may be separate over their entire run from equipment to earth ground, or may be combined all or part of their length. Different systems are used to minimize the voltage difference between neutral and local earth ground.
Current flowing in a grounding conductor will produce a voltage drop along the conductor, and grounding systems seek to ensure this voltage does not reach unsafe levels.
In the TN-S system, separate neutral and protective earth conductors are installed between the equipment and the source of supply generator or electric utility transformer.
Difference between Neutral and Earth
Normal circuit currents flow only in the neutral, and the protective earth conductor bonds all equipment cases to earth to intercept any leakage current due to insulation failure. The neutral conductor is connected to earth at the building point of supply, but no common path to ground exists for circuit current and the protective conductor. In the TN-C system, a common conductor provides both the neutral and protective grounding.