The Same electrode with same GCIM type and quantity behaves differently at various locations on the earth. As we have discussed earlier the factors which affect the performance and conductivity of earthing. Soil structure is one of them. Due to this variation in nature or structure of soil; we get different resistance value at various locations with the same earthing electrode. GCIM is Ground Conductivity Improving Material, which is mixed with soil and placed around the electrode during the process of earthing installation.
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Other terminologies[ edit ] While the national wiring regulations for buildings of many countries follow the IEC terminology, in North America United States and Canada , the term "equipment grounding conductor" refers to equipment grounds and ground wires on branch circuits, and "grounding electrode conductor" is used for conductors bonding an earth ground rod or similar to a service panel.
The neutral is grounded earthed at each consumer service point thereby effectively bringing the neutral potential difference to zero along the whole length of LV lines. In the UK and some Commonwealth countries, the term "PNE", meaning Phase-Neutral-Earth is used to indicate that three or more for non-single-phase connections conductors are used, i. Resistance-earthed neutral India [ edit ] A resistance earth system is used for mining in India as per Central Electricity Authority Regulations.
Due to the fault current restriction it is safer for gassy mines. By comparison, in a solidly earthed system, earth fault current can be as much as the available short-circuit current. The neutral earthing resistor is monitored to detect an interrupted ground connection and to shut off power if a fault is detected. Previously, a earth leakage circuit breaker is used. In industrial applications, earth leakage relays are used with separate core balanced current transformers.
This is used in the trailing cables of mining machinery. This type of circuit is a must for portable heavy electric equipment like LHD Load, Haul, Dump machine being used in under ground mines. Cost[ edit ] TN networks save the cost of a low-impedance earth connection at the site of each consumer. Such a connection a buried metal structure is required to provide protective earth in IT and TT systems.
However, to mitigate the risk of broken neutrals, special cable types and lots of connections to earth are needed.
Safety[ edit ] In TN, an insulation fault is very likely to lead to a high short-circuit current that will trigger an overcurrent circuit-breaker or fuse and disconnect the L conductors. Earlier TT installations may lack this important safety feature, allowing the CPC Circuit Protective Conductor or PE and perhaps associated metallic parts within reach of persons exposed-conductive-parts and extraneous-conductive-parts to become energized for extended periods under fault conditions, which is a real danger.
In a TN-C system, they would also be very vulnerable to unwanted triggering from contact between earth conductors of circuits on different RCDs or with real ground, thus making their use impracticable.
Also, RCDs usually isolate the neutral core. In single-ended single-phase systems where the Earth and neutral are combined TN-C, and the part of TN-C-S systems which uses a combined neutral and earth core , if there is a contact problem in the PEN conductor, then all parts of the earthing system beyond the break will rise to the potential of the L conductor.
In an unbalanced multi-phase system, the potential of the earthing system will move towards that of the most loaded line conductor. Such a rise in the potential of the neutral beyond the break is known as a neutral inversion. There is also a risk if a cable is damaged, which can be mitigated by the use of concentric cable construction and multiple earth electrodes. In IT systems, a single insulation fault is unlikely to cause dangerous currents to flow through a human body in contact with earth, because no low-impedance circuit exists for such a current to flow.
However, a first insulation fault can effectively turn an IT system into a TN system, and then a second insulation fault can lead to dangerous body currents. Worse, in a multi-phase system, if one of the line conductors made contact with earth, it would cause the other phase cores to rise to the phase-phase voltage relative to earth rather than the phase-neutral voltage.
IT systems also experience larger transient overvoltages than other systems. In TN-C and TN-C-S systems, any connection between the combined neutral-and-earth core and the body of the earth could end up carrying significant current under normal conditions, and could carry even more under a broken neutral situation.
Therefore, main equipotential bonding conductors must be sized with this in mind; use of TN-C-S is inadvisable in situations such as petrol stations, where there is a combination of lots of buried metalwork and explosive gases. Electromagnetic compatibility[ edit ] In TN-S and TT systems, the consumer has a low-noise connection to earth, which does not suffer from the voltage that appears on the N conductor as a result of the return currents and the impedance of that conductor.
This is of particular importance with some types of telecommunication and measurement equipment. In TT systems, each consumer has its own connection to earth, and will not notice any currents that may be caused by other consumers on a shared PE line. Regulations[ edit ] In the United States, National Electrical Code and Canadian Electrical Code the feed from the distribution transformer uses a combined neutral and grounding conductor, but within the structure separate neutral and protective earth conductors are used TN-C-S.
For an LV customer, it is a TN-C system from the transformer in the street to the premises, the neutral is earthed multiple times along this segment , and a TN-S system inside the installation, from the Main Switchboard downwards. Looked at as a whole, it is a TN-C-S system. Rules are different when it comes to larger companies. In India as per Central Electricity Authority Regulations , CEAR, , rule 41, there is provision of earthing, neutral wire of a 3-phase, 4-wire system and the additional third wire of a 2- phase, 3-wire system.
Earthing is to be done with two separate connections. The grounding system must also have a minimum of two or more earth pits electrodes to better ensure proper grounding.
Neutral is double grounded at each distribution transformer. Neutral and earth conductors run separately on overhead distribution lines. Separate conductors for overhead lines and armoring of cables are used for earth connection. After this, separate earth and neutral cores are used in all the internal wiring.
Older urban and suburban homes in the UK tend to have TN-S supplies, with the earth connection delivered through the lead sheath of an underground lead-and-paper cable. Some older homes, especially those built before the invention of residual-current circuit breakers and wired home area networks, use an in-house TN-C arrangement.
This is no longer recommended practice. Laboratory rooms, medical facilities, construction sites, repair workshops, mobile electrical installations, and other environments that are supplied via engine-generators where there is an increased risk of insulation faults, often use an IT earthing arrangement supplied from isolation transformers.
To mitigate the two-fault issues with IT systems, the isolation transformers should supply only a small number of loads each and should be protected with an insulation monitoring device generally used only by medical, railway or military IT systems, because of cost. In remote areas, where the cost of an additional PE conductor outweighs the cost of a local earth connection, TT networks are commonly used in some countries, especially in older properties or in rural areas, where safety might otherwise be threatened by the fracture of an overhead PE conductor by, say, a fallen tree branch.
In Australia , New Zealand and Israel the TN-C-S system is in use; however, the wiring rules state that, in addition, each customer must provide a separate connection to earth, via a dedicated Earth electrode. This MEN Link is removable for installation testing purposes, but is connected during normal service by either a locking system locknuts for instance or two or more screws.
In the MEN system, the integrity of the Neutral is paramount. In Australia, new installations must also bond the foundation concrete re-enforcing under wet areas to the Protective Earth conductor AS , typically increasing the size of the earthing i.
In older installations, it is not uncommon to find only the water pipe bond, and it is allowed to remain as such, but the additional earth electrode must be installed if any upgrade work is done.
IS 3043 EARTHING PDF
Other terminologies[ edit ] While the national wiring regulations for buildings of many countries follow the IEC terminology, in North America United States and Canada , the term "equipment grounding conductor" refers to equipment grounds and ground wires on branch circuits, and "grounding electrode conductor" is used for conductors bonding an earth ground rod or similar to a service panel. The neutral is grounded earthed at each consumer service point thereby effectively bringing the neutral potential difference to zero along the whole length of LV lines. In the UK and some Commonwealth countries, the term "PNE", meaning Phase-Neutral-Earth is used to indicate that three or more for non-single-phase connections conductors are used, i. Resistance-earthed neutral India [ edit ] A resistance earth system is used for mining in India as per Central Electricity Authority Regulations. Due to the fault current restriction it is safer for gassy mines.
IS 3043 EARTHING PDF
Earthing And Lightning Protection In Electrical Construction Contract Works 0 The scope of this specification covers the supply, installation and testing and earthing system of the entire installation and for lightning protection. IS Code of practice for the protection of building and allied structures against lightning. Earthing System The earthing system shall comprise of earth electrodes at substation and other convenient places, with an interconnecting earth grid. The earth electrodes shall be in conformity with IS of plates or pipes of GI with test links, internal connecting leads, earthing mixture of salt, charcoal, etc. The number of each electrodes shall be determined from measurement of the earth resistance which finally should not exceed 1 ohms.
Nakazahn Anaesthetic room M x x x1 x 6 V, for a period of at least 5 a. However, this imposed a The upper limit should not exceed the value separately to the alternator neutral where required for the protective devices to operate and the latter is bonded to the vehicle chassis; disconnect the load in a time not exceeding the and safe value. Since a ing transformers. How to calculate the internal earthing cable for the panel?