171:(AC) electrical systems. The neutral conductor receives and returns alternating current to the supply during normal operation of the circuit; to limit the effects of leakage current from higher-voltage systems, the neutral conductor is often connected to earth ground at the point of supply. By contrast, a ground conductor is not intended to carry current for normal operation, but instead connects exposed metallic components (such as equipment enclosures or conduits enclosing wiring) to earth ground. A ground conductor only carries significant current if there is a circuit fault that would otherwise energize exposed conductive parts and present a shock hazard. In that case, circuit protection devices may detect a fault to a grounded metal enclosure and automatically de-energize the circuit, or may provide a warning of a ground fault.
889:. Triplen harmonic currents (odd multiples of the third harmonic) are additive, resulting in more current in the shared neutral conductor than in any of the phase conductors. In the absolute worst case, the current in the shared neutral conductor can be triple that in each phase conductor. Some jurisdictions prohibit the use of shared neutral conductors when feeding single-phase loads from a three-phase source; others require that the neutral conductor be substantially larger than the phase conductors. It is good practice to use four-pole circuit breakers (as opposed to the standard three-pole) where the fourth pole is the neutral phase, and is hence protected against overcurrent on the neutral conductor.
908:
the receptacle. Typically such receptacles are supplied from two circuit breakers in which the handles of two poles are tied together for a common trip. If two large appliances are used at once, current passes through both and the neutral only carries the difference in current. The advantage is that only three wires are required to serve these loads, instead of four. If one kitchen appliance overloads the circuit, the other side of the duplex receptacle will be shut off as well. This is called a
384:. Since normal circuit currents in the neutral conductor can lead to objectionable or dangerous differences between local earth potential and the neutral, and to protect against neutral breakages, special precautions such as frequent rodding down to earth (multiple ground rod connections), use of cables where the combined neutral and earth completely surrounds the phase conductor(s), and thicker than normal
33:
147:
440:
considered safe since the devices were permanently wired to the supply and so the neutral was unlikely to be broken without also breaking both supply conductors. Also, the unbalanced current due to lamps and small motors in the appliances was small compared to the rating of the conductors and therefore unlikely to cause a large voltage drop in the neutral conductor.
881:
In a three-phase linear circuit with three identical resistive or reactive loads, the neutral carries no current. The neutral carries current if the loads on each phase are not identical. In some jurisdictions, the neutral is allowed to be reduced in size if no unbalanced current flow is expected. If
523:
The connection between neutral and earth allows any phase-to-earth fault to develop enough current flow to "trip" the circuit overcurrent protection device. In some jurisdictions, calculations are required to ensure the fault loop impedance is low enough so that fault current will trip the protection
327:
In the TN-C-S system, each piece of electrical equipment has both a protective ground connection to its case, and a neutral connection. These are all brought back to some common point in the building system, and a common connection is then made from that point back to the source of supply and to the
323:
In the TN-C system, a common conductor provides both the neutral and protective grounding. The neutral conductor is connected to earth ground at the point of supply, and equipment cases are connected to the neutral. The danger exists that a broken neutral connection will allow all the equipment cases
481:
Another specialized distribution system was formerly specified in patient care areas of hospitals. An isolated power system was furnished, from a special isolation transformer, with the intention of minimizing any leakage current that could pass through equipment directly connected to a patient (for
252:
states that the neutral and ground wires should be connected at the neutral point of the transformer or generator, or otherwise some "system neutral point" but not anywhere else. That is for simple single panel installations; for multiple panels the situation is more complex. In a polyphase (usually
515:
In a three-phase circuit, a neutral is shared between all three phases. Commonly the system neutral is connected to the star point on the feeding transformer. This is the reason that the secondary side of most three-phase distribution transformers is wye- or star-wound. Three-phase transformers and
486:
for monitoring the heart). The neutral of the circuit was not connected to ground. The leakage current was due to the distributed capacitance of the wiring and capacitance of the supply transformer. Such distribution systems were monitored by permanently installed instruments to give an alarm when
477:
There are special provisions in the NEC for so-called technical equipment, mainly professional grade audio and video equipment supplied by so-called "balanced" 120 volt circuits. The center tap of a transformer is connected to ground, and the equipment is supplied by two line wires each 60 volts to
439:
appliances often have components that use either 120, or both 120 and 240 volts, there is often some current on the neutral wire. This differs from the protective grounding wire, which only carries current under fault conditions. Using the neutral conductor for grounding the equipment enclosure was
361:
created in grounding (earthing) conductors by currents flowing in the supply utility neutral conductors can be troublesome. For example, special measures may be required in barns used for milking dairy cattle. Very small voltages, not usually perceptible to humans, may cause low milk yield, or even
150:
A shorting bar connecting ground and neutral in Swiss industrial building (outlined in red). A hunk of copper is visible that is designed to be easily connected or disconnected from its place between two screws, rated for 600 A (as stamped on it). We also see the thick wires in standard colors (two
907:
in a North
American kitchen, devices may be connected with a cable that has three conductors, in addition to ground. The three conductors are usually coloured red, black, and white. The white serves as a common neutral, while the red and black each feed, separately, the top and bottom hot sides of
315:
are designated with letter symbols. The letter symbols are common in countries using IEC standards, but North
American practices rarely refer to the IEC 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
519:
A system could be made entirely ungrounded. In this case a fault between one phase and ground would not cause any significant current. Commonly the neutral is grounded (earthed) through a bond between the neutral bar and the earth bar. It is common on larger systems to monitor any current flowing
452:
can be used to maintain the identity of the neutral conductor into the appliance but neutral is never used as a chassis/case ground. The small cords to lamps, etc., often have one or more molded ridges or embedded strings to identify the neutral conductor, or may be identified by colour. Portable
319:
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). Normal circuit currents flow only in the neutral, and the protective earth conductor bonds all equipment cases to earth to
920:
A ground connection that is missing or of inadequate capacity may not provide the protective functions as intended during a fault in the connected equipment. Extra connections between ground and circuit neutral may result in circulating current in the ground path, stray current introduced in the
478:
ground (and 120 volts between line conductors). The center tap is not distributed to the equipment and no neutral conductor is used. These cases generally use a grounding conductor which is separated from the safety grounding conductor specifically for the purposes of noise and "hum" reduction.
316:
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.
264:
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.
847:
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464:
cannot ensure that a system neutral conductor is connected to particular terminals of the device ("unpolarized" plugs), portable appliances must be designed on the assumption that either pole of each circuit may reach full main voltage with respect to the ground.
925:. Extra ground connections on a neutral conductor may bypass the protection provided by a ground-fault circuit interrupter. Signal circuits that rely on a ground connection will not function or will have erratic function if the ground connection is missing.
342:
The neutral conductor of a 3-phase, 4-wire system and the middle conductor of a 2- phase, 3-wire system must have at least 2 separate and distinct earth connections with a minimum of 2 different earth electrodes to have a satisfactory earth
151:
yellow/green ground and two blue neutral), as well as markings PEN (protected earth and neutral), PE (protective earth) and N (neutral). The three bars for the three "live" phases (marked L1, L2 and L3) are also visible on the bottom right.
527:
In the case of two phases sharing one neutral and the third phase is disconnected, the worst-case current draw is one side has zero load and the other has full load, or when both sides have full load. The latter case results in
320:
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.
237:
is more common in
British English. 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,
473:
In North
American practice, equipment connected by a cord set must have three wires if supplied exclusively by 240 volts, or must have four wires (including neutral and ground), if supplied by 120/240 volts.
745:
531:
641:
912:. Common trip is required when the connected load uses more than one phase simultaneously. The common trip prevents overloading of the shared neutral if one device draws more than rated current.
281:(three-wire single-phase) service, the neutral point of the system is at the center-tap on the secondary side of the service transformer. For larger electrical installations, such as those with
428:
appliances to be connected to the neutral conductor for grounding. (Canada did not adopt this system and instead during this time and into the present uses separate neutral and ground wires.)
331:
In a TT system, no lengthy common protective ground conductor is used, instead each article of electrical equipment (or building distribution system) has its own connection to earth ground.
190:. 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.
448:
In North
American and European practice, small portable equipment connected by a cord set is permitted under certain conditions to have merely two conductors in the attachment plug. A
277:
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
876:
994:
For example, in North
American practice an overhead service-entrance cable has two insulated conductors which are wrapped around and supported by the bare neutral conductor
369:
Connecting the neutral to the equipment case provides some protection against faults, but may produce a dangerous voltage on the case if the neutral connection is broken.
261:, the 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.
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to rise to a dangerous voltage if any leakage or insulation fault exists in any equipment. This can be mitigated with special cables but the cost is then higher.
349:
The neutral conductor shall also be earthed at one or more points along the distribution system or service line in addition to any connection at the user end
885:
The current drawn by non-linear loads, such as fluorescent & HID lighting and electronic equipment containing switching power supplies, often contains
335:
304:
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366:(inflammation of the udder). So-called "tingle voltage filters" may be required in the electrical distribution system for a milking parlour.
174:
Under certain conditions, a conductor used to connect to a system neutral is also used for grounding (earthing) of equipment and structures.
1138:
376:' wiring and occasionally for fixed wiring in buildings and for some specialist applications where there is little alternative, such as
50:
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524:(In Australia, this is referred to in AS3000:2007 Fault loop impedance calculation). This may limit the length of a branch circuit.
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842:{\displaystyle I_{\mathrm {m} }\angle {120}^{\circ }+I_{\mathrm {m} }\angle {-120}^{\circ }=I_{\mathrm {m} }\angle {180}^{\circ }}
1108:
242:), which is safer. Adding new grounds requires a qualified electrician with knowledge particular to a power distribution region.
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97:
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is the magnitude of the current. In other words the magnitude of the current in the neutral equals that of the other two wires.
631:{\displaystyle I_{\mathrm {m} }\angle {0}^{\circ }+I_{\mathrm {m} }\angle {-120}^{\circ }=I_{\mathrm {m} }\angle {-60}^{\circ }}
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735:{\displaystyle I_{\mathrm {m} }\angle {0}^{\circ }+I_{\mathrm {m} }\angle {120}^{\circ }=I_{\mathrm {m} }\angle {60}^{\circ }}
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path to the earth to prevent hazardous voltages from appearing on equipment (high voltage spikes). The terms
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Canadian
Electrical Code Part I, Nineteenth Edition, C22.1-02 Safety Standard for Electrical Installations
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the neutral is smaller than the phase conductors, it can be overloaded if a large unbalanced load occurs.
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is a connection in which a plurality of circuits use the same neutral connection. This is also known as a
289:. Other arrangements of polyphase transformers may result in no neutral point, and no neutral conductors.
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For uses of the term "grounding" or "earth" in electricity but not in the context of mains wiring, see
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in the 1996 edition, but existing installations (called "old work") may still allow the cases of such
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https://www.powerandcables.com/wp-content/uploads/2020/01/2008-National-Electrical-Code-NFPA-70.pdf
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through the neutral-to-earth link and use this as the basis for neutral fault protection.
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appliances were grounded through their neutral wires as a measure to conserve copper from
311:) codifies methods of installing neutral and ground conductors in a building, where these
298:
1070:, National Fire Protection Association, Inc., Quincy, Massachusetts USA, (2002). no ISBN
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service, the neutral point is usually at the common connection on the secondary side of
1074:
IEE Wiring
Regulations Regulations for Electrical Installations Fifteenth Edition 1981
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their associated neutrals are usually found in industrial distribution environments.
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appliances never use the neutral conductor for case grounding, and often feature "
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1076:, The Institution of Electrical Engineers, (1981) Hitchin, Herts. United Kingdom
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is a circuit conductor that normally completes the circuit back to the source.
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carried on a grounding conductor can result in objectionable or dangerous
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The earth electrodes must be interconnected to reduce earth resistance
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139:"Neutral point" redirects here. For aircraft stability in pitch, see
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In mains electricity, part of a circuit connected to ground or earth
1057:, Canadian Standards Association, Toronto, Ontario Canada (2002)
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used to supply both 120 volt and 240 volt loads. Because these
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Combined neutral and ground conductors are commonly used in
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bonding must be considered to ensure the system is safe.
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57:. Unsourced material may be challenged and removed.
1105:(link dead but multiple sources via Google search)
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273:Neutral wires are usually connected at a neutral
233:is more common in North American English, and
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1026:Handbook of Electrical Hazards and Accidents
338:, Rule 41, makes the following provisions:
1003:Thomas J. Divers, Simon Francis Peek (ed),
217:system is a conductor that provides a low-
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396:In the United States, the cases of some
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950:Electrical wiring in the United Kingdom
392:Fixed appliances on three-wire circuits
229:are used synonymously in this section;
1068:NFPA 70, National Electrical Code 2002
1087:Lessons In Electric Circuits Vol 1 DC
903:In split-phase wiring, for example a
420:. This practice was removed from the
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55:adding citations to reliable sources
487:high leakage current was detected.
1098:EDISON CIRCUITS POSE SAFETY HAZARD
1007:, Elsevier Health Sciences, 2008,
955:Electrical wiring in North America
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1103:The Complete Guide To Home Wiring
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871:{\displaystyle I_{\mathrm {m} }}
287:delta/wye connected transformers
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42:needs additional citations for
921:earth or in a structure, and
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431:This practice arose from the
354:Combining neutral with ground
374:electricity supply companies
1139:Electric power distribution
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899:Split-phase electric power
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163:(earth and neutral) are
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134:ground (electricity)
66:"Ground and neutral"
51:improve this article
469:Technical equipment
444:Portable appliances
169:alternating current
1028:, CRC Press, 1995
1024:Leslie A. Geddes
940:Electrical bonding
916:Grounding problems
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484:electrocardiograph
165:circuit conductors
161:ground and neutral
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18:Neutral and ground
1134:Power engineering
1129:Electrical wiring
1124:Electrical safety
1081:Electrical Safety
945:Electrical wiring
935:Appliance classes
905:duplex receptacle
433:three-wire system
400:(ranges, ovens),
293:Grounding systems
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1036:, pp. 90-91
1015:pp. 389–390
893:Split phase
279:split-phase
255:three-phase
194:Definitions
1118:Categories
1053:, editor,
1034:0849394317
971:References
343:resistance
307:standard (
184:enclosures
77:newspapers
1090:book and
887:harmonics
835:∘
825:∠
805:∘
797:−
792:∠
772:∘
762:∠
728:∘
718:∠
698:∘
688:∠
668:∘
658:∠
624:∘
616:−
611:∠
591:∘
583:−
578:∠
558:∘
548:∠
402:cook tops
309:IEC 60364
283:polyphase
269:Circuitry
259:AC system
219:impedance
929:See also
378:railways
364:mastitis
328:earth.
180:voltages
167:used in
416:during
334:Indian
246:Neutral
213:power)
176:Current
91:scholar
1092:series
1061:
1051:et al.
1032:
1011:
849:where
437:listed
426:listed
410:listed
231:ground
223:ground
199:Ground
93:
86:
79:
72:
64:
382:trams
235:earth
227:earth
207:mains
205:in a
203:earth
98:JSTOR
84:books
1059:ISBN
1030:ISBN
1009:ISBN
380:and
336:CEAR
303:The
240:GFCI
225:and
70:news
830:180
800:120
767:120
742:or
693:120
586:120
422:NEC
305:IEC
275:bus
250:NEC
201:or
155:In
53:by
1120::
723:60
638:,
619:60
507:.
495:A
404:,
257:)
211:AC
159:,
1094:.
863:m
858:I
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814:I
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786:m
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777:+
756:m
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682:m
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673:+
663:0
652:m
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567:I
563:+
553:0
542:m
537:I
209:(
143:.
136:.
120:)
114:(
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105:(
95:·
88:·
81:·
74:·
47:.
20:)
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