Grounding zgіdno z pue. Razdіl eight. Grounding of electrical installations

Zahisne grounding - navmisne electrically grounded from the ground or її equivalent to metal non-current-carrying parts, yakі can be opinitisya pіd nagruzіdі zamikannya on the case of those other reasons (inductive influx of sudіdnі strumovіdnih parts, vnesenya potenya).

It is not necessary to ground it for the use of a problem of damage by an electric jet near the dot to the body of the electrical installation and other non-jet metal parts, which leaned against the pressure of the electric jet on the case for other reasons.

Galuz zastosuvannya zahisnogo grounding- electrical installations for a voltage of up to 1000 V in the strands from an insulated central lumen and more than 1000 V in the strands with a neutral mode, a struma was connected (both insulated and dead-earthed).

Vidpovidno to GOST 12.1.030-81

at rated voltage 380V and higher snake strumaі 440В і more postyny ​​strumu zavzhda;

at rated voltages of 42V to 380V of variable and 110V of up to 440V permanent stream in case of robots in the minds with advanced unsafety, especially unsafe and other installations.

Note: Characteristics of minds pointed to obov'yazykovy appendix to GOST 12.1.013-78.

The metal parts of electrical installations are given to the protective grounding, which are accessible to the dotik people, and they can’t think of other types of protection, for example, to the hull electrical machines, transformers, luminaires, frameworks of rozpodіlnyh shields, metal pipes and sheaths of electrical wiring, etc.

The principle of sound grounding in electrical installations up to 1000V:

decrease in the voltage of the dotik on a grounded body when the voltage drops to a new voltage.

Tse reaches for the rahunok of the small support of the grounding outbuilding (Ohm). Strum flow through the path of the smallest support, and since opir people (
kOhm), vіn pіde v zemlyuvach or yogo equivalent.

The principle diagram of the zahisnogo grounding is shown in fig.

(a) - three-phase mesh; (b) - a double-wire net of a change and (c) - a permanent struma.

Note: the marginally permissible value of the voltage of the dotik and strumov through the body of a person with improved trivality in the injection of induction according to GOST 12.1.038-82.

Grounding is provided for the help of special outbuildings grounding- the whole set of grounding conductors - metal conductors that stick from the ground, and grounding conductors, that connect parts of the electrical installation that are grounded, from the grounding conductor.

Fallow in the form of mutual expansion of grounding and possession, which are grounded, wines and contour grounding outbuildings are separated. The first of them are characterized by the fact that they are grounding faults for between the maidan, on which the possession is placed, which is grounded, or it is centered on the active part of the maidan (Fig. 20.4).

Contour grounding attachment (small 20.5), grounding of which is spread along the contour (perimeter) for a short period of time, which is grounded, on a small vіdstanі one type of one (depіlka metreіv)

Grounding workers are single and group, piece and natural.

Group grounding is made up of vertical shears and horizontal smugs, which are connected.

As a natural grounding vicorist:

Laying near the earth water;

Casing pipes of Sverdlovin (metal);

Lead sheaths of cables laid near the ground;

Іnshі metal structures, roztashovanі at ґruntі.

The ground support of the grounding outbuilding is built up on the support of natural and piece grounding devices:

de

- need (permissible) value of the support of the grounding outbuilding.

Wimogi to the support of the zahisnogo grounding are regulated by the PUE. Be it as it may be, this opir is not guilty of overshooting 4 ohm

BREAKED EIGHT

Grounding of electrical installations

1. Parts of installations that are grounded

In installations with a voltage of 500 and more than a changeable and constant stream, all metal parts are accessible to the dotik, if they are not under the voltage, but they can be supported under it, after a short time of insulation, due to grounding at all falls.

At a nominal voltage of 36 alternating struma and 110 constant struma, it is necessary to install grounding in places with a moving environment, especially in unsafe ones and in outdoor installations.

Before the parts, which provide grounding, you can see the cases of accessories, devices, electrical machines and transformers, frames of separate outbuildings and shields, cases cable boxes, fittings for insulators in separate outbuildings, metal fittings for pipes and fences.

Transformer windings lower voltage(up to 500 u inclusive), so as not to be grounded without a middle ground, it is necessary to ground it through the punches.

Opir zahisnogo grounding is not guilty of revisiting 4 ohm, for the sake of the installations of small intensity (handicraft maisters, scorching installations, living huts, etc.) from outsiders on the introduced no more than 25 a, if the value of zakhischnogo grounding is not guilty of but more than 10 ohms.

For earthing elements lighting installation vikoristovuyutsya zero droti (otherwise natural grounding conductors that replace them). The zero wire is not guilty of being protected by the defenders, the crime of vipadkiv, if the wines are not victorious for grounding.

If there is a grounded zero point, it is necessary to follow the following:

screw-metal cutting of the cartridge of the rear with a zero dart;

grounding to the body of the lamp that vimikacha vikonati for the help of a well-kept dart, otherwise they lived a dart to come to the zero dart of the group line;

single-pole vimikachi to put in a phase drota;

at a pressure of 380/220 V from a grounded zero point at any time, do not stop socket outletsіz zabіzhniki ї koї konstruktsії, yak posobnіє mozhlivіst dоtik up to strumovedih chastіv іn zminі zabіzhnika pіd narugou.

ZAKHISNI ZANULENNYA, GROUNDING AND VIMKNENNYA. Bliskazkazakhist. PROTECTION TYPE OF STATIC ELECTRICITY

ZAKHISNI ZANULATION, GROUNDING AND VIMKNENNYA

Zagalni understand. Dotik to the parts of electrical installations, which are under pressure, can cause damage electric jet. So, for example, a strum with a power of mA (0.02 - 0.025 A) paralyzes the mind of a person and allows him to be able to break through the contact with the parts of the electrical installation, which is under pressure. With strums, the heart begins to work arrhythmically with the power of mA, the normal blood circulation is disrupted and after 1-2 s, the victim's heart beats, the pulse is dihanna. If the first help is not given in an hour and no piecework is carried out, the death of the victim is possible.

The main reasons of uzainlyanne with electric strop є Docili to the end-of-step admisters of Elektroobladannan, Shaho normally looked at the pіd dummy, І Dotika to the part of Elektroobladnnan, Shaho normally do not go to the pіd dummy, Alla Yaki Might Vipadkovo opiate a pip vulgarity at the sampling on them sickle wires, windings of electrical machines, cables as well.

For the protection of personnel from the bunker to the non-insulated jet parts, which are under pressure, zastosovyt fenced parts, bar'єri, casings and other equipment, which are recommended by the rules of safety engineering.

When reticuing to particle of electrical installations, Yakі does not obey PID pіd, ally, we can vipadkovo opens the piD vnaslіdd's sampling of Іzlozzi-ї зашинідний подина сбор и ин и и задение, go to Zahist Vіd Uzazhnia ELECTRICHIY STREM, SHO GIVE YOURSELF YOU or s insulated neutral. At the fences with a dead-earthed neutral, the neutral of the transformer (the zero point of the windings connected to the star) is connected to the grounding outbuilding; in the fences from the insulated neutral, the neutral of the transformer was not connected to the grounding outbuilding (so it was insulated from the ground).

Electrical installations with a voltage of up to 1000 zminny struma can be both with a dead-earthed, and with an insulated neutral; fast strumu- from a dead-earthed or insulated middle point. In the four-wire streaks of the streak and the three-wire streaks of the permanent strum, it is deafly grounded neutrally or the middle point of the obov'yazkovo.

To protect against damage by an electric strum when dotik to parts of the electric field, if it is not normal to be under a voltage, or it can be under a voltage when the insulation is poor, or for other reasons, stop the grounding, grounding that connection.

Zahisniy zanulennya. At the lines from a dead-earthed neutral, one phase flickering to the ground or to a conductor, connecting to a dead-earthed neutral, to single-phase short flickers. As soon as the humming happened on the body of the electric power, not tied to the ground, then the person who stood on the ground and touched the first electric power, leaned against the full phase voltage and through the new one passed the stream of single-phase stuttering. In order to prevent the possibility of damage by an electric jet, when it strikes the hull, the planted board is to blame, but it is turned on in the fence. short strings, to get around to a minimum of an hour, by stretching any kind of possession we become insecure for the staff. With the help of the method in the merezhs from the deaf-earthed neutral, zastosovuyut zakhisne zanulennya.

Zahisnym zanulennyam called navmisne metale z'ednannya with a solidly grounded zero point (neutral) of the transformer in the strands of the changeable stream and with a solidly grounded middle point of the dzherel of electrical supply in three-wire nets of a constant stream of parts of electrical installations Z'ednannya tse wink a conductor, which is called a null or zero zahisnym a conductor. When zamikannі odnієї of phases korpusі elektroobladnannya scho Got z'єdnannya nulovim zahisnim (zanulyuyuchim) provіdnikom of neytrallyu earthed transformer trammel zmіnnogo Strum abo serednoyu of earthed points B trammel postіynogo Strum, single-phase short vinikaє zamikannya, yak viklikaє spratsovuvannya) that vіdklyuchennya poshkodzhenoї dilyanki. The scheme for bringing electric power to zero is shown on Rice. XV.1, a.

Zahisne zastosovuyut at the tethers of the snake struma with a dead-earthed neutral or with a deaf-earthed zero dart at the three-wire tethers of the permanent struma for automatic switching on of the stray pole of the tether at the least possible short hour.

Zahisne grounding. At the strands with a voltage of up to 1000 V from an insulated neutral, the jets flicker to the ground, which is blamed for poor insulation of one of the phases, conditioned by the value of the support of the insulation of the conductors and to the ground, two or more phases were missing. Qi strums (called strums of the coil) are perceptibly small and less) and often insufficient for bringing the devices into operation and automatically switching them on. Ale, the stench can become deadly for a person who stands on the ground and touches the parts of the possession, who stooped under the strain under the hour of the earth and did not hit the ground. To the ages of the serus of the zminny strem, and it is a mellip of the post_ynyh stream of ІЗ ід ід заросной серной точений точина постика від подельный олестринаннаннаннанннаннаннаннаннаннаннаннаннаннаннаннанная подинилина від заходной наслідоксідний сідноківіва захина захихна на назденний.

Zahisnim Grounding nazivaєtsya navmisne metaleve z'єdnannya іz land in trammel zmіnnogo Strum іz іzolovanoyu neytrallyu Abo in trammel postіynogo Strum іz іzolovanoyu serednoyu point Chastain elektroustanovok scho normally not znahodyatsya pid naprugi, ale SSMSC mozhut vipadkovo opinitisya pid naprugi of quiet chi іnshih reasons. Z'ednannya is called a conductor, who is called a grounding one. The grounding conductor comes to the grounding conductor, which can be directly connected from the ground. When the phase closes to the body of the electrical power, more of the struma of the sound will pass through the grounding conductor, and less through the body of a person, which reaches the electrical power, so as the opir of the metal conductor is richer, the lower opir of the body of the person. The scheme for connecting electrical power to the grounding is shown on Rice. XV.1, b.

Zahisne grounding zastosovuetsya in the meshes from the insulated neutral to change the struma zamikannya to the ground, to pass through the body of a person, to a safe value.

The shards of the railings from the insulated neutral can work with non-connected faults to the ground or to the body of the electric field, such railings have the necessary remote control over the isolation mill and, in due course, it is possible that it is weak.

Merezhі with a voltage of up to 1000 V with an insulated neutral, connected through a transformer with a strand with a voltage of 1000 V, due to protection from the problem of the transition of the higher voltage to the lower battery with low insulation between windings of low і high voltage. Such a striker is a penetrating protector that is installed in neutral or in one of the phases on the lower voltage side of the transformer.

Zahysne inclusion. Induce more ways to prevent that zahista in the face of an electric strum attack, you may not be able to do it. So, for example, the grounding of the electric field in the meshes from the insulated neutral during single-phase shortings does not turn on and is overpowered by the voltage and for unfriendly environments can be the cause of an unfortunate drop. The zeroing of the electric control in the lines from the dead-earthed neutral gives the possibility to automatically turn on the poshkodzhenu line of the line, and then from the shutdown up to ten seconds (an hour of activation of the fusible insert of the fuse or the automatic switch). For an hour of zatrimka, the switch-on may cause damage to the personnel by an electric jet. Tsі nedolіki zahisnih zanulennya that zaglyadny usuvає system zahisnogo inclusion.

The system of protection is called for the shutdown, which is safe automatically turn on svidkodіyuchim pristroєm all phases emergency plot with the latest hour of switching on the fault of a single-phase fading of the troch more than 0.2 s. Shutdown can be stopped when the insulation level is reduced in voltage lines up to 1000 V from an insulated neutral at single phase on the body of the electrical supply in the meshes from a dead-earthed neutral. Outbuildings of a zahisnogo connection may have a high sensitivity and swidkodiya. Їх strumi spratsovuvannya even small mA), then the stench reacts both to strumi flickering to the ground, and to strumi coil with a reduced support of the insulation, and їhnya shvidkodiya (0.1 - 0.2 s) secures the installation. The quality of the outbuildings of the zahisnogo inclusion may even include the possibility of damage to the storms of the zamikannya, unsafe both for the magnitude and for the trivality of the force.

The circuit of the protected connection with a shvidkodіyuchy relay is shown in fig. XV.2. Between the body of electrical control and additional grounding relay, the voltage relay РН is switched on, which reacts to the magnitude of the voltage in relation to the earth. The electrical setting can either be grounded through the grounding switch rz or neutralized through the grounding switch r0. When the phase is switched off, the voltage is applied to the housing of the electrical installation. If the voltage is to overshoot the set value, the PH relay is spratsovu, its contact in the starter winding lance is Micked and magnetic launcher including an electric motor in the mesh. Button KNK to serve for perevіrki dії zahistu; KnP and KnS - start buttons and electric motor teeth.

Zahisne v_klyuchennya zastosovuyut at vipadki, if the safety of the staff can not be secured by the addition of grounding or grounding.

In vibrationally insecure zones, there is a frankness, which, when there is a difference in potentials between parts of the electric field and the earth, which has been used up, may be the result of a borrowing of an extra vibrational insecure sum. The presence of zeroing, grounding or a zahisnogo switch-on causes trouble.

Grounding (grounding) is applied to the body of electrical machines, machines, devices, lamps, cable structures, metal sheathing of cables, steel pipes and electrical wiring, trays, boxes, metal structures shields, panels too thin.

Grounding extensions. Attachments, which are made up of grounding devices (earthing electrodes) and conductors connected to them, which are grounded (grounded), are called grounding attachments.

Grounding and grounding conductors. As grounding and grounding conductors, vicorous conductors are specially laid for darts, as well as electrical wiring pipes, aluminum sheathing of cables, busbar casings, trays, boxes, crane tracks, metal trusses, colonies budivel.

At the merezhakh insulated neutral conductivity of grounding conductors may not be less than 1/3 of the conductivity of phase conductors. It is not necessary to stop for grounding midday guides spanning over 25 mm2, aluminum conductors spanning over 35 mm2 and steel conductors spanning over 120 mm2.

At the merezhakh dead-earthed neutral the conductivity of neutral conductors may not be less than half of the conductivity of phase conductors. With the same material of the phase and ground conductors, it will be possible to be safe, as the gap of the ground conductor will be no less than half of the phase conductor.

In lighting lines with a dead-earthed neutral of non-vibrated non-vibrating installations for zahisnoy zanulennya it is necessary to vicorate zero working darts. At vibration-unsafe installations for neutral grounding, a special conductor is laid, which can be passed along the same route and in direct proximity to the phase wires. In three-phase power lines for the circuit, mark the fourth core of the cable or the fourth wire, laying the steel pipes together with the phase wires. At double-wire lighting lines of vibration-insecure installations of the former classes (Crimea class B-I) as a zero-based droti, it is allowed to conduct a null working wire, and in applications of class B-I, a third wire is laid.

In electrical installations with a dead-earthed neutral, the crossover (and hence the conductivity) of the zeroing conductors of the fault must be such that, when the phase is shorted to the case, the phase wire, which leads to the loop, is the zero wire of the single-phase short hum zabezpechuvav spratsovuvannya zakhista - fuse fusible insert of the zabіzhnik or switching on the machine. For this strum of a single-phase short circuit in nonviolent non-violent installations, it is not less than 3 times to blame the rated strum with a fusible insert of the nearest fuse, or the strum of the machine’s settings from the reverse fallow strum characteristic (for example, with a thermal rozchnim - rozchіmіchіzvachem), and with automatic ,25 - 1.4 times the nominal strum of the setting of the automatic spratsovuvannya machine. Vibukhonebound installations for the register of the DII Zahishtu, the priomizyuyu is vibrating with such a jacket of a single-phase short zimikanny, Shah Vikniku, pressing the layer inserts insertion of a snap-free footprint, not Mensen Nіzh in 4 times, and nominal junction of the automaton ... razіv. Vymogi to zakhistu automation with electro-magnetic splitters for vibro-unsafe installations, as well as for vibro-unsafe ones. When shutting down automatic switches with a combination of a switch, which is combined with a thermal and an electromagnetic element, for switching on a single-phase short circuit, it is sufficient to ensure the safety of using only a thermal element, which is equal to an electromagnet.

The magnitude of the struma of a single-phase short circuit A, which is due to the phase in the loop - zero conductor in the case of a single-phase short circuit to the case, is assigned to the formula

rf i rn - active opir of phase and ground conductors, Ohm;

x - reactive opir, Ohm (only for electrical wiring steel pipes Oh);

Zt / 3 - transformer opir, Ohm.

The value of the active supports of the cores of wires and cables and aluminum sheath three-core cables, which vikoristovuetsya as a zeroing conductor, pointed in the table. XV.1 (reactive support is not protected through its insignificance). Opir is given at heating temperature, alive at resurfacing strumovo vanity, which is allowed according to the standards (for wires and cables with gum and plastic insulation 70 ° C, for cables with paper insulation 80 ° C).

The magnitude of the active and reactive supports of steel pipes of electrical wiring, which vikoristovuyutsya as a null conductor, is shown in Table. XV.2. Shards of pits of steel pipes should be deposited depending on the size of the stream, which should be passed through them, indicated in the table of the values ​​of active and reactive supports assigned for the magnitude of the struma of a single-phase short circuit, which can pass through the loop phase - zero when the table cuts the rods and the diameters of the pipes.

Table XV.1. Active Opir lived in wires and cables and aluminum sheathing of three-core cables
Peretin lived, mm2	Opir Ohm/km
wires and cables with gum plastic insulation	paper-insulated cables	aluminum sheath of three-core cables
aluminum		aluminum		aluminum

Table XV.2. Opir steel pipes
	Smart passage pipe, mm	Opir, Ohm/km	Three single-core darts with a retina, mm2	Smart passage pipe, mm	Opir, Ohm/km
more active r	reactive x	more active r	reactive x

For the selection of zero conductors in steel in the table. XV.3 induced steel smugs, equivalent for the conductivity of aluminum and middle darts indicated in the tables of revisions.

Rozrahunkovі supports of transformers Zт/3 at secondary voltage 400/230 induction in Table. XV.4.

Table XV.3. Zero conductors made of smug steel
Cross-section of wires, mm2		Cross-section of wires, mm2	Steel smog dimensions, which are zeroed, mm, with phase conductor
		aluminum				aluminum

Table XV.4. Rozrahunkovі poles of transformers
Transformer pressure kVA	Opir Zt / 3, Ohm, when windings are connected
zіrka - zіrka z vivedenim zero	trikutnik - zіrka with vivenim zero

Butt. An electric motor with an intensity of 40 kW, with a nominal jet In = 77 A and a starting jet Ip = 577 A was installed at a vibro-safe place. rose under the shield with a cable length of 95 m. The life of the shield is installed in the transformer with a voltage of 630 kVA with a cable length of 30 m, a span of 395 +135 mm2 with aluminum conductors. The transformer can be connected with a star - a star with a zero.

It is necessary to choose the brand of the cable, the wire lived that zahisniy device to the electric motor; to reverse the debacle for the hour of the phase flickering on the body of the electric motor.

Solution. It is possible to select the VBV cable up to the electric motor with the middle conductors of the cross section 325 + 1116 mm2, with the voltage of 105 A, which becomes 138% par strumu electric motor (according to PUE, it is required less than 125%). Yak Zehis A3124 automatic A3124 on Niznalny Roshm 100 A, COMBINOVY ROCHNIPUEZHEZHE - TEWN 100 A SHISTRY FOR SKISIST TRANSFERENCE TA ELEKTROMAGNIME FOR SKISIS VID STUDMIV SHUTTRUE NAMCANNY W IS INSTALLABLE MITTE SPACEVAVENNE AT 800 A. During the ELACTRODVIGUGUDA strum electric motor, and electromagnetic rozchipluvach spratsovuє for 800 A.

To re-verify the dip in the case of a single-phase short circuit on the body of the electric motor, the total loop reference phase is significant - zero.

1. Opir transformer 630 kV A 0.043 Ohm;

2. Active phase busbar support aluminum cable 95 mm2 = 0.408 Ohm/km; opir zero lived 35 mm2 = 1.11 Ohm / km (Table XV.1). Opіr at the distance of the plant 30 m (0.030 km): phase lived 95 mm2 ... 0.408 0.03 \u003d 0.01224 Ohm; zero lived 35 mm2 ... 1.110 0.03 \u003d 0.03330 Ohm.

3. Active support of the phase conductors of the copper cable 25 mm2 = 0.888 Ohm / km; opir zero lived 16 mm2 = 1.39 Ohm / km. Opir at a distance of 95 m (0.095 km):

phase lived 25 mm2, ..... 0.888 0.095 \u003d 0.08436 Ohm,

zero lived 16 mm2 ..... 1.390 0.095 = 0.13205 Ohm.

4. New phase-zero loop test:

Rp \u003d 0.043 + 0.01224 + 0.03330 + 0.08436 + 0.13205 \u003d 0.30495 Ohm.

The strum of a single-phase short circuit is assigned to the formula (IV.1):

how to change the nominal jet of the thermal element of the splitter automatic vimicach in

721/100 = 7.21 times

(For vibro-unsafe installations, it is required not less than 6 times). In this rank, vibrating the automatic machine suddenly turns on the poor litter.

A similar procedure is carried out in the case of victoria as a conductor of the aluminum sheathing of the cable, steel pipes of electrical wiring and steel smugs.

Grounding (grounding) conductors of steel smugs are fixed in dry applications without a middle to the supporting surface (Fig. XV.3, a), in applications with chemically aggressive mediums - on supports, on a stand in the surface base (Fig. XV.3, b). Uninterrupted electric lansyug steel pipes of electrical wiring are secured with threaded couplings, and thin-walled pipes are welded at two points of a suitable cuff to the pipe (Fig. XV.3, c). Okremі elements of budіvelny metal structures (trusses, beams, columns, which are vicorous, are connected between themselves with a jumper on the zvaryuvannі (Fig. XV.3, d), and in the places of the crossbar of temperature seams with a flexible jumper s steel cable from a good sleeve (Fig. XV.3, e).

For non-intermediate grounding of grounding and grounding parts of electrical installations, grounding devices are used, as they can be natural and piece.

Like natural grounding vicorous metal structures, budіvel і budіvel і sporud, scho mаyut nadіyne z'ednannya іz the earth, lead sheathing of cables and laying pipelines in the earth (krіm pipes with combustible gases rіdina). Aluminum sheaths of cables and cables aluminum darts it’s impossible to beat like a grounding, because the stench is covered with oxide smelting, so it’s bad to carry out a strum.

Piece grounding devices are installed horizontally and vertically. Vertical grounding devices are made from steel round shears with a diameter of mm, a length of 4.5 - 5 m, as well as from steel coils of 50¤50 mm and defective steel water pipes with a diameter of mm, a length of 2.5 - 3 m. can be assigned to the formula

R = ρ/l,(XV.2)

de ρ - pitomium opir ґruntu, Ohm m (Table XV.5); l- Dovzhina vertical earthing machine, m.m.

Table XV.5. Pitomy opir ґruntu ρ
Priming	Pitomy opir, Ohm m
Marl, vapnyak, coarse-grained sand
Loam
Zmіshany ґrunt (clay, vapnyak, rubble)
garden land
Chornozem

Call the grounding attachment to dig out the grounding decals (strings, coils, pipes) that are laid in the ground in a row or by a contour. The main opir of a group of vertical grounders is assigned to the formula

Rv. pro = Rv/nη,(XV.3)

de
Rв - opіr roztіkannu one vertical earthing machine, Ohm;
p - number of grounding workers;
η - coefficient, which should be deposited in the amount of grounding.
When the number of grounding machines is up to 10, one row is laid out every 3 m, η = 0.95-0.93; milling behind the contour, η = 0.86-0.74.

Horizontal earthing devices are used for connecting vertical earthing devices between themselves, more like independent earthing devices. They are made from steel smugs with a thickness of 4 - 5 mm or from steel bars with a diameter of mm and are laid near the ground on a depth of mm. Opir roztіkannya horizontal earthing machine is assigned to the formula

In electrical installations with a voltage of 1000 V, the earth flickering to earth is more than 500 A; In electrical installations with a voltage of more than 1000 V from strums, equal or less than 500 A, without compensation

de
R - opir of the grounding outbuilding (no more than 10 Ohm);
I- rosrachunkovy strum flickering to the ground, A.

At the fences from the compensation of єmnіsnyh strumіv opir of the grounding outbuilding, it is also rozrakhovuєtsya for suggestive formulas. In case of a rozrahunkovy strum, take: for grounding outbuildings, to which compensating devices are attached - strum, which costs 125% of the nominal strum of these devices; for grounding outbuildings, to which devices are not attached to compensate for the strum, - an excess strum flickering to the ground, which may be available in this area when the most powerful compensating device is connected, but not less than 30 A.

Opir grounding attachment, to which to connect the neutral of the transformer in electrical installations with a voltage of up to 1000 V with a dead-earthed neutral, and a grounding attachment, which should be used for grounding electrical installations in electrical installations with a voltage of up to 1000 V from an insulated neutral, it is guilty but With a transformer pressure of 100 kV A and less than the grounding extension, it can be increased up to 10 Ohm.

Butt. The number of vertical grounding devices for grounding the neutral of the transformer is determined. Zagalny opіr roztіkannu zemlyuvachiv Rв. pro = 4 ohms. Pitomy opir ґruntu ρ = 60 Ohm m

Solution. As a grounding device, it is accepted round steel shears with a diameter of 16 mm, a length of 5 m.

				= 12 ohm

When expanding grounding up to one row, η = 0.9. 3 formulas (XV.5): significant required quantity grounding

Vertical earthing machines from steel round shears are buried near the ground by twisting with an electric drill (Fig. XV.4), and for the duration of the living dzherel - with a hole drill, for which at the end of the shear the shear is welded straight, bent along the screw line (Fig. XV.5, a). Grounding pipes made of hull steel and pipes are hammered into the ground with an overhead mechanical pile driver or a vibrating hammer. The depth of laying a vertical earthing machine can be such that the upper end of the jogging beam at a depth of mm can be seen from the surface of the planned land. In areas with filthy soil to improve conductivity, stop laying the soil or adding kitchen salt (Fig. XV.5, b). Grounding conductors and horizontal grounding conductors are connected from vertical grounding conductors (Fig. XV.5, c).

Arrival of zeroing and grounding conductors. For the arrival of conductors, which are to be grounded and grounded, all kinds of electric power can be placed on the metal case with a grounding bolt (screw) with the symbol "Earth".

The skin element of the electrical installation is connected to the neutral (grounding) main line with a conductor (Fig. XV.6, a). The last arrival (Fig. XV.6, b) through the housing of the electrical installation is not allowed, so that when one of the electrical installation elements is taken for repair, the continuity of the grounding lance of the entire installation will be destroyed.

Power transformers are neutralized (grounded) by connecting the grounding conductor to the grounding bolt 1 on the transformer case (Fig. XV.7). To enable the transformer to be removed for revision, or to replace the grounding conductor 3 with the transformer, connect it with a jumper 2. zero bus come to the grounding station (Fig. XV.7, a); in the meshes from the insulated neutral, one of the phases is connected to the grounded transformer case through a penetrating baffle. XV.7, b).

Electric motors, which are installed on a concrete foundation or on a sled, are grounded (grounded) to the conductor connection, which is grounded, to the grounding bolt on the body of the electric motor. For electric motors installed on metal structures, it is sufficient to ground the structures by welding a grounding conductor 1 to them (Fig. XV.8, a). At the time of supplying the electric motor with a cable or insulated wires for steel pipes (Fig. XV.8, a) grounding conductors can serve as a metal sheath for the cable and a steel pipe of electrical wiring 2, which are connected by a jumper 3 to the grounding bolt 4 of the electric motor.

Starting devices (Fig. XV.8, b) ground (ground) the grounding conductor 1 to the metal roof structures, on any installations of the device 6, or to the grounding bolt 4 on the device itself. Cable armor 5 is grounded by jumper 3 to ground bolt 4.

Vibuhozakhisn_ elektrodviguni mayut two grounding bolts. One of them is used to install the middle of the input box and to be used for the connection of a neutral conductor at the fourth wire for electrical wiring in steel pipes, or the fourth lived for cable wiring and metal sheathing of the cable to introduce electric motor boxes. The second bolt of roztashovaniya zvnі, on the body of the electric motor, and appointments for the connection of ovnіshnіkh conductors in the grounding steel pipes and electrical wiring or steel smuga. For grounding and grounding, it is sufficient to bring a grounding conductor up to one of two bolts.

Luminaires in the strings with a dead-earthed neutral are grounded with the addition of a zero working rod 2 lighting strings to the ground screw 4 on the body of the lamp with a jumper 3 or when leaving zero dart from the pipe (Fig. XV.9, a), or on the nearest roller with insulators (Fig. XV.9, b). At the fences from the insulated neutral, as a grounding conductor, the vicorist pipe of the electrical wiring 1 (Fig. XV.9, c), for which the ensign 5 on the pipe should be connected with a jumper 3 from the grounding screw 4 on the lamp. As the pipe is screwed into the lamp, then the grounding is connected to the metal body of the lamp from the grounded pipe.

Pivodovodozashchicheni luminaires, which are powered by cables VRG, NRG і SRG (Fig. XV.9, d) in the meshes with a dead-earthed neutral, are zeroed without a middle at the luminaire attached to the zero drot 2 to the grounding screw 4 (grounding) lived on the cable.

Vibuhozahisnі luminaires (Fig. XV.9, e) in installations of all classes, except for class B-I, zero the zero operating rod to the grounding screw 4 in the middle of the luminaire, and in installations of the class B-I up to screw 4 of the adjacent (third) grounding conductor 7.

Bliskavkazakhist

An electric discharge is called a bliskavka, which is blamed between charged atmospheric electricity by gloomy earth, or between okremiy parts of gloomy.

Discharging flashes on ground objects can cause destruction of life and spores, as well as fire and vibrations of combustible and vibration-unsafe speeches that are found in them. Striking with direct blows of a blisk is the sound of the first splashes of a blisk.

Discharges of glare on the deakіy vіdstanі vіd object are accompanied by manifestations of electromagnetic and electrostatic induction, after which there is a difference in potential between metal parts object and earth. The range of potentials can show up as much as possible, so that you can increase the breadth and cause it. The phenomenon of electromagnetic and electrostatic induction sound like secondary flashes of glare.

With a method of fearing ruins, which are called out by direct attacks of blissavka and її secondary infusions, promissory budіvlі and arguably possess outbuildings of bliskavkozakhistu. Fallen in the face of the danger of a blissful attack, imovirnosti viniknennya later, or vibuhu and the scale of possible ruins, budіvlі that arguably, according to bliskavkozakhistu, are divided into three categories. Up to the I category lie budіvlі that sporudi, roztashovanі in vibuhonot-safe zones. class B-I that B-II; up to category II - roztashovani in zones of classes B-Ia, B-Ib, B-IIa and II-Ig. Up to category III, there should be budіvlі that sporudi, roztashovanі in fire-insecure zones class П-I, P-II, P-IIa and P-III, as well as high factory trumpets and others, with a height of over 15 m.

Zakhist in direct blows of a blisk is built up with blisks of water, as if they are formed from a blisk of a blisk, which without delay takes the blow of a blisk, a grounding device, which will lead the strum to the ground, that strumovidvod (descent), which will take the blisk. The object, which is being protected, is guilty of being in the middle of the zone for the protection of blisskavkovid.

Bliskavkovіvodі constructively pod_lyayutsya strizhnevі, trosovі and sіtchastі. Strizhnevі bliskavkovіvіdіvvygotavlyayut like vertical metal structures (Fig. XV.10, a, b). The zone of zahistu of a single shear blisskavkoviddennya to fall in the form of a height of h i є cone, the basis of which is to serve as a spike with a radius of r = 1.5h. Rope bliskavkovidvіd (Fig. XV. lO, c) with a cable, fasten at the looking antenna on two supports. Such blisskavkovіdvedennya zastosovuyut for zakhistu narrow and long spores. The zone of protection of the cable glazing is a trihedral prism, the upper face is a stretched cable, and the supporting area of ​​the prism is on equal ground with a width of 21.5h, where h - stand between the supports, on which the cable is fixed.

Strizhnevі bliskavkovіvodіvіgotovlyayut from steel rods with a diameter of mm, coil steel 3535 - 5050 mm and steel pipes with a diameter of mm. Rope bliskavkov_leads are made from a steel cable with a diameter of 7.5 - 9 mm.

Strumovіdvod (descents) are made from steel wire rod with a diameter of not less than 6 mm, or from smug steel with a span of not less than 48 mm2 and a thickness of not less than 4 mm. The grounding devices of the blisskavkozakhist are structurally not allowed to be connected to the grounding devices of the protective earthing (nulling).

Budіvlі that spores of the I category with a height of up to 30 m protect from direct blows of bliskavki with shear or cable bliskavkovіdvodami, which is okay to stand. With the help of this impulse, the strum of the skin grounding must be not less than 10 Ohm. For objects with a height of more than 30 m, if there are bliskavkovіdvodіv, that it's okay to stand, it's not possible, it's allowed, install them on the spore itself, and strumovіdvod lay along the wall of the spore. The number of strumovіdvodіv in tsikh fluctuations can be not less than two, and the impulse support of the skin grounding device is not less than 5 ohms. Grounding protection from direct strikes of the flashing of the fault, but insulated from the grounding outbuildings, protection from the secondary flashings and the protection of the grounding from the electric field.

Budіvlі that spores of the II category are protected from direct blows of blisks with shear or cable bliskavkovіddy, which can stand or be installed on buds. It is allowed to vicorate a mesh with a glitter, put on a non-metal cover, and also metal cover budіvlі. Impulse opir rozt_kannyu struma grounding maє but not more than 10 Ohm. It is allowed to combine grounding due to direct impacts of a blisk, grounding due to electrostatic induction and grounding due to electrical control. Up to category II spores, there are also containers with combustible rocks and gases. When the volume of metal is less than 4 mm, the capacity is due to protection from direct hits of the glare with blisks of water, which can stand or be installed on the spore itself. At the same time, metal dahu over 4 mm is sufficient to reach the grounding tank housing. Impulse opir of grounding in these fluctuations may be no more than 50 Ohm.

Budinki that spores of III category protect from direct blows of bliskavki with bliskavkopriymachs, which can stand or be installed on the spore itself. The value of the impulse support of the grounding of the skin strum water can be no more than 20 Ohm. Blow high trumpets, so that it’s okay to stand or stand on buds, protect from direct blows bliskavki with bliskavkopriymachs 3 m high, which are installed on the trumpet itself. For pipes with a height of more than 50 m, it is necessary to install two blisks on the diametrically opposite sides of the pipe.

Protection from the secondary splashes of bliskavka is brought to the grounding outbuilding of all metal structures, technological devices, reservoirs and other spores, which are considered to be the middle ground, so called. Grounding devices are laid horizontally in these slopes, along the perimeter of the object that is being protected. Budіvlі ta spores of the Іst category due to the mother grounding attachment with a support not more than 10 Ohm, okremium in the grounding extension in the form of direct strikes of the bliskavka. For budіvel ta spores of II and III categories of special protection from the second splashes, the bliss is not needed; their metal structures are connected to the grounding outbuildings of the electrically controlled grounding and protection from direct strikes of the glare.

Protection against atmospheric (lightning) overvoltages of wrapping machines to kV voltage at live rozpodіlnyh outbuildings repeating lines zdіysnyuєtsya valve arresters. The valve arresters are porcelain cylinders, in which sparks are subsequently included and supported by a special material that changes the opir with the appearance of an overvoltage in the mesh. Dischargers include between busbars rozpodіlnogo pristroy and ground workers. With the appearance of an overvoltage in the measure, the arrester spratsovuє and protect the insulation of machines from damage.

PROTECTION TYPE OF STATIC ELECTRICITY

Static electricity is called rubbing electricity. It settles as a result of rubbing naphthoproducts and gases that are pumped against the walls of pipelines, in the form of rubbing flat gears about electric motor pulleys and other similar reasons. With the appearance of charges of static electricity, it can be sincere, which can be the cause of unfortunate fluctuations, and in the minds of a vibrating, unsafe medium, it can be the cause of blame for vibrating and vibrating.

For the introduction of static electricity charges, which are blamed, on the stream-conducting parts of the technological possession and metal structures, they must be connected to the grounding outbuilding. Scatters of discharge streams of static electricity charges are even smaller (thousands of amperes), the value of the support of the grounding outbuilding can be taken up to 100 Ohm. In quiet situations, if the possession of that metal structure has already arrived at the grounding point, special grounding for the introduction of static electricity charges is not necessary.

"Electric control of industrial enterprises"
- M.: Budvidav, 1981

Work with electrical appliances, if not connected to a ground loop or grounded due to violation of electrical safety rules, may cause unfortunate fluctuations in virobnitstv. It is also necessary to bring to the exit from the fret like the electrical installations themselves, as well as the accompanying zahis and vimiruval possession. Properly connected to the grounding of electrical installations, ensure their protection during the operation of the insulation of the stream-conducting parts.

Zagalni vіdomostі

Grounded is called the connection between the contact between the body of the electrical installation and the earth, with the method of protection of the service personnel and electrical installations. At the time of the correct connection of the system of grounding of electrical installations, in case of breakdown of the insulation, the greater part of the struma under the ground loop, whichever is smaller, the lower elements of the lance.

Compliant with safety rules, electrical installations and other accessories that apply grounding can be connected up to natural grounding. Yak їх vikoristovuyut:

• metal frames are used to make direct contact with the ground;
• metal winding of cables buried near the ground;
• laying near the ground metal pipes (cream pipelines with combustible bags);
• salivary quantities.

Connecting such structures to electrical installations allows you to reduce the voltage to ground.

Importance support

The main parameter of the efficiency of grounding electrical installations is the value of the electrical support.

Vіdpovіdno up to the norms of PUE (Rules of Attachment of Electrical Installations) opіr zemlyuvacha on living objects with a voltage of 220 and 380 Volt may become no more than 30 Ohm.

Opir industrial equipment (transformer substations, generators, charging equipment and other accessories) is not more than 4 Ohm.
In order to reach the value of the support specified in the PUE, it is necessary to secure the grounding attachment with a high conductivity. To improve the conductivity of the grounding device in electrical installations, it is necessary to change one of the supports to change it.

First, you can increase the area of ​​​​the ground loop with the ground. It can be reached either by larger areas of the metal frame, grounding or by placement near the ground of additional steel vines.

In another way, you can increase the conductivity of the earth at the place where the grounding device is installed. Opir moves, as if watering the soil with salt rose.

Another way is to replace the cable, which goes through the body of the electrical appliance to the grounding circuit, onto the cable, which can have a great streak conductivity.

Protection of electrical appliances

For the safety of the necessary protection against electric shock, stop by this way:

• vstanovlenya zahisnyh fences;
• superficial insulation of all strum-conducting elements;
• zahisnі casings;
• obezhennya of a zone of reach;
• as far as possible, vikoristannya small voltage.

On the breakdown of that insulation and the current of the voltage on the body of the electric power, such a method is applied as a shield, like grounding, eliminating the potentials, and additionally isolating the strum-conducting parts of the power. In some cases, it is necessary to install insulating (non-conductive electrics) applications.

In case of accidents, if the order of the grounded people is stagnant and then you go in the face of an electric shock, the stench is not guilty of negatively pouring one on one and reducing the effectiveness of the attack on the staff.

Zastosuvannya of natural elements of grounding is more likely to happen in that moment, as it turns out the possibility of succumbing to it, be it shkodi, afterward passing through them an electric stream.

Vimogi to electrical safety

Yakscho see different electrical installations are to be installed in the summіzhnіy territorії, next vikoristovuvat one zagalny grounding attachment, which is in line with all the necessary parameters of safety.

Grounding attachment, which is zastosovuetsya for zakhistu electric power supply maybe one or the other different recognition, obov'yazkovo may comply with the safety rules. The skin, if presented to the grounding of electrical installations, is obliged to do so.

To connect the grounding circuit of a different electrical installation into one earthed earthing line, it is possible to stove both natural and piece grounding extensions.

The peak value of the voltage of the coil and the support of the grounding line may be supported by the power of electrical safety and the safety of the superfluous protection in case of any atmospheric phenomena, but it may be the time of fate. When re-roofing the support of the grounding outbuildings, it is necessary to repair the parameters of all natural and piece grounding devices.

All elements of the grounding circuit are due to resistance to extreme mechanical inflows, high temperature inflows and any atmospheric phenomena.

Basic types

Vіdpovіdno to the PUE (Rules for Attachment of Electrical Installations) to use the TN grounding system (which includes groups TN-C, TN-S, TN-C-S), TT і IT.
Latin letters may have the following meaning:

• T - zherelo zhivlennya z'ednany іz the earth;
• S - rozmikannya zdіysnyuєtsya different conductors;
• N - neutral;
• C - roam by one conductor;
• I - isolated strum part.

Knowing what the skin letter means, you can designate attachments and the principle of work and I will add, to which the electric power is connected.

TN system

The system of sound grounding, which is most often grounded. The main feature is the presence of a “tightly” neutral lifeline. In other words, zero exit of life without intermediary connection from the ground loop.

TN-C - this grounding system was widely used in the life of old living quarters, and in our time it is not victorious in the life of houses, the rocks are old and do not meet all safety standards. This type of grounding of electrical appliances is stagnant in three-phase meshes with a choti-core cable single-phase lines with cables that may have lived. Golovny nedolіkom this type, near the cables zahisnoy lived grounding.

TN-S is a system that is often used for connecting wake-up calls to electric lines. The most important step is to protect the middle of the earthing systems. The zero and working conductor, in this system, are laid only one or the other, with which the conductor is hung with a mustache-conducting part of the installation, which is cleaned. Up to a small amount of grounding, you can see the need to lay an additional cable.

TN-C-S - in my system, core good guide tied with a neutral working vein. According to the rules of electrical safety, for the TN-C-S system, additional grounding is required.

TT system

This system is widely used for ensuring the electrical safety of substations and installations, what to live, what to make an earth ground attachment. Often vikoristovuєtsya for zakhistu prismіschen, scho to stand still (garages, kiosks, hangars and other spores).

IT system

Dzherelo living in this system is insulated with a pro-shearer or with an element great support which allows you to accurately reduce the strum turn. An IT type grounding system is most often used in medical facilities and laboratories, for ensuring the correct operation of high-current, stress-sensitive devices.

Retail between grounded and grounded

Grounding and grounding of electrical installations are similar in understanding, but there is one difference.

When vikoristannye grounding zahist bezpechuetsya reduced voltage in the stremoprovidnіy part. And when the zahisna diya is at zero, the supply of voltage is turned on in the distance, which was in harmony.

Obov'yazkovoy - installation of grounding in all electrical installations, de neutral is insulated. As an electrical appliance, it can be a solidly grounded neutral, and the voltage in the working area is up to 1000 V, it can only be done with one zero.

Rozrahunku rules

It is necessary to carry out a survey of the grounding grounding in order to correctly assign the parameters of the grounding circuit, such as its type, shape, area, size, number of grounding conductors and between them. All these parameters, at the same time, from the values ​​of the stream conduction to the ground, without intermediary, add the support of the grounding system to the total value.

Rozrahunok grounding annex to be carried out obov'yazkovo before the cob installation circuit.

When rozrahunka zahisnogo grounding give special respect for the meaning pet support land. For rozrakhunkiv it is necessary to take this meaning, as it will give the most unfriendly seasonal minds.

Rules for inserting a figurative form

Portable grounding is installed with time robots for servicing and repairing the electrical installation. Installation of grounding is allowed only after rechecking the voltage in the lance.

Zahisne grounding, recognized for the protection of the worker on the line to the personnel in the event of a strum attack at the time of the pardon, the voltage is turned on, in the general order, it is installed on all the phases switched on from the sides, from which it can be applied to the voltage.

Installation of portable grounding in electrical installations with a voltage of over 1000 volts is allowed to be carried out by personnel whose electrical safety group is not lower than the fourth, and in installations up to 1000 volts - not lower than a third.

The grounding elements are harrowed as grounding elements, if they are not recognized for this, the grounding elements are also harrowed by the twisting method.