Approved and effected
by the Resolution of GosStandart of USSR
dd. May 15, 1981 N 2404
USSR STATE STANDARD
OCCUPATIONAL SAFETY STANDARDS SYSTEM
ELECTRIC SAFETY.
PROTECTIVE CONDUCTIVE EARTH, NEUTRALLING
GOST 12.1.030-81
(as revised, Amendment N 1, approved in March 1987)
Group Т58
Effective date
from July 1, 1982
to July 1, 1992
1. Developed and submitted by the Ministry of Installation and Special Construction Work of the
USSR.
Prepared by: R.N. Karyakin, Doctor of Engineering Science; V.A. Antonov, Candidate of Science
(Project Coordinators); L.K. Konovalova; V.K. Dobrynin; V.I. Solntsev; M.P. Ratner, Candidate of Science;
V.P. Korovin; A.I. Kustova; V.I. Syrovatka, Doctor of Engineering Science; A.I. Jacobs, Doctor of
Engineering Science; V.I. Bocharov, Candidate of Science; V.N. Ardasenov, Candidate of Science.
2. Approved and came into force by the Resolution of USSR State Standartization Committee dd.
15.05.1981 N 2404.
3. Reference normative-technical documents (NTD)
──────────────────────────────────────────┬───────────────────────
Index of NTD the reference is given to
│
Clause number
──────────────────────────────────────────┼───────────────────────
GOST 12.1.013-78
│1.3
4. Revision (November 1988) with Amendment N 1, approved in March 1987 (IUS N 7-87).
5. Checked in 1987. Validity term of the standard is extended to 01.07.1992 (Resolution of USSR
GosStandart dd. 27.03.1987 N 990).
This standard is applied to protective conductive earth and neutralling of DC and AC electrical
installations with frequency up to 400 Hz and establishes requirements to electrical safety by using
protective conductive earth and neutralling.
The standard is not applied to electrical protective conductive earth and neutralling used in
potentially explosive areas, for electrified transport, ships, in metal tanks, underwater, underground,
and for medical equipment.
Terms used in the standard and their explanations are given in Appendix 1.
Standard corresponds to ST SEV 3230-81 in terms of protective conductive earth
(As revised, Amendment N 1).
1. GENERAL PROVISIONS
Clauses 1.1 - 1.4 application on a voluntary basis ensures compliance with technical regulations
“On Safety of Machinery and Equipment” approved by the Resolution of the Russian Government dd.
15.09.2009 N 753 (Order of GosStandart dd.20.08.2010 N 3108).
1.1. Protective earth or neutralling should protect people against electric shock when touching
metal dead parts that can be under voltage as a result of damage to the insulation.
1.1.1. Protective earth should be performed with intentional electrical connection of electrical
metal parts with the “earth” or its equivalent.
1.1.2. Neutralling should be performed with electrical connection of electrical metal parts with
grounded power supply point using null protective conductor.
1.2. Electrical metal parts are subject to protective earthing or neutralling accessible for human
touch and without other protection ensuring electrical safety.
1.3. Protective earth or neutralling of electrical installations should be performed:
at a nominal voltage of 380 V AC and higher and 440 V DC and higher - in all cases;
at a nominal voltage from 42 V to 380 V AC and from 110 V to 440 V DC while working in increased
hazardous conditions and especially dangerous according to GOST 12.1.013-78.
1.4. As grounding devices for electrical installations, primarily natural groundings shall be used.
When reinforced concrete foundations of industrial buildings and structures are used as natural
groundings and acceptable contact voltages are ensured, construction of artificial groundings, laying of
leveling bands outside the buildings and grounding trunks inside the building are not required. Metal
and reinforced concrete structures, when used as grounding devices, should establish continuous
electrical circuit on metal and reinforced concrete structures should be provided with embedded parts
to connect electrical and process equipment (see reference Appendices 2 , 3 and 4).
Clauses 1.5 - 1.9 application on a voluntary basis ensures compliance with technical regulations
“On Safety of Machinery and Equipment” approved by the Resolution of the Russian Government dd.
15.09.2009 N 753 (Order of GosStandart dd.20.08.2010 N 3108).
1.5. Acceptable contact voltages and resistance of grounding devices shall be provided at any time
of the year.
1.6. Grounding device used for electrical installations grounding of one or different applications
and voltages should satisfy all requirements applied to grounding of these electrical installations.
1.7. Only specifically designed for this purpose conductors and metal, construction, industrial and
electrical fit-up structures shall be used as grounding and null protective conductors. Neutral working
conductor should primarily be used as null protective conductors . For grounding and conductive
neutralling only specially designed conductors shall be used what concerns portable single-phase
electric users and lighting fixtures when inputting open unprotected wires, DC electric users of stated
rate.
(Revised edition, Amd. 1).
1.8. Material, structure and dimensions of earth conductors, grounding and null protective
conductors should ensure resistance to mechanical, chemical and thermal effects for the entire period
of operation.
1.9. To equalize potential, metal building and production structures should be connected to the
earthing network or neutral earthing. In this case natural contacts in joints are sufficient.
2. ELECTRICAL INSTALLATIONS WITH VOLTAGE FROM 110 TO 750 KW
2.1. In electrical installations with voltage from 110 to 750 kW protective earth should be
performed.
2.2. Earth conductors should be performed according to the norms for contact voltage or norms
for their resistance.
Earth conductor, which is performed according to the norms for resistance, should have at any
time of the year resistance no more than 0.5 ohms. In case of electrical resistivity of “earth”  greater
than 500 ohms x m it is allowed to increase resistance of earth conductor depending on  .
2.3. Voltage on earth conductor, in case of ground current running-off to the land, shall not
exceed 10 kW.
Voltage above 10 kW is allowed on earth conductors, which capacity is not removed outside the
buildings and external enclosures of electrical installations.
At voltages on earth conductor higher than 5 kW, measures to protect insulation of outgoing
communication and telemechanical cables should be provided.
2.4. In order to equalize capacity on the territory occupied by electrical equipment, longitudinal
and transverse horizontal elements of earth conductor shall be laid and welded to each other as well as
with vertical earthing elements.
Section 3 application on a voluntary basis ensures compliance with technical regulations “On
Safety of Machinery and Equipment” approved by the Resolution of the Russian Government dd.
15.09.2009 N 753 (Order of GosStandart dd.20.08.2010 N 3108).
3. ELECTRICAL INSTALLATIONS WITH VOLTAGE HIGHER THAN 1000 V
IN CURCUIT WITH INSULATED NEUTRAL
3.1. In electrical installations with voltages higher than 1000 V in circuit with insulated neutral
protective earthing should be performed, in this case it is recommended to provide a unit of automatic
search of short to earth. It is recommended to provide tripping protection against short to earth (via
electrically connected circuit), if it is required for safety.
3.2. The biggest resistance of earthing device R in ohms should be no more than
R
250
I ,
where I is design current intensity of short to earth, А.
In case of earthing device use simultaneously for electrical installations with voltage up to 1000 V
R
125
I .
Design current intensity of short to earth should be determined for the circuit layout possible in
operation in which current intensity of short to earth has biggest value.
3.3. With soil resistivity  greater than 500 ohm x m it is allowed to include multiplying
coefficients depending on  for specified values of earth device resistance.
Section 4 application on a voluntary basis ensures compliance with technical regulations “On
Safety of Machinery and Equipment” approved by the Resolution of the Russian Government dd.
15.09.2009 N 753 (Order of GosStandart dd.20.08.2010 N 3108).
4. ELECTRICAL INSTALLATIONS WITH VOLTAGE UP TO 1000 V
IN CURCUITS WITH GROUNDED NEUTRAL
4.1. Neutralling shall be performed in fixed three-phase electrical installations in circuit with
earthed neutral or grounded terminal of single-phase power supply source, as well as with grounded
mid-point in three-wire DC mains.
4.2. With neutralling, phase and neutral protective conductors should be selected so that the
short to housing or to neutral conductor caused short-circuit current ensuring machine switch off or
electric fuse melting in closest protective device.
4.3. No tripping and protecting devices should be available in circuit of protective neutral
conductors.
In circuit of neutral conductors if they serve in parallel for neutralling, it is allowed to apply
tripping devices, which disconnecting neutral conductors simultaneously disconnect all conductors also
under voltage.
4.4. Resistance of earth device, to which generators (transformers) neutrals or terminals of single
phase power supply source are connected, taking into account natural earthing and re-earthing of
neutral wire, should be less than 2.4 ohm and 8 ohm, correspondingly, with line-to-line voltages 660,
380 and 220 V of three-phase power supply source or 380 or 220 and 127 V of single-phase power
supply source.
With electrical installations resistivity of soil  above 100 ohm x m, it is allowed to increase said
norm in  / 100 times.
4.5. On overhead power lines neutralling should be implemented by neutral conductor laid on the
same supports as phase conductors.
Section 6 application on a voluntary basis ensures compliance with technical regulations “On
Safety of Machinery and Equipment” approved by the Resolution of the Russian Government dd.
15.09.2009 N 753 (Order of GosStandart dd.20.08.2010 N 3108).
5. ELECTRICAL INSTALLATIONS WITH VOLTAGE UP TO 1000 V
IN CURCUITS WITH INSULATED NEUTRAL
5.1. In AC electrical installations in circuits with isolated neutral or isolated terminals of single
phase power supply source, protective earth should be performed together with the control of
insulation resistance.
5.2. Resistance of earth device in fixed circuits should be less than 10 ohms. With resistivity of soil
bigger than 500 ohm x m it is allowed to include multiplying coefficients depending on  .
6. MOBILE ELECTRICAL INSTALLATIONS AND PORTABLE ELECTRIC
DEVICES OF CLASS I IN CIRCUITS WITH VOLATGE UP TO 1000 V
6.1. Neutral regime and protective measures for mobile power sources used to power fixed users
of electric energy shall comply with neutral regime and protective measures taken in the circuits of fixed
users of electric energy.
6.2. If portable users of electric energy and portable electric tools of class I are powered from
fixed circuits with earthed neutral or from portable electrical installations with earthed neutral,
neutralling should be performed together with protective shutdown.
It is allowed to perform neutralling - for portable electric tools of class I; neutralling or neutralling
with re-earthing - for portable users of electric energy.
6.3. If portable users of electric energy and portable electric tools of class I are powered from
fixed circuit or portable power supply source having isolated neutral and control of insulation resistance,
protecting earth should be used together with metallic bonding of electric housings or protective
shutdown.
6.4. Earth device resistance in portable electrical installations with insulated neutral if powered
from portable power supply sources shall be determined by values of allowable contact voltages with
single-polar short to housing or set in accordance with the normative and technical documents
requirements.
(Revised version, Amendment No.1).
6.5. Protective grounding of portable power supply source with isolated neutral and constant
control of insulation resistance is not allowed to perform:
if calculated resistance of earth device is more than resistance of earth device of device working
earth with constant control of insulation resistance;
if portable power supply source and electric energy users are located directly on a portable
mechanism, their housings are connected with metallic bonding and source does not power other users
of electric energy beyond this mechanism;
if portable power supply source is designed to power specific users of electric energy, their
housings are connected with metallic bonding and number and length of cable network is determined
either by value of allowable contact voltage in single-polar short to the housing or set by normative and
technical documents.
6.6. In portable electric tools with power supply source and users of electric energy located on the
common metal frame of portable mechanism and having no users of electric energy beyond this
mechanism are allowed for use, as the sole protective measure, metallic bonding of equipment housings
and neutrals of power supply source with metal frame of portable mechanism.
Section 7 application on a voluntary basis ensures compliance with technical regulations “On
Safety of Machinery and Equipment” approved by the Resolution of the Russian Government dd.
15.09.2009 N 753 (Order of GosStandart dd.20.08.2010 N 3108).
7. CONTROL OF PROTECTIVE EARTH AND NEUTRALLING DEVICES
ConsultantPlus: Note.
Since July 1, 2001 by the Order of the Ministry of Energy of RF dd. 27.12.2000 No. 163 Interindustry regulations on labor protection (safety rules) for electrical installations POT R M-016-2001 RD
153-34.0-03.15-00 are effected.
ConsultantPlus: Note.
Since July 1, 2003 "Rules for technical operation of consumer electrical installations" approved by
the Order of the Ministry of Energy of RF dd. 13.01.2003 No. 6 are effected.
7.1. Protective earthing or neutralling compliance with requirements of this standard should be
established during acceptance testing of electrical installations after their installation on site in
accordance with the “Rules for Electrical installations” approved by USSR GosEnergoNadzor, as well as
periodically during operation of said devices following the “Rules for technical operation of consumer
electrical installations” and “Rules for safety in operation of consumer electrical installations” approved
by USSR GosEnergoNadzor.
Appendix 1
Referential
TERMS AND DEFINITIONS
APPLIED IN STANDARD
Term
1. Earth
2. Natural earth
3. Earth conductor
4. Earth device
5. Earth (neutralling) main line
6. Earthed neutral
7. Insulated neutral
Explanation
Conductor or set of metallic connected
conductors, being in contact with earth or its
equivalent
Earthing, which is used as conductive parts
of construction and industrial units and utilities
Conductor connecting earthed parts with earthing
Set of structurally combined earth conductors and
earthing
Earthing (neutralling protective) conductor with
two or more branches
Generator (transformer) neutral connected to
earth device directly or via small resistance
Generator (transformer) neutral not connected to
earth device or connected to it via big resistance
Appendix 2
Referential
EVALUATION OF THE
POSSIBILITY TO USE REINFORCED CONCRETE
FOUNDATIONS OF INDUSTRIAL BUILDINGS
AS GROUNDING
In case of reinforced concrete foundations of industrial buildings use as earthing resistance,
resistance to spreading of earth device R in ohms should be evaluated by the formula
R  0, 5
э
S , (1)
where S is an area restricted by building perimeter, m2;
э is specific equivalent electrical resistance to earth, Оm х m.
To calculate
э in Oms х m the following formula should be used
h1
S
)]   2 [1  exp( 
)]
h1 ; (2)
S
 э  1[1  exp(
where
1 is specific electrical resistance to top layer of the earth, Оm х m;
 2 is specific electrical resistance to the lower layer, Оm х m;
h1
is power (thickness) of the top layer of the earth, m;
 ,  are dimensionless coefficients depending on specific electric resistance to earth layers ratio.
1 >  2 ,  = 3.6,  = 0.1;
2
2
 
if 1 < 2 ,  = 1.1 х 10 ,  = 0.3 х 10 .
If
Example of calculation:


If 1 = 500 Оm х m; 2 = 130 Оm х m; h = 3.7 m;
Then according to the formula (2) we obtain

э  500 1  e

3,6
3,7
55
S = 55 mm.
55
0,1



3,7

130
1

e





 = 208 Оm х m.
Top layer shall mean layer of earth, which resistivity

1 is more than 2-fold different from specific
electric resistance to the lower layer 2 .
In electrical installations with voltage from 110 to 750 kW leveling conductors are not required to
be laid, including at inputs and outputs, except locations of neutral earthing of power transformers,
short-circuiters, valve-type arresters and lightning-arresters, if the following condition is satisfied.
I к.з  (5, 4  7 103 1 ) 
I
S
э ,
where к.з is design current intensity of single-phase short running off to soil from the building
foundations, kA.
(Revised version, Amendment No.1).
Appendix 3
Referential
CONNECTION OF
STEEL REINFORCEMENT OF CONCRETE ELEMENTS
1 - lightning protection grid; 2 - current tap;
3 - column reinforcement; 4 - bonding;
5 – foundation reinforcement
Appendix 4
Referential
CONNECTION OF
METAL COLUMN WITH
STEEL REINFORCEMENT OF CONCRETE ELEMENTS
1 – foot reinforcement; 2 – foundation reinforcement;
3 - foundation; 4 - foundation bolts (at least two)
connected with foundation reinforcement; 5 – steel column;
6 - plates for earthing conductors welding