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 7 103 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