EN 50522:2022

The standard EN 50522:2022 is applicable to specify the requirements for the design and erection of earthing systems of electrical installations, in systems with nominal voltage above 1 kV AC and nominal frequency up to and including 60 Hz, so as to provide safety and proper functioning for the use intended.

NOTE 1 The technical and procedural principles of this document can be applied when 3rd parties’ installations and facilities are planned and/or erected in the vicinity of HV electrical power installations. For the purpose of interpreting this document, an electrical power installation is considered to be one of the following: a) substation, including substation for railway power supply; b) electrical power installations on mast, pole and tower; switchgear and/or transformers located outside a closed electrical operating area; c) one (or more) power station(s) located on a single site; the electrical power installation includes generators and transformers with all associated switchgear and all electrical auxiliary systems. Connections between generating stations located on different sites are excluded; d) the electrical system of a factory, industrial plant or other industrial, agricultural, commercial or public premises; e) electrical power installations on offshore facilities for the purpose of generation, transmission, distribution and/or storage of electricity; f) transition towers/poles between overhead lines and underground lines. The electrical power installation includes, among others, the following equipment: — rotating electrical machines; — switchgear; — transformers and reactors; — converters; — cables; — wiring systems; — batteries; — capacitors; — earthing systems; — buildings and fences which are part of a closed electrical operating area; — associated protection, control and auxiliary systems; — large air core reactor.

NOTE 2 In general, a standard for an item of equipment takes precedence over this document. This document does not apply to the design and erection of earthing systems of any of the following: — overhead and underground lines between separate installations;

NOTE 3 The standard, EN 50341 series Overhead lines exceeding AC 1 kV, specifies requirements for the design and erection of earthing systems in overhead lines. — electrified railway tracks and rolling stock; — mining equipment and installations; — fluorescent lamp installations; — installations on ships and off-shore installations; — electrostatic equipment (e.g. electrostatic precipitators, spray-painting units); — test sites; — medical equipment, e.g. medical X-ray equipment.

NOTE 4 The scope of this document does not include the requirements for carrying out live working on electrical power installations.

NOTE 5 The scope of this document considers safety requirements for HV installations and its influences on LV installations. For electrical installation up to 1 kV, the standard IEC 60364 series applies.

The price of the Standard EN 50522:2022 included all amendments and correcturs.

Contents
European foreword
Introduction
1 Scope
2 Normative references
3 Terms, definitions and abbreviations
4 Fundamental requirements
4.1 General requirements
4.2 Electrical requirements
4.2.1 Methods of neutral earthing
4.2.2 Short-circuit current
4.3 Safety criteria
4.4 Functional requirements
5 Design of earthing systems
5.1 General
5.2 Dimensioning with respect to corrosion and mechanical strength
5.2.1 Earth electrodes
5.2.2 Earthing conductors
5.2.3 Bonding conductors
5.3 Dimensioning with respect to thermal strength
5.3.1 General
5.3.2 Current rating calculation
5.4 Dimensioning with regard to touch voltages
5.4.1 Permissible values
5.4.2 Measures for the observance of permissible touch voltages
5.4.3 Design procedure
6 Measures to avoid transferred potential
6.1 Transferred potential from high voltage systems to low voltage systems
6.1.1 High and low voltage earthing systems
6.1.2 LV supply only within HV substations
6.1.3 LV supply leaving or coming to HV substations
6.1.4 LV in the proximity of HV substation
6.2 Transferred potentials to telecommunication and other systems
7 Construction of earthing systems
7.1 Installation of earth electrodes and earthing conductors
7.2 Lightning and transients
7.3 Measures for earthing on equipment and installations
8 Measurements
9 Maintainability
9.1 Inspections
9.2 Measurements
10 Inspection and documentation of earthing systems
Annex A (normative) Methods of calculating permissible touch voltages
A.1 Method of calculating permissible touch voltages UTp
A.2 Method of calculating prospective permissible touch voltages UvTp
A.3 Method of calculating permissible step voltages
Annex B (normative) Calculation of Permissible touch voltage UTp, Prospective permissible touch voltage UvTp
B.1 General
B.2 Calculation of permissible touch voltage
B.3 Calculation of the permissible touch voltage UTp curve values of Figure 8
B.4 Calculation of prospective permissible touch voltage
Annex C (normative) Type and minimum dimensions of earth electrode materials ensuring mechanical strength and corrosion resistance
Annex D (normative) Current rating calculation of earthing conductors and earth electrodes
Annex E (normative) Description of the recognized specified measures M
Annex F (normative) Measures on earthing systems to reduce the effects of high frequency interference
Annex G (normative) Detailed measures for earthing of equipment and installations
G.1 Fences around substation installations
G.2 Pipes
G.3 Traction rails
G.4 Pole mounted transforming and/or switching installations
G.5 Secondary circuits of instrument transformers
Annex H (normative) Measuring touch voltages
Annex I (informative) Reduction factors related to earth wires of overhead lines and metal sheaths of underground cables
I.1 General
I.2 Typical values of reduction factors of overhead lines and cables (50 Hz)
I.3 Influence of the resistances to earth on current in cable sheath
Annex J (informative) Basis for the design of earthing systems
J.1 Soil resistivity
J.2 Resistance to earth
Annex K (informative) Installing the earth electrodes and earthing conductors
K.1 Installation of earth electrodes
K.1.1 Horizontal earth electrodes
K.1.2 Vertical or inclined driven rods
K.1.3 Jointing the earth electrodes
K.2 Installation of earthing conductors
K.2.1 General
K.2.2 Installing the earthing conductors
K.2.3 Jointing the earthing conductors
Annex L (informative) Measurements for and on earthing systems
L.1 Soil resistivity measurement and analysis
L.1.1 Introduction
L.1.2 Soil resistivity measurement
L.1.2.1 General
L.1.2.2 Wenner Method
L.1.2.3 Guidance on appropriate Wenner spacings
L.1.2.4 Sources of error
L.1.2.5 Seasonal variations
L.1.3 Soil resistivity analysis
L.1.3.1 General
L.1.3.2 Uniform soil model
L.1.3.3 Two-layer soil model
L.1.3.4 Multi-layer soil model
L.2 Measurement of resistances to earth and impedances to earth
L.3 Determination of the earth potential rise
L.4 Measurements of touch voltage and prospective touch voltage
L.5 Elimination of interference and disturbance voltages for earthing measurements
Annex M (informative) The use of reinforcing bars in concrete for earthing purpose
Annex N (informative) Global Earthing System
Annex O (normative) Special national conditions
Annex P (informative) A-deviations
Bibliography