Engineering Standard 09 November 2021

SAES-P-111
Grounding
Document Responsibility: Electrical Systems Designs and Automation Standards
Committee

Previous Revision: 09 October 2019 Next Revision: 09 November 2026

Contact: (MAHANRX) Page 1 of 27
© Saudi Arabian Oil Company, 2021

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 Document Responsibility: Electrical Systems Designs and Automation Stds. Committee SAES-P-111
Issue Date: 09 November 2021
Next Revision: 09 November 2026 Grounding

Contents

Summary of Changes .............................................................................................................. 3

1 Scope ................................................................................................................................ 6

2 Conflicts and Deviations .................................................................................................... 6

3 References ........................................................................................................................ 6

4 Terminology....................................................................................................................... 9

5 General ........................................................................................................................... 10

6 Materials and Installation ................................................................................................. 11

7 Substation Grounding ...................................................................................................... 13

8 Grounding Electrodes ...................................................................................................... 16

9 System Grounding ........................................................................................................... 17

10 Equipment Grounding................................................................................................... 19

11 Offshore Platform Grounding ........................................................................................ 23

12 Fence Grounding.......................................................................................................... 24

13 Tank Grounding............................................................................................................ 25

14 Lightning Protection ...................................................................................................... 26

15 Static Electricity Grounding .......................................................................................... 27

Revision Summary ................................................................................................................. 27

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 Document Responsibility: Electrical Systems Designs and Automation Stds. Committee SAES-P-111
Issue Date: 09 November 2021
Next Revision: 09 November 2026 Grounding

Summary of Changes
Paragraph Number
Change Type Technical Change(s)
(Addition, Modification,
Previous Revision Current Revision Deletion, New)
09 October 2019 09 November 2021
Addition of definitions
4 4 Addition
section.
Measurements of earth
4.5 5.5 Modification resistivity using four-point
method as per IEEE 81.
Grid/electrode resistance
per fall-of-potential or
NA 5.6 Addition
slope method as per
IEEE 81.
Soil model selection
based on soil
NA 5.7 Addition
measurements
variations.
Modification of the
5.1 6.1 Modification conductor material
selection requirements.
Modification of the
5.1 6.2 Modification ground rod material
selection requirements.
Addition of bitumastic
NA 6.3 Addition paint and mastic tape for
exothermic connections.
Addition of reference to
GIS requirements per
NA 7.2 Addition
IEEE 80 and TES-P-
119.10.
Ground grid burial depth,
conductor sizing,
NA 7.3 Addition
conductor spacing and
GPR limit.

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 Document Responsibility: Electrical Systems Designs and Automation Stds. Committee SAES-P-111
Issue Date: 09 November 2021
Next Revision: 09 November 2026 Grounding

Paragraph Number
Change Type Technical Change(s)
(Addition, Modification,
Previous Revision Current Revision Deletion, New)
09 October 2019 09 November 2021
Restricting the use of
other calculation methods
of step and touch
6.4 7.5 Modification
potentials including finite
element method to multi
ground grid connection
Exception for the backup
NA 7.5.2 Addition protection duration for
34.5kV and 13.8kV.
Ground fault current and
NA 7.5.3 Addition ground grid design for
low voltage level
Two-layer soil resistivity
NA 7.5.6 Addition
measurement
Reference to NGR
NA 9.3.5 Addition design, installation and
testing
Grounding requirement
NA 9.6 Addition for directly connected MV
generator(s)
Grounding requirement
NA 9.7 Addition
for LV generator
Exception of cable armor
10.1 10.1 Deletion
as equipment grounding.
Cable tray system
NA 10.4 Addition bonding and grounding
requirements
Shield/Sheath/Armor
NA 10.8 Addition
grounding requirements
Reference to surge
NA 10.17 Addition
arresters grounding
Grounding requirements
NA 12.4 Addition for fences made of non-
conductive materials
Maximum intervals for
12.1 13.1 Modification
tanks grounding points
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 Document Responsibility: Electrical Systems Designs and Automation Stds. Committee SAES-P-111
Issue Date: 09 November 2021
Next Revision: 09 November 2026 Grounding

Paragraph Number
Change Type Technical Change(s)
(Addition, Modification,
Previous Revision Current Revision Deletion, New)
09 October 2019 09 November 2021
Requirements for
external floating roof
12.1 13.2 Modification
tanks with primary and
secondary seals
Requirements for
external floating roof
NA 13.3 Addition
tanks with primary seals
only
Lightning protection
13.3 14.3 Modification requirements for
hydrocarbon facilities
Update of Isokeraunic
13.3 14.3 Modification level and annual flash
density calculation

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 Document Responsibility: Electrical Systems Designs and Automation Stds. Committee SAES-P-111
Issue Date: 09 November 2021
Next Revision: 09 November 2026 Grounding

1 Scope

This standard prescribes the mandatory requirements for design, application,

and installation of grounding/earthing systems for Saudi Aramco facilities. In
addition, it provides general guidance for lightning protection system design.

2 Conflicts and Deviations

Any conflicts between this document and other applicable Mandatory Saudi
Aramco Engineering Requirements (MSAERs) shall be addressed to the
EK&RD Manager.

Any deviation from the requirements herein shall follow internal company
procedure SAEP-302.

3 References

All referenced specifications, standards, codes, drawings, and similar material

are considered part of this engineering standard to the extent specified,
applying the latest version, unless otherwise stated.

3.1 Saudi Aramco References

Saudi Aramco Engineering Procedure

SAEP-302 Waiver of a Mandatory Saudi Aramco Engineering
Requirement

Saudi Aramco Engineering Standards

SAES-A-112 Meteorological and Seismic Design Data
SAES-J-902 Electrical Systems for Instrumentation
SAES-M-006 Saudi Aramco Security and General Purpose Fencing
SAES-P-100 Basic Power System Design Criteria
SAES-P-104 Wiring Methods and Materials
SAES-P-107 Overhead Distribution Systems
SAES-T-Series Communications Engineering Standards
SAES-X-400 Cathodic Protection of Buried Pipelines

Saudi Aramco Materials System Specifications

15-SAMSS-502 Medium Voltage Power Cables 5 kV though 35 kV
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17-SAMSS-510 Form-Wound Synchronous Turbine Generators

Saudi Aramco Standard Drawings

AA-036572 Grounding Arrangement for Disconnect Switch Structure

Saudi Aramco Library Drawing

DB-950387-001 Tank Grounding
DB-950387-002 Connections Details of Shunt
DD-950022 Grounding Connections Details Ground Rod to Ground
Grid

Saudi Aramco Pre-commissioning Form

SA-P-080 Grounding Systems

3.2 Industry Codes and Standards

American Petroleum Institute

API 650 Welded Tanks for Oil Storage

API RP 2003 Protection against Ignitions Arising out of Static,

Lightning, and Stray Currents

Institute of Electrical and Electronics Engineers

IEEE C2 National Electrical Safety Code
IEEE Std C57.32 Standard for Requirements, Terminology, and Test
Procedures for Neutral Grounding Devices
IEEE Std. 80 Guide for Safety in Alternating-Current Substation
Grounding
IEEE Std. 81 Guide for Measuring Earth Resistivity, Ground
Impedance, and Earth Surface Potentials of a Ground
System
IEEE Std. C37.101 IEEE Guide for Generator Ground Protection
IEEE Std. 142 Recommended Practice for Grounding of Industrial and
Commercial Power Systems
IEEE Std. 575 IEEE Guide for Bonding Shields and Sheaths of Single-
Conductor Power Cables Rated 5 kV through 500 kV

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IEEE Std. 602 IEEE Recommended Practice for Electric Systems in

Health Care Facilities
IEEE Std. 998 IEEE Guide for Direct Lightning Stroke Shielding of
Substations
IEEE Std. 1100 Powering and Grounding Sensitive Electronic Equipment

International Electrotechnical Commission

IEC 62305-1 Protection against Lightning - Part 1
IEC 62305-2 Protection against Lightning - Part 2
IEC 62305-3 Protection against Lightning - Part 3
IEC 62305-4 Protection against Lightning - Part 4
IEC 61892 Mobile and fixed offshore units – Electrical installations
IEC 60364-5-54 Low-voltage electrical installations- Part 5-54: Selection
and erection of electrical equipment – Earthing
arrangements and protective conductors

National Fire Protection Association

NFPA 70 National Electrical Code
NFPA 99 Health Care Facilities
NFPA 780 Lightning Protection Code

Saudi Building Code (SBC)

SBC Saudi Building Code

Saudi Electricity Company Standards

TES-P-119.06 Surge Protection
TES-P-119.10 Grounding
TES-P-119.41 Non-Linear Resistor Application in GIS

Underwriters Laboratories
UL 96 Lightning Protection Components
UL 96A Installation Requirements for Lightning Protection
Systems
UL 467 Grounding and Bonding Equipment

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 Document Responsibility: Electrical Systems Designs and Automation Stds. Committee SAES-P-111
Issue Date: 09 November 2021
Next Revision: 09 November 2026 Grounding

4 Terminology

4.1 Acronyms

MSAER: Mandatory Saudi Aramco Engineering Requirements.

SEC: Saudi Electricity Company.

EGC: Equipment Grounding Conductor.

4.2 Definitions

Bonding: The permanent joining of metallic parts to form an electrically

conductive path that will assure electrical continuity and the capacity to safely
conduct current likely to be imposed.

Earthing: Grounding are synonyms terms in IEC.

Effectively Grounded: As defined in IEEE Std. 142.

Equipment Grounding: An equipment ground is the physical connection to

earth of non-current carrying metal parts.

Grounding Electrode: A conductor that have a direct contact with earth for
grounding a power system.

Grounding Electrode Conductor: A conductor used to connect the system

grounded conductor or the equipment to a grounding electrode or to a point on
the grounding electrode system.

Grounding Grid: A system of horizontal ground electrodes that consists of a

number of interconnected, bare conductors buried in the earth, providing a
common ground for electrical devices or metallic structures, usually in one
specific location.

Ground Potential Rise (GPR): The maximum electrical potential that a

substation grounding grid may attain relative to a distant grounding point
assumed to be at the potential of remote earth. This voltage, GPR, is equal to
the maximum grid current times the grid resistance.

Grounding System: Comprises all interconnected grounding facilities in a

specific area.

Hydrocarbon Facilities: Process plants treating petroleum, natural gas or

petrochemical.

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Step Potential: The difference in surface potential experienced by a person

bridging a distance of 1 m with the feet without contacting any grounded
object.

Touch Potential: The potential difference between the ground potential rise
(GPR) and the surface potential at the point where a person is standing while at
the same time having a hand in contact with a grounded structure.

5 General

Grounding/ earthing and/or bonding for electric power distribution systems shall
be designed and installed in accordance with relevant parts of IEC 60364-5-54,
IEC 61892, API RP 2003, NFPA 70, IEEE Standards 80, and 142.

5.1 For 1 kV nominal voltage and below, grounding and ground systems shall be in
accordance with IEEE Std. 142 and meet the requirements of ANSI/NFPA 70
(NEC), and IEEE C2, as supplemented or amended by this standard.
This includes:
a) Residential facilities.
b) Recreational facilities.
c) Schools.
d) Office buildings (including those associated with plants and
industrial facilities).
e) Swimming pools and fountains including equipotential bonding
requirements stated in the Saudi Building Code (SBC) and/or NEC.

5.2 For systems having equipment operating at a nominal system voltage

exceeding 1 kV, a ground grid meeting the requirements of IEEE Std. 80 for
step and touch potential shall be installed.
Exception 5.2:
When the system is low resistance grounded, a ground loop/ring is sufficient.

5.3 Supplementary grounding electrodes shall be used where bonding is needed to

ensure equipotential, per Section 10.

5.4 Grounding and ground system requirements for specific facilities are as follows:
a) Health Care Facility grounding shall meet additional requirements of
NFPA 99 and IEEE Std. 602;
b) Communications System grounding shall be in accordance with the
SAES-T-Series;
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c) SAES-J-902 shall take precedence over this standard for grounding

of process control instrumentation and process control systems.
Refer to SAES-J-902 for grounding sensitive electronic equipment
associated with process control systems.
Note 5.4:

It is intended that the terminology used in this standard be consistent with the NEC.

5.5 Measurements of earth resistivity shall be made using the four-point method as
per IEEE Std. 81. Unless physical obstacles are faced, probe spacing shall be
increased gradually up to three times the grid length. At least two perpendicular
measurements profiles shall be conducted.

5.6 Grid/electrode resistance shall be made using fall-of-potential or slope method

in accordance with IEEE Std. 81.

5.7 If variations in soil measurements are not significant, any of the uniform soil
model equations in IEEE Std. 80 can be used. For other type of non-uniform
soil structures that show distinct variations in the soil measurements, the two-
layer model approach presented in IEEE Std. 81 appendix B shall be used to
approximate the equivalent two-layer earth structure.

6 Materials and Installation

This section applies to electrical installations in industrial facilities, residential

areas, recreational facilities, and office buildings.

6.1 Conductors shall be as follows:

a) All conductors shall be soft or annealed stranded copper.

Exception 6.1 (a):

In the cases where bare copper will affect cathodic-protection currents,

tinned copper shall be used.

Annealed copper clad steel wires can be used for grounding tower
structures of 69 kV and above overhead transmission lines in outside
facilities.

b) Substation grid conductors and grounding loop/ring conductors shall

be bare.
Exception 6.1 (b):

In soils less than 70 ohm-meters resistivity, grid conductors/ grounding loop

conductors shall be tinned copper.

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c) Equipment ground conductors and bonding conductors in process

facilitates shall be insulated.
Note 6.1:

All underground conductors that are not part of an IEEE 80 step- and touch-
potential grid shall be insulated for corrosion control and to eliminate interference
with cathodic protection systems.

d) Stranding of ground conductors shall comply with the stranding

requirements of SAES-P-104.
e) If insulated, shall have a green jacket with yellow stripes.
f) Insulation for exposed above ground conductors shall be UV
resistant.

6.2 Ground rods shall have the following specifications:

a) Be copper.
Exception 6.2 (a):

In soils with less than 70 ohm-meters resistivity, copper clad steel shall be
used and meet the requirements of UL 467 or equivalent.

Galvanized steel shall be used in areas protected by cathodic protection or

in soils with less than 70 ohm-meters resistivity outside the substation.

Note 6.2 (a):

Soils in Saudi Aramco areas which are lower than 70 ohm-meters resistivity
normally have high salt content and are corrosive to copper. Galvanized
steel is very durable in low resistivity soils. Buried bare copper has a
detrimental effect on pipeline cathodic protection.

b) Have a minimum length of 2.45 meters. Jointed rods are permitted

but each joint must be at least 2.45 meters long.
c) If copper or copper clad steel rods, be a minimum of 16 mm in
diameter, and if galvanized steel rods be a minimum of 19 mm in
diameter.
d) When grounding is required at pipeline valve stations, zinc or
magnesium anodes interconnected with insulated copper cable may
be used in lieu of copper clad or galvanized steel ground rods. Each
ground rod shall be replaced with a zinc or magnesium anode. A
minimum of two zinc or magnesium anodes spaced a minimum of 2
meters apart shall be installed. Installation of the anodes shall be in
accordance with SAES-X-400.
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6.3 Below ground connections to grounding grids and ground rods, or between
conductors and/or grounding rods, shall be made using one of the following
methods:
a) By thermite welding
Note 6.3 (a):

All exothermic connections shall be bitumastic painted and mastic taped.

b) By compression(crimped)-type connectors listed as grounding and

bonding equipment, and have a manufacturer's reference
compression die number and conductor size printed or stamped on the
connector.
c) By mechanical connectors where it is necessary to disconnect
ground conductors for tests at ground test stations.
Note 6.3:

Library Drawing DD-950022 shows recommended details for making grounding

connections.

6.4 Above ground grounding system connections shall be made in accordance with
NEC.
Exception 6.4:
To structural steel, by compression type connectors bolted to bare steel.

6.5 Grounding conductors extending through concrete or asphalt shall be run in

PVC conduit (preferred) or PVC coated rigid steel conduit.

6.6 Underground ground conductors that are within 3 meters of a buried metal
pipeline or metal piping, shall be insulated or sleeved with PVC conduit.

7 Substation Grounding

Per Section 5, the design for the substation grid and the associated overall
plant grounding system shall account for hazards due to transferred potentials
caused by a fault in the substation.

7.1 All electrical equipment in the substation, substation yard, and within 5 meters
of the substation fence shall be connected to the grid or to a ground bus
connected to the grid.

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Note 7.1:

See IEEE Std. 80 for discussion of transferred potentials

7.2 Special considerations for gas-insulated substations (GIS) shall be as per IEEE
Std. 80 section 10 and TES-P-119.10 section 13.

7.3 The design package for ground grids and systems for substations with
equipment operating at above 15 kV shall be performed and submitted for
review.
Note 7.3:

Grounding grid shall be buried at a depth ranging 0.5 to 1.5 m below final
ground grade, typical conductor spacing range from 3 m to 15 m. For the typical
conductor size ranging from 2/0 AWG (70 mm2) to 500 kcmil (240 mm2).

GPR shall not exceed 5kV and shall be minimized, as low as possible, to
safeguard communication and microprocessor-based equipment.

7.4 Cross section for conductors utilized in substation ground grids shall be 70
mm² (2/0 AWG) or greater.

7.5 Calculations of allowable and actual step and touch potentials shall be done in
accordance with IEEE Std. 80 using the following parameters:
Note 7.4:

Calculations using other methods, including Finite Element Analysis, will be

accepted for multi ground grid connection.

7.5.1 A body weight of 50 kg shall be assumed.

7.5.2 Duration of ground faults used in calculations for maximum allowable

step and touch potential shall be the time (based on known operating
conditions) it would take for the breaker backup protection to clear the
fault and shall not exceed 0.5 sec.
Exception 7.5.2:
For substation with incoming power supply of 34.5 or 13.8kV nominal
voltages with solidly grounded system, the duration shall not exceed 1
sec.

7.5.3 Ground fault current shall be the higher of the symmetrical line-to-line to
ground (LLG) or line to ground (LG) fault currents. The fault current shall
not be based on local faults with local grounded neutral.
Note 7.5.3:

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 Document Responsibility: Electrical Systems Designs and Automation Stds. Committee SAES-P-111
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In many cases, the available ground fault current at the low voltage level
is the highest fault current in the substation. However, this fault current
shall not be considered in sizing the grid conductors nor in determining
GPR, step and touch potentials, with presence of one of the following:

1. Auxiliary MCC inside high voltage substation is fed from a low

voltage switchgear located in a downstream substation.

2. Presence of an effective metallic path between the low voltage

equipment’s ground bus and the supply transformer’s ground
terminal/pad. This can be achieved by having a dedicated EGC
(sized based on NEC article 250) within the cable bus’s enclosure.
The enclosure shall be bonded to the switchgear’s ground bus from
one end and to the transformer’s ground terminal/pad from the other
end. The LV grounding system (i.e. Ring or Loop) shall be sized to
withstand the maximum low voltage short circuit current.

7.5.4 In calculations of the grid current, the current division factor shall be site
specific as per Annex C of IEEE Std. 80. If no detailed analysis is
conducted, the current division factor shall be 1.0.
Note 7.5.4:

The current division factor is used to account for the current that returns
to the source through an overhead ground wire rather than through the
substation ground grid and earth.

7.5.5 The resistivity of the surface material shall be assumed based on Table
1.
Table 1 – Resistivity of Surface Material

Material Resistivity Ωm Min. Layer Thickness

Asphalt 10,000 or higher 50 mm

Gravel / Crushed rock 3,000 or higher 80 mm

Concrete 200 or higher 80 mm

For all other surface 100 or higher or the

40 mm
materials actual measured top layer

Note 7.5.5:

SAES-P-119 requires substation yards to have a minimum thickness of

asphalt of 10 cm (100 mm).

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Surface material layer shall be extended at least 1m outside the fence

perimeter.

7.5.6 Calculations of mesh voltage and ground potential rise shall be based on
actual measured soil resistivity. Soil resistivity of backfill material used
for ground grids and ground rods shall be the same as or less than that
of the surrounding soil.
Note 7.5.6:

For two layers soil model, where the upper layer has the higher soil
resistivity, deep driven rods shall be considered to be in contact with the
lower soil resistivity layer.

7.6 Commissioning tests shall be performed to verify that resistance to remote

earth of substation ground grids and/or ground electrodes used for system
grounding meet design requirements.
Note 7.6:

The result of all test performed shall be documented on Saudi Aramco pre-
commissioning form SA-P-080, or an equivalent form containing the same
information.

7.7 New ground grids shall be provided with test stations (wells) to facilitate future
tests. Test wells shall be reasonably distributed to cover the entire grid evenly.

8 Grounding Electrodes

8.1 Grounding electrode systems for residential areas, recreational facilities,

schools, and office buildings, shall be in accordance with the NEC with the
following additions/exceptions:

8.1.1 Reinforcing bar of buildings shall not be used as a grounding electrode.

8.1.2 Structural steel of a building may be used as a grounding electrode in

accordance with the NEC provided it is continuous and effectively
grounded by connecting at least every other structural steel column on
the perimeter of the building to a ground ring installed per the NEC and
this standard.

8.1.3 If a concrete-encased electrode is used, the conductor must be bare

copper.

8.1.4 The ground electrode for system grounding shall consist of either (1) rod
or (2) a combination of rod and a grid or loop of bare copper conductors
buried a minimum of 500 mm. Multiple rods shall be interconnected by
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bare or insulated copper conductors using thermite welding or approved

connectors per Section 6. Conductors used to interconnect rods shall be
buried at minimum depth of 500 mm.
Note 8.1.4:

Minimum conductor burial depth and length requirements of the NEC are
applicable for “Ground Rings” encircling a building or structure that
constitutes the only made electrode for the building. Minimum burial
depth requirements of this paragraph apply to conductors used to
interconnect rods or other made electrodes.

8.2 When required, supplementary grounding electrodes per NEC Article 250 shall
be provided in outdoor industrial areas, process plant areas, and in substations
not covered by Section 7. Resistance to ground of each supplementary
grounding electrode system shall be minimum 25 ohms as specified in NEC.

8.3 If an above ground bus or loop is used for extending the supplementary
grounding electrodes, this bus or loop shall have two connections.

8.4 Conductors used for interconnecting ground rods shall be minimum of 70 mm²
(2/0 AWG).

9 System Grounding

9.1 Three-phase electrical systems shall be grounded in accordance with Table 1 of

SAES-P-100. The system grounding connections shall be made directly to the
grounding electrode and be routed separately from equipment grounding
connections.
Exception 9.1:

Systems fed from a transformer with a primary voltage less than 600 V shall be
grounded in accordance with NEC rules for separately derived systems.

Dry-type lighting or building service transformers in substations, in switchgear

rooms, or in equipment rooms may be connected to a ground bus that is directly
connected to the grid or other grounding electrode.

9.2 Solidly grounded systems below 1 kV

9.2.1 The ground resistance of made electrodes (ground ring and/or ground
loop) used for system grounding shall not exceed 5 ohms.

9.2.2 Neutral conductor shall be selected based on 3 seconds fault duration.

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9.3 Impedance grounded systems above 1 kV

9.3.1 The ground resistance of made electrodes (ground rods and/or ground
grid) used for system grounding shall not exceed 5 ohms.

9.3.2 For industrial facilities, grounding impedance shall be 400 A, 10 Seconds

rated Resistor.

9.3.3 For commercial facilities and residential areas, grounding impedance

shall be 1,000 A, 10 Second rated Resistor.

9.3.4 Neutral conductors shall be selected based on 10 seconds fault duration.

9.3.5 Neutral Grounding Resistors shall be designed, installed and tested in

accordance with IEEE Std. C57.32.

9.4 Solidly grounded systems above 1 kV

9.4.1 The ground resistance of made electrodes (ground rods and/or ground
grid) used for system grounding shall not exceed 1 ohm.

9.4.2 Neutral conductors shall be selected based on 3 seconds fault duration.

9.5 Generator neutral grounding shall be as specified in SAES-P-114 and

17-SAMSS-510.

9.6 When medium voltage generator(s) is/are directly connected to a switchgear

bus, each generator shall be high resistance grounded to reduce damage due
to internal ground faults. Alternative ground fault source (i.e. grounding
transformer) shall be considered to meet worst-case ground fault relaying
sensitivity requirements. This grounding configuration will provide a similar
functionality to the hybrid high resistance grounding referenced in IEEE Std
C37.101.
Exception 9.6:

This grounding requirement does not apply to a single directly connected

standby generator rated three 3MW or less as defined in SAES-P-116.

9.7 Low voltage generators shall be solidly grounded. When the available ground
fault current exceeds the three-phase fault current resulting in a short circuit
overduty, each generators shall be effectively grounded through a neutral
grounding reactor to reduce the ground fault current to a value in the range of
60 and 100% of the three-phase fault current as stipulated in IEEE Std. 142.

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9.8 Neutral conductors for LV generators shall be selected based on 10 seconds

fault duration.

9.9 All grounding electrodes used for system grounding in plants, bulk distribution
facilities, or other industrial areas shall be interconnected to form a single
ground system. The grounding electrode used for system grounding (including
separately derived systems) for each area in the facility or plant shall have a
minimum of two connections to the ground grid or ground loop used in the area.
This requirement can be met by connections to the grounding electrode of the
substation(s) which supply the area.

9.10 Provided that the motor controller has ground fault detection and the
transformer is located at the same well site as the pump being served, the
system grounding of dedicated (captive) transformers supplying electric
submersible pumps in water or oil well applications shall be determined by the
ESP system supplier.

10 Equipment Grounding

10.1 Equipment grounding conductor shall be provided with each power circuit or
inside the multiconductor cable jacket. An insulated copper conductor shall be
installed in the same conduit, cable tray, cable trench or shall otherwise
accompany the power conductors. Sizing of equipment grounding conductor
shall be as per NEC Article 250.
Exceptions 10.1:

69 kV cables and above, equipment grounding conductor is not required for

cross-bonded sheath systems as per IEEE Std. 575.

Note 10.1:

In accordance with the NEC an equipment grounding conductor is not required

between the neutral point of a transformer and a service disconnecting means.
The grounded circuit conductor (neutral) required by the NEC is sufficient.
See NEC Article 250.

10.2 Regardless of whether or not this standard permits conduit or cable tray to be
relied on as the equipment grounding conductor, the conduit, or cable tray
installations must meet NEC bonding and grounding requirements for such use.

10.3 In hazardous locations, equipment grounding conductors run in conduit or cable

tray shall be insulated or enclosed within the jacket of a multi-conductor cable.

10.4 On metallic cable trays, a common equipment grounding conductor external to

the cables in the tray may be used under the following conditions:

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• This common conductor shall be sized in accordance with NEC Table

250-66 for the largest power conductor in the tray, with a minimum size
of 25 mm² (#4 AWG).
• Connections shall be made between this common grounding
conductor and other grounding conductors for intersecting or branch
trays, and to extend the equipment grounding conductor beyond the
tray.
• This common conductor (or the largest individual grounding
conductor, if more than one are installed) shall be bonded to each
section of the cable tray system with a connector approved for a
copper to aluminum connection.
• Cable tray system shall be grounded at both ends and shall be
bonded across expansion joints as required per NEMA VE2.

10.5 A cable concentric neutral, if properly sized and not used as a current carrying
grounded circuit conductor (3 phase 3 wire system; no neutral loads are
served), may be used as the equipment grounding conductor.
Note 9.5:

The cable must meet the requirements of 15-SAMSS-502 that requires an overall
jacket to protect the concentric neutral.

10.6 Electrical submersible pump motors in oil and water well service do not require
a dedicated equipment grounding conductor, provided the motor controller has
ground fault detection. The well head must be bonded by an approved means
to the ground bus at the motor controller or supply transformer.

10.7 Armored submarine cables do not require equipment grounding conductors.

10.8 Shield/sheath and armor of power cables shall be grounded independently at

both termination ends. Continuity at splices shall be maintained by bonding
across the splice. For circuits with single core conductors, circulating currents
and associated potential rise shall be minimized. Cables shields, sheaths,
joints, braided leads, and grounding bonds shall be rated for the maximum
currents including motor acceleration periods.
Exception 10.8:

For 69 kV cables and above, IEEE Std. 575 shall be utilized for design aspects of
sheath-bonding methods for single-conductor cables depending on cable
lengths.

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Note 10.8:

When splicing single core armored to unarmored cable, the induced voltage of
the armor layer at the splice point shall be calculated to ensure that it is within the
cable jacket tolerance.

Terminating cable shield/sheath at gland earthing tags is forbidden.

10.9 Metallic conduits shall be grounded at both end points by bonding to a

grounding conductor, a grounded metal enclosure, or to a grounded metal cable
tray. This may be accomplished:
• With listed or marked grounding clamps and conductors connected
externally to the conduit.
• By bonding to a grounded enclosure using integral threaded bushings
or using a conduit hub which is listed or marked for grounding
purposes.
• Bonding to a grounding conductor using listed or marked grounding
bushing. Grounding with locknuts is not acceptable.
• Where non-PVC coated rigid conduit is used to protect cable entering
or exiting a grounded metal cable tray, by bonding with a conduit
clamp to the cable tray. A grounding bushing must be used with PVC
coated conduit.
Exceptions 10.9:

Where EMT is permitted it may be grounded and bonded in accordance with the
NEC.

Isolated sections of rigid metal conduit that are buried at all points at least
0.5 meters below grade are not required to be grounded. (e.g., Conduit sleeves
for road crossings.)

Conduit sleeves used to enclose power cables transitioning from above grade to
below grade are required to be grounded only at the above grade end.

10.10 Metallic cable trays shall be bonded to the local ground grid or ground electrode
at both end points ensuring that bonding continuity is met throughout all the
racks in the system.

10.11 Ground busses in switchgear, switchboards, and motor control centers shall
have two connections to the local ground grid or the main ground electrode.

10.12 Electrical manholes shall be grounded using two ground rods located close to
diagonally opposite corners of the manhole. These rods shall be connected to
each other, to a ground loop or bus accessible from inside the manhole, and,
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where applicable, to a minimum 120 mm² (4/0 AWG) grounding conductor that
is connected to the local (within 15 m) grounding grid.

10.13 Raised computer floors shall be grounded by bonding a minimum of two

pedestals at opposite corners to the nearest ground bus or grounding electrode.
Refer to IEEE Std. 1100 for guidance on grounding of raised floors used with
sensitive electronic equipment.

10.14 The following equipment shall be connected to the local ground grid, grounding
electrodes, or supplementary grounding electrodes described in Section 8.
This is in addition to equipment grounding conductors running with the power
conductors that are required by the NEC and this standard.
Exception 10.14:

See Section 11 for supplementary grounding on offshore platforms.

10.14.1 All structural steel supports (including coated structural steel) that
support insulators, electrical equipment, process equipment or piping
and structural steel columns shall be connected with a minimum of two
connections at opposite corners of each structure, connections shall
be made at least every 25 m (i.e., No part of the base of the structure
shall be more than 25 m from a grounded support or column). For
pipe-rack designs that do not have horizontal structural steel
connecting the adjacent vertical steel supports, each vertical support
must be grounded.

10.14.2 Frames of equipment (motors, generators, and transformers)

operating at 1,000 V or greater shall have two connections to the
grounding electrode.

10.14.3 Motors, transformers, and generators operating at a nominal voltage

of 400 or 480 V shall have a minimum of one connection to the
grounding electrode.

10.14.4 Motor Operated Valves (MOV), lower voltage motors and transformers
are grounded through the associated equipment grounding conductor.

10.14.5 The following equipment when not bolted to grounded structural steel
shall be connected to a supplementary grounding electrode:

10.14.5.1 Metallic enclosures for panelboards, circuit breakers,

switches, fuses, motor controllers, switchgears,
switchracks, motor control centers, and motors and
transformers not covered above.

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10.14.5.2 Metal vessels, stacks, exchangers, and similar

equipment.

10.14.5.3 Loading and unloading facilities.

10.15 Manually operated switches for overhead power lines shall have operating
platforms and be grounded as shown on Standard Drawing AA-036572.

10.16 Minimum conductor size used for connection of equipment to ground rods or
ground grid shall be based on the calculated short circuit level at the equipment
but not less than 25 mm² (#4 AWG).
Exception 9.16:

See SAES-P-107 for pole ground wires.

10.17 Grounding of surge arresters shall be as per TES-P-119.06, TES-P-119.41 and

IEEE Std. 142, with separation as per NESC C2.097.

11 Offshore Platform Grounding

11.1 The main ground electrode for the platform shall consist of a copper cable or
copper bar minimum size 120 mm² (4/0 AWG) which is connected to two
platform legs. In addition, the main ground electrode shall be connected to the
structural steel in a minimum of two locations at opposite sides of the main
substation area. Connections to the platform legs, structural steel and any
splices in this main ground electrode shall be made by exothermic welding or
brazing. System grounding connections shall be made directly to this ground
electrode.

11.2 Tanks of medium and high voltage transformers and ground busses for
switchgear and motor control centers shall have two paths for current to flow to
this ground electrode. The main ground electrode is not required on platforms
that do not have transformers or generators which require system grounding
connections.

11.3 Where two or more platforms which require main ground electrodes are
connected by walkways, two insulated conductors, minimum size 120 mm²
(4/0 AWG) shall be installed between the respective main ground electrodes.

11.4 Equipment grounding shall be done per Section 10 of this standard except that
required local supplementary grounding of motors, low voltage transformers,
etc. which are not in the main substation area may be done by using a bonding
jumper that is connected to structural steel or deck plate by brazing or
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exothermic welding or connection to a copper ground bus that is connected to

structural steel or deck plate by brazing or exothermic welding.

11.5 Exposed grounding conductors shall be insulated. Insulation shall be green, or

green with yellow stripes. Exposed connections and terminations shall be
thoroughly covered with a suitable weather resistant compound for protection
from corrosion.

12 Fence Grounding

12.1 Electrical substation fences shall be grounded as follows:

12.1.1 Substation fences shall not be PVC coated and shall be grounded in a
minimum of two locations to the local ground grid or loop.

12.1.2 All fences (including grillwork and gates used to control access to the
area under the substation) for substations containing equipment fed
from solidly grounded systems operating at above 1,000 V line to line
shall be bonded to a grounding conductor buried approximately 1 m
outside the fence and parallel to the fence. A second conductor shall
be buried 1 m inside the fence if the substation ground grid does not
extend into this area. The grounding conductor(s) shall be connected
to the substation ground grid at a minimum of four locations spaced
equally around the loop. The fence shall be connected to the
grounding conductor(s) at intervals not exceeding 15 m. Corner posts
and gateposts shall be connected to the grounding conductor. Gates
shall be bonded to the gateposts with flexible connectors. Grillwork
and gates used to control access to the area under the substation
shall meet the bonding and grounding requirements for substation
fencing.

12.2 Non-substation fences shall be grounded as per below table:

Table 2 – Non-Substation Fences Grounding
Specific
No Fences Location Grounding Coating
Notes
Fences within 10 m of an
enclosed ground grid or
At intervals not exceeding
ground loop that is shall not be PVC
1 15 m to the ground grid or
connected to equipment Coated
loop.
operated at 1,000 V or
greater.

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Specific
No Fences Location Grounding Coating
Notes
Shall be bonded at the
All fences within 3 meters
nearest fence post to the shall not be PVC
2 of a ground grid or ground
ground grid or ground Coated
electrode
electrode.
Shall be grounded at
Fences that pass under a intervals not exceeding 15
shall not be PVC
3 transmission line operating m per 11.2.1 on that
coated
at 34.5 kV and above portion of the fence within
100 m of the power line.
Shall have a bond between
Fences that cross over a the grid or conductors and
ground grid, or conductors the nearest post. If the shall not be PVC
4 S1
that connect two ground crossing area is extensive, coated
grids the bond is required every
50 m.
Specific Note(s):

S1 If the ground conductors used to connect the ground grids are insulated and sleeved
with PVC conduit at points within 10 m of the fence, then the bond is not required.

12.3 Non-substation fences, other than described in 12.2, constructed with concrete
posts and PVC coated fencing material are not required to be grounded.
Note 12.3:

See SAES-M-006 for fence requirements.

12.4 Fence made of non-conductive materials is not required to be grounded, except

possibly at exposed metallic hardware or sections, such as gates. Fences not
required to be grounded by this standard shall not be grounded.

13 Tank Grounding

13.1 The shells of onshore storage tanks in hydrocarbon service shall be grounded
as follow:

13.1.1 At a minimum of two points on diagonally opposite sides of the tank

and/or at maximum 100 ft (30 m) intervals along the perimeter of the
tank.

13.1.2 Each point shall be bonded to the area ground grid or to a local
electrode. The tank shell to remote earth resistance shall not exceed
10 ohms.

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13.2 Bonding of tanks with internal floating roof shall fully comply with the API 650
Annex H requirement. A minimum of four stainless steel strap conductor 0.4
mm thickness X 50 mm wide shunts shall be uniformly distributed.

13.3 External floating roof tanks shall have stainless steel shunts between the tank
roof and the metal sealing ring. The shunts shall be uniformly spaced not more
than 3 meters apart. The shunts shall be installed above the primary seals, and
bolted to the sealing ring and the roof in accordance with library drawing DB-
950387. The resistance between sealing ring and the roof shall not exceed 0.03
ohm.

14 Lightning Protection

14.1 Lightning protection system design and installation shall be based on:
• NFPA 780, UL 96, UL 96A, and IEEE Std. 998.
• or IEC 62305-1,2,3,4.

14.2 The following facilities shall have lightning protection system without a need for
risk assessment:

14.2.1 Buildings and occupied structures over 30 m in height;

14.2.2 Schools;

14.2.3 Hospitals;

14.2.4 High Voltage outdoor substations and switchyards if the area is

3250 m² or greater.

14.3 Lightning protection system design and installation of hydrocarbon facilities

shall comply with NFPA 780 and API RP 2003.
Exception 14.3:

External roof tanks bonding shall be installed per section 13. Bypass conductors
shall not be installed.

The following shall be used as the basis in the calculations:

a) Isokeraunic level (I) shall be as per value listed in SAES-A-
112.

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b) “Annual Ground Flash Density” (Ng) shall be calculated

using the formula Ng=0.12xI (annual ground strikes per
square kilometer) as per IEEE Std. 998 (Nk).

14.4 Lightning protection components shall be listed or labeled in accordance with

UL 96 for lightning protection service or equivalent certification.

15 Static Electricity Grounding

Tank trucks, tank cars, tanks, other large containers, associated filling
apparatus, and other equipment which during normal operation can cause
accumulation of sufficient static charge to cause an ignition of hydrocarbon
vapors in the area shall be bonded and grounded in accordance with relevant
parts of API RP 2003, IEC 60364-5-54, IEC 61892.

Revision Summary
25 December 2012 Major revision.
24 January 2017 Major revision incorporating various comments received from key standard stakeholders
such as Power Systems Engineering Department, Inspection Department and PMT.
The new revision address one major topic on grounding conductor requirements for 69 kV
and above power cables.
09 November 2021 Major revision incorporating various comments received from key standard stakeholders
such as Power Systems Engineering Department, Inspection Department and PMT.
The new revision is primarily to incorporate enhanced generator, tank and fence grounding
requirements.

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