HFY3-3125-ELE-SPC-0006_0_Code A

7/23/2019 HFY3-3125-ELE-SPC-0006_0_Code A

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7/23/2019 HFY3-3125-ELE-SPC-0006_0_Code A


Petrochina (Halfaya)

HALFAYA PROJECT

SURFACE FACILITY

PHASE THREE

DETAIL DESIGN DOC.NO.: HFY3-3125-ELE-SPC-0006 REV.: 0 PAGE 2 OF 11

CONTENT

1.0

SCOPE ..................................................................................................................... 3

2.0 CODE, REGULATIONS AND STANDARDS ............................................................ 3

3.0 SERVICE CONDITIONS ........................................................................................... 5

4.0

LANGUAGE AND SYMBOLS .................................................................................. 5

5.0 EARTHING OF ELECTRICAL CIRCUITS AND EQUIPMENT .................................. 5

6.0 ELECTRICAL EQUIPMENT ..................................................................................... 8

7.0 NON-ELECTRICAL EQUIPMENT ............................................................................ 9

8.0 LIGHTNING PROTECTION .................................................................................... 10

9.0 EARTHING MATERIALS ....................................................................................... 11

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SURFACE FACILITY

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1.0 SCOPE

This specification gives the minimum requirements for earthing and bonding. It covers:

Electrical installations and power distribution systems.

Static earthing systems.

Lightning protection systems.

2.0 CODE, REGULATIONS AND STANDARDS

Vendor shall meet or exceed the requirements of the latest edition of the following codes,regulations and standards, except as superseded herein. In cases where more than onecode, regulation or standard apply to the same condition, the most stringent shall befollowed. In the event of a conflict between this specification and other specifications orcorrespondence, the owner shall be consulted and a ruling, in writing, shall be obtainedbefore any work is started.

2.1 International Standards

IEC 60364-3 Electrical installations of buildings - Part 3: Assessment ofgeneral characteristics.

IEC 60364-4 Electrical installations of buildings - Part 4: Protection forSafety. Protection against over-voltages and Protectionagainst over-voltages of atmospheric origin or due toswitching.

IEC 60364-5 Electrical installation of buildings – Selection and erection ofelectrical equipment – Devices for protection against over-voltages.

IEC 61024-1 Protection of structures against lightning – Part 1: Generalprinciples.

IEC 61024-1-1 Protection of structures against lightning – Part 1: Generalprinciples – Section 1 – Guide A : Selection of protectionlevels for lightning protection systems.

IEC 60079-0 Explosive atmosphere – part 0: Equipment – GeneralRequirements

IEC 60079-10-1 Explosive atmospheres – Part 10-1: Classification of areas –Explosive gas atmospheres

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SURFACE FACILITY

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IEC 60079-14 Explosive atmospheres – Part 14: Electrical installationsdesign. selection and erection

IEC 60079-15 Electrical apparatus for explosive gas atmospheres – Part 15:Construction. test and marking of type of protection "n"electrical apparatus

IEEE 80-2000 Guide for safety in AC Substation Grounding

2.2 British Standards

BS 7430 Code of Practice for Earthing.

BS 6651 Code of Practice for protection of structures against lightning.

BS 5958 Code of Practice for control of undesirable static electricity.

Part 1 General considerations.

Part 2 Recommendations for particular industrial situations.

BS 6006 Specification for PVC insulated cables (non-armoured) for

electric power and lighting.

BS 4630 Specification for weldable structural steels

BS 2654 Manufacture of vertical steel welded non refrigerated storagetanks with butt welded shells for the petroleum industry.

BS 1432 Copper for electrical purposes with drawn or rolled edges.High conductivity copper rectangular conductors.

BS 1433 Copper for Electrical purpose. Rod and Bar.

BS 7671 Requirements for Electrical Installations IEE WiringRegulations, Sixteenth Edition.

Codes, Regulations and Statutes of Authority having jurisdiction in the location ofinstallation.

Some requirements in this specification may be modified by specific requirements in thePurchase Specification. In case of conflict, the specific requirements supersede thisspecification.

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Any deviation from this specification must be approved, in writing, by owner. Such writtenapproval must be obtained prior to the commencement of any work which wouldconstitute such a deviation.

3.0 SERVICE CONDITIONS

The Vendor shall make due allowance for the environmental conditions when makingtheir offer, in the design and when selecting materials. The equipment and materialsshall be entirely suitable for operation in this environment.

The Contractor shall at an early stage of the project take soil resistivity measurements atthe proposed earth electrode locations to ensure that the earthing design and theelectrode locations are compatible and conflicts with plot layouts and foundations areavoided.

For the details of environmental conditions please refer to the site condition.

4.0 LANGUAGE AND SYMBOLS

All document and drawings shall be in English language.

Electrical symbols and definitions shall be in accordance with IEC recommendations.Where no applicable IEC symbol definitions exist, BS symbols and definitions shall beused.

5.0 EARTHING OF ELECTRICAL CIRCUITS AND EQUIPMENT

5.1 General Requirements

Overall underground earthing loops shall be provided, for buildings, process, utilities andfor structure, piping etc, these loops shall be interred connected by underground earthwires. Each loop shall be linked to others by at least two branches. The integratedsystem includes protective earthing, anti-lightning, anti-static, working grounding oftransformer or generator neutral.

The earth resistance of each electrode shall be as low as is practicable, but shall in anyevent be such that the electrical resistance between the earth grid and the general massof earth ensures the operation all electrical protective devices. It shall not exceed 1 ohmwhen any one of electrodes is disconnected.

The substation is provided with an underground horizontal earth conductor which shallbe fault rated. Size shall be 70 mm2 minimum for bare copper.

Earth electrodes should be made of copper rod, 20 mm diameter, L=2500mm.

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For some of these connections shall be through a removal link for testing and inspection,inspection pits shall be provided. The arrangement for testing earth pits shall be suchthat the disconnection of one earth pit does not disconnect other pits from the earthnetwork.

The earthing above ground network shall be made of green/yellow PVC insulated coppercables.

Underground earthing conductor can be routed with cables buried, or in the cable trench.When their route is in the same trench, they are run on either side. The earthingconductor buried with cables shall be accessible without requiring displacement ofelectric cable. When their route does not follow electric cable trenches, they are runpreferably in separate excavated trenches.

When crossing road the depth shall be 800mm minimum.

The earthing conductor is located at least 0.3m from any piping when running parallel toor crossing piping.

The cross-section area of branch conductors connecting equipment and structures to theearthing grid (Min.) shall be as follows:

1 To metallic enclosures of MV electrical equipment 70 mm2

2To metallic enclosures of LV electrical equipment, having asupply cable cross-sectional area > 35mm2

70 mm2

3To metallic enclosures of LV electrical equipment, having asupply cable cross-sectional area < 35mm2

25 mm2

4 To control panels, etc. 25 mm2

5To non-electrical equipment exposed to lightning, e.g. columnsand tall structures

70 mm2

6 To other non-electrical equipment 25 mm

Protective conductors may consist of one or a parallel combination of the following:

i) Cable armouring or metallic sheath

ii) Rigid screwed conduit

iii) Earth core within a multicore cable

iv) Separate conductor

v) Structural steelwork (See Note 1)

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Sole reliance on cable armouring and/or metallic sheathing shall only be made if it isadequately fault rated as a protective conductor. (See Note 2)

Notes:

a. Structural steelwork may be considered as a protective conductor provided it is partof the common static and lightning earthing system and there is a permanentmetallic path for fault current via such steelwork and other earthing conductors backto the source of the power supply.

b. This is a fundamental requirement which should be met in the case of faults withinthe electrical equipment. In the case of faults within the cable, it may not be possibleto have armour which is fully fault-rated, particularly if the armour is of the steel braidtype.

The cross-sectional area of every protective conductor and bonding connection betweenexposed and extraneous conductive parts shall be such that they are capable of carryingthe earth fault current, or an appropriate fraction of the total fault current, for the durationof the fault without damage to the conductor or associated insulation.

The minimum size of copper earthing/bonding connections shall be 4 mm2 withoutmechanical protection and 2.5 mm2 with mechanical protection.

Copper earthing/bonding connection of 2.5 mm2 cross-sectional area shall be multi-stranded.

All the earthing conductor of different cross-section shall be as per the equipmentvendor’s requirement.

Insulated protective conductors shall have a green and yellow outer covering.

Buried earthing conductors shall be bare copper cable, unless they are to be installedwhere there is a likelihood of corrosion. In such locations buried earthing conductorsshall have an overall protective green and yellow covering.

Joints in protective conductors may be avoided. Where unavoidable, effective measuresshall be taken to prevent corrosion or other forms of deterioration or inadvertentdisconnection of such joints.

Joints and tees of buried earthing conductors shall be clamp connection.

Earthing connections shall be arranged so that continuity of the earthing system is notbroken by the removal of any one piece of equipment.

The terminating arrangement for high voltage cables shall incorporate a lug for bonding

the cable armour to earth or to the equipment enclosure.

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Non-metallic enclosures shall incorporate internal brass strips to maintain earthcontinuity between cable entries.

6.0 ELECTRICAL EQUIPMENT

The substation shall be provided with an underground earth conductor laid in aseparated excavated trench surrounding the substation.

A main sub-station earth busbar of high conductivity hard drawn copper shall be providedin the switchgear building.

Electrical continuity between metal parts such as reinforce steel of concrete foundationspoles and floors, metal frames, rails and doors of transformer cells, and earth conductorshall be constructional provided.

Each 11kV system neutral earthing resistor shall be directly connected to the externalearthing grid.

The sub-station earth busbar shall be directly connected to an earth electrode system orto a combined earth mat/grid and electrode system installed in the vicinity of theswitchgear building.

At least one more electrode than the required minimum shall be installed to enable eachto be disconnected for testing without affecting the integrity of the earth system.

The secondary winding neutral points of star of power transformers shall be solidly earth-connected (or others base on requirement of the project and bureau), in addition to beingelectrically and mechanically bonded to the main earthing network.

Final connection (even if there is resistance etc) shall be done directly to earth.

The earthing conductor for the switchgears shall be connected to the earthing system attwo positions.

The various components which required to be earthed shall be connected to the earthconductor, namely:

Frame, structure, panels;

Secondaries of instrument transformer;

Cable shields, lead sheaths and steel belts, if any.

High voltage motor enclosures shall be directly connected locally to the plant static andlightning earthing system or failing this to a local earth electrode. A common earthelectrode may be used for several high voltage motors in the area.

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High voltage cable glands shall be bonded to the motor enclosure by means of a bondingconductor.

Metallic enclosures of motor control stations or other electrical devices local to the motorshall be bonded to the associated motor enclosure or to the associated motor earthing.

Frames of motors, generators, and transformers, metallic housing of electrical equipmentsuch as control stations, welding sockets, lighting apparatus, and panel boards shall beconnected to the earthing system.

Cable steel wire armoring and lead (or semi-conductor) sheaths should be bondedtogether at cable ends, between cables where more than one cable, and to earthingsystem. In any case the resistance of the earth continuity system should be such as topermit adequate current flow to ensure operation of circuit protective devices.

Metal cable tray shall be connected to the unit earthing system network at two points.Electric continuity is ensured by the metal junction plates of the cable trays (or by copperbonding strips).

7.0 NON-ELECTRICAL EQUIPMENT

In these areas earthing wires should be connected to the earthing system at twopositions. For separated removed equipment may be connected to earthing grid directly.

Storage tanks shall be earthed through an earthing ring, 2 points minimum up to 30meters diameter, 3 points minimum up to over 30 meters diameter.

These earthing points shall be spaced symmetrically around the tank.

Floating roofs shall be electrically connected to tank shell by the tank manufacturer.

Earthing ring around the tank will be connected to the main earthing net in two points.

Each steel structure shall be connected to the earthing network in two locations.

The pipe-rack shall be provided connections approximately every 30 meters.

Bolts and welded metallic parts are considered as electrically bonded.

Pipes are bonded together and solidly grounded to the earthing networks at least at onelocation.

But in no case special insulating flanges for cathode protection must be bonded together.

Anti-static shall be provided for where static occur and gather making hurt. Whenstructures have been connected with earth gird no requirement for anti-static.

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Metallic equipment such as columns, towers, drums, exchangers, furnaces, turbineframes, etc, shall be connected directly to the earthing network in two locations. Theearthing lugs shall be provided on the equipments body.

Isolated structures or equipments such as flare, isolated storage tank or pipe way shallbe considered satisfactorily earth-connected if:

They are tied to the earthing network or to self-reliant earthing pits;

Their resistance values in keeping with earth are not in excess of 4 ohms.

Instrument earthing shall be done by instrumentation. Electricity install special earthingbar in control room, and connected to the main earthing loops.

8.0 LIGHTNING PROTECTION

8.1 General Requirements

The lightning protection system shall be in accordance with BS 6651.

The lightning earthing system shall be connected to the main earthing system at twopoints in the sub-station area.

To protect against a direct lightning strike the tallest structure on the station shall bedirectly earthed as close to the base as possible by means of at least two electrodes.

Structures made of poorly conducting material e.g. brick or concrete and which arevulnerable to lightning strike shall be provided with down conductors and an air terminal.

Structures outside the zone of protection of other structures shall be earthed asdescribed in paragraph above.

8.2 Lightning for Equipment

The steel structure shall be connected to the common earthing system by 35 mm2 minimum copper conductor.

Earthing connections shall be 35 mm2 minimum copper conductor except for directconnections for lightning which shall be 50 mm2 minimum copper conductor.

Storage tanks shall be provided with earthing lugs or bolts welded to the tank shell.

Tanks of up to and including 30 meters diameter shall have at least two earth lugs orbosses. Tanks exceeding 30 meters diameter shall have at least three. The earth lugs orbosses shall be symmetrically spaced around each tank.

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Where tanks are grouped, each electrode common to the group may be installed.Electrodes common to the group shall be bonded together by means of buriedconnections.

The armouring of cables entering a tank shall be bonded to the shell at the point of junction box.

Metallic guy ropes used for supporting stacks or structures shall be bonded at their upperends to the stack or structure if it is metallic or to the lightning protection system if it isnon-metallic. The lower end of each guy rope shall be directly earthed. Guy ropescomprising two ropes in parallel shall additionally be bonded together at the upper andlower ends.

Where the driven machine and the drive machine are in direct metallic contact withearthed steelwork no further earthing is required.

Where both machines are on a common metallic bed plate mounted on a poorlyconducting foundation, the bed plate shall be earthed to the common earthing system bycopper conductor.

Where the driven machine and the drive machine are on separate metallic bed platesmounted on separate plinths of poorly conducting material, the bed plates shall bebonded together and a single connection taken to the common earthing system.

9.0 EARTHING MATERIALS

Earthing materials shall comply with BS 6651.

Earth rods shall be of copper.

The bolts in the earthing well shall be stainless type or other anti-corrosion material.

Documents

HFY3-3125-ELE-SPC-0006_0_Code A