qa-es-004 earthing specifications for optical network

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Earthing Specifications forOptical Network Equipment

Course No.: QA-ES-004

Prepared by: Engineering CenterService Management Dept.Issue Date: 2004-11-15


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Table of Contents

1. General Purposes

2. Basic Earthing Principles

3. Earthing Optical Network Equipment:

3.1 Method for Earthing Cabinet-type Optical

Network Equipment

3.2 Method for Earthing Case-shape OpticalNetwork Equipment

4. Earthing Optical Network Equipment Connected

with Other Communication Equipment

5. Earthing Cable Distribution Frame DDF or MDF6. Earthing for the Maintenance Terminal7. Selection of the Cross-sectional Area of a Protection

Earthing Wire


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General Purposes

1

This specification is to standardize the lightningprotection & earthing design and the installation method

of the optical network equipment;

2 This specification is to ensure that the optical networkequipment has good performances of lightning protection,anti-electric shock and anti-interference;

3The lightning protection & earthing design of the opticalnetwork equipment should accord with the existingrelative national and industrial standards in addition to

this specification.


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1The earthing design of the communication bureau (station)should follow the equipotential principle, i.e. the jointearthing mode in which the DC return conductor and theprotection earth (including the shielded layer and thelightning protection earth of the distribution frame) share onegroup of earthing electrodes.

2The un-energized metal parts of both the cabinet and theauxiliary devices of the optical network equipment should be

earthed.3Protection earthing wires should be yellow/green interwoven

and plastic insulated.

4Earthing wires must be copper wires to reduce the highfrequency impedance. The earthing wires should be as shortand thick as possible and should not be made of aluminum.

5The connecting points at both ends of an earthing wireshould be in good electrical contact and protected withappropriate anti-corrosion and rustproof measures.

6Other devices should not be used as part of the electricalconnection of earthing wires.

Basic Earthing Principles


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Basic Earthing Principles

7 Earthing wires should not intertwine with signal cables.8Aerial inlead of earthing wires is strictly prohibited. They

must be buried in the ground or laid indoors.

9It is strictly prohibited to install switches or fuses along aprotection earthing wire.

10Protection earthing wires should be no longer than 30m andas short as possible. If a protection earthing wire is longer

than 30 m, an earthing busbar should be set nearby.11The external conductor of a coaxial cable and the shielded

layer of a shielded cable should have their two ends in goodelectric contact with the outer surface of the metal shell ofthe connected device.

12It is strictly prohibited to use neutral wires as protectionearthing wires. Both the cabinet shell and the protectionearth must be insulated from the neutral wires of AC powercables.

M h d f E hi C bi


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Method for Earthing Cabinet

Equipment Inside


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Equipment Cabinet Earthing 1

Earthing for Optical Network Equipment

Powered from our Power Distribution Frame:

M th d f E thi C bi t


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Equipment Cabinet Earthing 2

Earthing for the Optical Network Equipment

Powered from users power distribution frame


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e o or ar ng a neEquipment Cabinet Earthing 3

Earthing for the Optical Network Equipment

Powered from DC Power Supply


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e o or ar ng a neEquipment Cabinet Earthing 4

Following the joint Earthing principle, the 48V DC positive

busbars of the PDB, users DC power distribution panel orusers DC supply should all be connected to the PGND

Earthing bar of the equipment room.

M th d f E thi h


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Method for Earthing case-shape

Equipment Inside

Special whole equipment Earthing terminals should be

provided on the shell of the case-shape Optical NetworkEquipment.


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e o or ar ng case-s apeEquipment AC Power Supply 1

Earthing for the Case-Shape AC Equipment when There Is a Protection

earthing bus in the Equipment Room

Method for Earthing case shape


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Equipment AC Power Supply 2

Note: When this mode is adopted, the Earthing reliability of the

equipment should be ensured with a multimeter after the engineering

installation.

E thi h E i t


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Earthing case-shape Equipment

DC Power Supply 1

DC case-shape Equipment

Protection earthing bar of the equipment room or the earthing bus

inside the cabinet in/on that the case-shape equipment is installed

2.5mm2ToPowerSupply

PGND Earthing terminal of whole

equipment-48V

-48VRTN

Method for Earthing case shape


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Equipment DC Power Supply 2

ToPowerSupply

DC case-shape Equipment

-48V

-48VRTN

PGND

Protection earthing bar of the equipment room

Or the earthing bus inside the cabinet in/on that

the case-shape equipment is installed

Earthing Optical Network Equipment


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Earthing Optical Network Equipment

Connected with Other Communication Equipment

To ensure the quality of communication signals, when the optical

network equipment is connected to other communicationequipment through coaxial cables, the external shield layers of

both the receiving and sending ends should be connected to

PGND at the same time, but disconnection should also be

provided at the receiving end.


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Earthing the Cable Distribution Frame

1When being led out of an office (station), TDA audio cablesmust pass the Main Distribution Frame (MDF) with a securityunit, with its shield layer being reliably connected to the

protection earth of the MDF; the security unit on the MDF

should have protection against over-voltage and over-current

and the failure alarm function; the equipment maintenance

personnel should check periodically to timely check-up andreplace the failed security unit.

2 The distribution frame (including MDF/DDF) should beprovided with a separate earthing wire with a cross-sectional

area of no less than 6 mm2 that is as short as possible toconnect its earthing busbar to the protection earthing bus in

the equipment room.

Earthing Maintenance Terminal


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Equipment- with AC Power 1

Earthing for the Maintenance Terminal Using Network Cables

for Communication



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Earthing Maintenance TerminalEquipment- with AC Power 2

Earthing for the Maintenance Terminal Using a Non Network

Cable for Communication



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Earthing Maintenance TerminalEquipment-with AC Power 3

Earthing for the Maintenance Terminal of

the Case-Shape AC Equipment



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Earthing Maintenance TerminalEquipmentwith DC Power

When the maintenance terminal is powered from a -48 V

power supply, the shell of the maintenance terminal shouldbe reliably connected to the protection earthing bus in the

equipment room, or the earthing terminal of the optical

network equipment or the earthing bus of our power

distribution frame or users power distribution frame

powering up the optical network equipment through a

yellow/green interwoven protection earthing wire with a

cross-sectional area of no less than 2.5 mm2.

Selection of the Cross sectional Area


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Selection of the Cross-sectional Area

of a Protection Earthing Wire

The major factor to be considered for selecting the Cross-

sectional area of the PGND wire of the equipment is the

working current of the equipment.

Lightning protection requirement: The sectional area of the

earthing wire should meet the requirement of safely

discharging the lightning current to the earth. Generally this

requirement is easy to meet.

Anti-external force requirement: If the protection earthing wire

is led from the equipment to the outside, it should not be

broken due to the accidental contact of people or other objects.


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qa-es-004 earthing specifications for optical network

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