Condiciones iniciales

1.0 GENERAL

Faraday cage type lightning protection systems shall be installed to cover the complete building as per BS EN 62305.

A 25x3mm copper tape air termination network shall be fixed at 1m intervals using DC tape clips to the building roof. Air termination network shall be following class I LPS with 5x5m mesh.

Items of roof-mounted plant shall be bonded to the air termination network via same copper tapes. All exposed metalwork on the roof or the structure shall also be securely bonded to the air termination network. A bimetal clamp shall be used to bind different metal.

25 x 3mm copper tape down conductors shall be installed within the structural column and clamped using ‘U’ clamps to structural rebar. Down conductors shall not be positioned more than 10m apart around the perimeter. The connection between tape and cable shall be by welded rod to tape clamp or prewelded if required.

The complete installation shall be inspected and certified by the authorized representative of the manufacturer for compliance with standards.

The connection between the down conductor and the earth electrode shall be made below ground level in a small purpose-made pit with test link and removable concrete cover to facilitate future testing and maintenance. Each electrode shall consist of 1200x16mm or equal stainless steel rods complete with stud, spike, driving cap and a conductor strip clamp. Sufficient number of rods of suitable length shall be installed to provide an overall resistance to earth not exceeding 10 ohms.

All metal work on or around the building must be bonded to the lightning protection network to avoid side flashing.

Where it is necessary to form tape to tape joints, they shall be tinned soldered and riveted.

Soldering alone will not be accepted. Clamped or bolted joints will only be accepted at test points and for connection of down conductors to earth rods.

All materials used throughout the installation except earth rods shall be either copper or copper based components which are corrosion resistant and compatible with the application.

The Contractor shall submit fully detailed shop drawing for the air termination network, down conductors, earth termination network and bonding and shall be responsible to provide all the necessary accessories to integrate the system with the architectural finish of the building.

2.0 ELECTRONIC SYSTEM SURGE PROTECTION

Electronic system surge protection shall be used for the, Incoming Main Power Supply : A suitable protection should be installed in the main LV MDBs.

The ESP shall be connected in parallel with the supply. ESP should be installed within the LV MDB by the panel assembler.

HRC Fuses shall be provided in the connecting leads as required by the Specialist.

ESP to have neutral earth warning light, to detect if there is excessive voltage present between neutral and earth.

Protection shall be tested in accordance with the requirement of:

BS EN 62305 : Protection against lightning.

BS2914 :1972 ‘Specification for surge diverters for alternating current power circuits’.

IEEE C62.41 – 1991 ‘Recommended practice on surge voltage in low voltage AC Power circuits.’

The protector must not interfere with or restrict the system normal operation. It should not:

- Corrupt the normal mains power supply.

- Break or shutdown the power supply during operation.

- Have an excessive earth leakage current.

The protector shall be rated for a peak discharge current of no less than 10 KA (8 / 20 microsecond waveform) between any two conductors (phase to neutral, phase to earth, neutral to earth).

The protector shall limit the transient voltage to below equipment susceptibility levels.

Unless otherwise stated, the peak transient let-through voltage shall not exceed 600 volts.

For protectors with a nominal working voltage of 230 or 240 volts, when tested in accordance with BS 6651 : 1999 Category B – High (6kV 1.2 / 50mircorsecond open circuit voltage, 3kA 8 / 20 microsecond short circuit current).

This peak transient let through voltage shall not exceed for all combinations of conductors:

- Phase to neutral - Phase to earth.

- Neutral to earth.

Mains protectors (installed in shunt / parallel) should have continuous indication of its protection status and the presence of power. Status indication should clearly show per phase.

- Full protection present.

- Reduced protection – replacement required.

- No protection – failure of protector.

The status indication should warn of protection failure between all combinations of conductors, including neutral to earth. (Otherwise a potentially dangerous short circuit between neutral and earth could go undetected for some time). This should include early warning of excessive neutral to earth voltage.

The protector shall be supplied with detailed installation instructions. The installer must comply with the installation practice detailed by the protector manufacturer.

Protection for Data Communication and Telephone lines

Transient overvoltage protectors shall be installed on all data communication / signal / telephone lines entering or leaving the building, in order to protect equipment connected to the line, against transient overvoltages. (Where data lines travel between buildings linking equipment in each building, transient overvoltage protectors should be installed at both ends of the line in order to protect both pieces of equipment).

Protectors shall conform to BS EN 62305 Protection against lightning The protector must not impair the systems normal operation. It should not:

- Restrict the system bandwidth or signal frequency.

- Introduce excessive inline resistance.

- Cause signal reflections or impendence mismatches (on high frequency systems).

The protector will have a low transient ‘let – through’ voltage for tests conducted in accordance with BS EN 62305

This ‘let – through’ performance will be provided for all combinations of conductors : - Signal line to signal line.

- Signal line to screen / earth.

The protector shall be rated for a peak discharge current of 10kA.

The protector shall be supplied with detailed installation instructions. The installer must comply with the installation practice detailed by the protector manufacturers.

The protector manufacturer should allow for the facility to mount and earth large numbers of protectors through an accessory combined mounting and earthing kit.

SECTION 13

EARTHING

SECTION 13 EARTHING

INDEX

1.0 MAIN EARTHING SYSTEM