SURGE PROTECTION

2.1

Requirements

The lightning surge protection devices (SPD) shall be installed at specific locations for specific equipments and panels as per design, drawing and engineer’s specifications.

The SPD shall be installed with care to minimize the amount of let through voltage into equipments. The SPD shall conform to various international standards for its surge handling capability, let-through voltage and short circuit current handling capability.

All materials, equipment and components for a safe & durable lightning SPD must be UL certified. Standards & Regulations

Section 7 - Earthing, Lightning and Surge Protection

Electrical Works Specifications Sec 7 - 4

Issue 01 / Revision 01 February 2007

ANSI/IEEE C62.41 High Energy Lightning & Switching Standard

IEC 61643 Surge Protection Devices connected to low-voltage distribution systems UL1449 Electrical Safety Standard

2.2

Specifications

2.2.1 Surge Protection Device

The surge protection device (SPD) shall be compatible with the system it is protected and shall provide phase-to-neutral, phase-to-earth and neutral-to-earth protection for either single phase or three phase power supply system. The normal operating voltage of the SPD for phase-to-neutral connection shall be 240 V and the maximum operating voltage is 275 V. SPD for phase-to-earth and neutral-to-earth connections shall be rated at 415 V and the maximum operating voltage of 475 V. The leakage current shall not exceed 3.5 mA. Unless otherwise specified, the type of SPD to be installed with respect to the location of switchboard shall be as in Table 1 below: -

Location of switchboard

Main switchboard or Sub switchboard receiving energy from

licensee or other building

Switchboard and/or distribution board receiving energy from main switchboard and or Sub switchboard located in the same

building

Location Category C B

Exposure Level High High

Peak Discharge Current (8/20 µs test

waveform)

40 kA 20 kA

Peak Transient Let ≤ 800 V (20 kV, 1.2/50 ≤ 600 V (6 kV, 1.2/50 Through Voltage for

all modes µs and 10 kA, 8/20 µstest waveforms)

µs and 3 kA, 8/20 µs test waveforms) Table 1 - Types of Surge Protection Device

The peak transient let-through voltage or voltage protection level for all modes (phase-to-neutral, phase-to-earth and neutral-to-earth) shall be as in Table 1 above. Unless otherwise specified, the SPD shall be of the type complying with BS 6651 and/or IEC 61024-1 and IEC 61643-1, IEC 61312-1 and IEC 61312-3.

Section 7 - Earthing, Lightning and Surge Protection

Electrical Works Specifications Sec 7 - 5

Issue 01 / Revision 01 February 2007

The surge protection device shall incorporate continuous indication of its protection status, via full protection present, reduced protection - replacement required and no protection - failure of protection. The connecting leads shall be as short as possible and not more than 1,000 mm in length, and shall be tightly bound together over throughout the whole length. Unless otherwise specified, four-pole moulded case circuit breaker or fuses of rating as recommended by the SPD manufacturer shall be provided to enable full isolation of SPD from the system for maintenance.

2.2.2 Sub Circuit – circuit connected to sensitive equipment e.g. Compact

PLC, PLC.

SPD shall be installed as secondary protection for sensitive electronics equipments to minimize the risk & danger of lightning surge current (let through voltage of MSB SPD). The power SPD shall have a minimum 16 kA 8/20µs surge handling capability.

The SPD shall be equipped with series LC filter to ensure low let-through voltage of not more than 600 V when tested using 3 kA 8/30µs wave shape as per IEC 61643-1 Class II.

Status indication of SPD shall be of either mechanical flag or LED.

Surge protection shall be provided at the main incoming supply of the panels/switchboards where there is electronic devices are connected or those with incoming breaker ratings of 100 A and above. Protection shall be provided between live and earth as well as neutral and earth.

Surge protection units shall be designed for multiple applications (as lightning consists of a number of pulses) and components shall be able to withstand the vibration caused by the pulses. Surge protection devices shall be designed so that alarm outputs can be retrofitted whenever required. The total surge rating in a 8/20 microsecond waveform shall not be less than 100 kA.

The let-through voltage shall not exceed 900 V. The surge protection device shall comply with the following standards: - • IEC - 801 - 5 • IEC - C -62.41 - 1991 • BS EN 60099-1:1994 • IEC 587 Category E • IEC 1024 - 1 (Zone O)

3.0 LIGHTNING PROTECTION

3.1

Requirement

The lightning protection system (LPS) network shall comprise of the following (but not limited to):- • Aluminium air terminal

• Aluminium tape roof & down conductor • Aluminium tape saddle

Section 7 - Earthing, Lightning and Surge Protection

Electrical Works Specifications Sec 7 - 6

Issue 01 / Revision 01 February 2007

• Copper tape down conductor • Copper Plate type test clamp

• Earthing network termination system

The LPS network shall comply with the latest applicable provisions and recommendations of: - • BS 6651 Code of practice for Protection of Structures Against Lightning • BS 7430 Code of practice for Earthing

• IEC 62305 Code of practice for lightning protection system

3.2

Installation

Air terminations shall be firmly secured by suitable mounting mast, fixing bolts, screws and clamps to establish good electrical continuity from air terminal to downconductor and to ensure they are securely held in position under the influence of mechanical stresses during the passage of lightning currents.

All roof air terminations shall be of aluminium type material.

The number of downconductor shall be in accordance with BS 6651. Downconductors shall be brought down from roof air termination using the least number of loops as possible.

The aluminium downconductor shall be terminated at approximately 1,800 mm from finish floor level as indicated in the design drawing. Thereafter, Bi-Metallic connector shall be used to connect the aluminium downconductor to copper earth termination conductor.

The copper earth termination conductor shall be embedded within the wall. The copper earth termination conductor shall be routed directly to ground point and terminated.

Termination of the copper earth conductor to ground points (copper ground rods) shall be by means of Exothermic Welding connection for a permanent & long lasting termination as well as to prevent loosening & disconnection.

The earth termination network shall consist of copper ground rods conductor with minimum driven depths of not less than 3,600 mm and equally spaced (using the < 2 × L formula as per BS 7430) to maximize each points’ potential. Each ground points (ground rods) shall be interconnected using bare copper tape conductor buried underground with buried depth of not less than 600 mm.

A complete lightning protection network shall be provided in accordance with MS 939:1984.

All exposed non-conducting metal parts in the plant shall be bonded to earth. The lightning protection system shall comply with BS 6651 and shall take the form of a closed network and down conductors using aluminium strip.

Conductors shall be fixed to the roof of any buildings in an approved manner. Waterproof barriers shall not be penetrated. Where fixings are required to pass through waterproof membranes, the approval of the Technical Committee of the Sewerage Services Department shall be obtained prior to the commencement of work.

Section 7 - Earthing, Lightning and Surge Protection

Electrical Works Specifications Sec 7 - 7

Issue 01 / Revision 01 February 2007

Final connection to the earth electrode shall be made using aluminium strip installed in high impact heavy gauge PVC Class D conduit for below ground level installation.

Wherever possible natural contact between dissimilar metals shall be avoided. Joints between copper and aluminium conductor shall be made as follows:

• Contact area of copper shall be tinned

• Contact area of aluminium shall be cleaned and coated with an oxide resisting paste • Make off joint using copper rivets or purpose made clamps