The following provides sample specifications that can be used in a lightning surge suppressor installation contract for a multi-storey office building.
1.0 GENERAL
1.1 This document describes the tender specification requirement of lightning and surge protection system for essential and critical equipment installed as per design drawing. Heavy duty industrial grade type of lightning surge protection system is essential to prevent equipment from damage, degradation of components or parts as well as down time resulting from system disruption.
1.2 In view of the above, the superintending officer / consultant shall fully ensure and authorize that the protection system offered, strictly comply or fulfill the technical specification requirement.
1.3 The tenderer shall be required to submit catalogue and a schedule for the lightning and surge suppressor system indicating the type of installed suppressor and location to the consultant for approval. The tenderer is also required to provide upon request warranty certificates from the manufacturer or distributor. The consultant shall reserve the right to inspect the lightning and surge suppressor system at site.
2.0 TECHNICAL BACKUP, ENGINEERING SUPPORT AND TRACK RECORD
2.1 The supplier/local agent of the protection equipment shall be able to provide full technical and continuous engineering support in the event of any lightning/surge/power problems. As such it is mandatory that the local agent must have at least 10 years proven experience in the lightning and surge protection field or hold an agency/representation in lightning surge products for at least 10 years.
2.2 It also important that they must have qualified engineers, trained technician and appropriate laboratory to ensure that their products are compatibly matched with the power supply safety requirements, testing quality assurance certification and good & proven track record in tropical condition.
3.0 WARRANTY
3.1 As part of contract requirements, the local authorized agent must provide pre and post local authorized warranty or certification. As such, only genuine products with a local authorized distributor will be considered and all products offered must be provided with country of origin certification for originality marking and minimum 5 years spare part support. A letter of support from the manufacturer shall be submitted.
3.2 A warranty certificate shall be obtained from the local authorized agent stating clearly a full 2 year warranty against in both materials and workmanship defect.
3.3 A service warranty shall available for service and maintenance based on 6 months duration after handling over upon requested.
4.0 STANDARDS
4.1 All stages of equipment shall comply with the specifications. The suppressor units shall be tested in accordance to ANSI/IEEE C62.41, IEEE 587, VDE 0675, and IEC 61024-1/IEC 61312-1.
4.2 In meeting with Malaysia safety standards, the lightning surge protection devices shall also be tested by international laboratories that are recognized by the Electrical & Electronics Association of Malaysia and Energy Commission, JBEG.
5.0 ON-SITE TECHNICAL SUPPORT
5.1 Upon installation, the supplier/local agent shall be able to provide an on-site testing & commissioning to check the status of the installed suppressor units. The respective suppressor modules shall be checked using a dedicated suppressor tester where applicable, including visual inspection of suppressor type, location, etc...
5.2 In event of extreme lightning and surge discharges, a suppressor unit often sacrifices itself in protecting the equipment. An optional on-site warranty must be provided to monitor the condition of the suppressor units at regular intervals (not longer than 6 months). The respective suppressor modules shall be checked using a dedicated suppressor tester where applicable including visual inspection of the flag status.
6.0 PROTECTION REQUIREMENT
The protection system shall comprise of the following:-
6.1 Low Voltage (L.V.) System
1. Lightning Horn Surge Suppressor (LHSS-MDB)
(Cat 1 protection at MSB/EMSB)
2. Fine Surge Suppressor - Duplex (FSS-D/AG)
(Cat 2 protection at Genset AMF board)
3. Combined Lightning Surge Suppressor (CLSS)
(Cat 1&2 protection at Remote Building)
4. Fine Surge Suppressor (FSS-AG)
(Cat 2 protection at DB SSB)
5. Series Surge Suppressor (SSS)
(Cat 3 protection at incoming power for Critical/Sensitive Equipments)
6.2 Extra Low Voltage (E.L.V.) System
1. Telephony Surge Suppressor (TSS)
(Cat 4 protection for Telephony cables)
2. CXSS – Coaxial Surge Suppressor
(Cat 4 protection for MATV antenna cables)
3. DSS – Data-line Surge Suppressor
(Cat 4 protection for data/signal line cables)
6.3 Reliability of Equipment System
The Lighting Surge Protection Equipment shall be able to operate continuously up to maximum voltage of 275V per phase suitable with local electricity supply voltage variation.
6.4 Experience and Track Record
The products / protection devices offered shall have a proven track record of implementation / installation in projects of similar nature. Domestic or commercial type of products are not acceptable for critical application projects.
6.5 Factory Acceptance Test
In the event of schedule Factory Acceptance Test, the Lightning Surge Protection Equipment shall be fully integrated during the test of overall L.V. or E.L.V. system.
7.0 LOW VOLTAGE PROTECTION-CAT 1 AT MSB/EMSB
LIGHTNING HORN SURGE SUPPRESSOR-MDB (LHSS-MDB)
7.1 The Lightning Horn Surge Suppressor (LHSS-MDB) shall be a heavy-duty electronic controlled surface arrester unit utilizing the arc chopping principle to limit and discharge lightning surges.
7.2 The Lightning Horn Surge Suppressor (LHSS-MDB) unit shall be a single channel modular type mountable on standard DIN rails and of non-fusible elements capable of limiting surge voltages from indirect and direct lightning strikes and have a long service life.
7.3 The Lightning Horn Surge Suppressor (LHSS-MDB) unit shall be tested to withstand up to 50kA of 10/350us lightning waveform in accordance to latest revision of IEC 61024-1 and IEC 61312 standards.
7.4 The lightning gap unit (neutral to earth) shall also be tested to withstand up to 100kA of 10/350us lightning waveform and rated at 260V.
7.5 The LHSS-MDB unit shall conform to the following specifications:-
1. Nominal rated voltage - 240V AC per phase
2. Continuous rated voltage - 335V AC per phase
3. Maximum lightning current (as per IEC):
a. Phase Lightning suppressor
10/350us waveform - 50 kA per phase
b. Net follow current
self extinguishing at 400VAC - 50 kA
4. Neutral - Earth Lightning gap
10/350ms waveform - 100 kA
5. Voltage limitation at Max. lightning
current (50kA, 10/350ms) - < 900 V
6. Rated voltage - Lightning Gap - up to 260V
7. Response Time - < 1 us
8. Surface discharge arrester - Electronic Arc
Chopping Gap
9. Connection - ‘3 + 1’ configuration
suitable for TT-system.
10. Suppressor fuse - Non-welding type
11. Lightning Surge Monitoring (Optional)
a. Continuous line voltage monitoring - Yes
b. 8 mode suppressor fuse monitoring - Yes
c. Output signal for remote monitoring - Yes
d. Audible alarm signal - Yes (Optional)
8.0 LOW VOLTAGE PROTECTION-CAT 2 AT GENSET AMF BOARD
FINE SURGE SUPPRESSOR/DUPLEX (FSS-D/AG)
8.1 The Fine Surge Suppressor/Duplex (FSS-D/AG) unit shall be a rail mountable, modular two-piece construction type with base element and a protection plug suppressor suitable for protection of distribution boards and its loads.
8.2 The protection plug shall be equipped with a flag to indicate the status of the components and a remote warning contact shall also be integrated in the suppressor unit to act as a remote warning switch in the event of suppressor failure.
8.3 The Fine Surge Suppressor/Duplex (FSS-D/AG) unit shall be suitable for TT-system and configured to match installation option before and after Earth Fault device.
8.4 The FSS-D/AG unit shall conform to the following specifications:-
1. Phase to Neutral Fine Suppressor
a. Rated nominal voltage - 240V
b. Continuous rated voltage - 275V
c. Voltage limit at 5kA,8/20ms - < 1kV
d. Voltage limit at 20kA,8/20ms - < 1.35kV
e. Rated surge current - 40kA
2. Neutral to Earth Fine Suppressor
a. Rated voltage - 260V
b. Voltage limit at 5kA,8/20ms - < 150V
c. Voltage limit at 20kA,8/20ms - < 1kV
d. Rated surge current - 40kA
3. Phase to Phase Fine Suppressor
a. Rated voltage - 600V
b. Rated surge current - 30kA
4. Connection - ‘3 + 1’ configuration
suitable for TT-system
5. Suppressor fuse - Non-welding type
6. Suppressor Monitoring - 7 modules cum with 14
mode remote signaling.
9.0 LOW VOLTAGE PROTECTION-CAT 1 & 2 AT REMOTE BUILDING
COMBINED LIGHTNING SURGE SUPPRESSOR - CLSS
9.1 The combined lightning surge suppressor (CLSS) shall consist of combined lightning and surge protection modules, which are fully coordinated via active energy control to provide maximum protection against lightning and surges at LV service entrances and remote power units.
9.2 The lightning element of the combined lightning surge suppressor (CLSS) unit shall be electronically controlled and of heavy duty and non-degradable construction. It shall be configured based on multistage protection elements and suitable for TT network.
9.3 The lightning element of the combined lightning surge suppressor (CLSS) unit shall be a single channel modular type mountable on standard DIN rails and of non-fusible elements capable of limiting surge voltages from indirect and direct lightning strikes and have a long service life.
9.4 The surge element unit shall be a rail mountable, modular two-piece construction type with base element and a protection plug suppressor.
9.5 The surge protection plug shall be equipped with a flag to indicate the status of the components and a remote warning contact shall also be integrated in the suppressor unit to act as a remote warning switch in the event of suppressor failure.
9.6 The CLSS unit shall be specified to provide sufficient protection level and it shall conform to the following specification.
1. Nominal rated voltage: - 240V AC
2. Total Lightning Current Exposure: - >200kA of 10/350 us wave
3. Surge Rating per phase - 40kA of 8/20 us wave
4. Lightning Gap Rating per phase - 100kA of 10/350 us wave
5. Protection level on 10/350us - <900V
6. Connection - ‘3 + 1’ configuration
suitable for TT-system
7. Suppressor fuse - Non-welding type
8. Surge Suppressor Monitoring - Individual double-mode remote signaling.
10.0 LOW VOLTAGE PROTECTION – CAT 2 AT DB SSB
FINE SURGE SUPPRESSOR (FSS-AG)
10.1 The Fine Surge Suppressor (FSS-AG) unit shall be a rail mountable, modular two-piece construction type with base element and a protection plug suppressor suitable for protection of distribution boards and its loads.
10.2 The protection plug shall be equipped with a flag to indicate the status of the components and a remote warning contact shall also be integrated in the suppressor unit to act as a remote warning switch in the event of suppressor failure.
10.3 The Fine Surge Suppressor (FSS-AG) unit shall be suitable for TT-system and configured to match installation option before and after Earth Fault device.
10.4 The FSS-AG unit shall be specified to provide sufficient protection level and it shall conform to the following specification.
1. Phase to Neutral Fine Suppressor
a. Rated nominal voltage - 240V
b. Continuous rated voltage - 275V
b. Voltage limit at 5kA,8/20ms - < 1kV
c. Voltage limit at 20kA,8/20ms - < 1.35kV
d. Rated surge current - 40kA
2. Neutral to Earth Fine Suppressor
a. Rated voltage - 260V
b. Voltage limit at 5kA,8/20ms - < 150V
c. Voltage limit at 20kA,8/20ms - < 1kV
d. Rated surge current - 40kA
3. Connection - ‘3 + 1’ configuration
suitable for TT-system
4. Suppressor fuse - Non-welding type
5. Suppressor monitoring - 4 modules cum with 8
mode remote signaling
6. Intelligent remote signal/monitoring - Optional audio alarm &
over voltage limiter
disconnection signal.
11.0 LOW VOLATEGE PROTECTION – CAT 3 AT INCOMING CRITICAL/SENSITIVE EQUIPMENT
SERIES SURGE SUPPRESSOR (SSS)
Series Type Multistage Surge Suppression System
11.1 The series suppressor shall employ the Transient Tracking Technology multistage and multi-level suppression system to provide full time protection of the incoming power to sensitive equipment.
11.2 The main stage of the series suppressor shall be operated in a series connection with transient tracking control technologies for intelligent tracking and suppression for transients, spikes and noise along the sine wave.
11.3 Instant absorption and suppression of the transients shall be provided by a combination system of reliable series and shunt surge absorption components utilizing the high energy transient tracking control module.
11.4 It shall also be equipped with an output stage for bi-directional protection against internally generated transient and with an overall lower let through voltages.
11.5 EMI and RFI noise rejection modules can be incorporated into the three phase series suppressor system for units above 100A as per specification requirements or drawings.
11.6 The Series Surge Suppressor (SSS) shall have a total withstand capability in accordance with ANSI/IEEE C62.41 and complying with the following specifications:-
1. Response time - < 25 ns
2. Operating frequency - 50 - 60 Hz
3. Surge Attenuation - 40 dB / 60 dB
4. Bandwidth protection - 10kHz – 50Mhz
5. Surge exposure/ phase - 40kA, Maximum up to 140kA
6. Surge suppression system - Multistage & multilevel series,
in-corporate Transient
Tracking Technology
7. Performance - Bi-directional protection
8. Manufacturing standards - AS 3000
9. Construction - Metal clad or polycarbonate
enclosure
10.Overload safety protection - 5 x rated capacity for 1 sec.
11.Temperature Range - -40 to 60 deg C
12.Indicator Status - Yes
13.Power Meter (Optional) - Yes
14.Remote Monitoring Interphase - Yes
15.Bypass Feature (Optional) - Yes
11.7 The series surge suppressor (SSS) shall be suitably configured to
ensure that it operates effective with upstream Level 1 and Level 2 systems. The supplier shall / may be required to provide documentation / tests to prove that the various levels of protection are properly matched and compatible.
12.0 E.L.V SURGE PROTECTION - CAT 4 FOR TELEPHONY CABLES
TELEPHONY SURGE SUPPRESSOR (TSS)
12.1 The telephony surge suppressors (TSS) shall provide protection against line transients or over-voltages on all incoming STM as well as PABX incoming and outgoing extension lines as per specification drawing requirement.
12.2 They shall be of plug-in modular to telephone MDF Krone system and these plug-in modules shall permit on site repair without rewiring required.
12.3 The TSS units shall able to handle surge withstand capability of up to 10 kA with arresting time of less than 1 hs matches with the equipment criteria to suit its applications, such as frequency, operating voltage, impedance etc.
12.4 The TSS unit shall be complying with the following specification.
1. Protection pair - single pair protection per module
2. Maximum line voltage - 170 VDC
3. Protection level - 220 VDC tested at 5kA, 8/20us
4. Rated surge capacity - 10kA, 8/20us
5. Response time - <1 ns
6. Protection circuit - Multi stage MBB type
7. End of life - Short circuit
13.0 E.L.V PROTECTION - CAT 4 FOR COAXIAL CABLES
COAXIAL SURGE SUPPRESSOR (CXSS)
- For MATV Antenna Receiver Application
13.1 The coaxial surge suppressor shall be designed to provide protection against over voltage during lightning and electrical transients in the coaxial cables for MATV antenna systems.
13.2 It shall be suitable for protection of antenna system without introducing a large insertion loss into the system.
13.3 The coaxial surge suppressor shall have a surge withstand capability of 10kA and be fully operational up to frequencies of at least maximum up to 300MHz. It shall incorporate a sleek design with a wide range of connectors for easy and quick installation.
13.4 The CXSS unit shall be complying with the following specification;
1. Rated surge capacity - 10 kA (8/20us)
2. Frequency Range - up to 300 MHz
3. Insertion Loss at 300 MHz - < 0.5 dB
4. Insulation Resistance - > 1 GW
5. Residual Voltage - < 600 V (1kV/us)
6. Impedance - up to 75 ohms
7. Connection - suitable to equipment
8. Construction - Solid state in die cast aluminum
14.0 E.L.V PROTECTION - CAT 4 FOR SIGNAL COMMUNICATION CABLES
DATA-LINE SURGE SUPPRESSOR (DSS)
- For data lines, control signal lines and communications circuits
application.
14.1 The DSS unit shall provide protection against line transients or over-voltages sensitive and critical datalines, control signal and communications circuit as specified in drawings.
14.2 They shall be a series in-line protection type which shunt or parallel type of protectors are not acceptable.
14.3 The DSS units shall able to handle surge withstand capability of up to 10 kA with arresting time of less than 1ns matches with the equipment criteria to suit its applications, such as frequency, operating voltage, impedance etc.
14.4 The DSS units shall be of multi level protection designed and din-rail mounting construction and bi-directional protection system shall be provided as per design requirements.
14.5 The DSS units shall be complying with the following specification;
1. Rated surge capacity - 10 kA (8/20us)
2. Range of voltage - from 6 VDC to 170 VDC
3. Response time - < 1 ns
4. Maximum line current - up to 500mA
5. Construction - Din-rail mounted
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Showing posts with label Lightning protection. Show all posts
Showing posts with label Lightning protection. Show all posts
Tuesday, November 10, 2009
Thursday, October 29, 2009
Lightning protection specifications
The following provides some example specifications that can be used in a contract for the installation of the lightning protection system in a multi-storey office building.
General
The installation of the Lightning Protection must comply with the specifications below, and the information given in the accompanying drawings, but in any case must always be in accordance with the British Standard Code of Practice BS 6651: 1985 and to the satisfaction of the S.O.’s representative. All materials should conform to the latest edition of B.S. Specifications.
Air Termination
Materials for the air termination must be medium or hard drawn copper or phosphor bronze rod of at least 15mm in diameter.
The terminations shall project at least 460mm above the highest point of the building.
They shall be firmly and permanently fixed with saddles or brackets and protected from mechanical damage.
Roof conductors
Materials for the roof conductors must be high conductivity annealed copper tape with the dimensions of 25mm x 3mm.
The roof conductors shall interconnect all air terminations to all down conductors and form a conducting air termination network covering the area to be protected with closed metal loops.
All exposed metallic structures shall be bonded in a solid and permanent manner to the roof conductor network.
Care should be exercised to avoid corrosion by the bonding of dissimilar metals.
Ferrous metals should not be used.
All joints and conductors shall be protected against mechanical damage.
Roof conductor runs shall be as direct as possible with spacer bars or tape clips at two meter intervals.
Bends shall be made as large as possible and in any event the bending radius shall not be less than 150mm.
Down conductors
Materials for the down conductors shall be of high conductivity annealed copper tape with the dimensions of 25mm x 3mm.
Down conductors shall interconnect the roof conductor network to the earth termination.
The route shall not interfere with the architecture and shall as direct as possible.
The down conductors shall be firmly and permanently fixed to the outside of the building or structure with spacer bars or tape clips at one meter intervals.
All independent metallic structures and other building structures within 600mm of any down conductor route shall be bonded to the nearest down conductor.
Lift shafts and duct shafts shall not be used as down conductor routes.
There shall not be any “up-turn” for the down conductor routes.
Joints and bonds
All joints shall be tinned and soldered and double riveted.
Clamped, bolted and screwed joints shall not be used, except at testing points and at rod connections.
Joints or bonds shall be as few as possible. All joints shall be coated with bituminous paint and protected against moisture and corrosion.
The maximum resistance of a joint shall not exceed 0.5 miliohms.
Tape to tape bonding clamps shall be “Furse” type having tinned contact surfaces complete with 8mm phosphor bronze fixing screw.
Test and junction clamps
Materials for the clamps should be phosphor bronze.
Test clamps shall be provided on each down conductor in an easily accessible position for testing purposes at a height of 2000mm from finished ground level.
Test clamps shall be protected from unauthorized interference.
Test clamps shall be provided on the roof conductor network in such a way that all parts of the network can be tested independently.
The test clamps shall be of approved type and shall not constitute an electrical resistance within the system.
After installation and testing they shall be painted with bituminous paint to prevent corrosion.
Earth termination
Materials for the earth terminations shall be of hard drawn copper or phosphor bronze rod. The minimum diameter of the rod shall not be less than 16mm.
The diameter of the rod shall be chosen according to the site condition but it shall always be such that it can be driven into the soil without bending or deforming the rod. Proper driving head and coupling similar to “Furse” type shall be employed.
The length of the rods shall be made up from the standard 1200mm lengths with internal screws and socket joints.
Minimum lengths of earth driven electrodes shall be 2400mm.
The length or the number of rods shall be increased if the maximum permissible earth resistance of five ohms cannot be achieved with the standard electrodes as specified.
The distance between two driven electrodes shall be equal to or greater than their driven length.
When more than one down conductors are used and terminated at earth terminations, all earth rods shall be bonded together to form one network.
The lightning protection earthing shall not be used in whole or in part as part of electrical earthing without the approval of the S.O.
Chemical treatment of soil at termination points to decrease the earth resistance shall not be carried out without the approval of the S.O.
Connections to the earth electrodes shall be by means of approved connector clamps adequately tightened. Earth connections shall be protected from damage by means of suitable electrode housing. The actual connection of the rods must be accessible and clearly visible when the housing cover is removed.
Testing
Testing of earth resistance and conductor continuity shall be carried as specified in the British Standard Code of Practice BS 6651: 1985.
The test shall be carried out in the presence and to the satisfaction of the S.O.
The resultant earth resistance of the electrodes shall not exceed five ohms and this resistance value shall be determined by an Earth Resistance Megger.
Copyright http://electricalinstallationblog.blogspot.com/ - Lightning protection specifications
General
The installation of the Lightning Protection must comply with the specifications below, and the information given in the accompanying drawings, but in any case must always be in accordance with the British Standard Code of Practice BS 6651: 1985 and to the satisfaction of the S.O.’s representative. All materials should conform to the latest edition of B.S. Specifications.
Air Termination
Materials for the air termination must be medium or hard drawn copper or phosphor bronze rod of at least 15mm in diameter.
The terminations shall project at least 460mm above the highest point of the building.
They shall be firmly and permanently fixed with saddles or brackets and protected from mechanical damage.
Roof conductors
Materials for the roof conductors must be high conductivity annealed copper tape with the dimensions of 25mm x 3mm.
The roof conductors shall interconnect all air terminations to all down conductors and form a conducting air termination network covering the area to be protected with closed metal loops.
All exposed metallic structures shall be bonded in a solid and permanent manner to the roof conductor network.
Care should be exercised to avoid corrosion by the bonding of dissimilar metals.
Ferrous metals should not be used.
All joints and conductors shall be protected against mechanical damage.
Roof conductor runs shall be as direct as possible with spacer bars or tape clips at two meter intervals.
Bends shall be made as large as possible and in any event the bending radius shall not be less than 150mm.
Down conductors
Materials for the down conductors shall be of high conductivity annealed copper tape with the dimensions of 25mm x 3mm.
Down conductors shall interconnect the roof conductor network to the earth termination.
The route shall not interfere with the architecture and shall as direct as possible.
The down conductors shall be firmly and permanently fixed to the outside of the building or structure with spacer bars or tape clips at one meter intervals.
All independent metallic structures and other building structures within 600mm of any down conductor route shall be bonded to the nearest down conductor.
Lift shafts and duct shafts shall not be used as down conductor routes.
There shall not be any “up-turn” for the down conductor routes.
Joints and bonds
All joints shall be tinned and soldered and double riveted.
Clamped, bolted and screwed joints shall not be used, except at testing points and at rod connections.
Joints or bonds shall be as few as possible. All joints shall be coated with bituminous paint and protected against moisture and corrosion.
The maximum resistance of a joint shall not exceed 0.5 miliohms.
Tape to tape bonding clamps shall be “Furse” type having tinned contact surfaces complete with 8mm phosphor bronze fixing screw.
Test and junction clamps
Materials for the clamps should be phosphor bronze.
Test clamps shall be provided on each down conductor in an easily accessible position for testing purposes at a height of 2000mm from finished ground level.
Test clamps shall be protected from unauthorized interference.
Test clamps shall be provided on the roof conductor network in such a way that all parts of the network can be tested independently.
The test clamps shall be of approved type and shall not constitute an electrical resistance within the system.
After installation and testing they shall be painted with bituminous paint to prevent corrosion.
Earth termination
Materials for the earth terminations shall be of hard drawn copper or phosphor bronze rod. The minimum diameter of the rod shall not be less than 16mm.
The diameter of the rod shall be chosen according to the site condition but it shall always be such that it can be driven into the soil without bending or deforming the rod. Proper driving head and coupling similar to “Furse” type shall be employed.
The length of the rods shall be made up from the standard 1200mm lengths with internal screws and socket joints.
Minimum lengths of earth driven electrodes shall be 2400mm.
The length or the number of rods shall be increased if the maximum permissible earth resistance of five ohms cannot be achieved with the standard electrodes as specified.
The distance between two driven electrodes shall be equal to or greater than their driven length.
When more than one down conductors are used and terminated at earth terminations, all earth rods shall be bonded together to form one network.
The lightning protection earthing shall not be used in whole or in part as part of electrical earthing without the approval of the S.O.
Chemical treatment of soil at termination points to decrease the earth resistance shall not be carried out without the approval of the S.O.
Connections to the earth electrodes shall be by means of approved connector clamps adequately tightened. Earth connections shall be protected from damage by means of suitable electrode housing. The actual connection of the rods must be accessible and clearly visible when the housing cover is removed.
Testing
Testing of earth resistance and conductor continuity shall be carried as specified in the British Standard Code of Practice BS 6651: 1985.
The test shall be carried out in the presence and to the satisfaction of the S.O.
The resultant earth resistance of the electrodes shall not exceed five ohms and this resistance value shall be determined by an Earth Resistance Megger.
Copyright http://electricalinstallationblog.blogspot.com/ - Lightning protection specifications
Monday, July 6, 2009
Lightning Protection System: An Overview
From the outset, a lightning seems far removed from an electrical system. Yet the protection from lightning strikes and from the damages caused by surges due to lightning strikes is an integral part of any electrical installation.
Men since the ancient times believed that a lightning strike was a demonstration of God's power, which He used as a weapon to punish those who commit great sins on earth.
Whatever the truth is, men today has developed a far more advanced knowledge and technology with regard to the lightning strikes and their effects than their ancient ancestors. Yet throughout the world the lightning strikes cause countless fatalities and material damages. Either through ignorance or an insufficient understanding of the principles underlying the theory and the practice of lightning protection.
Seen from the perspective of a building structure, lightning protection generally consist of 3 sections: aerial conductor network, the down conductors, and the earthing system. By design, the function of the aerial conductor network is to present at the highest point of the structures an area that will attract the lightning strike away from other parts of the building. The current of the strike will then be routed down through the down conductors to the earth grounding rod at the ground level or the lowest level in multiple basement structures.
The purpose of the earthing part is to help dissipate the discharge of the 200 kilo-ampere electrical energy into the earth mass as quickly as possible. This is very critical to the performance of the whole system, because a lower rate of dissipation will expose a higher risk of injuries or fatalities due to gradient voltage. Also damage to properties from flashover to ungrounded nearby metal parts.
Aerial Conductor Network
The aerial conductor network is designed to basically attract the lightning strikes. It is supposed to be where the lightning will strike when they attack a building structure. Therefore the aerial conductor network must be installed at the highest floor of the building structure.
Basically the intention is to create a network of conductors so that no point on the roof is more than five meters away from the nearest conductor of the network. Where a structure is raised above the roof level of a building (eg. lift motor room) then that part of the structure shall have their own aerial network conductor which shall be properly bonded to the overall buildings lightning protection scheme.
With the popularity of the new technology of lightweight all-metal roofing system, questions often arises whether the whole metal roofing system can be bonded to and form part of the lightning protection system without the need for a separate aerial conductor network.
Theoretically "Yes", these metal roofing system scan be used as the aerial conductor network and they have been practically installed to also serve that puspose for a while. Even though in many cases the aerial conductor network are still installed as a precaution.
However the development in the metal roofing system has resuled in the use of very thin roofing sheets that they require some form of metal parts to hold them together and to the roof structure. The effect is basically a complete isolation of a sheet fro the adjacent one, and to the roof structure. In these cases it is absolutely necesary to install a separate aerial conductor network.
Down conductors
The down conductor carries the 200kA electrical surge straight down to the earth mass. Due to the magnitude and the extremely steep front of the electrical surge, the current must be carried to the ground by the shortest possible route. Failure to do so will increase considerable the risk of side flashover.
The down conductor should be arranged to spread as uniformly as possible around the perimeter of the building at approximately 20 m spacing. They must follow the most direct path to the ground with a minimum number of bends. In difficult situations like at parapet walls, a loop-around turn must be avoided to prevent flashover. At 1.5 meter above ground, a test point must be provided at each down conductor. Here a bimetallic connector must also be installed if aluminum is used as the down conductor and the conductor below the test point to earth is copper.
Below the 1.5m test points, until terminations at the earth terminals inside the earth chambers, the down conductors must be installed inside a PVC pipe to protect it from the effects of corrosion and damage. Also to prevent a person or other metal parts from touching the conductors during lightning strike.
Copper used to be the conductor of choice for the whole lightning protection system including the down conductor in this country. But in the last ten years many engineers turn to aluminum for all parts above the test points. Parts of the reasons are the rising cost of copper materials. The other reason is vandalism. The vandalism factor is highly dangerous to the integrity of a lightning protection. This is due to the fact that it operates in silence and it is generally maintenance-free. A missing part at a few down conductors may not be noticed until the damages have been done.
This brings us to the very reason a lightning protection system must be regularly inspected. It will also ensure i is providing optimum protection. This will also check if there are other metal works within the flashover distance that is not properly bonded to the system.
Earth electrodes
The down conductors are routed along the most direct path to the ground and terminates to the lightning protection earthing system. These earthing systems usually steel reinforced copper rod half an inch in diameter, and driven a few feet deep into the ground.
Other methods are also used instead of the deep driven steel rods to provide the best possible contact with the earth mass. The choice depends on the prevailing ground conditions: the soils resistivity and the soil moisture content.In urban areas, a few earth rods are installed first and their combined resistance is measured. More rods are driven and connected until the 10-ohm requirement is met. However in locations away from recent developments, the soil conditions are not known. So the soil resistivity tests must be carried out to determine the earthing method most suitable and the extent of the work required.
At times when the soil is sitting on rocky subsoil below ground, a hole has to be drilled down 100 m or more and a long copper rod inserted deep into the hole to get the 10-ohm requirement. In more extreme cases, even this is not enough and soil conditioning agents like Bentonite or conductive cement need to be used. These compounds are prepared as a slurry or mix, and poured down the vertically drilled hole, creating a lower resistance between the embedded copper earth electrode and the surrounding soil.
The performance of a lightning protection is only as good as it weakest link. Any weakness along the flow path of the surge from the aerial conductor network down to the earth chamber can cause a side flashover to the building structure. A flashover means the surge current has taken an un-controllable path to the ground, causing damage to properties and possibly injuring persons along the way.Therefore it is vital that a lightning protection system is inspected properly and regularly. Recording of the tests must be done according to the latest international standards.
By the very nature of lightning strikes, no international standard can guarantee a total protection from their strikes. However, by obeying the latest international standards, we can ensure that the risk of damage and danger to human lives has been reduced to minimal.
Men since the ancient times believed that a lightning strike was a demonstration of God's power, which He used as a weapon to punish those who commit great sins on earth.
Whatever the truth is, men today has developed a far more advanced knowledge and technology with regard to the lightning strikes and their effects than their ancient ancestors. Yet throughout the world the lightning strikes cause countless fatalities and material damages. Either through ignorance or an insufficient understanding of the principles underlying the theory and the practice of lightning protection.
Seen from the perspective of a building structure, lightning protection generally consist of 3 sections: aerial conductor network, the down conductors, and the earthing system. By design, the function of the aerial conductor network is to present at the highest point of the structures an area that will attract the lightning strike away from other parts of the building. The current of the strike will then be routed down through the down conductors to the earth grounding rod at the ground level or the lowest level in multiple basement structures.
The purpose of the earthing part is to help dissipate the discharge of the 200 kilo-ampere electrical energy into the earth mass as quickly as possible. This is very critical to the performance of the whole system, because a lower rate of dissipation will expose a higher risk of injuries or fatalities due to gradient voltage. Also damage to properties from flashover to ungrounded nearby metal parts.
Aerial Conductor Network
The aerial conductor network is designed to basically attract the lightning strikes. It is supposed to be where the lightning will strike when they attack a building structure. Therefore the aerial conductor network must be installed at the highest floor of the building structure.
Basically the intention is to create a network of conductors so that no point on the roof is more than five meters away from the nearest conductor of the network. Where a structure is raised above the roof level of a building (eg. lift motor room) then that part of the structure shall have their own aerial network conductor which shall be properly bonded to the overall buildings lightning protection scheme.
With the popularity of the new technology of lightweight all-metal roofing system, questions often arises whether the whole metal roofing system can be bonded to and form part of the lightning protection system without the need for a separate aerial conductor network.
Theoretically "Yes", these metal roofing system scan be used as the aerial conductor network and they have been practically installed to also serve that puspose for a while. Even though in many cases the aerial conductor network are still installed as a precaution.
However the development in the metal roofing system has resuled in the use of very thin roofing sheets that they require some form of metal parts to hold them together and to the roof structure. The effect is basically a complete isolation of a sheet fro the adjacent one, and to the roof structure. In these cases it is absolutely necesary to install a separate aerial conductor network.
Down conductors
The down conductor carries the 200kA electrical surge straight down to the earth mass. Due to the magnitude and the extremely steep front of the electrical surge, the current must be carried to the ground by the shortest possible route. Failure to do so will increase considerable the risk of side flashover.
The down conductor should be arranged to spread as uniformly as possible around the perimeter of the building at approximately 20 m spacing. They must follow the most direct path to the ground with a minimum number of bends. In difficult situations like at parapet walls, a loop-around turn must be avoided to prevent flashover. At 1.5 meter above ground, a test point must be provided at each down conductor. Here a bimetallic connector must also be installed if aluminum is used as the down conductor and the conductor below the test point to earth is copper.
Below the 1.5m test points, until terminations at the earth terminals inside the earth chambers, the down conductors must be installed inside a PVC pipe to protect it from the effects of corrosion and damage. Also to prevent a person or other metal parts from touching the conductors during lightning strike.
Copper used to be the conductor of choice for the whole lightning protection system including the down conductor in this country. But in the last ten years many engineers turn to aluminum for all parts above the test points. Parts of the reasons are the rising cost of copper materials. The other reason is vandalism. The vandalism factor is highly dangerous to the integrity of a lightning protection. This is due to the fact that it operates in silence and it is generally maintenance-free. A missing part at a few down conductors may not be noticed until the damages have been done.
This brings us to the very reason a lightning protection system must be regularly inspected. It will also ensure i is providing optimum protection. This will also check if there are other metal works within the flashover distance that is not properly bonded to the system.
Earth electrodes
The down conductors are routed along the most direct path to the ground and terminates to the lightning protection earthing system. These earthing systems usually steel reinforced copper rod half an inch in diameter, and driven a few feet deep into the ground.
Other methods are also used instead of the deep driven steel rods to provide the best possible contact with the earth mass. The choice depends on the prevailing ground conditions: the soils resistivity and the soil moisture content.In urban areas, a few earth rods are installed first and their combined resistance is measured. More rods are driven and connected until the 10-ohm requirement is met. However in locations away from recent developments, the soil conditions are not known. So the soil resistivity tests must be carried out to determine the earthing method most suitable and the extent of the work required.
At times when the soil is sitting on rocky subsoil below ground, a hole has to be drilled down 100 m or more and a long copper rod inserted deep into the hole to get the 10-ohm requirement. In more extreme cases, even this is not enough and soil conditioning agents like Bentonite or conductive cement need to be used. These compounds are prepared as a slurry or mix, and poured down the vertically drilled hole, creating a lower resistance between the embedded copper earth electrode and the surrounding soil.
The performance of a lightning protection is only as good as it weakest link. Any weakness along the flow path of the surge from the aerial conductor network down to the earth chamber can cause a side flashover to the building structure. A flashover means the surge current has taken an un-controllable path to the ground, causing damage to properties and possibly injuring persons along the way.Therefore it is vital that a lightning protection system is inspected properly and regularly. Recording of the tests must be done according to the latest international standards.
By the very nature of lightning strikes, no international standard can guarantee a total protection from their strikes. However, by obeying the latest international standards, we can ensure that the risk of damage and danger to human lives has been reduced to minimal.
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