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Cell Sites Protection From Ground Potential Rise (GPR)
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Lightning and Grounding Course
………… Introduction
………… Lightning and Ground Potential Rise (GPR)
………… Materials and Grounding Kits
………… Types of Wires
………… Grounding Systems
………… Ground Testing
………… Protection & Safety Measures
CONTENTS
INTRODUCTION
The term "ground" refers to a current return path through the earth.
The earth was an electrically neutral body, i.e. an equal number of negative and positive charges are distributed throughout the earth at any given time.
Earth is considered to be at zero potential.
A true earth ground physically consists of a conductive pipe or rod driven into the earth to a minimum depth of 6 feet.
The electrical symbol for Ground is:
Grounding is protection for both human & equipment .
Lightning:
Current ………………… approximately 9kA to 400kA
Frequency ……………... approximately dc to 1MHz
Ground Potential Rise (GPR):
The voltage that develops on a grounding system from electrical current flowing through the impedance of that grounding system. One source of
this current is from lightning discharging down into the grounding system.
Lightning GPR:
A minimum voltage of approximately 7.5kV in the earth at the point of a 30kA lightning strike.
Lightning and GPR Studies
Materials and Grounding Kits
Typical Dimensions are :1. 5mm X 100mm X 300mm 2. 5mm X 100mm X 400mm
Internal Ground Bar (IGB) and External Ground Bar (EGB).
Tightening Pin, Nuts & Bolts
1X16 Sqmm Grounding cable, with copper lug along with Nut Bolt Washer assembly.
Grounding kit is used to divert Trans electric current from lightning of the transmission line to an earth grounding system to prevent damage to cable & radio equipment.
Grounding Rod
Grounding Kit
Aluminum Foil
Paper Foil (Grease-proof / Water-proof / Heat-proof)
Drill MachineToll Box
Measuring Tape
Terminals Earth Cable
Earth Strip Roll
Crimping Tool
Terminal Block
Copper Clamp
Tools & Earthing Components
HacksawEarth Shield
GreaseAluminum Foil
Different Sizes for Single Core Earth Cable
16MM G/Y EARTH CABLE
25MM G/Y EARTH CABLE
35MM G/Y EARTH CABLE
50MM G/Y EARTH CABLE
70MM G/Y EARTH CABLE
95MM G/Y EARTH CABLE
Earth Meter & Accessories
Earth Meter 4105A
Grounding Wires
A ground wire is a wire that is literally connected to the earth. This wire acts as a backup wire in case a neutral wire fails.
Ground wires are usually green or yellow in color in order to differentiate between neutral wires and hot wires. Thus, it is easy to discern a ground wire from other wires.
At least two of the main foots of tower should be ground with 35 mm Grounding cable.
Each of the grounding cables of equipments should be connected to the IGBSeparately and should be in on piece.
The equipments and metal structures should be connected to the IGB with a 25mm cable directed to the IGB with a PVC cover .
For battery rack 35mm grounding cable should be used.
Grounding Systems
There are three Grounding systems implemented on the BTS sites :
Grounding system for Lightning protection
Grounding system for protecting Feeders
Grounding system for protecting Tower, Shelter and Equipment
In BTS sites it‘s necessary to have ground impedance less then 1 Ohms.
Ground Testing
After implementing the grounding and connecting it to the ground bar the impedance should be checked & tested with Earth Tester to make sure it is less than 1 Ώ. A Priscian Digital Earth tester is capable of measuring Earth Voltage drawn by the system.
Grounding Protection and Safety
Safety measures at the cell sites can be acknowledge by installing Surge Protection Arrestor units in the electrical circuit
The Earth connections should always tightened by nuts & bolts, and proper grease should be applied
Earth Points should be kept wet so that the earth pit can behave more properly
Tower Arrestor Rod should be connected to the system so that system be protected in case of lightning and raining period.
16
Thank You
