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MATERIAL FOR GROUNDING SYSTEMS:
Grounding conductors or electrodes installed underground or above ground must conform to certain minimum dimensions for mechanical strength and to wistand possible corrosive degradation.
Some of the basic characteristic of cable used for grounding application are sumarized as follow:
a.- Bare Copper: Very durable above or underground.
b.- Coated Copper:
b.1 Tin or zinc coated: From the electrochemical stand point, the performance is very durable for underground application. Is comparable with bare copper.
b.2 Lead sheath: This provide a good protective layer for underground installation in normal soils. However,is not recommended in a strong alkaline soils with pH >10.
c.- Steel:Steel along is not recommended since can be corroded in normal environmental conditions.
c.1 Hot galvanized: Very durable in almost all kind of soil. Can be used as foundation electrodes, earth conductor embedded in concrete,equipotential bonding conductors and lightning conductor leads of galvanized steel can be connected to reinforcing steel if the junction points are not exposed to prolonged temperature > 40C
c.2 Steel Clad: Aluminum-Covered Steel (ALUMOWELD or similar) has comparable corrosion resistance to aluminum, one third the conductivity, and eight times the strengh approximatelly. Is suitable for overhead shield wire. However, is not recommended in underground installation. The aluminum covering must be protected from scraches and other physical damages.
c.3 Copper-Covered Steel (COPPERWELD or similar) is available in 40 % or 30% conductivity. Dead soft Annealed copper clad made it suitable for grounding conductor in substation ground grid, pole ground wire and counterpoise. Aluminum: Is not recommended for underground installations.
The NESC (250-92) and the NEC (93E5, note 1) do not permit it use in direct contact with the earth or masonry or where to subject to corrosive conditions. Where used outside, aluminum or aluminum clad shall be installed within 18 inches of the earth in minimum size of # 6 AWG.
DIN (German )standard accept ground aluminum conductor above ground for a minimum size of 32 mm^2 (~ #2 AWG).
The fusing of a conductor under short circuit stress may be estimated as follow:
Area Conductor = Fault currentx Conductor ConstantxSQRT(Duration of SC).
The conductor constant is available from the manufacturer. I do have several values that could be good for preliminary consideration that I will gald to share if you should be interested. The fault current is the max. design current that the conductor will carry and the time may be the time of the protective device clearing time.
Grounding conductors or electrodes installed underground or above ground must conform to certain minimum dimensions for mechanical strength and to wistand possible corrosive degradation.
Some of the basic characteristic of cable used for grounding application are sumarized as follow:
a.- Bare Copper: Very durable above or underground.
b.- Coated Copper:
b.1 Tin or zinc coated: From the electrochemical stand point, the performance is very durable for underground application. Is comparable with bare copper.
b.2 Lead sheath: This provide a good protective layer for underground installation in normal soils. However,is not recommended in a strong alkaline soils with pH >10.
c.- Steel:Steel along is not recommended since can be corroded in normal environmental conditions.
c.1 Hot galvanized: Very durable in almost all kind of soil. Can be used as foundation electrodes, earth conductor embedded in concrete,equipotential bonding conductors and lightning conductor leads of galvanized steel can be connected to reinforcing steel if the junction points are not exposed to prolonged temperature > 40C
c.2 Steel Clad: Aluminum-Covered Steel (ALUMOWELD or similar) has comparable corrosion resistance to aluminum, one third the conductivity, and eight times the strengh approximatelly. Is suitable for overhead shield wire. However, is not recommended in underground installation. The aluminum covering must be protected from scraches and other physical damages.
c.3 Copper-Covered Steel (COPPERWELD or similar) is available in 40 % or 30% conductivity. Dead soft Annealed copper clad made it suitable for grounding conductor in substation ground grid, pole ground wire and counterpoise. Aluminum: Is not recommended for underground installations.
The NESC (250-92) and the NEC (93E5, note 1) do not permit it use in direct contact with the earth or masonry or where to subject to corrosive conditions. Where used outside, aluminum or aluminum clad shall be installed within 18 inches of the earth in minimum size of # 6 AWG.
DIN (German )standard accept ground aluminum conductor above ground for a minimum size of 32 mm^2 (~ #2 AWG).
The fusing of a conductor under short circuit stress may be estimated as follow:
Area Conductor = Fault currentx Conductor ConstantxSQRT(Duration of SC).
The conductor constant is available from the manufacturer. I do have several values that could be good for preliminary consideration that I will gald to share if you should be interested. The fault current is the max. design current that the conductor will carry and the time may be the time of the protective device clearing time.
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