ETL 1110-9-10(FR)

5 Jan 91

acceptable. As the required current increases, the total

resistance should be reduced. See table 3-10.

is

calculated in different ways according to the type of anode

installation. The anode-to-electrolyte resistance for a

single anode is given by RA.

For a single vertical anode:

RA =

(0.0052)

[ln (8L/d)-1]

(eq 1-4)

(L)

Where

RA is the anode-to-electrolyte resistance for a

single anode, * p *is the electrolyte resistivity in ohm-cm,

L is the length of the backfill column in feet, and d is

the diameter of the backfill column in feet.

It should be noted that the anode dimensions are the over-

all length and diameter including backfill, if the backfill

is coke breeze and is not significantly more than 2 ft

longer than the anode or not significantly more than 20 ft

longer than the anode column in a deep vertical groundbed

configuration.

For earth backfill, the backfill column

dimensions should be the dimensions of the manufacturer's

standard packaged anode can. Bare ceramic anodes shall not

be installed in ground without coke breeze backfill. Coke

breeze allows venting of gases and effectively reduces RA.

If vertical anode dimensions are assumed to be 6 in. in

diameter and 8 ft in length, the following empirical

relations may be used:

(eq 1-5)

RA =

398

If the anode dimensions are different, a different empiri-

cal relation may be used:

RA =

(eq 1-6)

L

where RA is the anode-to-electrolyte resistance, *p *is the

electrolyte resistivity in ohm-cm, L is the length of the

backfill column in feet, and K is a shape function that is

selected from table 3-4.

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