ISA T 2000 - Page 104

DOC. MIE11110 Rev. 5
Page
104
of
110
If there are two parallel lines, it is important to measure the
mutual factor, that is taken into account with KE in case of
ground fault. Defining line 1 the one with the fault, and line 2 the
parallel line, the computation formula is the following.
Where:
. VF is the voltage on line 2;
. Beta is the matching parameter.
In our test we open line 1, so that I1 = 0, inject a current into line
2, and measure VF, that is:
From which we compute:
1
*IZ
V
L
F
=β
Note that ZL has already been measured. The connection
schematic is the following.
(
)
pELF
IIKIZV
211
*** β++=
pLF
IZV
2
**β=