MI 3290 Earth Analyser
Tests and Measurements
108
11.8 Pylon Ground Wire Test (PGWT)
11.8.1 PGWT Measurement
The PGWT measurement is performed to check the overhead grounding wire connection.
E a r t h
Z
e2
/1
R
c
tower 1
Z
e1
/1
F2
F1
Flex clamp
tower 2
Z
e2
/2
Z
e1
/2
ne
x
to
w
er
overhead grounding wire
Ig_w
H
E
MI 3290 Earth Analyser
G
A
H - auxiliary
earth rod
Ig_w
Ig
_w
fset
If2
If1
Igen
Ig
en
Figure 11.83: Pylon Grounde Wire Test (PGWT) example
During the measurement a sinusoidal current
I
gen
is injected into the earth through an
auxiliary probe (H). The resistance of the auxiliary probe (H) should be as low as possible in
order to inject a high test current. The resistance
R
c
can be decreased by using more probes
in parallel. A higher injected current improves the immunity against spurious earth currents.
In the example following current
I
g_w
is measured according to following equation:
𝐼
𝑔_𝑤
= 𝐼
𝑔𝑒𝑛
[
mA
] − 𝐼
𝑓_𝑠𝑢𝑚
[
mA
] = [
mA
]
𝐼
𝑓_𝑠𝑢𝑚
= 𝐼
𝑓1
[
mA
] + 𝐼
𝑓2
[
mA
] = [
mA
]
where:
I
g_w
.................................... Overhead ground wire current
I
gen
..................................... Generator current (injected test current)
I
f_sum
.................................. Total flex clamp current
