User Manual

EI-162BN
Users Manual
8
Determining Transformation Ratio Connections
Before you connect the Transformer to the Tester, you need to determine a
suitable transformation ratio for the minimum measuring and maximum
parasitic currents expected to flow through the transmission line pylon.
The Transformer has 1000 windings, with connections at winding ratios of
1000, 500, 200 and 0 (⊥). Depending on the combination of connections used,
the Transformer can provide transformation ratios of 1:1000, 1:800, 1:500,
1:300, and 1:200.
See Table 2 to determine a suitable transformation ratio for the expected
minimum measuring and maximum parasitic currents, and then see Figure 3
for the Transformer connections that will provide that ratio. These connections
will be used for connecting the Transformer to the Tester’s Ajack.
Note
Be sure to adjust your earth ground tester to the selected
transformation ratio.
Table 2. Transformation Ratios
Ratio
Current
1:1000
[1]
1:800 1:500 1:300 1:200
Min. Measuring
Current
[2]
0.50 mA 0.40 mA 0.25 mA 0.15 mA 0.10 mA
Max. Parasitic
Current
[3]
3.0 A 2.4 A 1.5 A 0.9 A 0.6 A
[1]
For nearly all selective earth ground resistance measurements, a ratio of
1:1000 is recommended
[2]
At 94, 105, 111, and 128 Hz
[3]
At 50, 60 and 16-2/3 Hz