MI 3152(H)
Eurotest
XC (2,5 kV)
Tests and measurements
144
Insulation resistance between L2-PE is decreased automatically according to limit
value
*)
every time interval selected with timer. To speed up the test press the
or
keys until IMD alarms an insulation failure for L2.
Press the
or the
key.
If IMD switches off voltage supply, instrument automatically proceeds to the
PASS / FAIL / NO STATUS indication.
Use
to select PASS / FAIL / NO STATUS indication.
Press
or the
key to confirm selection and complete the
measurement.
Save results (optional).
*)
When MANUAL R or AUTO R sub-function is selected, starting value of insulation resistance
is determined by
𝑅
𝑆𝑇𝐴𝑅𝑇
≅ 1.5 × 𝑅
𝐿𝐼𝑀𝐼𝑇
.
When MANUAL I or AUTO I sub-function is selected, starting value of insulation resistance is
determined by
𝑅
𝑆𝑇𝐴𝑅𝑇
≅ 1.5 ×
𝑈
𝐿1−𝐿2
𝐼
𝐿𝐼𝑀𝐼𝑇
Figure 7.77: Examples of IMD test result
Test results / sub-results
R1
Threshold insulation resistance between L1-PE
I1
Calculated first fault leakage current for R1
R2
Threshold insulation resistance between L2-PE
I2
Calculated first fault leakage current for R2
Calculated first fault leakage current at threshold insulation resistance is given as
𝐼
1(2)
=
𝑈
𝐿1−𝐿2
𝑅
1(2)
,
where U
L1-L2
is line-line voltage. The calculated first fault current is the maximum current that
would flow when insulation resistance decreases to the same value as the applied test
resistance, and a first fault is assumed between opposite line and PE.
