ABB Excount II User Manual page 58

6. Surge arrester monitoring theory
58
Leakage current measurements with EXCOUNT-II
When the EXCOUNT-II is optionally equipped for measurement of
resistive leakage currents, the measurement is based on third har-
monic analysis of the total leakage current with compensation for the
third harmonic in the system voltage. The compensation is performed
by simultaneous measurements of both the total leakage current of
the arrester and the current induced in a field probe, the latter being
proportional to the harmonic content in the system voltage.
The principle for measurement of the resistive leakage current with the
EXCOUNT-II is the same as for the original leakage current monitor,
LCM, developed by ABB Switchgear and TransiNor, and described in
detail in [2].
The procedure for total leakage current and field probe current
measurements with EXCOUNT-II is presented step-by-step in the fol-
lowing:
Zero-flux current
transformer
Internal parts of the EXCOUNT-II sensor
Figure 6.3.4
1HSA 801 080-15en EXCOUNT-II Users Manual
Field probe