ABB Excount II User Manual page 60

6. Surge arrester monitoring theory
60
By means of the EXCOUNT-II software, the total leakage, field probe
current and surge counting data are analyzed and presented for
each arrester. The resistive leakage current level (optional) is calcu-
lated in two steps: First, the resistive third harmonic of the arrester
resistive leakage current, with compensation for the third harmonic in
the voltage, is determined by the equation below (for a three-phase
horizontal installation). For a detailed explanation of the equation and
its basis, see [2]. Secondly, the resistive leakage current is determi-
ned from the resistive third harmonic current by means of information
supplied by the arrester manufacturer.
The ratio of the total resistive leakage current to the third harmonic
current depends on the operating voltage stress (the operating voltage
divided by the rated voltage) and the arrester temperature (in practice,
the ambient temperature). These parameters are therefore recorded
at the time of the total leakage current and field probe current measu-
rements. The ambient temperature is automatically measured by the
sensor, while the operating voltage is entered into the transceiver at the
time of the total leakage current and field probe measurement.
Resistive leakage current information from the
surge arrester manufacturer
The information from the arrester manufacturer is given in accordance
with IEC 60099-5 [1] for each arrester type. All ABB type arresters are
included in the EXCOUNT-II software to allow measurements of resis-
tive leakage currents. To be ably to correctly calculate the resistive lea-
kage current for non-ABB type of arresters the characteristics of that
type must be added to the data base. Please contact your ABB office
for further information. The manufacturer's information comprises:
• Maximum recommended levels of total resistive leakage current and
resistive third harmonic current at a specified voltage stress (U/Ur =
0,7) and a specified ambient temperature (+20°C). These conditions
are referred to as "standard operating conditions".
Figure 6.3.6
1HSA 801 080-15en EXCOUNT-II Users Manual