ABB Excount II User Manual page 41

4. Using the transceiver
4.9.1 Tower and Gantry layout
Experience has shown that specific special configurations, arrangements,
locations, geography etc can affect the robustness of the performance
of EXCOUNT-II. For this reason, it is strongly recommend undertaking a
field trial prior to full-scale installation. Since many factors are inter-related,
a simple trial made at the base of the transmission tower or gantry may
not be adequate to guarantee performance when mounted in service.
Instead, what is preferred is a trial with sensors fitted on a 3-phase set
of arresters mounted on each different tower/gantry configuration under
consideration. Communication should be checked both with the line de-
energized and energized. The final functionality at a given location with a
specific special configuration can then be determined.
As a further consideration, whilst the use of the external antenna may
assist in achieving effective communication, the tower/gantry layout and
configuration can affect the ultimate accuracy of the resistive leakage
current measurements (if available), since the positioning of the surge
arresters in relation to each other may alter the field-strength factor based
in the measuring principle (refer section 6). See figure 4.9.2 for example.
In such cases, the measured values must be treated subjectively. Nevert-
heless, absolute values are of lesser interest, since a rising trend gives a
better indication of potential arrester deterioration over time.
Figure 4.9.2
Example of vertical tower arrangement (double circuit)
41
1HSA 801 080-15en EXCOUNT-II Users Manual