The primary reason for the use of surge counters on modern gapless MO arresters is to check if a particular transmission line or phase suffers from an exceptionally high number of overvoltages leading to arrester operation — lightning faults on a line, for example. If this is the case, while it validates the need for the arresters, use of some preventative counter-measures may be warranted to limit the number of surges. A sudden increase in the counting rate may also indicate an internal arrester fault, in which case the arrester should be investigated further.
Surge counters can be complimented with the facility to mea¬sure leakage currents (total and/or resistive), with the intention of monitoring and diagnosing the condition of the arrester and its state of fitness for continued service. However it is impor¬tant to understand the validity of the information provided. It is generally recognized that the only reliable indicator for the condition of a gapless arrester that can be assessed during normal service is to measure the resistive component of the leakage current (or estimate it from the 3rd harmonic). This obtained value can then be compared with the maximum allowable resistive current as given by the manufacturer under those particular prevailing service conditions.
High Voltage Products
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