ABB EXCOUNT-II, Руководство пользователя

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1HSA 801 080-15en EXCOUNT-II Users Manual
6. Surge arrester monitoring theory
6.1 Introduction
The rising demands for improved reliability of power supply and
reduced maintenance costs have increased the attention on condi-
tion monitoring of equipment in HV substations. As far as metal-oxide
surge arresters are concerned, there are two important aspects which
are related to the reliability of the arresters:
• The stress on the arrester in terms of the intensity
and frequency of impulse currents
• The condition of the arrester in terms of its insulating
properties in normal service
The first aspect is addressed by performing continuous surge coun-
ting and the second by leakage current measurements on regular
basis.
The EXCOUNT-II is designed to handle both surge counting and
leakage current measurements in a single monitoring system. The
EXCOUNT-II system comprises a sensor, permanently mounted at the
base of the arrester, a transceiver for wireless communication with the
sensor, and proprietary software installed on a personal computer.
In the following, the bases for surge counting and leakage current
measurements are described, and the corresponding functions of the
EXCOUNT-II are presented. For general information on various diag-
nostic methods for metal-oxide arresters, please refer to IEC 60099-5.
6.2 Surge counting
General
The primary aim of a surge counter is to give an indication of the
stress on the arrester from impulse currents caused by overvoltages.
In addition, surge counters may be helpful in analysing the occur-
rences of overvoltages on the system, provided the surge counting
information is sufficiently detailed.
Surge counting with EXCOUNT-II
Surge counters operate at impulse currents above a certain ampli-
tude. The EXCOUNT-II sensor is equipped with an impulse current