The AT-100 is a two stick, live line tester designed to test disconnected lightning arresters prior to energising them on a power distribution system. The tester is designed to warn the user that an arrester is damaged or deteriorating and should not be energised.
The AT-100 tests lightning arresters with high voltage DC. The high voltage DC is equal to the peak AC voltage; for example, on a 15kV system with a phase to earth voltage of 7200V, the AT-100 DC test voltage is about 10kV. The tester measures and displays the arrester DC leakage current. It is rated for use on systems from 4kV (2.4kV phase to earth) up to 25kV (15.2kV phase to earth). The instrument can be used on systems up to 69kV (40kV phase to earth) with the addition of the optional R-69 add-on resistor stick pair. The AT-100 can be used on 50Hz and 60Hz systems.
For overhead arresters two different test connections are possible. First, with the arrester earthed, the AT-100 is connected between an energised phase and the top electrode of the arrester.
Secondly, with the arrester connected directly to an energised phase the AT-100 is connected between the bottom electrode of the arrester and earth. The meter displays DC leakage current, if any.
Arresters with leakage currents greater than 20 microamps are classified as high leakage and should not be energised.
The AT-100 Lightning Arrester & Leakage Tester can be used as a general purpose DC high potential tester for testing the leakage current of devices other than arresters such as insulators, open switch contacts, crossarms, etc. Testing with DC minimises the much higher AC capacitive current and allows the user to test for actual DC leakage current.