ITU-T Recommendations

Recommendation ITU-T K.65 specifies the overvoltage requirements and test procedures for termination modules, with contacts for test ports or surge protective devices (SPDs), used for symmetric pair conductors subjected to overvoltages and overcurrents.

Overvoltages or overcurrents covered by this Recommendation include surges due to lightning on or near the line plant, short-term induction of alternating voltages from adjacent power lines or railway systems, earth potential rise due to power faults, and direct contacts between telecommunication lines and power lines.

Major changes compared with the 2004 version of this Recommendation include:
– the addition of a mains contact test to the equipment side of a module with series elements;
– a reduction of the current magnitude for test Figure C.2 and for the customer side test for test Figure C.3 (tests 2.2 and 2.3);
– a revision of Figure E.1 – 10/350 µs current generator to be in line with Recommendation ITU-T K.44, Figure II.4-1 – 10/350 µs current surge generator;
– the addition of information on the use of fail-safes;
– the addition of a coordination test, for modules with series elements, to check that surges under the firing voltage of the gas discharge tube (GDT) will not damage the series elements;
– the addition of a high voltage a.c. test to simulate a voltage > 230 V a.c. which will operate a 600 V GDT.