ITU-T K.28 PDF

This Recommendation applies to thyristor-based surge protective devices (SPDs) to be used for primary protection against surges due to lightning or power disturbances on telecommunication circuits, in accordance with [b-ITU-T K.11]. It covers the following device parameters:

a) Characteristics

1. Overvoltage function

i. Impulse limiting voltage

ii. Leakage current and insulation resistance

iii. Holding current

2. Series element

i. Hold current

ii. Trip current

iii. Time-to-trip

iv. Impulse let-through current

3. Signal

i. Capacitance

ii. Longitudinal conversion loss (LCL)

iii. Insertion loss

iv. Return loss

b) Ratings

1. Rated peak impulse current

2. Impulse durability

3. AC durability

c) Overload parameters

1. High impulse current

2. Power fault

d) Identification and marking.

This Recommendation does not deal with:

a) mountings for SPDs and their effect on arrester characteristics;

b) hybrid SPDs where the thyristor voltage limiting is augmented by other technologies;

c) mechanical dimensions;

d) quality assurance requirements;

e) units containing heat-coils.