DocID11830 Rev 2

3/16

AN2266

Telecom disturbances

16

1

Telecom disturbances

Figure 3 shows both classic (1) and new (2) telecommunication lines when they are

subjected to over voltages. These transients are mainly due to three kinds of disturbances.

The first one is linked to atmospheric effects (lightning); the second one is produced by the

50/60 Hz mains network, while the third one is produced by electrostatic discharge (ESD).

Today, simulations of these disturbances are well defined in worldwide or national

standards.

Figure 3. Line disturbance location

The standards used to qualify wired telecom equipment for European and Asian markets

refer to the ITU-T Kxx requirements (International Telecommunication Union). These

recommendations are based on the 10/700 µs surge tests for lightning simulation while

power induction and power crossing tests use 50 Hz alternating voltage from 230 to 600 V

of a duration of between 0.2 s to 15 min.

Figure 4 shows an example circuit for lightning surge simulation. This simulation is defined

by the ITU-T K20 standard. This simulation is based on the discharge of a 20 µF capacitor

through resistors. The 20 µF capacitor and the 50

Ω resistor define the surge wave duration

while the 15

Ω resistor and the 0.2 µF capacitor manage its rise time (see Figure 4a). In this

case the surge is defined as a 10/700 µs voltage waveform.

Subscriber terminal

Subscriber line cards

MDF

Central office

Primary protection

module

High speed

link

Line

Line

Subscriber terminal

Secondary protection

stage

Terminal

protections

Subscriber

location

Secondary protection

stage

Atmospheric effects

Electrostatic discharges

50/60Hz mains disturbances

(1)

(2)

Terminal

protections