Protect against what?

AN2053

2/15

Doc ID 10917 Rev 2

1

Protect against what?

Telecommunication lines are submitted mainly to two kinds of disturbances. The first one is

linked to atmospheric effects while the second one is produced by the 50/60 Hz mains

network (see Figure 2). These disturbances are well defined in individual country standards

and Table 1 shows the main standards in use.

Figure 2.

Main telecom line disturbance causes

Figure 3 shows an example of lightning surge definition. This is given by the ITU-T K20

standard (International Telecommunication Union). This simulation is based on the

discharge of a 20 µF capacitance through resistances. The 20 µF capacitance and the 50

Ω

resistance define the surge wave duration while the 15

Ω resistance and the 0.2 µF

capacitance manage the rise time. In this case the surge is defined as a 10/700 µs wave.

The tests shall be managed in both transversal and longitudinal modes.

Figure 3.

ITU-T K20 lightning surge test definition

Atmospheric effects

50/60 Hz mains effects

ESD

Central office

K20 transversal test

R3 = 25

Ω

Surge

generator

Figure 1

Coupling

network

Equipment

under test

A

B E

Surge

generator

Figure 1

Coupling

network

Equipment

under test

A

B E

Surge

generator

Coupling

network

A

B E

K20 longitudinal test

R5 = 25

Ω

Equipment

under test

Equipment

under test

A

B E

R4 = 25

Ω

K20 surge generator

Uc

20 µF

R1 = 50

Ω

R2 = 15

Ω

0.2 µF

Coupling

network

Surge

generator