Protection Design Guide
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38
Telecom & Networking Interfaces
Transient stress levels for each entry point into the system are
defined by installation class. The six classes are defined as :
Class 0 : Well protected environment
Class 1 : Partially protected environment
Class 2 : Well separated cables
Class 3 : Cables run in parallel
Class 4 : Multi-wire cables for both electronic & electrical circuits
Class 5 : Connection to telecommunications cables
and overhead power lines (Low density populated areas)
A class 0 environment is considered the lowest threat level and has
no transient stress requirements. The class 5 environment is the
most severe and requires the highest transient stress level testing.
Table 3 summarizes threat levels as a function of installation class.
Values of voltage stress using the 1.2 x 50s waveform are given.
Corresponding current values are calculated by dividing the open-
circuit voltages by the source impedances. The short-circuit current
values are more useful in choosing a suppression element.
The short circuit current stress levels are defined with the 8 x 20s
waveform for power supply applications with a 2 source
impedance. For data lines requiring a 42 source impedance,
the short-circuit current waveform is defined as 8 x 20s. For
telecommunications applications, the open-circuit voltage is
defined as 10 x 700s and the short-circuit current is a 5 x 300s
waveform. The source impedance is given as 40.
The type of suppression element needed for IEC 61000- 4-5 class
surges depends upon the threat level and installation class.
For power supply applications high power devices are required.
A discrete device or an assembly may be required depending
on the application. TVS diodes are the best choice for data line
applications and secondary board level protection because of their
superior clamping voltage characteristics and fast response time.
Class
Voltage
Current
Power Supply
Unsym Lines
(Long Distance Bus)
Sym Lines
Data Bus
(Short Distance)
Coupling Mode
Coupling Mode
Coupling Mode
Coupling Mode
Line-Line
Zs = 2
Line-GND
Zs = 12
Line-Line
Zs =42
Line-GDN
Zs =42
Line-GDN
Zs =42
Line-GND
Zs = 42
0
Voltage
NO REQUIREMENT
Current
1
Voltage
(n/a)
0.5KV
(n/a)
0.5KV
1.0KV
(n/a)
Current
42A
12A
24A
2
Voltage
0.5KV
1.0KV
0.5KV
1.0KV
1.0KV
0.5KV
Current
250A
83A
12A
24A
24A
12A
3
Voltage
1.0KV
2.0KV
1.0KV
2.0KV
2.0KV
(n/a)
Current
500A
167A
24A
48A
48A
4
Voltage
2.0KV
4.0KV
2.0KV
4.0KV
(n/a)
(n/a)
Current
1KA
333A
48A
95A
5
Voltage
(Note 1)
(Note 1)
2.0KV
4.0KV
4.0KV
Current
48A
95A
95A
WAVE
FORMS
Voltage
(1.2 x 50µs)
(1.2 x 50µs) (1.2 x 50µs) (1.2 x 50µs)
(1.2 x 50µs)
(1.2 x 50µs)
Current
(8 x 20µs)
(8 x 20µs)
(8 x 20µs)
(8 x 20µs)
(8 x 20µs)
(8 x 20µs)
Note 1: Depends on class of local power supply system.
Table 3 IEC 61000-4-5 Severity Levels
Applications
Summary :
Class Voltage Current Power Supply Unsym Lines (Long Distance Bus) Sym Lines Data Bus (Short Distance) Coupling Mode Coupling Mode Coupling Mode Coupling Mode Line-Line Zs = 2 Line-GND Zs = 12 Line-Line Zs =42 Line-GDN Zs =42 Line-GDN Zs =42 Line-GND Zs = 42 0 Voltage NO REQUIREMENT Current 1 Voltage (n/a) 0.5KV (n/a) 0.5KV 1.0KV (n/a) Current 42A 12A 24A 2 Voltage 0.5KV 1.0KV 0.5KV 1.0KV 1.0KV 0.5KV Current 250A 83A 12A 24A 24A 12A 3 Voltage 1.0KV 2.0KV 1.0KV 2.0KV 2.0KV (n/a) Current 500A 167A 24A 48A 48A 4 Voltage 2.0KV 4.0KV 2.0KV 4.0KV (n/a) (n/a) Current 1KA 333A 48A 95A 5 Voltage (Note 1) (Note 1) 2.0KV 4.0KV 4.0KV Current 48A 95A 95A WAVE FORMS Voltage (1.2 x 50µs) (1.2 x 50µs) (1.2 x 50µs) (1.2 x 50µs) (1.2 x 50µs) (1.2 x 50µs) Current (8 x 20µs) (8 x 20µs) (8 x 20µs) (8 x 20µs) (8 x 20µs) (8 x 20µs) Note 1: Depends on class of local power supply system.
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20s,50s,power,10k,20k,defined,applications,stress,05k,coupling,24a,source,enironment