TISP7072F3, TISP7082F3
TRIPLE BIDIRECTIONAL THYRISTOR OVERVOLTAGE PROTECTORS
MARCH 1994 - REVISED MARCH 2000
APPLICATIONS INFORMATION
deployment
These devices are three terminal overvoltage protectors. They limit the voltage between three points in the
circuit. Typically, this would be the two line conductors and protective ground (Figure 17).
Th3
Th1
Th2
Figure 17. MULTI-POINT PROTECTION
In Figure 17, protectors Th2 and Th3 limit the maximum voltage between each conductor and ground to the
±V
±V
of the individual protector. Protector Th1 limits the maximum voltage between the two conductors to its
value.
(BO)
(BO)
lightning surge
wave shape notation
Most lightning tests, used for equipment verification, specify a unidirectional sawtooth waveform which has an
exponential rise and an exponential decay. Wave shapes are classified in terms of rise time in microseconds
and a decay time in microseconds to 50% of the maximum amplitude. The notation used for the wave shape
is rise time/decay time, without the microseconds quantity and the “/” between the two values has no
mathematical significance. A 50A, 5/310 waveform would have a peak current value of 50 A, a rise time of
®
5 µs and a decay time of 310 µs. The TISP surge current graph comprehends the wave shapes of commonly
used surges.
generators
There are three categories of surge generator type: single wave shape, combination wave shape and circuit
defined. Single wave shape generators have essentially the same wave shape for the open circuit voltage and
short circuit current (e.g. 10/1000 open circuit voltage and short circuit current). Combination generators have
two wave shapes, one for the open circuit voltage and the other for the short circuit current (e.g. 1.2/50 open
circuit voltage and 8/20 short circuit current) Circuit specified generators usually equate to a combination
generator, although typically only the open circuit voltage wave shape is referenced (e.g. a 10/700 open
circuit voltage generator typically produces a 5/310 short circuit current). If the combination or circuit defined
generators operate into a finite resistance the wave shape produced is intermediate between the open circuit
and short circuit values.
ITU-T 10/700 generator
This circuit defined generator is specified in many standards. The descriptions and values are not consistent
between standards and it is important to realise that it is always the same generator being used.
Figure 18 shows the 10/700 generator circuit defined in ITU-T recommendation K.20 (10/96) “Resistibility of
telecommunication switching equipment to overvoltages and overcurrents”. The basic generator comprises
of:
capacitor C , charged to voltage V , which is the energy storage element.
1
C
switch SW to discharge the capacitor into the output shaping network
P R O D U C T
I N F O R M A T I O N
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