Siemens SWT-3000 User Manual

Functional Description SWT 3000 Equipment Manual
Page - 20 Edition p3_3_2x 08/09 © SIEMENS AG 2008
Unblocking mode
The unblocking mode is a release procedure. Short circuits on overhead lines may cause a dis-
turbance of PLC links. To guarantee in this case the release for the permissive protection device,
the unblocking impulse is used.
If the signal to be transmitted does not reach the other line end, because a short circuit on the line
causes excessive attenuation or reflection of the signal, the receiver recognizes a fault and emits
the unblocking impulse. It is carried out via the interface module IFC-P/D command output 4 and
connected to the unblocking logic of the protection relay ensuring the release (for 10-300 ms) in
case of fault.
IFC-x
IFC-x
Rx Alarm
t
unbl
= 10 - 300 ms
CO4
SWT 3000
SWT 3000
Figure 12: Principle of the unblocking mode
The unblocking function is activated when the time for the unblocking impulse is more then 0 ms
(tunbl > 0 ms).
Possible tripping codes used in the SWT 3000
The coded tripping is combining always two frequencies from the VFx_CT variants. For this vari-
ants 7 trip frequencies, the guard and the sync. frequencies are used. Depending on the PLC con-
figuration, the frequencies are transmitted in the VF or IF range. The following table shows the
combinations for the tripping codes C1 up to C16.
Table 4: Possible frequency combinations for the coded tripping commands
Code f
Guard
f
s
f
1
f
2
f
3
f
4
f
5
f
6
f
7
Guard
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
f
1
…f
7
trip frequencies from the variants M5A
f
s
clock synchronizing frequency from the variants M5A

Siemens SWT-3000 Specifications

General

Brand	Siemens
Model	SWT-3000
Category	Industrial Electrical
Language	English