SWT 3000 Equipment Manual Functional Description
© SIEMENS AG 2008 Edition p3_3_2x 08/09 Page - 11
Mode of operation: digital
General The digital line interfaces LID-1 and LID-2 are needed for transmitting the
protection commands over a digital network. The data for the interfaces
RM (Remote Maintenance) and SC (Service Channel) and system-
internal control information are transmitted additionally.
Transmission concept Information is transmitted over the digital interface by means of the peri-
odic transmission of 4 message types of constant length. The messages
have the following priority among themselves:
z Command transmission
z Service channel
z Remote maintenance
z System information
Command transmission Each command message is transmitted 4 times with a Hamming distance
of 4. The receiving end checks whether three identical command mes-
sages have been received. The command is not valid until this check has
been carried out.
Features
z
Frequency generation and evaluation by digital signal processor (DSP).
z Full utilization of the available transmit power since only one of the possible frequen-
cies is ever transmitted.
z Burst interferences with significantly greater amplitudes than the wanted signal is
largely suppressed.
z Noise analysis in the unused wanted signal circuits.
z Analog and/or digital line interfaces
z Alternative paths possible by combination of analog and digital interfaces.
z Event memory (Data retention over several days, at least 5 hours)
z It is also possible to read out the event memory remotely via RM or service channel.
z Configuration of the device with PC.
Operating modes with PLC equipment
Power system protection signals can be transmitted over the high-voltage and medium-voltage
overhead line to be protected in conjunction with PLC equipment. For this purpose the devices of
the SWT 3000 system are connected to special inputs and outputs of the PLC unit. In case of using
a PowerLink PLC system it is also possible to integrate SWT 3000 in PowerLink. When using PLC
equipment several variants of teleprotection signaling are possible as described in the following:
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