ABB LD 800HSE, Руководство пользователя

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Appendix C Technical Reference Redundancy Concept
3BDD011677-600 A 113
same H1 links. The redundant set of devices behaves like one logical linking
device. By duplicating the physical linking device, it is possible to tolerate one fault
in one of the two devices.
In a redundant set of devices one linking device acts as Primary Device and
performs actively all communication functions, including the Link Active Scheduler
(LAS) function on the H1 links. In a redundant set it is the Primary Device that has
to be addressed by hosts and configuration tools.
The second linking device, named Secondary Device, acts as backup device. It
receives automatically the same configuration as the Primary Device, but uses
different node addresses on the H1 links and a different IP address on HSE.
The Secondary Device is able to take over the function of the Primary Device if the
Primary Device fails. In that case the linking device is reduced to a non-redundant
system that is not able to tolerate any further failure. Therefore it is necessary to
replace the defective device as soon as possible to recover redundancy.
The Secondary Device acts as Backup Link Master on each H1 link attempting
to take over the LAS role if required. Additional Link Master devices may be
configured to act as Backup Link Master on the H1 links.
The two devices forming a redundant set communicate via a serial communication
line (RS-232) and via Ethernet. The serial line is used to establish a redundant set
of devices, to exchange signs of life, and to control redundancy switch-over, while
the Ethernet is used to transfer configuration information from the Primary Device
to the Secondary Device. Therefore an operational serial communication path
and an operational Ethernet path between both devices are required for proper
operation.
The two physical linking devices forming a redundant set of devices are determined
by the serial link between them. Without that serial link, both devices operate like
independent, non-redundant Primary Devices.