H-System – Isolated Barriers and Termination Boards for HIMA
Operation
20
16-11
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4
Operation
4.1
Fault Monitoring
Numerous faults can occur between measurement of the process variable and
evaluation in the control system. This can lead to undesirable process statuses
under certain circumstances. These process statuses may result in plant
downtime or quality problems or even present a hazard to persons and the
environment. Depending on the device version, the isolators enable monitoring of
the following faults:
• Line faults
Here, the connection cables between the isolator and field device are
monitored for lead breakages or short circuits. If a fault is detected, it is output
at the fault message output or collective fault message. The relevant switching
outputs are then switched to a de-energized state. The red fault indication
LEDs signal the fault.
• Device faults
The isolators are designed so that internal faults are detected and reported. In
the case of a power failure, the outputs are switched to a de-energized state.
4.2
Fault Output
Several H-System isolators monitor the field leads for lead breakage and short
circuits. This means that faults are immediately identified in the system, and that
lead faults are not interpreted as a signal.
Depending on the parameterization of the devices, these lead faults are output on
the control-side outputs and displayed as additional information on the separate
fault signal output.
Fault Signal Output
If the device has a fault indication output (FAULT), lead and device faults are
output. The fault indication output is active in normal status and is deactivated in
fault status (closed-circuit principle). In the case of fault indication output, it is not
possible to reverse the direction of operation.
Figure 4.1
1b
SL2
5a
5b
SL1
8a
7a
24 V DC
FAULT
1a, 1b
2a, 2b
6b
System Description H-System
–
Isolated Barriers and Termination Boards for HIMA