managed manually. The device's intelligent overload protection function, for
example, the resetting and adjustment of the current pick-up level, is managed
remotely from a utility dispatch center, using a system such as SCADA. The overload
protection is coordinated with the possible MCB in the same circuit so that the current
pick-up setting is lower than the MCB operational level to avoid unnecessary site
visits.
4.3.3
Monitoring of the pressure of SF6 gas
The SF6 insulated primary equipment is arranged by wiring the pressure sensor
contact to one input of the device, used for monitoring the SF6 gas pressure. When the
gas pressure drops below the acceptable limit, the falling edge of the digital signal
triggers and activates an alarm signal. This information can be obtained as an alarm
event from the network control system.
4.4
Battery charging and monitoring functions
Power backup for the station can be arranged by connecting 24 V (2 × 12 V) sealed
lead acid batteries to the device. The batteries supply power to both the device and the
communication device during a mains failure. As the batteries are charged by the
device, the communication between the unit and the network control center is always
operating irrespective of distribution network faults or planned outages.
The battery condition is secured by a battery load and condition monitoring test,
activated remotely via a command from the SCADA system. In the test, a discharge
resistor is connected in parallel to the batteries. During the test, the battery capacity is
measured and reported as an Ah value to indicate the remaining capacity, so that
maintenance can be optimized. The battery test can be started directly from the control
room or run automatically according to the agreed timetable. During the battery load
test, which takes 2...5 h, the voltage of the battery charger is shut off and the control
functionality is blocked.
If the battery voltage drops to less than the set value, for example, 22 V, during the
battery load test, the device generates an alarm event. This indicates that the lifetime
of the batteries is ending or that an internal fault has occurred in the battery or its
circuitry. In both cases, the battery must be replaced.
During normal control operations, the device makes condition measurements, such as
the battery voltage minimum value and the maximum current. The battery condition
and lifetime can be estimated based on these recorded values.
4.4.1
Power backup
Power backup for the station can be arranged by connecting 24 V (2 × 12 V) sealed
lead acid batteries to the device. The batteries supply the device and keep the
1MRS758459 C
Section 4
Functional description
ARC600
29
User Manual