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Theory of Operation
74
Firmware
The operator interface enables you to monitor the STS2/PDU, to configure setpoints for transfers,
monitor system parameters and access event and history logs. The firmware is accessible through the
LCD touch screen or the RS-232 interface. The firmware includes:
• View and set the preferred source.
• View and configure setpoints.
• View alarms, faults and status.
• The mimic graphical representation of the systems operation.
• Menu driven monitoring and configuration.
• Step-by-step instructions to assist you in the start-up, shut-down and bypass operations.
• Help on event messages.
• Touch screen alarm reset and silence buttons.
Events in the system, both faults and alarms, are detected and displayed on the LCD. See 11.0 -
Alarms and Faults for more information on events.
• A set of event masks can be configured through the LCD to trigger a system response to an event.
See 11.1 - Event Mask.
• Report event conditions from other components of the system.
• Monitor and report changes in event condition states. If the event condition’s state changes from
inactive to active, a new event is detected. If the transition is from active to inactive, the event
condition has cleared.
• Process new faults and alarms and clear inactive alarms.
• Provide the alarm reset and silence options.
9.2.2 Circuit Breakers and Non-Automatic Circuit Breakers
Input circuit breaker for each source provides over current protection for the STS2/PDU. Three non-
automatic circuit breakers provide total isolation of the solid-state switching devices with an input
non-automatic breaker for each source and a load isolation non-automatic breaker. Two non-automatic
breakers provide for maintenance bypassing of the solid-state switching devices to either input source.
All breakers in the STS2/PDU are plug-in types, which allows any breaker to be replaced without de-
energizing the output bus. The breakers have an interlock in the plug-in base, which prevents the
switch from being withdrawn in the CLOSED position. The switch trips OPEN before it disconnects
from the plug-in base.
See 14.2.5 - Circuit Breakers for specifications and more information pertaining to the circuit
breakers. See Figures 23 through 36 for circuit breaker locations.
The circuit breaker schedule is provided in Tables 9 through 11.
9.2.3 SCRs
Brick-type SCRs are used rated to carry the full 100% rated load. The unit is a fuseless design with
input circuit breakers providing overcurrent protection.
9.2.4 Logic Modules
The logic contains three separate redundant logic modules. The modules contain the logic necessary
to run the STS2/PDU and control transfers and shunt trips under all circumstances, without any out-
side assistance once set-up and started properly.
9.2.5 Audible Alarm
An audible alarm is installed on the control board. This alarm is triggered by an alarm condition
detected on the unit. The alarm can be turned off from the touch screen. Turning off the audible alarm
does not clear or reset the condition that triggered the alarm.
9.2.6 RS-232 Port
An RS-232 serial port is provided to allow an external terminal to be connected as another user inter-
face. See 12.1 - Using the RS-232 Port for more information.