eterrapipeline Events and Alarms

eterrapipeline detects and notifies operators of events and conditions in the monitored system that can lead to operational problems. For example, eterrapipeline_can detect when a normally running pump or compressor trips, and it can take action that causes an audible alarm to be issued for that unit. eterra_pipeline can detect problems that occur for analog, status, tank, and count points; RTUs and other equipment in the communications system. Individual analog or status points can optionally be configured to suppress the alarm until the analog or status has remained in the abnormal state for a specified period of time. In addition, SCADA can detect when control operations fail.

Some of the common conditions and events that SCADA considers abnormal, and therefore alarmable, are as follows:

Abnormal and illegal conditions for analog, status, and count points in the monitored system

An analog or status point’s return to normal operation after being in an abnormal or illegal state

Problems in the communications system, in particular with RTUs and scan groups

Topology issues that set the islands, devices, or bays in an abnormal state.

Abnormal and Illegal Conditions

In SCADA’s database, a definition exists that specifies each status and analog point’s normal operating state. When SCADA detects that a status or analog value conflicts with the point’s normal operating state, SCADA considers the point to be abnormal, or illegal, and therefore alarmable.

In SCADA, the following conditions are abnormal:

The value of an analog point violates one or more of the limits associated with the analog (for the types of limits that may exist for an analog, see section 1.5.2 Analog Data).

The value of a status point is an illegal state for the point type.

The value of a status point transitions to an abnormal state.

The energization state of a device becomes ambiguous, or is not known.

A device loses or regains its energized state.

An analog or status point transitions from an un-initialized state to an abnormal or illegal state.

A low voltage condition is detected at a substation.

Bay is in a non-expected topological state (configured).

If the valve status point is modeled as MCD, valves can trip and re-close within the span of a single scan. SCADA notifies the operator of such valve re-closures by logging each re-closure event on the SYSACT display, and by issuing an alarm. The alarm can be set up to require operator acknowledgment or not to require acknowledgment.

Return to Normal Events

SCADA can be instructed (through database definitions) to issue alarms when the following events occur:

Return from a low voltage condition at a substation.

An analog point returns to normal from a limit violation (SCADA can be instructed to automatically acknowledge alarms of this type).

A status point returns to normal from an illegal state or an abnormal state (SCADA can be instructed to automatically acknowledge alarms of this type).

Communication Errors and Equipment Failures

SCADA can be instructed to issue alarms when the following event occurs in the communications system:

The communications path to an SCADA site or SCADA Front End comes up or goes down.

For information about additional communication alarms that can be issued from the SCADA Front End, see the eterracontrol Reference Manual – Applications.

If a communications path to an SCADA site or SCADA Front End is down, the corresponding site is usually considered to be in the “Failed” state.

How SCADA Responds to Alarmable Conditions and Events

After SCADA detects an abnormal condition in the monitored system, it can respond by taking various actions to alert the operator of the condition. SCADA’s response to a specific condition occurring on a specific point is defined in the SCADAMOM database.

The actions SCADA takes in response to alarmable conditions and events are called “exception reporting” actions. The following actions are possible:

Log the abnormal condition on the Alarm Summary (ALARM, ALARM) display.

Log the abnormal condition on an exception list display.

Log the abnormal condition on the System Activity Log (SYSACT, ALARM) display.

Mark the abnormal point as unacknowledged, which results in an audible alarm (tone) being issued for the point.

To filter the alarms for a given equipment group, log the abnormal conditions on the Equipment Group Alarm summary.

The above actions are carried out by the Alarm application. When SCADA detects an alarmable event or condition, it sends the Alarm application that information. Alarm can log the event, issue an audible alarm, and display the alarm type and location on the console screen.

In addition to using the reporting capabilities of Alarm, SCADA can generate changes on one-lines and tabulars to alert the operator of alarmed conditions and events. For example, an alarmed valve can change from a solid red box (representing the normal state) to a hollow, green, blinking box (representing the abnormal state). Such visual indicators of alarmed states are set in SCADA when system one-lines are built.