Supervisory control and data acquisition (SCADA) system alarms are a key tool for managing maintaining safe operations. However, the number of alarms generated can be excessive, overloading controllers and creating a significant safety hazard, making effective alarm management a necessity.
The definition of alarm management centers around two major components — managing the notifications generated by the SCADA system and developing a program to analyze and continually improve the alarm system. In other words, reducing the number of false alarms and improving the management of real alarms to reduce controller load.
Building an Alarm Management Program
There are several steps to building a successful and compliant alarm management program that operators should follow. Developing best practices is a continuously repeating process of evaluation and audit that considers:
- Alarm Philosophy
- Measurement, through benchmarking, and performance audit
- Rationalization (rules of engagement), including identification of the ‘bad actor’ and clean up of repeat offender
- Dynamic and state-based alarming, including parent/child suppression
- Continuous improvement
- Management of change
Alarm Philosophy shapes and guides an alarm management program. It is a performance-based written plan that describes your executive mission statement for your program, the owners of the program, and owners and responsibilities for the actual alarm program. A philosophy would include:
- Purpose — why do you have an alarm management program and what do you expect from it?
- Definition — what do you consider an “alarm”? Does it signal an event that requires action, or does it merely signal development of a deviation from normal?
- Executive mission statement — important for executive buy-in because of the costs associated with alarm management.
- Ownership — who is responsible for alarm management? Clear roles and responsibilities must be laid out.
- Alarm documentation and rationalization — includes process, methodology, preparation, alarm priorities, alarm set-points and information storage (master alarm database).
- Alarm audits and performance monitoring — how are audits to be conducted, by whom, and what indicators are considered?
- Management of change — documentation of how notification and training are conducted.
Benchmark and Performance Audit
Operators want to see continuous improvement in their alarm management program. To do that, benchmark alarm activity levels need to be measured and referenced against current levels over time. By creating dashboards in the SCADA system that monitor these values, operators can compare current alarm levels with historic performance (e.g., this shift versus last shift, this week versus last week, etc.) for a continual performance audit.
A primary function of alarm management is to determine which alarms need responses and which are repetitive or “bad actors.” A common control industry for an alarm is a notification that requires a response. The rationalization process is a point-by-point review of the pipeline system to determine which SCADA alarms do, in fact, require a response and developing a prioritization level for them. As well as documenting the appropriate response to the alarm once it has been verified.
It is during this review that operators begin to develop a clear picture of the alarm system. Rationalization provides the information needed to begin the implementation phase of the alarm management plan.
As the rationalization process takes place, the most egregious “bad actors” will be identified relatively quickly and operators can take immediate steps to address them. After dealing with this “low hanging fruit,” alarm levels will drop off and allow operators to begin looking for more subtle alarm issues. This is an ongoing process and can be dependent on the guidelines used in crafting the Alarm Philosophy.
All of this needs to happen within an audited program, so that when you need to make a change to an alarm limit, you can prove that any changes to the operating procedures were communicated to the controllers and well documented.
Alarm Management Improvement Strategies
As operators enter the implementation phase, there are a variety of resources available to guide the process. At Schneider Electric, we follow EEMUA 191 guidelines published by Engineering Equipment and Materials Users’ Association. In an effort to prioritize the strategies based upon the resulting improvements to system performance, the EEMUA recommends applying first basic, then advanced techniques to achieve the necessary improvements.
Based upon this process, the following strategies should be considered in approaching an alarm management improvement process —
High Benefit Strategies
These strategies, while providing the highest value, involve little advanced technology, having more to do with reviewing alarms and adjusting alarm settings properly:
- Review alarm storms to determine noise vs. value—a true system upset can generate a storm of alarms, not all of which are valuable to addressing the area of concern.
- Tune alarm settings on nuisance alarms, fix known issues—many times, operators and controllers have identified chattering alarms or alarms resulting from broken field equipment and just ignore them. These are easily identifiable fixes.
- Adjust deadbands of repeating alarms—adjusting or adding a deadband to reduce noise.
- Eliminate alarms with no defined response—as stated before, an alarm is defined as an event with a defined response. Identified alarms with no defined response should be given a low priority setting. These alarms can also be changed to alerts.
- Ensure alarm priorities are correctly assigned
- Introduce Alarm Shelving—rather than turning off alarms, lower priority alarms can be shelved, marking the controller as acknowledging the alarm but being held for later action so as to clear alarm noise.
- Introduce single line annunciation of repeating alarms—rather than generating repeating notifications from the same alarm, one alarm is generated with a counter showing the number of times it has been triggered.
Medium Benefit Strategies
- Suppress alarms from “out of service” stations—stations that are offline, during calibration for instance, may generate many nuisance alarms. These alarms can be grouped and suppressed on the display.
- Replace absolute alarms with deviation alarms—setting alarm triggers as a deviation from an acceptable range rather than a set point.
- Eclipsing—if one alarm goes from a lower priority to a higher priority, rather than leaving both alarms displayed the lower priority alarm is eclipsed.
- Apply filtering, de-bouncing, suppression on repeating alarms—alarms can be filtered into various classes that suppress repetition.
- Using logic to combine redundant sets of alarms—grouping similar alarms that require the same action or denote a pattern and eliminating all but the most critical.
Additional Benefit Strategies
There are additional advanced alarm improvement strategies that can be applied once the highest and medium benefit strategies have been implemented. They include using dynamic alarm thresholds, operator-set alarms, and operational mode suppression.
As these strategies are implemented and reviewed over time, operators should be able to see not only a reduced number of alarms but a general improvement in safety and performance of the alarm system, as well as more efficient control room operation overall. Schneider Electric customers that were skeptical at being able to achieve an alarm rate of six to ten alarms per hour just a few years ago, are now seeing significant drops in their alarm loads as they continue to refine their alarm management program. It is important that these performance measures are tracked carefully, especially as operations are scaled up into larger point counts.
SCADA alarms are necessary for effective and safe operations. Yet the industry advises that operators carefully assess how much alarm is too much for its particular infrastructure and operations. Excessive alarms can overload controllers and actually undermine safe operations. Best practices in control room management and alarm management help the operator implement a program to analyze and continually improve the alarm system for better pipeline safety and operational efficiency.
Source: Whitepaper on Alarm Management, July 2012.