Operational Historian SCADA - basics

What is an Operational historian?

The operational historian or data historian is a software program or a set of time-series database applications that stores and retrieve process data. It stores data in time series and retrieves faster when requested.

An operation historian can capture all instrumentation data, using a lot less space compared to traditional relational databases.

In a process control system, the very common elements that are historicized include temperature, flow, pressure, level and other types of analogue data. Compared to paper records, it is much simpler to electronically manage compliance data and process data.

What might be stored in historian:

  • Analog data: Temperature, pressure, flow, level, weight
  • Digital reading: valves, limit switches, motors on/off, discrete level sensors
  • Product Info: product id, batch id, material id, raw material lot id
  • Quality Info: process and product limits, custom limits
  • Aggregate data: average, standard deviation, cpk, moving the average
  • Alarm Info: out of limits signals, return to normal signals

Data Historian operation:

It is in the plant where you’ll find DCS, SCADA, and PLC systems, Whereas DCS, SCADA and PLC systems reside at Levels 0 – 2, data historians are found at Level 3. Historians are architectured to pull data from a variety of systems, across different level of the process. In addition, the advanced analytical capabilities of a data historian allow operators to gain a deep understanding of the process, its variability, and how it can be improved.

It has the Wide range of capabilities including finding patterns in the data for root cause analysis. Can easily download information into spreadsheets for further analysis.

The data points that must be historicized and the historicization methods required must be configured in the DataWarehouse database. The labels that are historicized in the DataWarehouse database will be a subset of the labels for which ClearSCADA collects the history.

What kind of questions can a data historian answer?

  • How much fuel was burned by an equipment for a period of time.

  • How much time did a particular team work in a period of time (for example, during the last 24 hours)?

  • About average, maximum, and range of CPU temperatures

  • Does the use of #2 ball mills correlate with the increased carbon content in the ash at the coal power plant?

  • Can question the effects of an equipment failure

Advantages of an operational Historian:

  • Efficient data storage through compression; filtering the noise of the system and the values that can be calculated by interpolation.

  • High speed data collection

  • Allows period vice data analysis

  • Data acquisition redundancy, store and forward, and fail-over features

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