How Pipeline Monitoring calculates volumetric variation for each PLM region

The Pipeline Monitoring application (PLM) monitors volumetric variation for each PLM region. The definitions of these regions are configured by the Administrator.

PLM checks the PLM region for three short-term periods (ST1, ST2, ST3), three longterm periods (LT1, LT2, LT3), and three extended term periods (XT1, XT2, XT3) The short-term periods detect large leaks that occur over a short period of time, and the long-term and extended term periods detect slow leaks that occur over longer periods of time.

If there are no leaks, the line balance equation is true:

input metered volume =

output metered volume + change in linepack + change in tank volume

PLM sums both sides of this equation over each of the nine time periods. If the two sides are not equal, and if the difference exceeds the configured alarm limits for a given period, AVEVA Enterprise SCADA generates an alarm and an event. The alarm limits can be defined in terms of absolute volumes or volumes as percentages of the metered input flow.

The difference is considered over if the right side of the equation is greater than the left.

The deviation is considered short if the left side is greater than the right.