Profiles have long been used in hydraulic modeling to better predict actual system behavior. Non-transient (steady-state) models use the single highest point on the profile (the peak multiplier) to convert daily calculated loads to peak hourly loads. This allows the worst case condition to be simulated and ensures the design of distribution and transmission facilities is appropriate.

A theoretical flow profile with a 1.2 multiplier is commonly used when actual consumption data is poor or unavailable. This paper will walk through the steps of creating a typical two-dimensional regular-rate normalized profile and then introduce the concept of "deskewing". Deskewing allows you to further refine the data by adding temperature as the third-dimension. This allows the new profiles to be extrapolated out to a design day and characterized in a 3D surface graph. This graph can then be used to create peak hourly demand scripts and profiles that can be imported into hydraulic modeling software to predict system flows at any time of the day on any heating degree day (HDD).

Every hydraulic system is predicted to have its own unique 3D surface graph based on the mix of customer types (residential, commercial and industrial), their equipment and habits. Analyzing how the 3D surface graph (and specifically the design day profile) changes from year to year may help determine the effect of DSM (demand side management) on these systems.

Union Gas Limited is a Spectra Energy company providing natural gas storage, transmission and distribution services in Ontario. Union Gas serves about 1.4 million customers in more than 400 communities.

Flow Profiles

Profiles are used in hydraulic models to change flows and pressures over time. Typically the x-axis is time (measured in hours) while the y-axis is a dimensionless multiplier (see Figure 2).

This paper will focus on regular rate flow profiles and their use in modeling natural gas distribution and transmission systems. Regular rate customers are typically residential, commercial, and small industrial customers that are monthly billed.

This content is only available via PDF.
You can access this article if you purchase or spend a download.