The new TLC software package is a simplified analysis tool that quickly estimates line parameters, electric fields, and magnetic fields associated with arbitrary configurations of parallel transmission and distribution electric lines. It also estimates induced voltages and currents on other parallel metallic utilities, such as pipelines and railways. It has been designed with simplicity in mind, providing much useful information with minimal data entry; it is analogous to SESGSE, the Grounding System Estimator developed for the estimation of grounding requirements. TLC features new transmission & distribution line structure databases coupled with databases containing an extensive library of conductors, including rails and pipelines. These databases, together with the intuitive user interface, provide an efficient tool that can be applied directly to simple system configurations; this can be helpful for preliminary analyses of more complex systems. For more complex systems or more detailed studies, SES recommends the Right-Of-Way or HIFREQ software.

Analytical Methods and Algorithms Used in TLC

• Line Parameters. All line parameters (line constants) are computed using an enhanced algorithm based on the works of Gary, Deri and AbuelMa'atti, which is the method used by FCDIST. The bundle reduction, ground-wire elimination and sequence components algorithms are all derived from the TRALIN module.
• Magnetic Field. The computation of the magnetic field is based on the following observations. It is well known that the currents in the ground return conductors (i.e., neutral, shield, or static wires) contribute significantly to the magnetic fields in a balanced three-phase transmission system. The determination of the currents in the ground return conductors is based on two assumptions. First, the termination impedances are always small compared with the total self-impedance of the ground return conductors (this is true when these conductors are sufficiently long). With this assumption, the value of the termination can be set to zero. Second, it is assumed that the currents in the ground return conductors will not influence the current in the phase conductors. This is true as long as the average of the ground conductor currents is small compared to the phase currents along the length of the line being analyzed.
• Electric Field. The electric field is computed using a new powerful method that accounts for the presence of metallic tower structures. The main advantage of this approach, which is based on closed-form analytical expressions, is that it is fast but accurate. It uses a perturbation method to account for the presence of metallic tower structures and any ground return conductors connected to them.
• Inductive Interference. This portion of the computations allows a quick estimate of induced voltages and currents on any number of neighbouring buried or aboveground metallic utilities (such as pipelines, rails, or aqueducts) having a uniform coating or earth leakage resistance. The metallic utilities can have any length and arbitrary termination impedances.

Special Features

The TLC software package will have an extensive set of wizards to speed up the data entry session. Extensive databases will provide a wide selection of typical electric line configurations as well as a rich collection of conductor types. A graphical interface will simplify the specification of most data and various report and plotting utilities will provide an easy means to display and report the specified data and computation results.

Expected Completion Date

It is expected that the TLC software package will be ready by the end of 2002. It will be made available to all users of SES software with active maintenance on the following packages:

1. MultiLines+
2. MultiGround+
3. MultiFields+
4. Right-Of-Way
5. CDEGS