Calculations and Engineering Reports

We have carried out grounding calculations for the last 40 years. Initially we used computer software offered on main-frame computers. In the 1980's we developed our own software to carry out the calculations. We have applied the software many times to regular grounding engineering such as ground grid design and feeder fault level calculations. From this experience, we can apply it to unusual and complex grounding investigations.

Examples are:

Stray current flow in an elevated rapid transit system summed over a year of operation. Stray current will cause corrosion of the metallic parts of the structures. For this study the operation of the trains was simulated because leakage through the rail fasteners is variable.
Step and touch potential safety evaluation around interconnected substations and generating stations including the effects of fault currents circulating between the different ground grids.

Ground grids. We can calculate the resistance of a ground grid located in soil with non-uniform resistivity. If the grid is large enough that there is a voltage drop across it or it has a reactive component in the impedance, these effects can be modeled by the software. Separate grids, either floating or electrically interconnected by impedances can also be modeled.

Grounding safety from step and touch potential hazards. We can calculate potentials that develop in the soil around a ground grid and can compare them against the tolerable levels as defined by the IEEE. We have developed a rational method for calculating step potentials from soil potential information.

Power system modeling and fault studies. We can model complex single or multiphase power systems and determine the split of current during normal operation and ground faults. This can be used to calculate the ground component of ground fault current for applying to ground grid analyses in determining step and touch potential safety.

We can model very complex power systems using our software. A problem that often arises is how to determine the fraction of ground fault current at a substation that flows into the ground and the fraction that flows in transmission line ground wires that are connected to the substation. Various approximate methods have been developed over the years such as using shielding factors. With our software, the split of current can be calculated properly, allowing for effects like inductive coupling, line capacitance and tower footing resistances. We have used the software to model an extensive interconnected electrical transmission system with several voltage levels to determine the safety at a number of interconnected substations.

Pipeline interference effects. We can model and calculate the inductive coupling effects between power lines and gas or oil pipelines. These effects become more serious each year as utilities seek new rights-of-way for pipelines and are forced to place more pipelines along existing power line rights-of-way. The fault level on power lines is also increasing with system capacity and expansion.

We can calculate the combined effect of ground faults at a gas or oil processing facility and inductive coupling with a network of pipelines that may or may not be connected to it.

Reports

We can prepare comprehensive, sealed engineering reports on measurements and calculations done by us. These reports typically describe, in detail, how the measurements and/or calculations were carried out.

Ground-It.com Consulting Ltd is a wholly owned subsidiary of Pacific Powertech Inc. For a full list of our services, please visit www.pacificpowertech.ca