IEEE 2778-2020 pdf download

IEEE 2778-2020 pdf download.IEEE Guide for Solar Power Plant Grounding for Personal Protection.
The size of a typical SPP makes it impractical to install a grounding mesh sufficiently dense to maintain a near-equipotential plane across the entire facility or to install crushed rock surfacing throughout the entire facility. The large open areas generally require less grounding (similar to traditional power plant design), but it is imperative to pay attention to step and touch voltages in the vicinity of all exposed conductive equipment. A design model that can account for this wide variation in grounding system characteristics and requirements is necessary to design a grounding system that adequately protects personnel without being prohibitively costly.
4.1 Differences among SPPs, traditional power plants, and substations
While there are some similarities between SPP grounding systems and traditional power plants and substations, there are more significant differences. Utility-scale SPP grounding systems can often extend over hundreds or thousands of acres where substations and traditional plants are typically much smaller.
The general practice in a substation or plant grounding design is to produce a near-equipotential plane through the facility, or at least around grounded equipment. Using a relatively dense mesh, this is achieved to an acceptable level as determined by examining mesh, touch, and step voltages within the grounding system area.
Substations are small enough that grid spacing on the order of 5 m to 15 m (15 ft to 50 fi) is typical and presents a reasonable expense for the project. Similarly, applying an insulating surface layer around equipment and throughout the station is common practice. Since the total area is relatively small, analysis can be performed by most grounding software packages, and in some instances hand calculations, to provide acceptable results with relative ease.
Traditional power plants often have large rebar-reinforced concrete foundations or buildings that equalize the voltages in the vicinity of major equipment. Auxiliary equipment is grounded in similar fashion as in a substation environment, and the power plant is typically connected to a substation that follows typical substation grounding design. Many traditional plants have large areas where there is no equipment to touch which allows for less grounding in some areas. While power plants are often larger than substations, the grounding design and analysis is usually not significantly more difficult and can be handled readily by software.
Due to the larger size of SPPs, it is usually not practical to install an insulating crushed rock surfacing layer throughout the entire facility, nor is it practical to install a dense grounding mesh. These two omissions have an additive effect on personnel protection implications: the lack of crushed rock can significantly reduce allowable touch and step voltage limits and the lack of dense grid results in higher step and touch voltages.
4.2 Challenges with design and analysis
The cost of a large utility-scale SPP grounding system can often reach into the millions of dollars in materials alone. Unlike a substation grounding design, where some overdesign may be acceptable from a cost standpoint, even a small percentage of overdesign in a SPP can introduce significant cost. Thus, there is incentive to perform an accurate analysis and design that provides IEEE Std 80 compliant personnel protection while reducing unnecessary design margin costs.
The size of utility-scale SPPs cause modeling difficulties as well. Hand calculation methods are insufficient due to the assumptions they require, particularly the exclusion of internal grounding conductor resistance that becomes significant over large distances. Many software programs have limitations as well, including soil structure type, maximum number of conductors, or not accounting for conductor self and mutual-impedance. Even the most advanced grounding software packages cannot accommodate the largest utility-scale PV SPPs without some sort of compromise. Complex techniques, which require a detailed understanding of the problem.