The increased role in the distributed generation of small power plants requires the rethinking of their protection systems and behavior during grid faults. The signal processing algorithms of the protection functions can be tested with network simulation tools.
One of the most important task of inverters is the anti-islanding detection. Since the solution of this problem depends on grid conditions and is not always easy, several anti-islanding methods have been developed. Passive methods on their own cannot offer full reliability, thus they can be used together with other active detection methods, which probe the grid by sending signals to it. However the usage of the active methods can cause bad effects for other grid connected devices. Using active methods in systems, which include a lot of parallel working inverters can lead to false anti-islanding detection. That leads to decreased selectivity of protection systems.
The Power System Toolbox is a new feature of ATPDraw, which came out with version 5.9 of the software. The PST is able to provide help for the implementation of such simulations. With the help of available models of PST the minimal required protection functions of DNOs were implemented.