Web simulator for protection relay functions

The tests with digital protection relays are an essential step before their effective use in the power electrical system. That is why protection engineers need to verify the relay functions and their dynamic behavior when exposed to the different situations of the power system. The tests have to be safe and effective to make sure the protection device will work properly after being installed. These tests are executed in laboratories using relays and test devices to simulate different conditions. However, the kind of test devices needed are very expensive and only some laboratories and universities can have their own. With all that comes to the idea of a web-based virtual relay, that can be used for testing relay from anywhere, using only a computer. With a virtual relay it is possible to analyze, test, and improve protection relay function the same way it is done physically, but with the possibility to be anywhere.

The virtual protection relay developed can be divided into three fundamental blocks. The first block is the “Signal Processing” which processes the voltage and current data to be used for the protection algorithm. In this processing, the data will go through a low-pass filter, an A/D converter, a digital filter and then, the composition of the phasor signals. Next, there is the “Protection Algorithms” block where are found the mathematical formulas of the protection functions and it is possible to change some parameters of the algorithms for testing. Finally, the “Web Interface” block concentrates the graphical interface for data input and output. Input data can be through a COMTRADE file or as a test set interface. At this block, it is possible to analyze the protection relay actions during events and interact with the responses through a graphical visualization interface.

The virtual relay was conceived in a way that all blocks can be changed by the user. In this manner, the tool can be used to analyze the behavior of a relay using different signal processing, but it could be also developed as a commercial twin relay. As this is an extensive subject, this work will show all three blocks’ capabilities using COMTRADE files together with the distance protection function responses. The protection block uses also a processing control to simulate a real hardware behavior, maintaining the response times close to the physical devices, not only simulating the protection algorithm.

The testing results show that the protection relay simulator presents an adequate answer, both concerning the performance of the protection function calculations and about the time responses. In conclusion, it is possible to perform tests of protection functions in a more agile way and with less investment. The program also facilitates some analysis needed in the daily routine of system protection professionals and for educational purposes, proving its efficiency and applicability for both the technical and scientific community.