This paper is aimed at the main transformer of substation of the design of second part, and had done the following design which is based on the digital protection as a starting point. According to the power system and the main transformer of substation features, the author made the calculation of short-circuit current, chose a suitable model of the protection device ,thus made the calculation for various setting, and analyzed weather the calculation results was reasonable so that to confirm the parameters and values for the device of relaying protection. To make the selectivity, sensitivity and reliability of relaying protection of main transformer meet the requirements, so that the relaying protection device could make full of its effects and guarantees the stability of the power system operation.
Using matlab software for UFLS(Under-Frequency Load Shedding) simulation modeling, the model made up of discrete 3-phase PLL(phase Locked Loop) block measurement block, relay block, three-phase circuit breaker block etc, had realized the simulation of the process of shedding the corresponding load automatically when the frequency fell to a certain value . The author had analyzed changes in the extent and trait of each electric element of this model during the process of simulation and summarized the characteristics of each electricity element, thus to make sure the simulation is feasible and correct.
Key Words substation, the design of second part, matlab, Under-Frequency Load Shedding
