Relay Protection System on Bus Bar and Power Transformer in Electrical Grid Substation 4

In the substation, it is very important to receive and provide electricity from the terminal or other substations. The fourth substation is connected to Takeo, GS7, GS6, and TR, and has a 230kV voltage (GS4) Double Bus Bar and have 230KV / 115KV
transformer for S = 200MVA.The GS4 is equipped with a wide range of advanced equipment and accessories, and inevitably damage to any part, especially on voltage bars and power transformers, which results in loss of budget, time and customer use. To protect the transistor bars and transformers in this project, the EDC select a Schneider Roller, a product of Schneider Electric. Determination by PSSE Program for calculating the circuit current Icc = 7392.60A, 230KV, % Z = 3.396 and Icc = 6157.57A, 115KV, % Z = 8.154.
There are two types of protection relays: the P741 receives two signals from the voltage bar when a fault occurs and the P743 connects to the CT to cut the circuit breaker through each voltage bar when a fault occurs. The minimum fault current of the 230kV voltage bar (1,917A), the maximum erroneous current fault (392.20A) and the maximum load current (1,500A), finally set the value IDCZ = 1,500A for (P741).There are two power transformers, each of which has a power of 200MAV and selects the size of the CT (750 / 1A) current (513A) in the primary CT (1,500 / 1A) current (1,004A) in the secondary.
The relays selected to protect the transformer are P642 for the differential of the transformer and P127 for the over current of the transformer (I>: 0.87In, TMS: 0.09s and I >> 6.80In, TMS: 0s.