Answer Happy

CO3: design a simple protection system using CT, PT, relay, and CB in order to protect the rotating machines, bus bars, transformers, transmission lines, and distribution network. A 3-phase transmission line operating at 33 kV and having a resistance of 5 2 and reactance [3+4*3] of 2022 is connected to the generating station through 15,000 kVA step-up transformer. Connected to the bus-bar are two alternators, one of 10,000 kVA with 10% reactance and another of 5000 kVA with 7.5% reactance. (i) Draw a single line diagram of the complete network indicating the rating, voltage and percentage reactance of each element of the network. (ii) Corresponding to the single line diagram of the network, draw the reactance diagram showing one phase of the system and the neutral. Indicate the % reactances on the base KVA in the reactance diagram. The transformer in the system should be represented by a reactance in series. Calculate the short-circuit kVA fed to the symmetrical fault between phases if it occurs (iii) at the load end of transmission line (iv) at the high voltage terminals of the transformer