Question

# Your task is to study the operation of the directional elements of a 132 kV transmission line protection scheme with the 90-degree connection as shown in class. The phase elements have a MTA of 45 degrees (current leading) and the ground element has a MTA of 60 degrees(current lagging). Two faults were simulated with the following results for the phase voltages and currents "seen" by the relays: For each case, determine which of the four directional relay elements will operate. Use graphical and analytical methods. _Use CTR=250/5, VTR= PTR=(132000/ /3)/67 Determine the operation time in each case for the directional overcurrent phase and ground relays if the overcurrent element settings are: \text { Phase relays: } I_{p u}=4.5 A, T D=2.5 \text { and } t=T D-\left(5.95 /\left(M^{2}-1\right)+0.18\right) ; \text { INST=\infty } \text { Ground relay: } \mathrm{I}_{\mathrm{pu}}=0.5 \mathrm{~A}, \mathrm{TD}=2.5 \text { and } \mathrm{t}=\mathrm{TD}-\left\{5.95 /\left(\mathrm{M}^{2}-1\right)+0.18\right) ; \text { INST }=\infty  Fig: 1  Fig: 2  Fig: 3  Fig: 4  Fig: 5  Fig: 6  Fig: 7