Although when we draw our graphs using Belly lattice diagram, we tend to draw step wise Olathe increment or decrement, in real simulation due to inductance and capacitance presence the voltages cannot changes instantly. Hence the simulation graphs have very small ramp type voltage changes rather than purely step wise changes. The other differences may be occurred due to following reasons, When we draw Belly Lattice Diagram, for the calculation We take round off values.
Hence the final output may be effect from those rounding offs which is not present in simulation process. Specially when we take the time constant, depend on the rounding off value the Belly Lattice Diagram changes significantly so the voltages values also change according to that. In manual calculation method of over voltages (Belly Lattice Diagram), human errors can be occurred. And once there is an error occurred it will effect to the subsequent results also.
But in CASCADE simulation process the effect from human errors are very minimum Using of Belly Lattice Diagram is getting significantly complex when the numbers of substations are increase. So due to complexity, it is very difficult to draw the Belly Lattice Diagram beyond certain time period. But with the presence of simulation cages we can simulate any number of substations transient behavior for any time duration.
Current values of substations are shown following figures, At substation A, At substation B, At substation C, At substation D, When we compare the surge currents with the surge voltages, we can clearly see that current pattern is closely following voltage pattern. The magnitude of the current is depends on the surge voltage divided by surge impedance. Although substation D end is an open circuit, that line shows current values because of the charging and discharging of the line.