@Indranil Deo
In Real Time, There are 3 phase voltages. They need to Phase Angle harts.
For Example ,see this Below Link,
https://www.chegg.com/homework-help/questions-and-answers/draw-label-generic-phase-diagram-containing-critical-temperature-label-horizontal-vertical-q29244408
See this below link,for this Example,
in Real time, There are 3 phase voltages. So they need to Phase Angle Charts.