The over current relays for the line protection and loads connected at the buses are shown in the figure.

The relays are IDMT is natural having the characteristic
$${t_{op}} = {{0.14\, \times \,time\,\,multiplier\,\,setting} \over {{{(plug\,\,setting\,\,multiplier)}^{0.02}} - 1}}$$
The maximum and minimum fault current at bus $$B$$ are $$2000A$$ and $$500$$ $$A$$ respectively. Assuming the time multiplier setting and plug setting for relay $${R_B}$$ to be $$0.1$$ and $$5$$ $$A$$ respectively, the operating time of $${R_B}$$ (in seconds) is __________.

A 2-bus system and corresponding zero sequence network are shown in the figure.

The transformers T₁ and T₂ are connected as

The undesirable property of an electrical insulating material is

A two bus power system shown in figure supplies load of $$1.0+j0.5$$ $$p.u$$

The value of $${V_1}$$ in $$p.u$$ and $${\delta _2}$$ respectively are