WHAT ARE THE BASIC THINGS AND SAFETY PRECAUTIONS ELECTRICAL DESIGNER NEEDS TO BEAR IN MIND IN DESIGNING A VILLAGE UP TO 250 HOUSING UNITS?

Make sure that everything that you design meets all the codes and standards for the location and type of occupancy. Also get the local code officials involved very early in the design.

It is important that the design is done by an experienced engineer with at least 5 years experience in this sort of work or by a younger engineer working under the direct supervision of an experienced engineer.
With all matters, inexperience will lead to unsafe designs. One aspect that contributes to unsafe installations is a designer that "does not know that they do not know". It is better that someone knows they are uncertain about some aspect of the design and they know when to seek the guidance of an experienced engineer..
Stay safe.