Isotonic exercises involve moving your joints and muscles rhythmically and repetitively through their ranges of motion using low resistance, while isometric exercises are static and require you to contract your muscles without joint motion.
Substations are normally outdoors and are enclosed by a wire fence. However in residential or high density areas, the substation may be indoors and housed inside a building to restrict the humming noise of the huge transformers. slide 2 of 6 View of a Substation
The substation is protected from faults on feeder and tie lines by circuit breakers and/or reclosers located inside the substation. Most of the faults are permanent on an underground distribution system, thereby requiring a different protection approach.