2-18. What is the device identified by the  letter  “D”? 1. Insulator 2. Lightning  arrester 3. Fused  cutout 4. Circuit  breaker 2-19. What is the device identified by the  letter  “E”? 1. Recloser 2. Circuit  breaker 3. Air  switch 4. Fused  cutout 2-20. The transformers shown are what type? 1. Completely   self-protected 2. Self-protected 3. Conventional Learning  Objective:  Describe conductor  supports,  methods  of guying  poles,  and  factors considered  in  pole  layout. 2-21. In  an  electrical  power  system,  the supporting  structures  for  the conductors  must  be  designed  to 1. support the ueight of the conductors 2. support the ueight of all transformers  or  other  equipment mounted on the support 3. provide  required  clearances from the ground to the conductors  and  between  the conductors 4. do all of the above 2-22. Which  of  the  following circumstance  provide  the  best justification  for  placing  an electrical distribution system underground,  rather  than  overhead? 1. When the system is to be installed in an area subject to major  termite  damage 2. When underground installation is justified on the basis of initial  construction  cost  only 3. When  an  economic  analysis  shows that construction and long-term maintenance costs are less for underground installation 4. When the system to be installed would  impede  airfield  traffic 2-23. The availability of wood poles at any  given  naval  installation depends  upon  which  of  the  following factors? 1. Strength 2. Species 3. Size 4. Class 2-24. When designing an overhead distribution  system,  for  which  of the following reasons might an engineer select a Class 2 pole, rather than a Class 5 pole? 1. When a longer pole is needed to obtain  necessary  clearances 2. When a stronger pole is needed to support the loads that will be applied to the pole 3. When a pole having a smaller butt  circumference  is  required due to local conditions on the ground 4. When the design loads are less than those requiring a Class 2 pole 2-25. Which of the following criteria is/are  NOT  considered  when  an engineer  determines  the  required length of a wooden power distribution pole? 1. Usage of the pole 2. Future growth index of the area 3. Both 1 and 2 above 4. Safety  and  working  clearances 10