Questions

Multiple-choice questions you can practise one by one. Open a question, tap an answer and see at once whether it is right. For a random set, try Quick practice.

138 questions

• Why can a thermosetting resin such as fully cured Bakelite not be repeatedly remoulded like a conventional thermoplastic?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• A winding requires a rigid insulating encapsulant with good adhesion and mechanical protection. Which material is generally a suitable candidate?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why can XLPE generally operate at a higher conductor temperature than conventional thermoplastic polyethylene in appropriately rated power cables?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• A cable insulation must tolerate moisture, chemicals and normal mechanical handling. Which selection principle is most appropriate?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why were traditional PCB-containing insulating liquids such as Pyranol phased out or severely restricted in many applications?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Which property is particularly important when evaluating whether transformer oil can circulate effectively and transfer heat?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why must dissolved moisture and solid particles be controlled in transformer oil?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Which combination best describes the two principal functions of mineral oil in an oil-filled transformer?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why is a suitably high flash point desirable in transformer oil?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Transformer oil has acceptable breakdown voltage but unusually high acidity. What is the most appropriate interpretation?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why should transformer oil be tested under controlled electrode spacing and prescribed test conditions?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• A sample of transformer oil has a significantly lower breakdown voltage than expected. Which action is most appropriate before deciding whether the oil is serviceable?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Which statement correctly distinguishes nitrogen from SF6 as an insulating medium?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why is gas pressure an important design parameter in gas-insulated switchgear?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• An SF6 circuit breaker has experienced an internal arc. Which maintenance precaution is most appropriate before personnel handle the affected compartment?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Which statement best describes the principal electrical advantage of SF6 in high-voltage switchgear?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why can moisture and contamination significantly reduce the dielectric performance of an insulating gas system?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• A gaseous insulator is subjected to increasing electric field intensity. Breakdown occurs when ionisation develops into a self-sustaining discharge. This phenomenon is primarily a…

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Which statement about Class C insulation is the most appropriate?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why does prolonged operation above the thermal rating of an insulation system generally reduce its service life?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard