HV Exit Exam • Set 6 Question 24 of 30
The DC contact resistance across closed main contacts of a healthy high-voltage circuit breaker is typically in the order of:
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Direct Answer
Option A: 20 to 50 micro-ohms (μΩ)
Main contact resistance measured with a micro-ohmmeter (ductor test) must be very low (typically 20 to 50 micro-ohms) to prevent severe I²R overheating under full load currents.
All Options
A
20 to 50 micro-ohms (μΩ)
(Correct Answer)
B
20 to 50 milli-ohms (mΩ)
C
20 ohms (Ω)
D
200 ohms (Ω)
Detailed Explanation & Context
Main contact resistance measured with a micro-ohmmeter (ductor test) must be very low (typically 20 to 50 micro-ohms) to prevent severe I²R overheating under full load currents.
Relevant Framework: STCW 2010 Manila Amendments • DG Shipping E-Learning & Exit Exam Standards • High Voltage Safety Officer & Switchgear Operations (HV).
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