Introduction To Cable Fault Locating Flashcards
Why is fast fault locating important in underground cables?
It allows service restoration quickly, even if full repairs take longer.
What is a key skill for Qualified Electrical Workers regarding faults?
Mastery of the employer-provided fault-locating equipment.
What two goals are essential in fault locating?
Finding the fault and restoring service safely.
What safety procedures must be followed during fault locating?
Isolation, proper grounding, PPE use, and tagging cables.
What can happen if cables aren’t properly isolated or grounded?
Workers may be seriously injured.
What should companies have in place for safe fault locating?
A tested “attack plan” and trained personnel.
Where do most cable faults typically occur?
In ordinary residential systems.
Why is no single method ideal for every fault?
Field conditions vary, requiring different tools and techniques.
What are the two most common fault-locating methods?
Thumper (impulse tracer) and A-frame tracer.
Why can fault locating in plastic conduit be inaccurate?
Water can redirect current to a distant ground path.
What might a thumper locate in conduit with water present?
The conduit crack, not the actual insulation fault.
What equipment might be needed for faults in conduit?
A radar unit.
What might engineers choose to do if the cable is in conduit?
Pull a new cable run instead of digging
What is a thumper in cable testing?
A capacitor-discharge impulse generator used to locate faults.
What components are in a typical thumper unit?
Step-up transformer, rectifier, capacitor, calibrated discharge gap.
How does a thumper locate a fault?
By inducing a high-voltage impulse that arcs at the fault, producing a sound.
Why is it called a “thumper”?
The faulted cable produces a “thump” sound when the arc occurs.
What might be necessary before arcing occurs?
Burning or carbonizing the fault path.
What can happen if the thumper voltage is too high?
It may cause additional cable damage or future faults.
Who should determine the maximum voltage for testing?
An engineer.
Why is “cranking up the voltage” unsafe?
It may exceed the grounding system’s capacity and endanger workers.
What does the MODE SELECT switch do on a thumper?
Sets the operation mode such as Ground or Surge.
What happens in the GROUND position?
The output is connected directly to the thumper chassis’ ground.
Why must a thumper unit in a van be grounded?
To avoid dangerous current flowing through an ungrounded chassis.
