Practice Test Geeks(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test
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Cable Testing and Diagnostics Flashcards

6 cards from real NETA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 Cable Testing and Diagnostics flashcards as text

  1. A DC hi-pot test on a shielded power cable measures:

    Answer: The cable's insulation integrity by applying DC overvoltage and monitoring leakage current

    DC hi-pot tests apply a DC overvoltage (per IEEE 400 or cable manufacturer specifications) to cable insulation and monitor leakage current. Excessive current, current instability, or sudden increases indicate insulation defects.

  2. The VLF (Very Low Frequency) test for medium-voltage cables uses a test frequency of approximately:

    Answer: 0.1 Hz, which reduces the charging current requirement by a factor of 600 compared to 60 Hz testing

    VLF tests at 0.1 Hz (one-tenth of a cycle per second), which reduces the capacitive charging current by a factor of 600 compared to 60 Hz (since Ic = 2*pi*f*C*V). This makes portable test equipment practical for field cable testing.

  3. Time Domain Reflectometry (TDR) is used on power cables to:

    Answer: Locate the position of faults, splices, and discontinuities by measuring the travel time of reflected pulses

    TDR sends a fast electrical pulse down the cable and measures the time for reflections to return from impedance discontinuities (faults, splices, terminations). Using the cable's propagation velocity, the distance to each discontinuity is calculated.

  4. The dielectric loss tangent (tan delta) test on cables measures:

    Answer: The ratio of resistive (loss) current to capacitive current, indicating insulation quality and aging

    Tan delta (dissipation factor) measures the ratio of power loss (resistive current) to reactive power (capacitive current) in the insulation. Values increase with moisture contamination, chemical degradation, or water treeing.

  5. Cable jacket testing (sheath integrity testing) using DC current verifies:

    Answer: That the outer jacket/sheath has no breaches allowing moisture to reach the metallic shield

    DC sheath testing applies low DC voltage (typically 1 to 5 kV) between the metallic shield and the outer jacket, measuring insulation resistance to verify no holes, cuts, or abraded areas allow moisture ingress that could cause shield corrosion and insulation moisture treeing.

  6. Partial discharge (PD) measurement on a medium-voltage cable system identifies:

    Answer: Localized defects in the insulation or accessories (splices, terminations) where PD activity is concentrated

    PD measurement on cables detects and locates localized insulation defects — voids, contamination, water trees at critical size — primarily at terminations and splices where field enhancement occurs, before these progress to complete insulation failure.