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Power Cable Test Methods Flashcards

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

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  1. In a DC hipot test, which component of leakage current is most indicative of insulation condition?

    Answer: Resistive (conduction) leakage current

    The resistive component represents true conduction through the insulation and reflects the insulation's dielectric quality; capacitive current decays after initial charging.

  2. What minimum insulation resistance value does NETA MTS typically cite for 600 V rated cables in field maintenance testing?

    Answer: 1 MΩ

    NETA maintenance tables set a minimum acceptance threshold of 1 MΩ for low-voltage insulation; values below warrant investigation.

  3. What is the significance of the Polarization Index (PI) in cable insulation testing?

    Answer: Ratio of 10-minute IR to 1-minute IR, indicating insulation dryness and integrity

    The PI is the ratio of the 10-minute IR to the 1-minute IR; values above 2.0 for most insulation types indicate acceptable dryness and integrity.

  4. During a TDR test, a reflected pulse arrives back sooner than expected for the cable's known length. What does this indicate?

    Answer: There is an open-circuit fault closer to the test end than the far end

    A reflection arriving earlier than the far-end open means an impedance discontinuity (fault) exists at a shorter distance along the cable.

  5. Why is DC hipot testing generally discouraged for service-aged XLPE cables per IEEE 400?

    Answer: DC stress can cause space charge buildup that damages water-treed XLPE insulation

    Space charge accumulation in aged XLPE under DC stress can cause localized field enhancement that leads to breakdown, making DC hipot potentially destructive.

  6. Which parameter measured during a VLF tan delta test indicates early-stage water treeing in XLPE cable?

    Answer: A rising tan delta value with increasing test voltage (tip-up)

    Voltage-dependent increase in tan delta (tip-up) is a classic signature of water tree degradation in XLPE cable insulation.

  7. What safety action must be performed on a test cable immediately after completing a DC hipot test?

    Answer: Slowly discharge the cable through a resistor and verify zero voltage before touching

    Cable capacitance stores charge at the full test voltage; it must be discharged slowly through a resistor and then verified with a voltmeter before personnel contact.