Which test is done on cable before covering? - PowerPoint PPT Presentation

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Which test is done on cable before covering?

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Since cables are the most expensive equipment in an installation, they must be thoroughly tested using the methods listed above. This setup is just with two-wire continuity tests and may be used throughout the switching matrix. – PowerPoint PPT presentation

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Title: Which test is done on cable before covering?


1
What Is Cable Testing, And How It's Done?
2
  • The purpose of power cable testing is to
    guarantee that the cables insulation is intact
    and that they operate correctly. Durability,
    high-voltage resistance, and partial discharge
    detection are tested. Poor installation causes 99
    percent of cable issues during new electrical
    equipment commissioning.
  • Power cable suppliers in UAE do rigorous testing
    to ensures that any potential flaws are addressed
    before they cause more harm. They provide cable
    protection from minor lacerations to punctures
    that result in current discharge.

3
Why Test Cables?
  • Cable conformity
  • Cabling quality
  • Cable functionality
  • A cable fault may often be identified before it
    becomes a problem.
  • A visual inspection of your facility's wiring
    might uncover issues before they cause downtime.
    We look for copper corrosion, insulation cracks,
    dampness on wires, and other indicators of cable
    degradation.
  • It is critical to ensure that cables and
    couplings are in great operating order and that
    cable problem are detected immediately.
  • Cable testing should be a priority for Power
    cable suppliers in UAE to prevent and solve
    issues. Even with a range of test techniques and
    equipment, cable testing may be a challenging
    operation.
  • As a result, choosing and operating the best test
    equipment is as important as the test equipment
    itself.

4
What Happens When Cables Are Tested?
  • The tests and inspections required before
    energizing 600V or less low voltage cable are
    given below.
  • Compare the cable data to the drawings and specs.
  • Think about the number of sets and their
    insulation ratings.
  • Examine exposed cable portions for material
    degradation. Inspect the cable jacket and exposed
    insulation for damage.
  • Verify that the single-line diagram's connecting
    points match.
  • Check for excessive resistance using a calibrated
    torque wrench, low-resistance ohmmeter, or
    thermographic survey.
  • ANSI/NETA Table 100.12 US Standard Fasteners,
    Bolt Torque Values for Electrical Connections
  • Using a low resistance ohmmeter, compare the
    values of equivalent bolted connections to find
    which one moves more than 50 of the lowest
    value.
  • Examine the exposed cable jacket and insulation
    on low voltage wire and cable.
  • Before checking compression-applied connections,
    ensure the connector is rated for the cable size
    and has the appropriate indentations.

5
  • Each conductor should be tested for insulation
    resistance and ground resistance. The test must
    last one minute and utilize the manufacturer's
    recommended voltage.
  • If no manufacturer information is provided, use
    500/1000 volts dc for 300/600-volt cable. To
    calculate insulating resistance, use the
    manufacturer's data. Otherwise, the values should
    be at least 100 megohmstest for continuity to
    ensure appropriate cable connection and phasing.
  • Examine the resistance of parallel wires with a
    low-resistance ohmmeter. Identify resistance
    variations between parallel wires by measuring
    each cable independently.

6
How Is Cable Testing Done?
  • Power cable suppliers test the following things
    to avoid leakage
  • Continuity Check
  • The continuity test measures the low resistance
    of cables from 1 to 250 meters in length.
  • The continuity test can be done with two or four
    wires, depending on the resistance to be
    measured.
  • It includes injecting a preset current and
    measuring the resistance's terminals for voltage
    and current. Ohms law will decide that.
  • Divide the switching matrix into two internal
    buses using the Kelvin technique.
  • Directing the test current
  • transmitting voltage between the element's
    terminals
  • Opposing points are allocated to the
    measurement's SENSE and current injection. This
    setup is suitable with two-wire continuity tests
    and may be used throughout the switching matrix.

7
Insulation Testing
  • A high resistance test (insulation) is usually
    done in DC.
  • This test is combined with a short circuit and
    high voltage test in DC.
  • The insulation test has several uses.
  • The insulation test can reveal
  • calculating high voltage insulating resistances
    from 50-kilo ohm to 2000 megaohm
  • Detection of short circuits and dielectric
  • So, here's how it works
  • A low-voltage test (continuity measurement)
    detects short circuits (1). If a short circuit is
    found, the insulation test fails (the message
    SHORT CIRCUIT appears in the error list).
  • If there is no short, the high voltage is
    applied. Breakdown happens within the increasing
    time and the test is stopped (the breakdown
    voltage is given in the error list).

8
  • If there is no breakdown and the voltage does not
    reach the required level, the message UUprog
    displays (ten percent).
  • The voltage is then supplied for the set time
  • If a failure occurs within this period, the test
    is terminated, and the error time is displayed.
  • To conclude the application time, the insulation
    test is done, and the insulation resistance is
    measured
  • (4). An extra measurement time is added depending
    on the intended range. The measurement time
    varies from 20ms - 240ms.
  • To finish the test, the tester lowers the high
    voltage and discharges the object to the ground
    (total time 20ms).
  • Every insulation measurement ends with this step.
  • The dielectric strength test detects any rapid
    shift in the current test increase outside the
    specified limit.
  • Short circuit and high voltage testing can be
    disabled.

9
Experiment With Phasing
  • The proper phasing of all LV circuits must be
    verified at all locations where LV cables are
    terminated into fuse bases and while moving LV
    cables.
  • This test requires specifically designed
    equipment. A 240-volt mains voltage is
    insufficient for this test.
  • For this test, the neutral conductor must be
    grounded.
  • Earth Resistance Test
  • The earth resistance of an LV feeder in an
    overhead or underground network must be less than
    10 ohms before connecting to the existing
    network.
  • Any overhead or underground network must have a
    total resistance to earth of less than 1 ohm
    before joining.

10
High Voltage Test
  • A/C or DC high voltage testing (also known as
    dielectric strength testing or hipot testing) In
    DC, the high voltage test is linked with
    insulation in AC, the high voltage test is more
    demanding for the sample and is done as indicated
    below.
  • High voltage testing utilizes an alternating
    voltage (50Hz) adjustable from 50V to 1500V. In
    all cases, the high voltage test identifies any
    sudden increase in current up to a threshold.
  • The short circuit test is always active. The time
    between application and rise is at least a
    period.
  • The capacitance of the tested equipment penalizes
    the high voltage test. Remember that the
    generator's output is limited to 5 mA.

11
The Advantages of Cable Testing
  • Limited product warranties are available.
  • Repair is more costly than testing.
  • Testing regularly will ensure that the
    infrastructure is future-proof.

12
Conclusion
  • Since cables are the most expensive equipment in
    an installation, they must be thoroughly tested
    using the methods listed above.
  • Power cable suppliers install the cable in the
    proper directions, particularly in curvatures, to
    avoid bending and kinking and improve power
    transmission and avoid losses during
    transmission, thereby increasing the cable's
    reliability and suspension.

13
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