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SFT 11kV > SFT QUESTIONS > Flashcards

SFT QUESTIONS Flashcards

1
Q

Test prod checks

A
  1. Check in date for testing
  2. Correct prods for the switchgear
  3. No loose parts, general condition ok
  4. Check clean and contacts are good
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2
Q

What must you do to the test prod and why

A

Wipe with a lint free cloth before and after to prevent contamination from oil/dirt

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3
Q

HV insulations tests on overhead line

A

High leakage to earth may occur due to dirty/damp insulators

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4
Q

Normal 11kV test voltage and duration

A

18kV DC for 5 minutes less than 1mA leakage

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5
Q

What is a good HV test result

A
  1. Steady leakage of less than 1mA.
  2. If the test is unsatisfactory discuss with system controller

18kV = New cables
15kV <= 20 years old
13kV > 20 years old

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6
Q

Distribution ground mount transformer testing (prior to energising)

A

1000V DC IR test with winding to earth/tank in turn for HV and LV windings

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7
Q

Secondary switchgear

A
  1. Close switch, test between phases and each phase to earth 1000V DC/100MOhm
  2. Switch open test across each phase contacts
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8
Q

11kV GMT TX

A
  1. LV winding IR 1000V DC test with HV winding/tank grounded
  2. HV winding IR 1000V DC test with LV winding/tank grounded
  3. Test between HV/LV winding
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9
Q

11kV PMT tests

A
  1. LV winding IR 1000V DC test to earth
  2. HV winding IR 1000V DC test to earth
  3. Test between HV/LV winding
  4. Between Neutral and earth
    5 Continuity between HV winding phases and LV winding phases/neutral
    100MOHMs
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10
Q

Colour cartridge for armoured cables up to 80mm diameter/plain lead/covered sheath

A

Green

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11
Q

Heavy Charge for Steel Armoured Cables with a diameter between 80-150mm.

A

Red

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12
Q

Light Charge for all aluminium
corrugated sheathed cables up to
300mm² including
small plain lead cables.

A

Silver

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13
Q

Extra Light Charge for small XLPE
polymeric type cables without any solid
outer metallised sheath.

A

Yellow

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14
Q

Procedure for spiking pot ended cables

A
  1. Issue SFT/Carry out risk assessment for PE cable/Identify other cables/confirm with plan
  2. Spike cable whilst on phone to control
  3. Insulation test the cables to confirm the cores have been spiked
  4. Use spiking gun as short and IED cable at point of work (signal on one side but not the the other)
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15
Q

Misfire procedure

A
  1. Do not touch anything and inform control
  2. Wait 3 minutes
  3. Set safety catch to correct safe position
  4. Undo breech cap 1 turn, lift extractor to remove cartridge
  5. Remove breech cap and lift out cartridge
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16
Q

Methods of checking phasing

A
  1. Cold phasing (end to end before and after)
  2. Testing against and LV backfeed
  3. VT/Pfisterer on secondary side
  4. Use of HV phasing sticks or phasing pods across switch or spouts
17
Q

HV belted cable

A

L1, L2 to -ve L3 - earth, test set to earth then swap after 5 minutes on cores

18
Q

XLPE cable testing connections

A

All cores together for 5 minutes

18
Q

4 exceptions to spiking cables at point of work

A
  1. Traced visually to a CME
  2. Gas/Oil/Submarine cables
  3. Sheath repairs
  4. Pot ended cables
18
Q

Preparing ends for testing

A

Under immediate supervision of an SAP

18
Q

If you cannot get a clear signal on a cable ID

A

Switchout and ID all other cables

18
Q

If you cannot get a good signal on the point of work

A

Put in test prods, short 2 cores together and remove CME

18
Q

ID a HV cable connected to a transformer

A
  1. Connect cable IDer to LV windings and close remote HV earth switch
  2. Insert C carriage to fuse switch and use TX windings as a remote short
18
Q

Who records and retains the details of the issue and cancellation of each SFT

A

Control engineer or SAP if under NOP2, 3 or 4

19
Q

What can you do to avoid X-rays from vacuum switchgear

A

Stand clear of 3 m whilst switchgear is being tested

SFT 11kV (1 decks)

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