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SCE Transmission 1st Step > Grounding > Flashcards

Grounding Flashcards

1
Q

Why do we ground?

A

Grounding is required for protection of the worker when working on de-energized high voltage lines or equipment.

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2
Q

What does using personal grounds do?

A

Minimizes hazardous exposure associated with making contact with objects having a difference of electrical potentials.

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3
Q

What should workers do with grounds?

A

Avoid making contact with applied grounds wherever possible to minimize exposure to hazardous conditions.

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4
Q

What is important to understand about grounding?

A

While a power line may be grounded, it can still be hazardous if the line is inadvertently energized or if a worker is in close proximity with objects with a difference of potential.

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5
Q

What are high voltage sources of suppy?

A
  • Inadvertent closing of a breaker, switch, tap, or fuse
  • Crossings
  • Backfeed
  • Induction
  • Static Charge
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6
Q

What is Inadvertent closing breakers, switches, taps and fuses?

A

When de-energized conductors to be worked on can be energized by a breaker, switch, tap or fuse, this equipment shall be considered a high-voltage source of supply. Co-Gen facilities are considered a high-voltage source of supply

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7
Q

What are crossings?

A

Energized high-voltage lines (above 600kV) crossing over de-energized line shall be considered a source of supply. Unprotected energized lines that cross under a de-energized line shall also be considered a source of supply. Crossings can be attached or unattached.

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8
Q

What is Backfeed?

A

Backfeed is the reverse energizing of a high-voltage transformer from the low-voltage side tto the high-voltage side. Sources of backfeed include extension cords to a neighbor’s panel, motor homes, portable generators, solar panels, wind generators, and temporary poles at a construction site.

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9
Q

What is Induction?

A

Induced voltage can be the result of high-current values in parallel lines, such as high-voltage lines parallel to de-energized conductors being worked on. When a circuit is de-energized, it may have a voltage induced in it due to current in the other circuit. Transmission lines can induce dangerously high potentials even though they may be carrying small currents. In addition, radio, tv, or microwave antennas located within close proximity could also induce voltage.

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10
Q

What is Static Charge?

A

A static charge can accumulate when conductors are exposed to hot, dry winds. This is the same type of charge accumulated from walking on a wool rug. Static charge generated on overhead lines can become hazardous to workers when not eliminated using the grounding methods in the OGM.

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11
Q

When do we ground?

A

Grounding is required when working on a (de-energized) circuit that is normally energized above 600V, unless otherwise performing work with live line or other approved insulated tools.

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12
Q

When else are grounds required?

A

During wire stringing when high voltage sources are present.

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13
Q

All conductors shall be considered _______ until proven de-energized by testing and grounding.

A

Energized

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14
Q

What shall be added when working from a grounded or steel structure?

A

Personal grounds shall be installed between each conductor being worked on and the structure.

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15
Q

What might exist between the structure where the work is being performed and the ground mediums for grounding?

A

Hazardous difference of electrical potential

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16
Q

What is an Equipotential Zone?

A

Workspace

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17
Q

What is required when an Equipotential Zone is not created on grounded and/or steel structures?

A

Personal Grounds

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18
Q

What are the requirements grounds should meet?

A
  • Size
  • Test Date
  • Inspection
  • Maintenance
  • Length
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19
Q

What size grounds should you use if multiple sources can inadvertently energize the line?

A

The largest size of grounds that will provide protection for all sources involved.

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20
Q

What length of grounds should you use in all scenarios?

A

The shortest length

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21
Q

What does the shortest length possible do?

A

Keeps the resistance values as low as possible and reduces the need to coil excess length of installed grounds and restrain the slack grounds after installation.

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22
Q

Can you connect multiple lengths of short grounds between any conductors or structures?

A

NO

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23
Q

What is needed to connect multiple grounds together for connecting ground rods or anchor rods?

A

Ground Bar

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24
Q

What should you do with grounds and grounding equipment prior to use?

A

Inspect

25
Q

What should you do with grounds that have been exposed to fault current and/or accidental energizing?

A

Remove from service

26
Q

What is the priority of ground mediums?

A
  1. ) Ground Grid
  2. ) Multi-Grounded Primary Neutral
  3. ) Grounded Steel Structures
  4. ) Anchor Rods
  5. ) Temporary Ground Rods
27
Q

What are the grounding schemes in order of preference?

A
  1. ) Parallel
  2. ) Balanced
  3. ) Unbalanced
28
Q

What do you use to install, relocate and remove grounds?

A

Approved live-line tools

29
Q

What should you avoid doing when installing grounds?

A

Coiling of grounds.

30
Q

What should you do with grounds with excessive lengths?

A

Restrain them by securing with small ropes tied from the grounds to a secure anchorage.

31
Q

Why do you restrain grounds with long lengths?

A

Limits the amount of movement that may occur during a fault and reduces the mechanical stress imposed on the ground cable, clamps, and ferrules.

32
Q

What do you keep between de-energized conductors/equipment and ground medium(s) at a minimum?

A

Resistance

33
Q

What shall be installed when making or breaking continuity and how?

A

Shunts using approved live-line tools

34
Q

What is used to create an Equipotential Zone (EPZ)?

A

Pole bands, EPZ Mats, Anchor rods, or temporary ground rods.

35
Q

What do you create around TGRs, steel structures, and vehicles when grounding?

A

Clearance area

36
Q

Ensure that one set of the applied grounds is visible to at least one of the crew members unless?

A

The applied grounds are accessible only to authorized persons.

37
Q

Where would you use a parallel grounding scheme?

A

Circuits on Steel Structures

38
Q

How many grounds in series is permitted?

A

No more than 3 grounds/shunts

39
Q

How would you ground in parallel?

A

Each conductor is taken to its own ground

40
Q

Where would you use a balanced grounding scheme?

A

Circuits on wood poles

41
Q

How would you ground in balance?

A

Each conductor is grounded to a shared ground.

42
Q

Where would you use an unbalanced grounding scheme?

A

Circuits on wood structures where a balanced grounding scheme is not feasible

43
Q

Where would you not use an unbalanced grounding scheme?

A

Within 40’ of a substation ground grid.

44
Q

How would you ground unbalanced?

A

Daisy chaining the conductors together to reach ground.

45
Q

What would you do if there is a foreign ground in the equipotential zone?

A

It must be grounded with a minimum of #4 solid copper to the pole band

46
Q

What can a foreign ground be?

A
  • CATV and telephone grounded messengers
  • Secondary grounds
  • Surge arrestor grounds
  • Structure grounds
  • Fault Return Conductor (FRC)
  • Grounded anchor (down) guys and span guys
  • Umbrella (Communication Cable Protector)
  • Any other ground located within the workspace
47
Q

What does Fault Return Conductor do?

A

Provides a metallic bond between Light Weight Steel pole structures.

48
Q

What do you need to do when the FRC needs to be removed or electrically isolated from the structure?

A

Install a pole band and an approved ground jumper applied to the FRC.

49
Q

What do you do when the FRC needs to be cut?

A

Use an approved 2/0 minimum jumper/by-pass across the open ends of the FRC.

50
Q

What shall the FRC not be used as?

A

A ground medium

51
Q

What should you not do when working on or near the FRC?

A

Do not place yourself in series between the structure and the FRC.

52
Q

What does the term “grounded span and down guys” refer to?

A

Guy wires that do not have strain insulators or fiberglass strain rods.

53
Q

What is a span or down guy that has a strain insulator that has been jumpered considered?

A

Grounded

54
Q

What do you do with grounded down and span guys that are attached to the pole being worked on located in the workspace?

A

They shall be connected to the grounding scheme.

55
Q

What should you do if multiple down guys are in the workspace?

A

Bond anchors together

56
Q

What do you do if one down guy has a strain insulator?

A

Use the grounded down guy anchor. (One without the insulator)

57
Q

What do you do when and anchor rod cannot be used as a grounding medium?

A

An approved jumper shall be installed either from the conductor to the span guy or the pole band to the span guy

58
Q

What are the two preferred grounding methods?

A
  • Overhead Equipotential Bracket Grounding

- Overhead Bracket Grounding

SCE Transmission 1st Step (11 decks)

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