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SCE Transmission Groundman > Grounding Introduction > Flashcards

Grounding Introduction Flashcards

1
Q

Why do we ground?

A

To protect workers on de-energized high voltage cable and equipment.

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2
Q

When do we ground?

A
  • Working on a de-energized circuit that is normally energized above 600V, unless otherwise performing work with live line or other approved insulated tools.
  • During wire stringing, when high voltage sources are present.
  • Working in a Backfeed situation.
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3
Q

All conductors must be considered ________ until proven de-energized by testing and ________.

A

Energized; Grounding

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4
Q

How can Accident Energizing occur?

A
  • Inadvertent closing of Breakers, Taps, Switches or Fuses
  • Crossings
  • Backfeed
  • Induction
  • Static Charge
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5
Q

What are the two differences in potential?

A

Step Potential - Electrical potential difference between two points on the Earth’s surface, separated by distance of one’s pace.
Touch Potential - Electrical Potential difference between a grounded metallic structure and a point on the Earth’s surface.

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6
Q

What are different names for Personal grounds?

A

Shunts or Temporary Grounds

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7
Q

What are the sizes of grounds used?

A
  • # 2 Stranded Copper
  • 2/0 Copper
  • 4/0 Copper
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8
Q

What are the different styles of clamps on Grounds?

A
  • All-Angled Ground Clamp with Date Tag
  • Serrated Jaw Duckbill Clamp
  • Flat Jaw Clamp
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9
Q

What does an EPZ Mat do?

A

Provides an easy way to establish an EPZ for workers to stand on while performing work that could expose them to hazardous step and touch potential difference.

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10
Q

What are the key steps in the Grounding Process?

A
  • Conduct a thorough tailboard
  • Determine grounding requirements/size of grounds
  • Inspect grounds before each use
  • Clean ground connections
  • Test conductors de-energized
  • Apply Proper Grounds
  • Remove grounds when work is finished.
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11
Q

What should be included in a Grounding Tailboard?

A
  • Status of all lines and issued clearances
  • Identification of hazards and requires safeguards
  • Grounding method(s) and associated procedures to be utilized
  • The location(s) to which the personal grounds are to be applied
  • Verification of the size and number of grounds needed for the specific application
  • Requirement of testing to determine the lines or equipment are de-energized before installing grounds.
  • Review the process for applying grounds
  • Identify how the grounds should be placed in the bag
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12
Q

The larger the conductor size, the _____ the amount of ______ the conductor is capable of carrying before it overheats and fails.

A

Greater; Current

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13
Q

What is Maximum Fault Duty Current?

A

The calculated current that may occur during an accidental energizing of the conductor that is being grounded.

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14
Q

How is Fault Current primarily determined?

A

Voltage and Load

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15
Q

What can be found in Table 3-1 in the Overhead Grounding manual?

A

The quantity, size and length of grounds for the source voltage and fault-current duty at the worksite or source substations.

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16
Q

What is listed in the “Redbook” and here can it be found?

A

Fault duties of various substations, available online on the Protection Engineering website.

17
Q

How do you determine the size of grounds when grounding multiple circuits at one structure?

A

The maximum size conductor and/or greatest fault-current duty source.

18
Q

How do you determine the size of grounds when grounding multiple circuits at one structure?

A

The maximum size conductor and/or greatest fault-current duty source.

19
Q

Can you use a larger size ground than the size required?

A

Yes, unless otherwise noted in Notes 1 and 2 of Table 3-1 in the Overhead Grounding Manual.

20
Q

How do you ground if the primary protection on the circuit being worked on is not in service?

A

Contact Substation Construction and maintenance for site-specific grounding requirements.

21
Q

What length of grounds should you use?

A

The shortest length of grounds required for the job at hand.

22
Q

What size grounds can you use if the conductor is Cu and smaller than #2 regardless of source voltage and fault-current duty? 1/0 Al?

A

2 Copper Grounds

23
Q

What size grounds can you use if the conductor is Cu and smaller than 2/0 regardless of source voltage and fault-current duty? 4/0 Al?

A

2/0 Copper Grounds

24
Q

When should grounding components be inspected?

A

Prior to use.

25
Q

What do you look for when inspecting ground cable?

A
  • Cuts, nicks, and abrasions that may have penetrated through the jacket into the conductor
  • Kinks that could possibly damage strands
  • Ensure ground cable is not damaged (Ex: Flattened)
  • Swollen cable jacket or soft spot for indication of internal corrosion or damage to strands
  • Verify the GARP test date is current (within 24 mos)
26
Q

What do you look for when inspecting ground clamps?

A
  • Ensure all components are in place and tight
  • Loose threaded ferrule connections to the clamp assembly shall be tightened before use
  • Ensure ferrules and clamps are not cracked or broken
  • Visually inspect the clamped ferrule on the end of the conductor for broken strands or visual signs of corrosion
  • Inspect for indications of corrosion at the threaded connection, hinge points, or any surfaces of the clamp
27
Q

What do you look for when inspecting EPZ Mats?

A
  • Visually inspect EPZ mat and ensure it is clean and in good working condition
  • The braids shall be intact
  • Holes in the canvas are acceptable
  • EPZ mat can be cleaned, washed off with mild soap and water, towel and air-dried
  • Verify that the ground stud connection to the EPZ mat is clean and functional
  • Verify that bonding conductor clamps and connections are clean
  • Check for broken strands on the bonding conductor or damage to the protective covering that has migrated to the inner conductor
28
Q

What do you do if a ground cable, clamp, EPZ mat or accessory is found to be in unsatisfactory?

A

Remove from service

29
Q

How do you clean ground connections?

A
  1. ) Clean the ground mediums for suitable ground connections before making ground connections
  2. ) Remove any rust or paint
  3. ) Clean station ground grid pigtails using a wire brush, file card or emery paper
  4. ) After removal of grounds, re-paint and/or apply cold galvanizing to the disturbed surfaces of all structures
30
Q

What is the order for applying and removing grounds?

A

Grounding devices shall be attached to the medium first and then conductor and remove in the reverse order.

31
Q

What is the Grounding Priority for selecting a Grounding Medium?

A

1.) Substation Ground Grid
2.) Multi-Grounded Primary Neutral
3.) Grounded Steel Structures
4.) Anchor Rods
If none of these are available, approved temporary grounds rods may be used.

32
Q

Under what condition can you leave grounds overnight?

A

1.) The ground level connection shall be buried or placed in a secure enclosure. In, addition the first 10’ of the conductor from ground level shall be covered with wood molding or PVC covering. Before starting work again, the ground connection cover and ground conductor shall be removed and inspected.

33
Q

What is an EPZ?

A

An Equipotential Zone is a safe workplace created by using pole bands, EPZ mats, ground rods, and/or anchor rods. Everything within this zone should be at the same potential.

34
Q

What is Bracket Grounding?

A

A grounding method where the shorting and grounding of de-energized conductors is performed with a set of grounds located on each end of a section of downed conductors, between the work area and all electrical sources.

35
Q

What is the maximum distance bracket grounds can be spaced?

A

No further than 2,500’

36
Q

How do you install EPZ mats?

A

Do not install EPZ mats in such a manner as to conduct electrical current. Always connect the mats at a single point to the de-energized and grounded conductor, equipment, or vehicle. Mats can be connected to each other to create a larger workspace. Connect mats to each other by hand prior to the conductor using approved live-line tools.

37
Q

What are the two approved ground rods configurations?

A
  1. ) One single rod buried a minimum of 7’ deep, maximum 45-degree angle from center.
  2. ) Two parallel ground rods driven to a minimum of 30” deep and a minimum of 6’ apart.

SCE Transmission Groundman (7 decks)

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