By: Rick Kennerly Alive & Grounded!! Are your personal grounds really protecting you?

By: Rick KennerlyBy: Rick Kennerly

Alive & Grounded!!Alive & Grounded!!Are your personal grounds really Are your personal grounds really

protecting you?protecting you?

Overview

• Reactive Safety Process• Evolution of PPG Equipment• ASTM Qualification Testing• Buyer Beware• Changing Viewpoints• No Substitutions• In Service Testing and Maintenance• Final Lesson

Reactive Safety Process

• We do the best we can with what we know• Near miss or incident occurs• New work methods are developed• Different equipment is utilized• Education and training on the new work

methods and equipment is implemented• Near miss or incident occurs again and

this process starts all over

Evolution of PPG Equipment

• We tested for voltage using a crescent wrench and used any wire or chain we could find to lay across conductors

• 30 years ago we started using lights for testing voltage and welding cable attached to anything we could find for grounding.

• 20 years ago we started field testing the grounds and realized what we were doing wasn’t the best

• Today, we’re still learning how to improve our equipment, education methods, and working procedures to keep both the workers and the public safe as every utility builds and maintains the national electric grid.

Qualification Testing

• 1983 ASTM F855 specified testing needed to qualify equipment to be used

• 2009 a new table 2 was developed to accomodate higher fault currents

• 2009-2013 further testing revealed inadequacies with original Table 1 that allowed different methods for rating any particular assembly

Qualification TestingASTM F855 Table 1

Grade Cable

Size

Withstand Rating Ultimate Rating

15 cyc 30 cyc 15 cyc 30 cyc 60 cyc

1 #2 14 10 18 13 9

2 1/0 21 15 29 21 14

3 2/0 27 20 37 26 18

5 4/0 43 30 59 42 29

6 250MCM 54 39 70 49 35

7 350MCM 74 54 98 69 48

Qualification TestingASTM F855 Table 2

Grade Cable Size Rating (kA) X/R=30 1st Cycle Peak

X/R=30 last Cycle Peak

15 Cycles

1 #2 15 41 23

2 1/0 25 65 37

3 2/0 31 84 46

5 4/0 47 126 70

6 250MCM 55 148 82

7 350MCM 68 183 101

Mechanical Failure – Top Clamp Breaks

Mechanical Failure – Bottom Clamp Breaks

Mechanical Failure – Top Clamp Breaks

Mechanical Failure – Top Clamp Breaks

Thermal Failure – Plug Style Ferrule

Thermal Failure – Cable Separation

Thermal Failure – Cable Fusing at Ferrule

Mechanical Failure – Pole Step

Mechanical Failure – Pole Stud

Buyer Beware

• Misinterpretation of Table 1

• Rigid Bus vs AAC/ACSR

• Substations and High X/R

• Mechanical and Thermal Energy

• If a connector or cable fails to survive thermal or mechanical stress, it may fail electrically before the circuit clears, rendering the ground useless as protection

Changing Viewpoints• Testing is forcing manufacturer’s to make

better clamps

Finer threads allow for greater pressure applied to conductor

Lower Jaw adjustment accommodates bus sizes from 2” to 6” IPS

Stainless eye screw forces current through upper jaw only and allows smoother operation

Molded stud allows for 2 Clamps to be installed in parallel to reduce lifted weight of rated cable assembly

Changing Viewpoints

• Substation weld/bolt on studs fail

Changing Viewpoints

Changing ViewpointsSingle versus double ground testing

Changing ViewpointsSingle versus double ground testing

Changing ViewpointsOne 4/0 ground can out perform two 2/0’s

Changing Viewpoints

Qualification TestingASTM F855 Table 1

Grade Cable

Size

Withstand Rating Ultimate Rating

15 cyc 30 cyc 15 cyc 30 cyc 60 cyc

1 #2 14 10 18 13 9

2 1/0 21 15 29 21 14

3 2/0 27 20 37 26 18

5 4/0 43 30 59 42 29

6 250MCM 54 39 70 49 35

7 350MCM 74 54 98 69 48

Changing Viewpoints

• REVIEW test reports for ALL your grounding products (hire professional if help is needed)

• Before and After Photos

• Wave forms are important

• Video of equipment if possible

Changing Viewpoints

• NEVER use a protective ground above its tested value or outside its tested configuration

No Substitutions

• Ferrules – #1 Problem because of different dimensions, dies, material, and hardness levels

• Cable - #2 Problem because the manufacturing processes are mostly tailored to normal welding cable specs

In Service Testing & Maintenance

• Circulate alternating current through the cable assembly at its ASTM continuous current rating.

• Measure the voltage drop of the entire assembly to determine pass/fail criteria for the assembly.

• If a cable heats at it continuous current rating, then the same cable will melt at its ultimate current rating.

Visual Inspections

• Cracked or broken clamps

Visual Inspections• Cracked or poorly crimped ferrules

Visual Inspections• Broken strands

Visual Inspections

• Cut or badly mashed or flattened cable• Extensive damage to cable covering• Swollen cable jacket (internal corrosion)• Soft spots in conductor• Blackened strands

Grounding Equipment

• Cable – What is the difference between grounding cable and welding cable?

• Ferrules – Shrouded/Unshrouded Plain/Threaded

• Heat Shrink

• Clamps – “C”, Duckbill, Flat, Ball Socket, All Angle, Bus, Vice Grip, etc.

• Assemblies

Cable

• TPE jacketed using tight lay construction with no medium between copper strands and insulation

Ferrules

• CDA102 or CDA110 heat treated copper

• Impact Extrusion process

• Roll Threaded not machined

• Can be plated

• Both shrouded and unshrouded

Clamps

Final Lesson

• Substation Grounds – higher mechanical and thermal energy, rigid structure testing

• High current test reporting• Eyescrew Torque requirements• Ferrule to Cable pull out strength• Mechanical versus thermal• Single Ground vs Double Grounds• Regular maintenance inspection and testing• Maintenance Procedures

Special Thanks

Pacific Gas & Electric

Public Service of New Jersey

Entergy

Bonneville Power Administration

Powertech Labs

S&C Labs

Travis Pattern & Foundry

Trystar Cable Company

MLE Engineering Inc.