Temporary safety grounds are used to help protect electrical workers when working on de-energized and isolated conductors or equipment.

A temporary safety ground creates a temporary connection between de-energized voltage conductors and the earth, allowing workers to perform tasks with a safer path for fault current if accidental energization occurs. In most cases, this connection is made using a highly conductive copper cable with a suitable clamping device at each end.

For Canadian electrical contractors, utilities, industrial sites, and maintenance teams, temporary safety grounding should always be planned according to applicable site procedures, the Canadian Electrical Code where relevant, provincial or federal occupational health and safety requirements, and workplace electrical safety standards such as CSA Z462. CSA Z462 provides guidance around electrical safety programs, safe work procedures, PPE, safety devices, and qualified electrical worker criteria.

What Are Safety Grounds?

Safety grounds are temporary grounding assemblies used to connect isolated, de-energized conductors to ground.

Their purpose is not cosmetic and not procedural box-checking. They exist because a circuit that has been switched off may still become dangerous through accidental re-energization, induced voltage, backfeed, stored energy, incorrect switching, or unexpected contact with another energized source.

A proper temporary safety ground gives fault current a low-impedance path so protective devices can operate if the system is accidentally energized. It also helps reduce dangerous voltage differences in the worker’s immediate work area.

In practical field terms, a safety ground usually includes:

• A conductive grounding cable
• Rated clamps
• Ferrules or terminal connections
• Suitable connection points
• A planned grounding arrangement
• Inspection and testing records where required

The equipment must be selected for the actual system conditions. A ground set that looks heavy-duty is not automatically safe for every job.

How to Size Safety Grounds

Protective grounding equipment must be capable of conducting the maximum fault current that could flow at the grounding point for the time required to clear the fault. The original JM Test article also notes that protective grounding equipment should have ampacity greater than or equal to No. 2 AWG copper.

The key issue is fault duty. If the grounding assembly cannot withstand the available fault current, it may fail violently. In a high-energy event, an undersized grounding cable can behave like a fuse. That failure can create serious injury risk and equipment damage.

When sizing safety grounds, consider:

• Available fault current
• Fault-clearing time
• Cable size
• Cable length
• Clamp rating
• Ferrule condition
• Connection quality
• Grounding arrangement
• Mechanical forces during fault current
• Whether parallel cables are required

Cable length matters because longer cables add impedance. The goal is to keep impedance as low as practical so overcurrent protective devices operate quickly and fault energy is limited.

As a practical rule, grounding cables should be no longer than necessary. Excess slack can also create physical hazards because fault current can cause violent cable movement.

Impedance and Fault Clearing

Temporary safety grounds must have low enough impedance so they do not delay protective device operation if accidental energization occurs.

This is where many unsafe setups fail. A grounding assembly is not just a cable. The entire path matters.

Low impedance depends on:

• Cable size
• Cable length
• Clamp design
• Clamp tightness
• Clean contact surfaces
• Ferrule integrity
• Routing
• Connection to the grounding point
• Condition of the conductor being clamped

Dirt, oxidation, paint, corrosion, grease, and loose hardware all increase resistance. That extra resistance can reduce the effectiveness of the ground and increase the risk to the worker.

Temporary grounds should be installed to support an equipotential work zone as much as practical. The closer the grounding arrangement is to the actual work area, while still maintaining safe working distance and physical clearance, the better the protection strategy usually is.

Using Parallel Ground Cables

In some applications, one protective ground cable assembly may not have the required withstand rating. In that case, identical ground cables may be connected in parallel, but their ratings should not simply be added together at full value.

The original JM Test article gives the example of two parallel No. 2/0 AWG copper cables, each rated at 27,000 amps for 15 cycles, producing a combined derated rating of 48,600 amps rather than 54,000 amps.

This derating matters because current may not divide equally between parallel cables. One cable may carry more current than the other due to small differences in cable length, resistance, clamp contact, or routing.

Parallel grounding should only be used when the equipment, method, and job plan support it. It should not be improvised in the field.

Inspection, Cleaning and Testing

Ground sets should be inspected before each use, and contact surfaces should be cleaned before installation. The original JM Test article lists several inspection concerns, including loose connections, corrosion, contamination, damaged clamps, broken strands, damaged ferrules, and cable jacket damage.

A temporary ground set should not be used if there is any doubt about its condition.

What to Inspect Before Use

Before installation, inspect the grounding assembly for:

• Cracked ferrules
• Broken ferrules
• Cracked clamps
• Damaged clamps
• Exposed broken conductor strands
• Cut cable
• Mashed or flattened cable
• Kinked cable
• Swollen cable jacket
• Soft spots in the cable jacket
• Cracked insulation or jacket damage
• Corrosion
• Loose threaded ferrules
• Loose jam nuts
• Dirt, grease, oil, or oxidation on contact surfaces
• Poor clamp movement through its full range
• Any modification or field repair that has not been approved

If any of these conditions are found, the grounding jumper assembly should be removed from service. Depending on the condition, it may need to be tagged, repaired, tested, destroyed, or permanently marked to prevent reuse.

Why Visual Inspection Is Not Enough

Some damage cannot be seen during normal visual inspection.

Corrosion inside ferrules, poor internal connections, strand damage, and high-resistance connection points may not be obvious. That is why periodic low-resistance electrical testing should be performed to confirm that the ground set remains within acceptable resistance limits.

ASTM F2249 is commonly referenced for test methods and pass/fail resistance values for personal protective grounding sets. The source article also points readers to NFPA 70E, OSHA 1926.962, and IEEE 1048 for additional information.

For the Canadian version, those US references should be treated as technical references, not Canadian legal requirements. Canadian teams should verify requirements against applicable Canadian regulations, CSA Z462, site procedures, and the authority having jurisdiction.

Procedures for Installing Grounds

Temporary safety grounds should be installed using a disciplined procedure. The order matters because the worker should never become the lowest-resistance path to ground.

Step 1: De-Energize the Line According to Procedure

Before installing grounds, the line or equipment must be de-energized and isolated according to the documented procedure.

Use the site’s lockout/tagout process to confirm the circuit or equipment has been isolated from all hazardous energy sources. Temporary protective grounds should be placed to create an equipotential zone near the work location while maintaining safe distance from any potential violent movement if a fault occurs.

This should be planned before the job starts, not decided casually in the field.

Step 2: Test the Circuit for Voltage

Never assume a circuit is de-energized just because it has been switched off.

Other energy sources, including induction from nearby energized circuits, may create hazardous voltage. The source article recommends a 3-point test, commonly described as live-dead-live testing.

The sequence is:

1. Test the voltage tester on a known energized source to confirm it works.
2. Test the circuit or equipment where work will be performed.
3. Re-test the voltage tester on the known energized source to confirm the tester still works.

Workers should wear appropriate shock and arc-flash PPE when applying grounds.

Step 3: Clean All Connections

Grounding connections must be clean and conductive.

Extra resistance from dirt, oxidation, paint, corrosion, grease, or oil can reduce the effectiveness of the grounding path. If resistance is too high, the grounding arrangement may not perform properly during accidental energization.

Clean metal-to-metal contact matters. Ground clamps should be applied to suitable connection points and tightened according to the equipment instructions and site procedure.

Step 4: Apply Ground-End Clamps First and Remove Them Last

The ground-end clamp should be applied first. It should also be the last connection removed.

This sequence reduces the chance that the worker becomes the path to ground during installation or removal. The original JM Test article specifically notes that applying the ground-end clamp first helps prevent the operator from becoming the lowest-resistance ground path.

Mechanical connections should also be strong enough to withstand forces created by fault current and electromagnetic effects.

Step 5: Apply Conductor-End Clamps with Rated Hot Sticks

Conductor-end clamps should be applied and removed using hot sticks of adequate rating and length.

This is not optional field theatre. It controls worker distance from possible electrical hazards and mechanical movement if something goes wrong.

Only qualified workers using suitable tools, PPE, and procedures should apply or remove temporary safety grounds.

When Not to Use Grounding Jumpers

Grounding jumpers are not designed to protect personnel from lightning. They should not be treated as lightning protection equipment.

The source article also warns that for currents exceeding 50,000 amps symmetrical, extreme electromechanical separation forces can develop in ground cables and mechanical failure of the ground cable assembly is likely.

This is the hard truth: grounding equipment has limits. It is engineered protection, not magic. If the available fault current exceeds the rating of the ground set or the mechanical setup cannot withstand the forces involved, the setup is unsafe.

Do not use grounding jumpers when:

• The equipment is not rated for the available fault current
• The grounding assembly is damaged
• The cable or clamps show signs of overheating or mechanical abuse
• The grounding method is not covered by the job plan
• Lightning exposure is the hazard being considered
• The worker is not qualified to install or remove the grounds
• The connection points are unsuitable
• Required PPE, hot sticks, or test equipment are not available
• The site procedure requires a different control method

Practical Takeaway

Temporary safety grounds help protect workers by creating a low-impedance path for fault current and reducing hazardous voltage differences in the work area.

But they only work when properly selected, inspected, tested, installed, and removed. A damaged or undersized ground set can fail violently. A dirty connection can increase resistance. A poor installation sequence can put the worker directly in the hazard path.

For Canadian electrical teams, the safest approach is to combine proper lockout/tagout, live-dead-live voltage testing, rated grounding equipment, clean connections, qualified workers, and site-specific procedures aligned with applicable Canadian requirements.

Temporary safety grounding is not just a cable-and-clamp task. It is a controlled electrical safety procedure.