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Underground power systems provide a safer, more efficient and more reliable way to support electrical connections and the functioning of modern-day electricity delivery systems from power plants to commercial hubs, industrial areas and residences. However, burying electrical wiring underground requires expertise, experience and state-of-the-art equipment. 

Moreover, the expert crew should be certified and conform to the strict Australian guidelines for electrical cable installation to guarantee dependability, performance and safety. Hence, it is crucial to follow the right steps and have a solid understanding of the Australian guidelines to minimise any possible risk and ensure the unmatched functionality of your electrical delivery system. 

Here is a comprehensive step-by-step guide for installing an underground power cable 

Step 1- Planning 

Before commencing work, planning is crucial for project success and everyone’s safety. Careful planning must be done to prepare for underground power installation. Hence, when planning, the contractor must:

• Obtain the required permits, such as route and cable selection accessories, in conformance with AS/NZS 3100  
• Installation approvals
• Underground utility location marking 
• Creating a comprehensive plan for underground utility installation 

Planning is also vital for hazard management. So, a pre-start assessment at the planning stage should include the following:

• Hazard identification
• Risk assessment 
• Control measures for preventing and minimising risk
• Implementation of top control measures
• Traffic management while laying down cables underground
• Worker and public safety
• Potential weather conditions 

Step 2- Digging/Excavation

Once the planning and preparation work is done, the next step is digging. The contractor will dig up a trench to install underground power cables. The excavation process uses specialised equipment and tools like a trenching machine and backhoe.

In general, the trench depth is 750mm. However, it may vary depending on environmental and regional factors. Nonetheless, if trenches or pits are deeper than 1500mm, contractors must access them with a ladder. Plus, shorting, sloping and benching are required on their sides.

The trenches should be levelled and straight to prevent cable damage. And they should be large enough to accommodate the wires seamlessly and require conduit. Needless to say, contractors must adhere to high quality and safety criteria for excavation and installation work. These include:

• AS/NZS 3008
• AS/NZS 3000
• AS/NZS 1429

For example, the contractor may sometimes require rock-breaking equipment to dig up a trench if the location has rocks (like capstones, igneous rocks, and ironstone) in solid masses. However, the contractor must adhere to safety standards and maintain a minimum approach distance to use this equipment.

In some situations, blasting operations may be carried out to aid the excavation of rocks, clay and limestone. However, safety should be ensured. As per the regulations, blasting cannot be performed within the roads with other utilities like gas pipes nearby. Furthermore, all explosives used for blasting operations should be carried out under the supervision of a qualified and licensed shot firer and in compliance with the relevant Acts and Regulations like 

• The Explosives and Dangerous Goods (Explosives) Regulations 1963
• The Explosives and Dangerous Goods Act 1961

Step 3- Installing the Cables

The installation process begins after excavation. The conduit, including electrical wiring, is installed in a pipe for proper routing and protection of cables. Therefore, it must be selected carefully and installed with precision and accuracy. The installation process is also essential and should only be done by qualified professionals because during the process, it is very important to protect wiring from:

• Physical harm 
• Dampness
• Environmental elements

Once laid, the conduit’s electrical cables are pulled skillfully using a wire puller or manually. Next, the pulled wiring is spliced and later terminated at the right locations. It involves making electrical connections and installing electrical boxes, outlets and switches.

After that, the contractor tests and inspects the underground power cables. This stage is crucial to ensure optimum performance and avoid hazards or problems once the trench is covered. Therefore, the contractor tests the electrical system underground for functionality. They use top-notch and specialised testing equipment for checking problems, glitches, potential risks and hazards like open circuits and shorts. Once the tests are performed and the results are satisfactory, the contractor moves to the last stage of the underground power cable installation process, which is ground restoration. 

Step 4- Restoring the Ground Over the Cable

The contractor must take appropriate actions to restore the ground to its original condition as soon as the installation is complete. It is much needed to minimise disruptions to the people in the surrounding areas and other operational and ongoing activities. 

Furthermore, the contractor must follow the state guidelines for restoration work. For example:

• Backfilling should occur to ground level within five working days once the cable is installed and compacted to the same density as the soil in the surrounding area.
• All roads and work sites should be levelled appropriately and cleaned. In other words, all debris, stumps and soil dug during the exaction process should be removed from the location after backfilling the trench. 
• All equipment and materials used for digging up the trench should be removed, and the site should be left in a proper and safe condition. 
• Trenches should be compacted as per the Local Government Act 1960. The approved filling should be carefully placed while removing all rocks, stones, and paving materials. 

As the installation requires expertise, experience, and profound knowledge of the rules and regulations, ensure you hire the best contractor. This is where Brad Kennedy Electrical can help. We are certified in installing underground power cables. We have more than 20 years of field experience. 

At Brad Kennedy Electrical, we are your single point of contact for all installation work. In other words, we can manage all aspects of underground power cable installation from start to finish delivering you a stress-free experience. Schedule a free consultation to discuss your project with us today.