WAZIPOINT Engineering Science & Technology: Underground Power Cable Site Test after Installation

Wednesday, January 10, 2024

Underground Power Cable Site Test after Installation

High Voltage Cable Tester
Fig- Cable High Voltage Testing Kit

Site Test or Pre-commissioning Test Just after Underground Power Cable Installation

Many cable failures are the result of poor installation practices; so, all new installations should be thoroughly tested before they are put into service. Since the cable itself will have been tested at the factory, on-site testing of newly installed cables focuses on identifying localized problems that have occurred during installation. 

Site test after installation of the underground power cable is required to confirm that the line is installed correctly and there is no damage during laying.

The following site test should be carried out for the underground cable after installation:

1. Phase Checking Test
2. 10 kV Sheath Integrity Test
3. Insulation Resistance Test
4. DC High Voltage Test
5. No load Test

For safe and effective energization of underground cable power line site test after installation is necessary.

Check before starting the Test:
*Correct phasing and identification of a three-phase cable system, without having to remove any safety grounds on the cable,
*Prevents the user from inadvertently changing gain/sensitivity settings
*Connection error notification– instrument notifies the operator of a poor connection hookup.

Phase Test or Phase Checking: The correct identification of a cable along its length is often required for various applications - including, but not limited to the need to cut or "spike" cable to install a new transformer, switch/splice into an existing cable, or to identify the location of the phases in a cable(s) prior to spiking/cutting.

Sheath Test or Sheath Integrity Test: A sheath test to indicate whether there has been any mechanical damage to the outer cable sheath during installation is the first test that should be performed on newly installed cables.

IR Test or Insulation Resistance Test: The IR test is conducted using an IR tester, the IR tester is a portable ohmmeter (MΩ.km) with a built-in generator that produces a high DC voltage. The DC voltage usually measures 500V and causes a current to flow around the surface of the insulation.

DC High Voltage Test: DC high voltage test actually uses 3 times of rating voltage for 15 minutes, like for 33kV cable uses around 57kV DC for 15 minutes. If the cable stands for this pressure then it passes the DC high voltage test. 
Note: As per IEC standards DC high voltage test is discouraged for XLPE cables, DC high voltage is bad for XLPE cables, it may cause to damage insulation and decrease the cable lifetime. Alternately No Load test is sugested.

Shoak Test or No Load Test: No load test means the cable keeps a certain time period (normally 24 hours) without any load, just charging with nominal voltage.

Underground Power Cable Testing Safety Measure

When it comes to testing underground power cables, safety is of paramount importance. Here are some key safety measures to consider:

Personal Protective Equipment (PPE): Ensure that all personnel involved in the testing process wear appropriate PPE. This typically includes safety glasses, gloves, flame-resistant clothing, safety footwear, and a hard hat.

Risk Assessment: Conduct a thorough risk assessment before starting the testing procedure. Identify potential hazards, such as high voltages, confined spaces, or hazardous materials, and develop strategies to mitigate these risks.

Electrical Safety: Prioritize electrical safety by following established procedures and guidelines. De-energize the cable and implement lockout/tagout procedures to prevent accidental energization during testing. Use voltage detectors and test equipment rated for the voltage levels being tested.

Ventilation: If testing is conducted in a confined space, ensure adequate ventilation to prevent the buildup of toxic gases or fumes. Monitor the air quality regularly and provide respiratory protection if necessary.

Grounding and Bonding: Implement proper grounding and bonding techniques to maintain a safe working environment. Ensure that all equipment is properly grounded and bonded to prevent electrical hazards.

Testing Equipment: Use calibrated and appropriate testing equipment suitable for the type and voltage of the underground power cable being tested. Regularly inspect and maintain the equipment to ensure its reliability and accuracy.

Training and Competency: Ensure that all personnel involved in the testing process are properly trained and competent to perform their tasks. Provide ongoing training to keep them updated on the latest safety procedures and techniques.

Emergency Preparedness: Have a well-defined emergency response plan in place. Train personnel on emergency procedures and ensure they have access to first aid kits, fire extinguishers, emergency eyewash stations, and other necessary equipment.

Communication: Establish clear lines of communication among the testing team members. Use radios or other reliable means of communication to maintain contact, especially in situations where personnel may be working in different locations.

Compliance with Regulations: Adhere to all applicable local, national, and industry-specific safety regulations and standards. Stay informed about any updates or changes to these regulations to ensure compliance.

Remember, safety should always be the top priority when conducting underground power cable testing. If you are not familiar with the procedures or lack the necessary expertise, consult with qualified professionals or specialists in the field to ensure a safe and successful testing process.

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