The demand for high voltage (HV) cables continues to surge alongside the rapid development of the power industry. While the proliferation of manufacturers offers more choices, ensuring safety and maximizing service life requires a deep understanding of common failure points. HV cable systems are complex, typically comprising the cable body, joints, and grounding systems. Analyzing potential issues across these three components is essential for maintaining grid reliability.

1. Insulation Degradation and Electrical Failures

Insulation is the heart of an high voltage cable. Most failures stem from its deterioration over time:

• Insulation Aging:​ Prolonged exposure to high temperatures causes the insulation material to harden, become brittle, and lose dielectric strength.

• Partial Discharge:​ Internal voids or impurities within the insulation create air gaps where electrical discharges occur under high stress, accelerating breakdown.

• Surface Leakage:​ Damage, cracking, or moisture ingress leads to current leakage, posing severe safety risks.

• Electrical Treeing:​ Under intense electric fields, microscopic carbonized paths resembling tree branches form within the insulation, inevitably leading to ultimate failure.

2. Cable Joint Faults

Joints are often the weakest link in the system. Common defects include:

• Stress Cone Defects:​ Improper design or material flaws at the joint termination can lead to dangerous electrical field concentrations, resulting in breakdown.

• Poor Sealing:​ Inadequate sealing allows oil leakage or water ingress, compromising the insulating filling compound.

• Excessive Contact Resistance:​ Poor crimping quality creates high-resistance connections that generate excessive heat, potentially burning out the joint.

3. Grounding System Anomalies

A faulty grounding system can cause systemic failures:

• Water Ingress:​ Seals on grounding boxes or cross-bonding boxes often fail, allowing water to enter. This causes multiple grounding points, creating circulating currents.

• Induced Overcurrent:​ Multiple grounding points lead to excessively large induced currents in the metal sheath, causing the cable to overheat.

• Protector Failure:​ Incorrectly selected parameters or unstable varistor elements (such as zinc oxide) can lead to protector breakdown during overvoltage events.

4. Mechanical Damage and Environmental Factors

External forces account for a significant percentage of cable faults:

• Physical Damage:​ Municipal construction, excavation, ground subsidence, or heavy pressure can pierce or sever cables.

• Moisture Invasion:​ Damage to the outer sheath allows water and humidity to penetrate, forming "water trees" that degrade insulation.

• Biological Threats:​ In specific environments, termites and rodents can directly damage the outer protective layers.

Responsibility and Manufacturing Quality

When problems arise, investigation should focus on the three main components: the cable body, the joints, and the grounding system. The manufacturer plays a critical role in preventing these issues.

For the Cable Body:​ Manufacturers must avoid issues like insulation eccentricity, uneven cross-linking, moisture content, and poor metallic sheath sealing. These defects severely impact longevity and safety.

For the Joints:​ It is crucial that no air gaps exist between insulation layers and that no impurities invade the structure. Selecting a professional, certified manufacturer is the key to avoiding premature joint failure.

Design Professionalism:​ A cable manufacturer’s expertise is also reflected in their design capabilities. They must account for installation conditions and utilize principles like thermal expansion/contraction to ensure adaptability. Poor design can lead to overloads, rising conductor temperatures, and eventual breakdown.

Best Practices for Users

To ensure operational safety, users must adhere to the following guidelines:

1. Verify Certifications:​ Always check the product certificate and ensure the voltage, current, and power ratings match the application requirements.

2. Prevent Overload:​ Never exceed the rated load. Ensure the operating temperature does not surpass the long-term allowable limit specified by standards.

3. Proper Installation:​ Follow all regulations and operational procedures strictly. Pay close attention to phase colors during connection to avoid mismatching.

By understanding these common problems and working with reputable manufacturers, operators can significantly reduce the risk of failure and ensure the stable transmission of power.