In high‑voltage transmission systems, conductors must withstand long‑term mechanical loads and environmental changes—temperature swings, wind, self‑weight, and ice loading—without developing excessive permanent elongation. Too much creep increases conductor sag, jeopardizing clearances and system safety. The Creep Test is therefore critical for assessing the quality of ACSR (Aluminum‑Conductor Steel‑Reinforced) cables before installation.

Test Objectives

1. Measure permanent elongation of ACSR when subjected to sustained tension.
2. Evaluate the stability of the aluminum strands under simulated service conditions.
3. Provide creep‑rate data for accurate sag–tension design of transmission lines.

Test Principle

According to The Aluminum Association standard, an ACSR sample is tensioned to a fixed percentage of its Rated Tensile Strength (RTS)—typically 22 % RTS—and held for an extended period (e.g., 1 000 hours or more) at controlled temperature. During the test, technicians record:

• Accumulated permanent elongation
• Change in length versus time
• Conductor temperature

Acceptance & Reporting

Permanent elongation values are fitted to the log‑time creep equation, then reported at the following service intervals:

• 1 hour
• 6 months
• 1 year
• 10 years
• 20 years

Designers use this creep curve to set safe initial tensions and predict long‑term sag for the line.

Voltage‑Withstand and Partial‑Discharge Testing

for Medium‑ to High‑Voltage (MV–HV) distribution systems—especially underground cables

Test Objectives

1. Verify insulation strength—ensure the cable can withstand high voltage without breakdown.
2. Detect internal defects—such as voids, air pockets, contamination, or manufacturing damage.
3. Confirm overall insulation integrity before installation or energization.

Test Principles

1. AC Withstand Test

The cable is subjected to an over‑voltage AC stress (50/60 Hz) significantly above its service rating:

• Apply 3.5 × U₀ for 5 minutes
  (U₀ = phase‑to‑earth rated voltage)
• Example: a 12/20 kV cable is tested at 3.5 × 12 kV = 42 kV.

2. Partial Discharge (PD) Test

• Raise the voltage to 2.0 × U₀, then reduce to 1.73 × U₀.
• A PD detector records discharge activity inside the insulation, expressed in pC (pico‑coulombs).

Acceptance Criteria

1. AC Withstand:  Pass if no breakdown occurs during the 5‑minute test.
2. Partial Discharge:  Measured PD must not exceed 10 pC.

Electricity has become inseparable from our daily lives. For this reason, installing power cables underground is increasingly popular, thanks to its many advantages. Nonetheless, underground cabling also comes with certain constraints and obstacles. This article discusses the importance of underground power cables, together with their advantages and disadvantages.

What are underground power cables?

Underground power cables are conductors laid beneath the ground to carry electricity from generating stations to the locations where it is needed. They are typically used in densely built‑up urban areas or where there is not enough space for overhead lines. Underground installation is also considered safer than running cables above ground.

Importance of underground power cables

Underground cabling is crucial for urban development—especially in cities with tall buildings or high population density. Burying the lines reduces incidents involving power cables in public spaces, saves surface area, and prevents overhead wires from cluttering the skyline.

Advantages of underground power cables

1. Higher safety – Buried lines pose less risk of electrocution or contact with objects, leading to fewer accidents.
2. Long‑distance transmission – Underground cables can carry electricity over greater distances without significant power loss or interruption.
3. Minimal visual impact – With no overhead wires, cities look cleaner and more orderly.
4. Growing popularity – Underground cabling is seen as a safe, environmentally friendly option that avoids air‑pollution concerns.

Disadvantages of underground power cables

1. High installation cost – Underground work requires specialized machinery and tools (e.g., drilling rigs), and excavation may risk damaging existing utilities.
2. Difficult inspection and maintenance – Because the cables are buried and invisible, locating faults or damage demands special equipment and can be time‑consuming.
3. Potential interference – Roadworks or other construction projects can obstruct underground lines, often necessitating additional repairs.

Service life
International‑standard electrical cables typically last 15–20 years. Actual lifespan, however, depends on the environment in which they are installed. Sunlight, heat and moisture can all accelerate ageing. Running the cables inside conduit helps protect them and prolong their usable life.

How to Spot Cable Deterioration

1. Inspect the outer insulation.
   Look for signs such as tears, cracks, melting, splitting, or any other visible damage that suggests the cable jacket has been compromised.
2. Consult a qualified electrician.
   If you suspect internal issues or want a thorough assessment, contact a licensed professional to perform an in‑depth inspection.

Routine inspection
Have your wiring checked every 1–2 years. Age‑weakened or damaged cables raise the risk of short circuits and, in turn, potential fires that can seriously damage the surrounding area.

A busbar is essentially a common junction point that ties several electrical circuits together. Typically, only a few feeders enter the bar, while many outgoing circuits draw power from it. Because busbars must carry large currents, they are made of highly conductive materials—usually copper or aluminum. The most common profile is a flat rectangular bar, which dissipates heat efficiently and is easy to join to other conductors.

Types of Busbars

1. Bare Busbar (Copper Bar)

A bare busbar has no surface coating or paint on the conductor itself. Because its surface is exposed, it can carry slightly less current than a coated version. Over time, heat from high current plus ambient factors—temperature, humidity inside the panel, airborne contaminants—cause oxidation and residue to build up, especially at joints and connection points. This layer reduces the effective conductive area.

Mitigation: Designers often specify larger cross‑sections or bundle several bars per phase to improve heat dissipation and keep temperatures down.

2. Powder‑Coated Busbar

A powder‑coated busbar has its surface sprayed or dipped in a heat‑conductive, insulating powder coating. The coating:

• Enhances heat dissipation
• Shields the copper/aluminum from direct exposure, reducing oxidation and physical damage
• Allows higher current‑carrying capacity than a bare busbar because it stays cooler under load

As a result, powder‑coated busbars are preferred where higher performance and durability are required.