Fuhrer Wire & Cable Co., Ltd. was honored to welcome Associate Professor Dr. Peera-wut Yutthakovit, a faculty member from the Department of Electrical Engineering, King Mongkut’s Institute of Technology Ladkrabang, along with representatives from the Metropolitan Electricity Authority (MEA) for a hands-on technical training session on AC Withstand Testing and Partial Discharge Measurement—both critical procedures in assessing the quality and safety of high-voltage cables.

During the training, Associate Professor Dr. Peera-wut, together with the company’s engineering team, conducted a live demonstration using internationally certified testing equipment. The session included both theoretical explanations and practical applications of partial discharge detection systems, aiming to enhance the participants’ understanding and confidence in real-world operations.

Führer Wire & Cable Co., Ltd. extends its sincere gratitude to Associate Professor Dr. Peera-wut Yutthakovit and the Metropolitan Electricity Authority for their trust and the opportunity to support technical advancement in this capacity.

We remain committed to continuously developing and delivering high-quality knowledge, technology, and services to support the nation’s electrical systems with the highest standards of reliability and safety.

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.