Differences and Significance of Terminal-to-Case Withstand Voltage: 3/8kV vs. 6/15kV for Indoor Power Capacitors

1. Meaning of these two values

Terminal-to-case withstand voltage means the insulation strength between terminals and the capacitor case.

• The first value: Power frequency withstand voltage (normal operation insulation)
• The second value: Lightning impulse withstand voltage (surge and lightning protection)

 

2. Core differences between 3/8kV and 6/15kV

1) 3kV / 8kV

• Standard basic and minimum level in the industry
• Adopted by most general capacitors made in China, India and Southeast Asia
• Meets only basic indoor insulation requirements (barely qualified)
• Prone to leakage or breakdown in humid, dusty or unstable voltage environments
•  

2) 6kV / 15kV

• Top‑level outdoor‑grade insulation strength
• Only used for power grid, airport, data center and high‑end export products
• Insulation margin is directly doubled
• Greatly improved resistance to humidity, pollution, overvoltage and surge

 

3. Real significance (most critical)

6/15kV = double safety margin

• Thicker insulation layer
• Higher‑quality materials
• Stricter manufacturing process
• Significantly reduced failure rate
•  

6/15kV means indoor capacitors reach outdoor‑grade strength

Normally:

• Indoor capacitors: 3/8kV
• Outdoor capacitors: 6/15kV

 

Our product: 

Indoor type → reach to highest outdoor standard→ This is extra‑level safety and extra‑level protection.

 

4. Why 6/15kV is essential for airport projects?

• Airport environment:
• Closed power distribution room
• High humidity
• Mass electrical equipment
• Frequent surges, harmonics and overvoltages
• No breakdown, leakage or flashover allowed

 

6/15kV ensures:

✅ No breakdown

✅ No flashover

✅ No leakage

✅ Long‑term safe operation

✅ Smooth acceptance by supervision, fire control and inspection