High-Voltage Component Selection Guide – How to Choose the Right Switchgear Parts

Insulation Components (Insulators, Bushings, Contact Boxes)

Select by voltage level:

• 10kV system → 12kV rated components

• 24kV system → 24kV rated components

• 35kV system → 40.5kV rated components

Select creepage distance by pollution level:

• Clean area: 10kV≥178mm, 24kV≥355mm, 35kV≥518mm

• Medium pollution: 10kV≥240mm, 24kV≥480mm, 35kV≥700mm

• Heavy pollution: 10kV≥300mm, 24kV≥600mm, 35kV≥875mm

Post insulators require bending strength ≥5-6kN. APG process products are void-free with PD <10pC and consistent dimensions.

Instrument Transformers (CT & VT)

Select by accuracy class:

• Class 0.2: Precision metering, error ±0.2%

• Class 0.5: General measurement, error ±0.5%

• Class 5P10: Protection, composite error ≤5%

Current transformer primary current selection:
Choose 50-80% of normal load current. Standard ratios: 100/5, 200/5, 400/5, 600/5, 800/5, 1000/5, 1500/5, 2000/5, 2500/5, 3000/5A.

Voltage transformer ratios: 6000/100V, 10000/100V, 11000/100V, 22000/100V, 33000/100V, 35000/100V.

Part 3: Surge Arresters

Select by application:

• Distribution type (HY5WS): Transformer protection, cable heads

• Station type (HY5WZ): Switchgear, busbars, substations

• Capacitor type (HY5WR): Capacitor bank protection

• Neutral type (HY1.5W): Transformer neutral point

Match voltage rating:

• 6kV system → 10kV arrester

• 10kV system → 17kV arrester

• 24kV system → 30kV arrester

• 35kV system → 51kV arrester

Quick reference by cabinet type

KYN28 (12/24kV): CH3-24kV contact box + ZJ-24Q post insulator + LZZBJ9-10 CT + HY5WZ-17 arrester

KYN61 (40.5kV): CH3-40.5/660 contact box + ZJ-35Q post insulator + JDZ-35 VT + HY5WZ-51 arrester

Ring Main Unit / Compact Substation: 630A single bushing + ZJ-10Q post insulator

C-GIS: 202/235 through bushing