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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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HV transmission line uses
Pin type insulators
Suspension insulators
Both a and b
None of the above
Both a and b
High voltage (HV) transmission lines utilize various insulator types depending on the voltage level and tower design. Pin-type insulators are generally used up to 33 kV, while suspension-type insulator strings are employed for voltages above 33 kV due to their modular design and mechanical strength.
High voltage (HV) transmission lines utilize various insulator types depending on the voltage level and tower design. Pin-type insulators are generally used up to 33 kV, while suspension-type insulator strings are employed for voltages above 33 kV due to their modular design and mechanical strength.
Vstring=Vunit×n
String efficiency = n×Voltage across the disc nearest to conductorVoltage across the whole string
Insulators provide electrical isolation between the high-voltage conductor and the earthed cross-arm of the transmission tower. Suspension insulators consist of multiple ceramic or glass discs connected in series, allowing for easy scaling of the insulation level by increasing the number of discs, whereas pin insulators are mounted on a central pin and are limited by flashover risks at very high voltages.
Pin insulators are restricted to lower voltages due to the size increase required for higher insulation levels.
Suspension insulators allow for flexible stringing and higher mechanical load-bearing capacity.
The string efficiency of suspension insulators is always less than 100% due to shunt capacitance.
Higher voltage transmission utilizes long strings of suspension discs to prevent surface leakage.
Suspension insulators can be replaced individually if damaged.
Higher voltage rating can be achieved by adding more discs to the string.
Provides greater clearance to the tower cross-arm.
Pin insulators are susceptible to puncture at very high voltages.
Suspension strings require more vertical space on the transmission tower.
Pin insulators: Distribution and sub-transmission up to 33kV.
Suspension insulators: High voltage (HV) and Extra High Voltage (EHV) transmission.
| Feature | Pin Insulator | Suspension Insulator |
|---|---|---|
Voltage Range | Up to 33 kV | Above 33 kV |
The choice of insulator depends on the line voltage and the mechanical stress from the span length.
Option A is limited to sub-transmission, while Option B is standard for HV/EHV grids.
C is correct — High voltage transmission lines utilize both pin insulators (for lower voltage levels) and suspension insulators (for higher voltage levels, especially above 33 kV).
Always remember that pin insulators are economically constrained by weight and size as voltage increases beyond 33kV, necessitating the shift to suspension insulator strings.