A 35kV busbar typically requires a power-frequency withstand voltage of around 70–75 kV RMS for 1 minute, with higher impulse voltages for lightning or switching tests.Power-Frequency Withstand Volt...
For a busbar rated at 35kV, the IEC 62271-1 standard recommends that the busbar insulation be capable of withstanding approximately 2.0 to 2.2 times the rated voltage for a 1-minute AC test. This translates to a power-frequency test voltage of roughly 70–75 kV RMS between phase-to-phase and phase-to-ground under standard test conditions. This ensures that the busbar can safely operate without dielectric breakdown during normal and transient overvoltages .
In addition to AC testing, busbars are often subjected to lightning impulse tests. For a 35kV system, the standard impulse withstand voltage is typically 150–170 kV peak, depending on the insulation design and environmental conditions. This protects against transient overvoltages caused by lightning strikes or switching surges .
The physical spacing between busbars and between busbars and ground is critical to achieve the required withstand voltage. IEC 62271-1 provides minimum clearances for phase-to-phase and phase-to-ground distances, which are designed to prevent flashover under rated and overvoltage conditions. Proper selection of insulators and supports ensures mechanical and electrical integrity .
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