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Main >> Applications >> Sample problems >> ZnO overvoltage arrester

# ZnO lighting arrester

This is an example of the ZnO arrester simulation, performed with QuickField software.

Problem Type:
Axisymmetric problem of transient electric.

Geometry:

The arrester consists of ZnO tablet placed inside ceramic tube. Electrodes are connected to the end tablets.

Given:
Relative permittivity of the air ε = 1.
Relative permittivity of the ceramic ε = 2.
Relative permittivity of ZnO element ε = 60.
Conductivity of ZnO element - nonlinear.
Nominal voltage U0 = 35 kV.
Maximal current Imax = 520 A.
Surge peak voltage Umax = 200 kV.

Problem:
Calculate the varistor current.

Results:
The arrester can be represented by the equivalent schema with resistor R and capacitance C connected in parallel.

At nominal voltage the arrester acts as a capacitance (IC>IR). At overvoltage (surge) IR prevails and arrester acts like a resistor. QuickField can calculate both active (IR) and reactive (IC) currents.
 Voltage Active current 35 kV 0.67 mA 197 kV 433 A

Surge impulse passing through the arrester

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