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ZnO lighting arrester

zinc oxide varistor simulation, electric FEA finite element analysis of the varistor, lightning stroke protection with varistor

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 I_max = 520 A.
Surge peak voltage U_max = 200 kV.

Task:
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 (I_C>I_R). At overvoltage (surge) I_R prevails and arrester acts like a resistor. QuickField can calculate both active (I_R) and reactive (I_C) currents.

Voltage	Active current
35 kV	0.67 mA
197 kV	433 A

Surge impulse passing through the arrester