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ZnO lighting arrester

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

Problem Type:

Axisymmetric problem of transient electric.

Geometry:

ZnO arrester model

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.

surge impulse 8/20 us

Problem:

Calculate the varistor current.

Solution:

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 varistor acts like a resistor. QuickField can calculate both active (IR) and reactive (IC) currents.

Results:

Voltage

Active current

35 kV

0.67 mA

197 kV

433 A

Surge impulse passing through the arrester

ZnO arrester surge current

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