# TElec2: ZnO lighting arrester

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

Analysis Type:

An axisymmetric problem of Transient electric field.

Geometry:

Given:

Relative permittivity of air ε = 1.
Relative permittivity of 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 voltage Umax = 200 kV.

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

See the Telec2.pbm problem in the Examples folder.