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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.
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
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