M. Pühringer, Trench Austria - AT - Session 2 - Block 1- Question 3.3 page 1

Barcelona 12-15 May 2003

RESONANT GROUNDINGRESONANT GROUNDINGversusversus

LOW IMPEDANCE GROUNDINGLOW IMPEDANCE GROUNDING

M. Pühringer, Trench Austria - AT - Session 2 - Block 1- Question 3.3 page 2

Barcelona 12-15 May 2003

Resonant grounding is also applied in:

Scandinavia numerous Central European countries Eastern Europe

Neutral point treatment in Germany *Neutral point treatment in Germany *

System length [km] Total share10 kV 20 kV 110 kV [%]

Isolated 8467 95 - 2Resonant grounding 74621 177151 53247 89Solid grounding 13247 3901 12462 9Total grid length 96335 181147 65709 100

* VDEW Störungsstatistik 1998

Neutral Point TreatmentApplication Survey

M. Pühringer, Trench Austria - AT - Session 2 - Block 1- Question 3.3 page 3

Barcelona 12-15 May 2003

E

Voltages during earth fault

N

L1

L3L2

V3E V0 = V1N

ILIC

I2

I3

V2E

V2N V3N

L1=E

V3EV2EV1E

L1

L2

L3

V0

N

V1N

V2N

V3N

CE CE CEICIL

I2 I3

Resonant GroundingBasics - Theory

Ires / IC

undercompensation

overcompensation

d

M. Pühringer, Trench Austria - AT - Session 2 - Block 1- Question 3.3 page 4

Barcelona 12-15 May 2003

Arc Suppression Coil(ASC)

Earth FaultCompensationController

Earth FaultDetection

EPSY - Earth fault Protection SYstemSystem Components

M. Pühringer, Trench Austria - AT - Session 2 - Block 1- Question 3.3 page 5

Barcelona 12-15 May 2003

Resonant grounding

self-extinction by the ASC no influence on power supply

70 ... 80 % transient faults

20 ... 30 % steady faults

low fault current - increased human safety - reduced damage - reduced interference - reduced earthing effort

quality of power supply increased

Low impedance grounding

- high fault current (e.g. 2 kA)

- immediate tripping

high number of power interruptions

Resonant GroundingComparison

100 % Earthfaults