1. High Frequency Current Distribution at HV Tower with GSM System Between Earth Wires, Tower Grounding and LV/MV Cable Network L. GRCEV, J. B. M. van WAES, A. P. J. van DEURSEN Eindhoven University of Technology, Netherlands M. J. M van RIET and F. PROVOOST NUON Technical Projects & Consultancy, Netherlands CIRED 2003

2. LV systems coupled to HV grid Lightning current remains localized Power frequency involves larger region, km range Measurements performed for 50 Hz SSituation of GSM on HV Tower

3. PPossible lightning current distribution at a HV tower with GSM system

4. Insulating trafo 20 KVA Power from connection box To provider cabinet, local TN, ground connected to HV tower Insulating tube PVC ca. 6 meter 400/400 V  -Y. Insulation: interwinding: 20 kV 50 Hz 1 min, 75 kV 1/50  s. 3 kV 50 Hz 1min. Sec/core 3 kV 50 Hz 1min.. ZnO-varistor: Un 12 kV min. 10 kA

5. Overview of the situation

6. Layout of the simplified model

7. Impedance to ground of the tower grounding and connected MV/LV cable shields

8. Impedance to ground of the earth wires

9. FD current distribution between earth wires, tower grounding and MV/LV cable shields  = 100  m  = 1000  m

10. FD current distribution for stroke at the line ACSR earth wires Steel earth wires

11. TD current distribution for a stroke at the tower  = 100  m  = 1000  m T 1 / T 2 = 2  s / 50  s

12. Conclusions – First moments after stroke Tower grounding discharges nearly all current Performance better in more conductive soil. Earth wires in less conductive soil – Subsequent period Earth wires Performance is better for high quality conductors and in less conductive soil. Metallic cable shields took nearly constant part of the lightning current. Such part is larger in less conductive soil and with less conductive (steel) earth wires.