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. PROVOOSTNUON Technical Projects & Consultancy, Netherlands

 

  CIRED 2003

 

• 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

PPossible lightning current distribution at a HV tower with GSM system

E a rthw ire s

To w e rg ro u n d in g LV c a b le

m e ta l sh e a th

L ig h tn in gs tro k e to to w e r

Te le c o me q u ip m e n ta n d p ro te c tio nc a b in e t

Insulating trafo 20 KVAPower 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.

Sec/core 3 kV 50 Hz 1min. 3 kV 50 Hz 1min..

ZnO-varistor: Un 12 kV min. 10 kA

Overview of the situation

400m

150kV

10kV

Tower 33Ulft, Tower 40

DTC,Tower 1

LV 1

LV 2

250m

LV userMeasurement location

Lead Shielded PILC cable, 10 kVLead Shielded PILC cable, 400VInsulated LV cable, 400V

Transformer station,electrode 2-5 Ohm

200m

300m

Overhead Line, 150 kV

400V

TS

Layout of the simplified model

In su la te d C a b le

To w e r 3 3

2 k m

U n in su la te d C ab le

P o w e r L in e To w e r

LV U s e r

1 5 0 k V L in e

T ra n s fo rm e r S ta tio n

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

0

2

3

4

5

1 00 1 00 0 1 00 0 0 1 00 0 0 0 1 e+ 00 6F re q ue n c y (H z )

Mag

n itu

de o

f Im

peda

nce

to G

roun

d (

ohm

)

1To w e r G ro u nd ing w ithC o n ne c te d C ab le S h ie lds

Impedance to ground of the earth wires

1 0 0 1 0 00 1 0 00 0 1 0 00 0 0F re q u en c y (H z )

0 .1

1

1 0

1 0 0

1 0 00M

agn i

tude

of

Impe

danc

e to

Gro

und

(oh

m)

A C S R

S tee l

FD current distribution between earth wires, tower grounding and MV/LV cable shields

100 1000 10000 100000 1e+6Frequency (Hz)

0

20

40

60

80

100

Mag

nitu

de o

f C

urre

nt (

%)

Earthwires

MV/LVcables

Towergrounding

100 1000 10000 100000 1e+6Frequency (Hz)

0

20

40

60

80

100

Mag

nitu

de o

f C

urre

nt (

%)

Earthwires

MV/LVcables

Towergrounding

(a) (b)

= 100 m = 1000 m

FD current distribution for stroke at the line

ACSR earth wires Steel earth wires

1 0 0 1 0 00 1 0 00 0 1 0 00 0 0 1 e+ 6F re q u en c y (H z )

0

2 0

4 0

6 0

8 0

1 0 0

Mag

n itu

de o

f C

urre

nt (

%)

E a rthw ire s

M V /LVc ab le s

To w e rg ro u n d ing

1 0 0 1 0 00 1 0 00 0 1 0 00 0 0 1 e+ 6F req u en cy (H z )

0

2 0

4 0

6 0

8 0

1 0 0

Mag

n itu

de o

f C

urre

nt (

%)

E a rthw ire s

M V /LVcab le s

To w erg ro u n ding

TD current distribution for a strokeat the tower

0

20

40

60

80

100

120

10 20 30 40 500

Total Current

Cur

rent

(%

)

Time ( s)

Grounding

Cable Shields

Earth Wires

0

20

40

100

120

10 20 30 40 500

Total Current

Cur

rent

(%

)

Time ( s)

Grounding

Cable Shields

Earth Wires

0

20

40

100

120

10 20 30 40 500

Cur

rent

(%

)

Time ( s)

0

20

40

100

120

10 20 30 40 500

Total Current

Cur

rent

(%

)

(a)

Grounding

Cable Shields

Earth Wires

60

80

(b)

= 100 m = 1000 m

T1 / T2 = 2 s / 50 s

Conclusions

– First moments after strokeTower grounding discharges nearly all current

Performance better in more conductive soil.

Earth wires in less conductive soil

– Subsequent periodEarth 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.