71-2 © IEC: 1996

NOTE — The standardphase-to-earth.

—119—

Table A.1 — Correlation between standard lightning impulse withstandvoltages and minimum air clearances

.9 H

wt -

—14

Standard lightning impulse Minimum clearancewithstand voltage mm

kV Rod-structure Conductor-structure

20 60

40 60

60 90

75 120

95 160

125 220

145 270

170 320

250 480

325 630

450 900

550 . 1100

650 1300

750 1500

850 1700 1600

950 1900 1700

1050 2100 1900

1175 2350 2200

1300 2600 2400

1425 2850 2600

1550 - 3100 2900

1675 3350 3100

1800 3600 3300

1950 3900 3600

2100 4200 3900

C

C

lightning impulse is applicable phase-to-phase and

For phase-to-earth, the minimum clearance for conductor-structure and rod-structure is applicable.

For phase-to-phase, the minimum clearance fQr rod-structure is applicable

71-2 ©IEC: 1996 —121—

Table A.2 — Correlation between standard switching impulse withstandvoltages and minimum phase-to-earth air clearances

Standard switching impulse Minimum phase-to-earthwithstand voltage mm

kV Conductor-structure Rod-structure

750 1600 1900

850 1800 2400

950 2200 2900

1050 2600 3400

1175 3100 4100

1300 3600 4800

1425 4200 5600

1550 4900 6400

Table A.3 — Correlation between standard switching impulse withstandvoltages and minimum phase-to-phase air clearances

Standard switching impulse Minimuni phase-to-phase clearancewithstand voltage

mm

Phase-to-phasePhase-to- value Phase-to- Conductor-conductor Rod-

earth — phase parallel conductorPhase-to-earth

kV value <V

750 t,5 1125 2300 2600

850 1,5 1275 2600 3100

850 1,6 1360 2900 3400

• 950 1,5 1425 3100 3600

950 1,7 1615 3700 4300

1050 1,5 1575 3600 4200

1050 1,6 1680 3900 4600

1175 1,5 1763 4200 5000

1300 1,7 2210 6100 7400

1425 1,7 2423 7200 9000

1550 1,6 2480 7600 9400