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SPDs for Three Phase Systems

Application of Surge Protection Devices on three phase electrical systems

EARTHING SYSTEM
LIGHTNING PROTECTION LEVEL (LPL)
MAIN DISTRIBUTION BOARD (MDB)
SUB-DISTRIBUTION BOARD (SDB)
(unless feeding outside circuits) (figure given is cable length, not distance)
ELECTRONIC EQUIPMENT
(less than 5m cable length)
TN-C
I & II
KM1+2-25-3+0 SC
KM2-20-3+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-3+0 SC (>50m from MDB)
KM1+2-25-3+0 SC (>100m from MDB)
TN-C
III & IV
KM1+2-12.5-3+0 SC
KM2-20-3+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-3+0 SC (>50m from MDB)
TN-S
I & II
KM1+2-25-4+0 SC
KM2-20-4+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-4+0 SC (>50m from MDB)
KM1+2-25-4+0 SC (>100m from MDB)
TN-S
III & IV
KM1+2-12.5-4+0 SC
KM2-20-4+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-4+0 SC (>50m from MDB)
TN-C-S
I & II
KM1+2-25-4+0 SC
KM2-20-4+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-4+0 SC (>50m from MDB)
KM1+2-25-4+0 SC (>100m from MDB)
TN-C-S
III & IV
KM1+2-12.5-4+0 SC
KM2-20-4+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-4+0 SC (>50m from MDB)
TT
I & II
KM1+2-25-3+1 SC
KM2-20-3+1 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-3+1 SC (>50m from MDB)
KM1+2-25-3+1 SC (>100m from MDB)
TT
III & IV
KM1+2-12.5-3+1 SC
KM2-20-3+1 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-3+1 SC (>50m from MDB)