guide through verification on low-voltage electrical
Post on 03-Nov-2021
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Earth ElEctrodE / Earth loop rEsistancE
continuity of pE conductors / conductivE parts
nominal differntial current i∆n (ma) 10 30 100 300 500 1000
r earth (Ω) max. (uc<50 v) 5000 1666 500 166 100 50
r earth (Ω) max. (uc<25 v) 2500 833 250 83 50 25
1
2
insulation rEsistancE linE / nEutral to pE3
limits: Where no rcd, select limit from the fusE characteristics, test by Z loop. Where rcd:
GuidE throuGh vErification on loW-voltaGE ElEctrical installations : iEc 60364-6
protEction by automatic disconnEction of thE supply4
rEports and cErtificatEs on loW-voltaGE ElEctrical installations: iEc 603645
tn system - two clamps - clamps arround main N/PE cable
tt system - two wire - test from the socket N to PE
it system - three wire - test leads to rods in triangle
lightning system & Earth loops - test each loop
iEc 60364-6 61.3.6.2., b.3., equipment: iEc 61557-5 limits:2 Ω above ground10 Ω whole system 10 Ω underground per leg or 8% of Specific Earth Resistance
L1
L2L3
PETN
N
L1
L2L3
PE
N
TT
L1
L2L3
PE
N
TT
IEC 60364-6 61.3.2., equipment: IEC 61557- 4Parameters:±200 mA both directions, all exposed conductive parts to MPE and in between where distance < 2.5 m.
Limits:
or 2 Ω max. (where RCD built-in)
R ≤Uc
Ipfc
50V
200A0,25 Ω≤ ≤ (where Fuse C20A built-in)
iEc 60364-6 61.3.3., equipment: iEc 61557-2
parameters: 500 v dc 250 v dc for PELV/SELV limits on circuits: r min > 1 mΩ r min > 0.5 mΩ for PELV/SELV floor and wall resistance/impedance r > 50 kΩ (insulated) semiconductive coatings 1 mΩ < r > 1 GΩ Protection against static electricity (EN 61340-5-1)
leakage current - alternative method for testing and tracing insulation problems without disconnection parameters: trms Low range measurement limits: 1 ma/kW or 3.5 ma max. per app. 5 ma max. where heating app. 1/3 x idn where RCD protected circuits. Leakage < 100 ma for fire protection.
fuse: Z loop l-pE / Z line l-l, l-n iEc 60364-6 61.3.6.3., 61.3.11., equipment: iEc 61557- 3parameters / limits are characteristics of particular built-in Fuse, designed for trip-out time of:0.1 s (Explosive), 0.2s (3Phase Circuits), 0.4 s (1Phase systems) or 5 s (fixed connections). Measured values of Impedances from the end of the circuit must be lower than Zs from the table.
In (A)
tip b tip c tip GIa = 5x In (A)
Zs= (Ω) (0,2 s)
Ia= 10x In(A)
Zs= (Ω) (0,2 s)
In(A)
Zs= (Ω) (0,4 s)
2 10 22 20 11 16 13,7
4 20 11 40 5,5 32 6,8
6 30 7,3 60 3,65 47 4,6
10 50 4,4 100 2,2 82 2,6
16 80 2,8 160 1,4 110 2,0
20 100 2,2 200 1,1 147 1,4
rcd: trip out time, trip out current iEc 60364-6 61.3.6.1., 61.3.7., equipment: iEc 61557- 6
More Parameters/Limits could be found in Metrel Handbooks and inside Eurotest/Smartec testers.
RCDrcd trip out at differential id (ms)
1/2 x I∆N 1 x I∆N 2 x I∆N 5 x I∆N
General No trip t∆ < 300 t∆ < 150 t∆ < 40
Selective No trip 130 x t ∆ < 500 60 x t∆ < 200 50 x t∆ < 150
RCD slope range (from-to)
0,5 ÷ 1.0 x l∆N AC
A 0,35 ÷ 1.4 x l∆N
B 0,5 ÷ 2.0 x l∆N
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