40 Electrical design and installation
Manual Power Quality Filter PQFS
Table 18: Multiplication factors X for different cable sections
Cable section
[mm²]
Network frequency 50Hz
Network frequency 60 Hz
Al-cable
Cu-cable
Al-cable
Cu-cable
16
1.00
1.00
1.00
1.00
25
1.00
1.01
1.00
1.01
35
1.01
1.01
1.01
1.02
50
1.01
1.03
1.02
1.04
70
1.02
1.05
1.03
1.06
95
1.04
1.08
1.05
1.10
120
1.05
1.11
1.07
1.14
Step 3: Determine in a conventional way the cable section A2 (mm²) for the current
rating found by multiplying Irms by X.
If the new cable section A2 is equal to the initially found cable section A, the right cable
section taking into account the skin effect has been found.
If the new cable section A2 is bigger than the initially found cable section A, steps
2 and 3 have to be repeated with the new values until the cable section A2 found is
equal to the cable section A.
Remark: During this process it may be found that more than one cable per phase is
needed. The process then has to be applied to each cable.
As an illustration of the cable sizing process consider the following example:
PQFS 60 A/50Hz, 3-wire connection, cable material: Cu (copper)
Step 1: IN = 60A
cable section = 16 [mm2]
Step 2: multiplication factor for a 16 [mm2] copper cable at 50 Hz = 1.00
Step 3: I = IN x 1.00 = 60A x 1.00 = 60 A
Step 4: I = 60A
cable section: 16 [mm2]
This section is equal to the section found in the previous step.
Conclusion: one copper cable of 16 [mm2] per phase is sufficient.
Remark: The cable sizing process discussed in point 2 above only takes into account
the skin effect. Any further derating due to local standards and/or installation
conditions (e.g. distance between cables, number of cables connected in parallel …)
have to be taken into account by the company responsible for the PQF cable
connection.
As an example of the cable sizing procedure, consider
, which
show the allowed current for different parameters noting typical cable manufacturer
data.
