Voltage Drop Calculation Mining

[polijb2nd]

Hello,

I computed my system via IEC, Simaris Design
From 3.3kV / 400V IT System 50Hz,
Length is 100mts from Secondary of Transformer to Main of Low Voltage Switchgear
Leng is 50 mts from the Protection Devices to the Motor Loads
It calculates the voltage drop but is too high around 17%
Requirement of my Voltage drop atleast permissible 10% only.

I used EPR type of Cable for mining
Please help me reduce my voltage drop.

Thank you in advance

 

[ramsy]

Need load(s) in Amps, or legible diagram.

Wire & Raceway type would also help. Is it an underground duct bank?
How may conductors per cable, tray, or conduit?

 

[Julius Right]

It could be this?:angel:

 

[ramsy]

View attachment 21669
It could be this?:angel:

Now that's legible. My 480v Calculator gets this:
1) 630A 100m feeder 3 x 300mcm cu in PVC = 66°c
VD<2% @ 480v, 328ft, 100% Motors, 100% continuous loads.
NEC De-rating Adjustments for Motors & Continuous = 309A x 3-Parellels

2) 287A 50m motor feeder 1 x 500mcm cu = 67°c
VD<1% @ 480v, 164ft, 100% Motors, 100% continuous loads
NEC De-rating Adjustments for Motors & Continuous = 422A

Termination temp pushing limits of 75°C equipment, while VD is negligible @ <3% combined.

 

[Julius Right]

My calculator-it is actually my excel file using complex numbers-shows 18.5 % at motor terminals at start and 15% at switchgear busbar at one single motor start.
The input data are:
Transformer impedance Z=0.4^2/0.4*4%=0.016 ohm. The tolerance permissible is 7.5% according to IEC 60034-1 Table1 then Ztrf=(1+7.5%)*.016=0.0172 ohm.
The low voltage at no-load has to be 420 V
cable 3*185/185/95 EPR insulated copper conductor r=0.136 ohm/km ; x=0.102 ohm/km.
cable 3*120/120/70 EPR insulated copper conductor r=0.210 ohm/km ; x=0.108 ohm/km.
Induction motor of 160 kW/400 V 50 Hz 4 poles Flameproof
Irated=284 A p.f.[cos ϕ]=0.85 efficiency:95.5%
Ist/In=7.2; cos ϕ start=0.3
Start D.O.L.
The result: voltage on Switchgear busbar: 340 V [15% drop];
voltage on motor terminals: 326V[18.5% drop]
If we put 3*300 mm^2 instead of 3*185 and increase the number of parallel cables to 4 we shall get 349 V at switchgear busbar [12.75%] and 16.6% at motor terminals.
If instead of D.O.L. start we provide star-delta starter then the Ist/In=3.5 [at 400 V] and letting the cables 2*3*185
the result: voltage on Switchgear busbar: 371 V [7.3% drop] and 9.6% at motor terminals.