Design the electrical supply for a mine — crusher, hoist, ventilation-fan and conveyor loads, transformer and switchgear sizing, large-motor starting check, VFD harmonic mitigation and altitude/dust derating, with BOM and single-line diagram.
Mines combine the harshest operating environment with very large, intermittent motor loads. This calculator aggregates crushers, hoists, fans and conveyors, applies a demand factor and altitude derating, checks the largest-motor starting voltage dip, and sizes the transformer, reactive compensation and harmonic filtering per GB 50070 and IEC 60034.
Settings are illustrative starting points — confirm with a protection coordination study per IEC 60255 / IEEE 242.
📚 Calculation book
CALCULATION BOOK
1600 kVA - 10kV/0.4kV - single - illustrative
1. Load calculation
Standard: IEC 60076 - IEC 60364-5-52
Parameter
Formula
Value
Connected load
P = sum(kW)
1,321 kW
Demand factor
Kd
1
Demand power
Pd = P x Kd
1,321 kW
Power factor
cos(phi) before -> after
0.80 -> 0.95
Design apparent power
Sd = Pd / cos(phi)
1,391 kVA
Transformer loading
Sd / Srated
87%
2. Short-circuit calculation
Standard: IEC 60909
Parameter
Formula
Value
System impedance (pu)
Zs = S / Ssc
0.32% (on 1600 kVA base)
Transformer impedance
Zt = Z%
4%
Total impedance
Z = Zt + Zs
4.32%
LV prospective Isc
Isc = In / Z
53.5 kA
HV prospective Isc
Isc = Ssc / (sqrt(3) x V)
28.9 kA
Breaking check
Icu >= Isc
LV 65 kA (1.2x margin) PASS
3. Voltage drop
Standard: IEC 60364-5-52 Annex G
Parameter
Formula
Value
Main feeder
dU = sqrt(3) x I x L x R / V
300 mm2 - dU 1.80% @ 120 m
Limit
max 3%
within limit
Transformer volt. reg.
dU ~ loading x Z% x sin(phi)
1.1% at full load
4. Reactive power / harmonics
Standard: IEC 61921 (PFC) - IEEE 519 (harmonics)
Parameter
Formula
Value
Required compensation
Qc = Pd x (tan1 - tan2)
0 kvar
PFC bank
standard step
0 kvar
Detuned reactor
p = 6%
n/a
5. Grounding
Standard: IEC 60364-5-54 earthing arrangements and protective conductors LV earthing target 10 ohm (TN systems); 4 ohm used as a conservative design target - target 4 ohm
Parameter
Formula
Value
Single rod resistance
R1 = rho/(2 x pi x L) x ln(4L/d)
39.6 ohm
Rods required
n = R1 / (target x 0.8)
13 rod(s) <= 4 ohm
Rod spec
dia x length
20 mm x 2.5 m
This calculation book is illustrative it consolidates the computed values with the referenced standards. A licensed engineer must verify and seal final design documents for construction.
Cable & grounding pricing:Cable conductors and grounding are priced from the confirmed cables-trays-grounding price reference (per-metre copper YJV; aluminium remains POA). The main copper busbar is POA — its length is project-specific.
Busway (high-current feeders):For LV feeders above ~2500 A, a busway (母线槽) trunking system is recommended instead of parallel cables.
Motor starting:Largest motor 500 kW started Soft starter draws a 5.0% bus dip (within the 15% limit).
Altitude derating:1500 m elevation → 3% capacity derating applied per IEC 60076 / GB/T 6451 (0.5%/100 m above 1000 m).
Dust protection:Heavy dust environment → specify IP54 enclosure; underground mines should use dry-type transformers (fire safety).
VFD harmonics:40% VFD load — an active harmonic filter (APF) is recommended to meet GB/T 14549 limits.
Dedicated hoist / crusher drives:Hoists need a regenerative (four-quadrant) VFD to feed lowering energy back to the bus; crushers need a heavy-duty VFD with high overload and load-sharing for multi-motor drives. Both are quoted per project.
Scope:Electrical power side only — mining, hoisting and ventilation mechanical engineering is outside this calculator.
How it was calculated
How the sizing works
Connected load = Σ (units × kW). Demand = connected × Kd (0.7 typical for mining). Altitude above 1000 m derates the transformer (~0.5%/100 m per IEC 60076), so the effective load = demand ÷ derating factor. The largest motor starting kVA = P ÷ (η·cosφ) × kst, and the bus voltage dip = Sstart ÷ (Sstart + Ssc). Reactive compensation Qc = P × (tanφ₁ − tanφ₂); VFD harmonic current Ih is filtered with a detuned bank.
How does altitude affect transformer and switchgear rating?
Above 1000 m, thinner air reduces cooling and Dielectric Strength. Transformers derate about 0.5% per 100 m above 1000 m, and Switchgear derates similarly. A 1500 m site needs roughly 2.5% derating; a 3000 m site about 10%. The calculator applies Altitude Derating to the selected Transformer and panels per IEC 60076 and IEC 62271.
What is the typical voltage for underground mining power?
Underground mining uses 10 kV or 6 kV distribution into the mine, stepping down to 1.14 kV or 0.66 kV for crushers, hoists and conveyors, and 0.4 kV for auxiliaries. Long cable runs and motor starting favour the higher LV levels. The calculator models a 10/0.4 kV surface plant with motor-starting dip checks for the hoist and crusher.
Why do mine hoists need special starting consideration?
A mine hoist motor (often 500 kW-3 MW) draws 5-7 times rated current on DOL start, which can dip the mine bus below 85% and trip other drives. Soft-start or VFD limits the inrush, and the transformer must be sized for the starting kVA. The calculator checks the voltage dip of the largest motor and sizes supply accordingly.
How are VFD harmonics handled in a mining plant?
With 40% of load on VFDs, THDi can exceed 20%, so a detuned capacitor bank (7% reactor) or APF is needed to meet IEEE 519 (5% THD at PCC). The calculator sizes reactive compensation and detuning based on the VFD share; heavy-dust duty also calls for IP54 or higher enclosures.
What demand factor applies to a mining plant?
Crushers, hoists, fans and conveyors do not peak together; a demand factor of 0.6-0.75 is typical. A plant with 250 kW crushers, a 500 kW hoist, 160 kW fans and 90 kW conveyors rarely exceeds 60-70% of the 1,600+ kW nameplate simultaneously. The calculator applies kd before selecting transformer kVA.
What enclosure and protection does mining switchgear need?
Mining switchgear must resist dust and moisture: IP54 or IP55 for surface plants, flameproof Ex d for underground gassy mines (IEC 60079). Heavy-dust environments shorten creepage distances, so wider clearances and anti-tracking insulation are standard. The calculator flags dust level and applies the corresponding enclosure grade in the BOM.
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Results are engineering estimates for reference. Final design must be confirmed by a licensed local engineer against site conditions and applicable codes. Prices are FOB Qingdao (EXW) and do not include freight, duty or installation.
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