تحديد حجم التوزيع الكهربائي لمصنع أو منطقة صناعية — إجمالي حمل المعدات، معامل الطلب، نسبة المحركات ونسبة مصادر التوافقيات، مع اختيار المحولات والمفاتيح الكهربائية، والتعويض التفاعلي وقائمة المواد.
تخلط المنشآت الصناعية أحمال المحركات والتدفئة والأحمال الإلكترونية مع معامل قدرة طبيعي أقل من 0.9 وتوافقيات كبيرة. تحوّل هذه الحاسبة حمل المعدات المتصلة إلى حزمة محولات ومفاتيح كهربائية محددة الحجم، مع تعويض تفاعلي وتصفية توافقيات وفقاً لـ GB 50052 و GB 50055.
Worked Examples
Example 1 — 2 MW Factory Load (Demand Factor, Motor & Harmonic Share) · FOB $257,923
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)
2,000 kW
Demand factor
Kd
0.6
Demand power
Pd = P x Kd
1,200 kW
Power factor
cos(phi) before -> after
0.82 -> 0.95
Design apparent power
Sd = Pd / cos(phi)
1,263 kVA
Transformer loading
Sd / Srated
79%
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 1.20% @ 80 m
Limit
max 3%
within limit
Transformer volt. reg.
dU ~ loading x Z% x sin(phi)
1.0% 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.
Demand factor:0.6 demand factor avoids oversizing — not all plant equipment runs simultaneously at full load.
Motor & harmonic load:60% motor load (natural PF 0.82); 25% harmonic-source load (detuned PFC is sufficient.)
Zone / plant metering:For multi-tenant parks, per-zone / per-plant revenue-grade metering (分区分厂计量) at the LV feeder enables sub-billing and energy accountability — quoted per project.
Harmonic sources:Typical harmonic sources: VFD drives (THDi ~30%), rectifiers / electroplating (~25–35%), UPS (~10–20%), welding machines and LED lighting. The 25% share is applied as an aggregate — a detailed equipment list refines APF sizing.
Transformer loading:Transformer sized at the target PF 0.95; final capacity must be confirmed against the actual equipment schedule.
كيف تم الحساب
كيف يعمل تحديد الحجم
الطلب P = الحمل المتصل × معامل الطلب Kd (ليس كل المعدات تعمل في وقت واحد). نسبة المحركات تحدد معامل القدرة الطبيعي؛ التعويض التفاعلي Qc = P × (tanφ₁ − tanφ₂) يصححه إلى معامل القدرة المستهدف. نسبة مصادر التوافقيات تعطي تيار التوافقيات Ih = I₁ × THDi، يُصفى بواسطة بنك مكثفات منزوع التوليف.
المعايير المعمول بها
تحديد الحجم يستند إلى GB 50052 (تصميم مصدر الطاقة)، GB 50055 (تصميم التوزيع الصناعي منخفض الجهد)، GB/T 14549 (التوافقيات) و IEC 60076 (المحولات).
الأسئلة الشائعة
What demand factor applies to an industrial park?
An industrial park with many factories never runs every machine simultaneously; a demand factor of 0.55-0.7 is typical. A 2000 kW connected load at 0.6 kd and 0.9 pf gives ~1330 kVA demand, so a 1600 kVA Transformer or two 800 kVA units suit. The calculator uses demand factor and motor share to size the MV/LV plant.
How much harmonic filtering does a factory-heavy park need?
When 60% of load is motors on VFDs and 25% is non-linear (rectifiers, UPS), THDi can reach 15-25%. IEEE 519 limits THD to 5-8% at the point of common coupling, so a detuned capacitor bank (7% Reactor) or APF is required. The calculator sizes compensation and detuning from the harmonic share.
What is the standard MV/LV architecture for an industrial park?
Typical architecture: 10 kV (or 35 kV) utility feed -> ring or radial MV Switchgear -> one transformer per factory or block -> 0.4 kV switchboards -> motor control centers. A 10 kV ring with RMUs along the ring offers N-1 supply. The calculator sizes the transformers, switchgear and compensation for the aggregated park load.
How do I allocate transformer capacity per factory?
Give each factory its own transformer sized to its demand plus 20-25% headroom, or share one large transformer for small tenants. Separate transformers isolate faults and simplify metering, but shared units cost less. The calculator aggregates the park demand and shows the single-transformer and split-transformer options.
What power factor should an industrial park maintain?
Utilities usually require 0.9-0.95 Power Factor and levy penalties below ~0.9. Industrial parks with motor-heavy load typically start at 0.75-0.85 and add capacitor banks to reach 0.95. The calculator computes the required kvar compensation to correct from measured pf to target and sizes the LV capacitor bank.
What redundancy does a park MV network usually provide?
A ring-main MV network with normally-open tie provides N-1 redundancy: any cable or RMU fault is isolated and load restored from the other direction. Radial feeders are cheaper but lose supply on a fault. The calculator's architecture notes cover ring vs radial options and their reliability trade-off.
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