Rancang sistem kelistrikan pasokan ganda berkeandalan tinggi untuk kilang atau pabrik kimia — beban proses kontinu, redundansi N+1 / 2N, klasifikasi tahan ledakan dan penyaringan harmonisa rectifier, dengan BOM dan diagram satu garis.
Pabrik proses kontinu tidak dapat mentoleransi kehilangan daya. Kalkulator ini menentukan ukuran sistem distribusi pasokan ganda berkeandalan tinggi dengan redundansi, menerapkan klasifikasi tahan ledakan (Ex) sesuai GB 50058 / IEC 60079, dan menentukan ukuran penyaringan harmonisa detuned untuk beban rectifier — semua yang dibutuhkan EPC untuk desain daya awal.
Worked Examples
Example 1 — 2 MW Continuous Process (N+1, Zone 2, Rectifier Harmonics) · FOB $381,695
Petrochemical power system · N+1 · Zone 2 · 10kV/0.4kV
Settings are illustrative starting points — confirm with a protection coordination study per IEC 60255 / IEEE 242.
📚 Calculation book
CALCULATION BOOK
2000 kVA - 10kV/0.4kV - N+1 - 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
0.85
Demand power
Pd = P x Kd
1,700 kW
Power factor
cos(phi) before -> after
0.95 -> 0.95
Design apparent power
Sd = Pd / cos(phi)
1,789 kVA
Transformer loading
Sd / Srated
89%
2. Short-circuit calculation
Standard: IEC 60909
Parameter
Formula
Value
System impedance (pu)
Zs = S / Ssc
0.40% (on 2000 kVA base)
Transformer impedance
Zt = Z%
4%
Total impedance
Z = Zt + Zs
4.40%
LV prospective Isc
Isc = In / Z
65.6 kA
HV prospective Isc
Isc = Ssc / (sqrt(3) x V)
28.9 kA
Breaking check
Icu >= Isc
LV 80 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
240 mm2 - dU 1.34% @ 80 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):LV current 2887 A exceeds the 2500 A busbar limit — a 4000 A busway trunking system is specified instead of parallel cables.
Reliability:N+1 topology provides concurrent maintainability — required for continuous process plants.
Explosion protection:Zone classification Zone 2: switchgear and motors must be Ex-certified per GB 50058 / IEC 60079 (quoted per project).
Ex motors & VFD:Process pumps and compressors in Zone 2 need Ex-certified motors with VFD (or soft-start) control via an Ex-rated MCC — quoted per project.
Emergency / standby power:A standby diesel generator (≈600 kVA) covers critical process loads on loss of the normal supply — sized per project and the plant’s safety-instrumented-system (SIS) requirements.
Process loads:Continuous process load typically splits into compressors (~40%), pumps (~25%), heaters (~20%) and utilities/instrumentation (~15%) — adjust per your actual process list.
Harmonics:Rectifier load generates 25% THDi — a 7% detuned filter keeps the branch inductive at the 5th harmonic (safe).
Cara perhitungannya
Cara perhitungan ukuran
Transformator diukur dari beban proses kontinu pada faktor daya target; redundansi N+1 / 2N menentukan jumlah transformator paralel dan jalur independen. Arus harmonisa rectifier Ih = I₁ × THDi; bank kapasitor detuned Qc = P × (tanφ₁ − tanφ₂) dengan reaktor seri p% menjaga cabang tetap induktif di bawah harmonisa dominan.
Standar yang berlaku
Referensi penentuan ukuran GB 50052 (desain catu daya), GB 50058 dan IEC 60079 (atmosfer eksplosif), GB/T 14549 dan IEC 61642 (harmonisa) serta IEC 60076 (transformator).
Pertanyaan yang sering diajukan
What does Ex-proof / explosion-proof zoning mean for electrical equipment?
Hazardous areas are zoned by the likelihood of explosive gas (Zone 0/1/2 per IEC 60079) or dust (Zone 20/21/22). Electrical equipment in Zone 1/2 must carry Ex certification (e.g. Ex d, Ex e, Ex n) matched to the gas group and temperature class. Choosing the right Ex rating adds 20-50% to Switchgear cost; the calculator lets you select the zone and flags Ex-rated BOM.
Why do petrochemical plants need dual power supply?
Continuous process plants (refineries, ethylene, ammonia) cannot tolerate supply loss — a restart can take days and cost millions. They use dual independent feeds with automatic transfer (ATS) and N+1 or 2N redundancy for critical loads per GB 50052 load classification. The calculator models redundancy level and sizes the emergency/standby path accordingly.
How are rectifier harmonics managed in petrochemical plants?
Electrolyser and plating rectifiers inject 5th, 7th, 11th Harmonics. If total harmonic distortion exceeds IEEE 519 limits (5% THD at the PCC for most systems), a detuned capacitor bank (7% series Reactor) or an active harmonic filter (APF) is added. The calculator sizes compensation with a 7% detuning factor when THDi exceeds ~15-20%.
What transformer impedance is typical for petrochemical MV/LV units?
Distribution transformers in petrochemical plants usually have 6% impedance (uk) for LV networks, sometimes 8% for large motors to limit Fault Current. Higher impedance reduces short-circuit current but raises voltage regulation; 6% balances both for a 10/0.4 kV, 1000-2500 kVA unit. The calculator applies standard uk values when computing fault levels.
What load classification does GB 50052 define for continuous processes?
GB 50052 classifies loads into first, second and third class. Continuous petrochemical process units are first-class loads requiring two independent supplies; critical safety loads (emergency shutdown, fire pumps) are 'first-class important' loads needing an additional emergency source such as a diesel generator or EPS. The calculator's redundancy and emergency-power options map to these classes.
How is the process load demand factor set for a refinery?
Refinery process loads run near-continuously, so demand factor is high at 0.8-0.9 for main units, while utility and auxiliaries run 0.6-0.7. A 2000 kW connected process load with 0.85 demand and 0.95 pf needs about 1790 kVA, so select a 2000 kVA transformer. The calculator uses these factors to avoid both oversizing and undersizing.
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