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石化电力系统计算器

为炼油厂或化工厂设计高可靠性双电源电气系统 — 连续工艺负荷、N+1 / 2N 冗余、防爆分级和整流器谐波滤波，附 BOM 和单线图。

开始计算石油化工与炼化解决方案

为什么使用此计算器

连续工艺装置无法承受断电。本计算器为双电源、高可靠性配电系统进行选型，支持冗余配置，按 GB 50058 / IEC 60079 应用防爆（Ex）分级，并为整流器负荷选型失谐谐波滤波 — 满足 EPC 初步电力设计所需的一切。

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

2,000 kVA transformer

S13-M-2000/10 · process 2,000 kW · THDi 25%

Process load

2,000 kW

Redundancy

N+1

Ex zone

Zone 2

Harmonic filter

221 kvar

Est. total (FOB)

POA

📦 Bill of Materials

Equipment	Model	Spec	Qty
HV incoming panel	KYN28A-12-630-315	630 A / 31.5 kA · vacuum	2
HV bus-tie panel	KYN28A-12-630-315	630 A / 31.5 kA · vacuum	1
Main transformer (each)	S13-M-2000/10	2000 kVA · Oil-Immersed · Copper · S13	2
LV incoming panel	GGD-3150	3150 A busbar · In 2887 A	2
LV bus-tie panel	GGD-3150	3150 A busbar	1
LV feeder panel (×2)	GGD-3150	distributes 10 circuits	2
Cable branch box (LV)	DFW-0.4	1-in / 4-out · 0.4 kV · 630 A	2
Busway trunking (LV main feeder)	Busway 4000 A	4000 A · Cu/Al busway · 80 m · $1329/m	1
Feeder cable — Process feeder 1 (×10)	YJV 150 mm²	150 mm² Cu · 304 A · ΔU 1.6% · $86.0/m	10
Branch trunk cable (LV → branch box 1)	YJV 240 mm² ×3	3× 240 mm² Cu · 1215 A · ΔU 1.3% · $123.0/m	3
Branch trunk cable (LV → branch box 2)	YJV 150 mm² ×2	2× 150 mm² Cu · 608 A · ΔU 1.6% · $86.0/m	2
Main busbar (Cu)	Cu 125×10	125×10 · 2500 A rating · ref $147.8/m	included
Grounding electrode	Φ20mm × 2.5m rod	R₁ 39.6 Ω → 13 rod(s) ≤ 4 Ω	13
Detuned PFC capacitor bank	221 kvar	automatic · 7% detuned · 0.4 kV	1
Series detuning reactor (7%)	15.5 kvar	189 Hz tuning · below 5th harmonic	1
Explosion-proof (Ex) distribution board	Ex d Zone 2	Flameproof enclosure · IEC 60079 · quoted per project (POA — not included in estimate)	1
Ex-rated motor control center (MCC)	Ex d Zone 2	Ex motor starters + VFD for pumps/compressors · IEC 60079 (POA — not included in estimate)	1
Emergency / standby diesel generator	1000 kVA	life-safety / standby power · 600 kVA required	1

📐 Single-line diagram

⚙️ Electrical schematic (protection & metering)

⛳ Grounding grid layout

🔌 Cable schedule & routing

🗄 Switchgear arrangement

🛡 Protection configuration

📋 Protection settings

Circuit	Protection	Setting	Time	Standard
HV incoming 10 kV	50 instantaneous	924 A	inst	IEC 60255-151 / IEEE 242
HV incoming 10 kV	51 overcurrent	139 A	0.5 s	IEC 60255-151 / IEEE 242
HV incoming 10 kV	51N earth-fault	23 A	0.5 s	IEC 60364-4-41
Transformer 2000 kVA	87 differential	23 A	inst	IEEE C37.91 / GB/T 14285
Transformer 2000 kVA	49 thermal overload	89% of rated	alarm 90%	IEC 60076-7 / IEEE C57.91
LV incoming 0.4 kV	50 instantaneous	23094 A	inst	IEC 60947-2
LV incoming 0.4 kV	51 overcurrent	3464 A	0.3 s	IEC 60947-2 / IEC 60255
LV incoming 0.4 kV	51N earth-fault	577 A	0.3 s	IEC 60364-4-41
LV bus-tie	50/51 overcurrent	3464 A	0.3 s	IEC 60947-2
Process feeder 1	50/51/51N (MCCB)	Ir 334 A - Im 2431 A - Ig 61 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Process feeder 2	50/51/51N (MCCB)	Ir 334 A - Im 2431 A - Ig 61 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Process feeder 3	50/51/51N (MCCB)	Ir 334 A - Im 2431 A - Ig 61 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Process feeder 4	50/51/51N (MCCB)	Ir 334 A - Im 2431 A - Ig 61 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Process feeder 5	50/51/51N (MCCB)	Ir 334 A - Im 2431 A - Ig 61 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Process feeder 6	50/51/51N (MCCB)	Ir 334 A - Im 2431 A - Ig 61 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
+4 more feeders	50/51/51N (MCCB)	per feeder load	0.1 s (grading)	IEC 60947-2

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.

🔧 Secondary schematic (control & signal)

🔩 Terminal strip (typical)

🌀 Rectifier harmonic mitigation

Parameter	Value
Rectifier load	400 kW · THDi 25%
Fundamental current	770 A · harmonic current 192 A
Compensation	221 kvar bank + 7% reactor (15.5 kvar)
Resonance check	5th harmonic 250 Hz > 189 Hz → safe ✓

📏 Standard basis (依据标准)

Topic	Standard
Standard basis	IEC · IEC 60364-5-52
Conductor ampacity	IEC 60364-5-52 Table B.52.2–B.52.5 (copper, 3 loaded conductors, 30°C ambient, PVC) — typical/rounded values, conservative (±3%)
Voltage-drop limit	IEC 60364-5-52 Annex G · max drop 3%
Winding temp rise	IEC 60076-2 — winding temp rise 65 K (Class A insulation, ONAN)
kVA ratings	IEC 60076-1 R10 preferred numbers
Breaker frames	IEC 60947-2 frame sizes (In)
Grounding target	IEC 60364-5-54 earthing arrangements and protective conductors — LV earthing target ≤ 10 Ω (TN systems); 4 Ω used as a conservative design target · target 4 Ω
Power supply reliability	GB 50052 — code for design of electric power supply systems (dual-source for critical loads)
Explosive atmospheres	GB 50058 · IEC 60079 — electrical apparatus for explosive gas atmospheres (Ex)
Power quality (harmonics)	GB/T 14549 · IEC 61642 — harmonics in public/industrial networks & detuned filters
Power transformers	IEC 60076 — power transformers

🧮 How it was calculated

1. Continuous process load = 2,000 kW (N-1 continuity)

2. Redundancy N+1 → 2 transformers + bus-tie (100% backup)

3. Rectifier harmonic source: 400 kW · THDi 25% → Ih = 770 × 25% = 192 A

4. Detuned filter: Qc = 400 × (tanφ₁ − tanφ₂) = 221 kvar · 7% reactor (f_res 189 Hz)

5. Resonance check: 5th harmonic 250 Hz above 189 Hz → detuned (safe)

6. Loads: P=2,000 kW, PF 0.95, 10 circuits

7. Demand: 2,000 × 0.85 = 1,700 kW

8. PFC: Qc = 1,700 × (0.329 − 0.329) = 0 kVAR → 0 kVAR bank

9. Transformer: S = 1,700 ÷ 0.95 = 1789.5 kVA → 2,000 kVA standard

10. Loading: 1,789 ÷ 2,000 = 89% (good range)

11. Voltage regulation: 89% × 4% × sinφ ≈ 1.1% at full load

12. HV: In 115.5 A, Isc 28.9 kA → KYN28A-12-630-315

13. LV: In 2887 A, Isc 65.6 kA (Xfmr Z 4% + system 0.4%) → GGD-3150, 2 feeder panel(s)

14. Cable branch boxes: 2 × DFW-0.4 (1-in/4-out) for feeder grouping

15. Grounding: R₁ 39.6 Ω → 13 rod(s)

16. Main feeder: 7× 240 mm² · ΔU 1.34% — OK · busway 4000 A

Summary
Estimated total (FOB Qingdao, EXW) — priced equipment				$381,695

📋 Design notes

Pricing basis: FOB Qingdao (EXW) equipment price. Freight, duty and installation are not included — add for landed economics.

Transformer loading: 89% at design demand — good range.

Short-circuit check: HV 28.9 kA vs 31.5 kA (1.1× margin) · LV 65.6 kA vs 80 kA (1.2× margin).

Voltage regulation: ≈ 1.1% at full load (typical limit 5%).

Copper price linkage: Copper-wound transformer price tracks LME copper (current $14,115/t · 2026-09-14 · LME Copper (Sina hf_CAD)).

Parallel conductors: Single-cable ampacity exceeded — parallel conductors specified: main feeder 7× 240 mm², branch trunk 1 3× 240 mm², branch trunk 2 2× 150 mm² (per IEC 60364-5-52 / GB 50054).

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).

计算过程说明

选型计算方式

变压器按目标功率因数下的连续工艺负荷选型；N+1 / 2N 冗余决定并联变压器数量和独立供电路径。整流器谐波电流 Ih = I₁ × THDi；带 p% 串联电抗器的失谐电容器组 Qc = P × (tanφ₁ − tanφ₂)，使支路在主要谐波以下保持感性。

适用标准

选型参考 GB 50052（供电设计）、GB 50058 和 IEC 60079（爆炸性环境）、GB/T 14549 和 IEC 61642（谐波）以及 IEC 60076（变压器）。

常见问题

防爆（Ex）区域划分对电气设备意味着什么？

危险区按爆炸性气体（IEC 60079 的 Zone 0/1/2）或粉尘（Zone 20/21/22）出现的概率划分。Zone 1/2 内的电气设备须有与气体组别和温度等级匹配的 Ex 认证（如 Ex d、Ex e、Ex n）。正确选 Ex 等级会使开关柜成本增加 20-50%；计算器可选分区并标注 Ex 型 BOM。

石化厂为什么需要双电源供电？

连续流程装置（炼油、乙烯、合成氨）不能承受失电——重新开车可能需数天并损失数百万。按 GB 50052 负荷分级，关键负荷采用双路独立电源 + 自动转换（ATS）和 N+1 或 2N 冗余。计算器可设冗余等级并据此配置应急/备用回路。

石化厂的整流装置谐波如何处理？

电解和电镀整流器注入 5、7、11 次谐波。若公共连接点总谐波畸变超过 IEEE 519 限值（多数系统为 5% THD），需加装去谐电容器组（7% 串联电抗）或有源滤波器（APF）。计算器在 THDi 超过约 15-20% 时按 7% 去谐系数配置补偿。

石化中低压变压器典型阻抗是多少？

石化厂配电变压器阻抗通常 6%（uk），大型电机回路有时用 8% 以限制短路电流。阻抗越高短路电流越小但电压调整率越差，6% 对 10/0.4 kV、1000-2500 kVA 单元可兼顾两者。计算器计算故障水平时采用标准 uk 值。

GB 50052 对连续生产负荷如何分级？

GB 50052 将负荷分为一、二、三级。连续石化装置属一级负荷，需两路独立电源；关键安全负荷（紧急停车、消防泵）属『一级重要负荷』，还需柴发或 EPS 等应急电源。计算器的冗余与应急电源选项即对应这些分级。

炼厂工艺负荷的需用系数怎么定？

炼厂工艺负荷近乎连续运行，主装置需用系数高达 0.8-0.9，公用与辅助系统 0.6-0.7。2000 kW 装机工艺负荷、0.85 需用系数、0.95 功率因数约需 1790 kVA，取 2000 kVA 变压器。计算器用这些系数避免超配与欠配。

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