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城市基础设施电力系统计算器

为城市基础设施设计配电系统——道路和隧道照明、桥梁/隧道、泵站和 EV- 充电负载，配套预装式箱式变电站、SF6 环网柜和低压配电。

开始计算城市基础设施解决方案

为什么使用此计算器

城市电网紧凑、低噪声且高度可靠。本计算器汇总市政负载，应用同时系数，并按 GB 50052、CJJ 45 和 GB 50054 选型集成 SF6 环网柜的预装式（箱式）变电站及环网。

Worked Examples

Example 1 — Urban Ring Network (Lighting + Pumping + EV Charging) · FOB $897,825

Urban infrastructure power system · 12kV/0.4kV · dispersed

1,250 kVA box substation

YB-S13-1250/12 · demand 1,085 kW · SF6 ring main

Connected load

1,550 kW

Demand (Kd 0.7)

1,085 kW

Box substations

2 node(s)

Ring main units

2 × SF6

Est. total (FOB)

POA

📦 Bill of Materials

Equipment	Model	Spec	Qty
Main substation	YB-S13-1250/12	1250 kVA · Box-Type · oil internal · S13	1
LV feeder panel	GGD-2000	distributes 10 circuits	1
PFC capacitor bank	200 kVAR	automatic · GCK LV cabinet	1
Series reactor (detuned)	CKSG-12.0/0.4	12.0 kVAR · 6% · 0.4 kV	1
Main feeder cable (TX→LV)	YJV 0.6/1kV 300 mm² ×4	4× 300 mm² Cu · ΔU 5.86% @ 400 m ⚠ · $154.0/m	4
Feeder cable — Zone feeder 1 (×10)	YJV 300 mm²	300 mm² Cu · 249 A · ΔU 3.2% ⚠ · $154.0/m	10
Main busbar (Cu)	Cu 100×10	100×10 · 2000 A rating · ref $118/m	included
Grounding electrode	Φ20mm × 2.5m rod	R₁ 39.6 Ω → 13 rod(s) ≤ 4 Ω	13
Ring main unit (SF6, 环网柜)	XGN15-12	12 kV · SF6 · 3-way · ring main connection	2
Pole-mounted switchgear (柱上开关)	ZW32-12 / FZW28-12	12 kV · pole-mounted vacuum load-break switch · overhead MV sectioning	1
EV charging stations (充电桩)	500 kW total	AC/DC charging piles · dedicated feeders	1
Lighting control cabinet (照明控制柜)	street/tunnel lighting	time + photo-electric control · energy metering	1
Tunnel ventilation fan feeder (隧道风机)	150 kW	tunnel/bridge ventilation fan supply	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
Transformer 1250 kVA	49 thermal overload	91% of rated	alarm/trip	IEC 60076-7 / IEEE C57.91
LV incoming 0.4 kV	50 instantaneous	14434 A	inst	IEC 60947-2
LV incoming 0.4 kV	51 overcurrent	2165 A	0.3 s	IEC 60947-2 / IEC 60255
LV incoming 0.4 kV	51N earth-fault	361 A	0.3 s	IEC 60364-4-41
Zone feeder 1	50/51/51N (MCCB)	Ir 273 A - Im 1989 A - Ig 50 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Zone feeder 2	50/51/51N (MCCB)	Ir 273 A - Im 1989 A - Ig 50 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Zone feeder 3	50/51/51N (MCCB)	Ir 273 A - Im 1989 A - Ig 50 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Zone feeder 4	50/51/51N (MCCB)	Ir 273 A - Im 1989 A - Ig 50 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Zone feeder 5	50/51/51N (MCCB)	Ir 273 A - Im 1989 A - Ig 50 A	0.1 s (grading)	IEC 60947-2 / IEC 60255
Zone feeder 6	50/51/51N (MCCB)	Ir 273 A - Im 1989 A - Ig 50 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

1250 kVA - 12kV/0.4kV - single - illustrative

1. Load calculation

Standard: IEC 60076 - IEC 60364-5-52

Parameter	Formula	Value
Connected load	P = sum(kW)	1,550 kW
Demand factor	Kd	0.7
Demand power	Pd = P x Kd	1,085 kW
Power factor	cos(phi) before -> after	0.90 -> 0.95
Design apparent power	Sd = Pd / cos(phi)	1,142 kVA
Transformer loading	Sd / Srated	91%

2. Short-circuit calculation

Standard: IEC 60909

Parameter	Formula	Value
System impedance (pu)	Zs = S / Ssc	0.42% (on 1250 kVA base)
Transformer impedance	Zt = Z%	4%
Total impedance	Z = Zt + Zs	4.42%
LV prospective Isc	Isc = In / Z	40.9 kA
HV prospective Isc	Isc = Ssc / (sqrt(3) x V)	14.4 kA
Breaking check	Icu >= Isc	LV 50 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 5.86% @ 400 m
Limit	max 3%	EXCEEDS 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)	169 kvar
PFC bank	standard step	200 kvar
Detuned reactor	p = 6%	12.0 kvar @ 6% (anti-resonance)

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)

🏙️ Load profile

Parameter	Value
Road lighting	300 kW
Tunnel lighting	200 kW
Bridge/tunnel	150 kW
Pumping stations	400 kW
EV charging	500 kW

🔁 Ring network

Parameter	Value
Distribution	dispersed (800 m radius)
Box substations	2 node(s)
Ring main units	2 × XGN15-12 SF6 (3-way)

📏 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 design	GB 50052 — code for design of electric power supply systems
Urban road lighting	CJJ 45 — standard for lighting design of urban road
Low-voltage distribution	GB 50054 — code for design of low-voltage electric installations
Prefabricated substation	GB/T 17467 · IEC 62271 — high-voltage/low-voltage prefabricated substations

🧮 How it was calculated

1. Road lighting: 300 kW

2. Tunnel lighting: 200 kW

3. Bridge/tunnel: 150 kW

4. Pumping stations: 400 kW

5. EV charging: 500 kW

6. Connected load = 1,550 kW → demand = 1,550 × 0.7 = 1,085 kW

7. Dispersed load (800 m radius) → 2 box substation node(s) recommended

8. Ring main units: 2 × XGN15-12 SF6 (ring main connection)

9. Loads: P=1,550 kW, PF 0.90, 10 circuits

10. Demand: 1,550 × 0.7 = 1,085 kW

11. PFC: Qc = 1,085 × (0.484 − 0.329) = 169 kVAR → 200 kVAR bank

12. Transformer: S = 1,085 ÷ 0.95 = 1142.1 kVA → 1,250 kVA standard

13. Loading: 1,142 ÷ 1,250 = 91% (high — consider next size)

14. Voltage regulation: 91% × 4% × sinφ ≈ 1.1% at full load

15. HV unit integrated in substation (In 60.1 A)

16. LV: In 1804 A, Isc 40.9 kA (Xfmr Z 4% + system 0.4%) → GGD-2000 (integrated), 1 feeder panel(s)

17. Grounding: R₁ 39.6 Ω → 13 rod(s)

18. Main feeder: 4× 300 mm² · ΔU 5.86% — FAIL (exceeds 3% limit)

Summary
Estimated total (FOB Qingdao, EXW) — priced equipment				$897,825

📋 Design notes

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

Transformer loading: 91% at design demand — high, consider the next size up.

Short-circuit check: HV 14.4 kA vs 25 kA (1.7× margin) · LV 40.9 kA vs 50 kA (1.2× margin).

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

Power factor correction: 200 kVAR automatic bank corrects PF to 0.95.

Voltage-drop check — FAIL: ΔU exceeds the 3% limit on: main feeder 5.9%, Zone feeder 1 3.2%, Zone feeder 2 3.2%, Zone feeder 3 3.2%, Zone feeder 4 3.2% … +6 more — increase cross-section or add a parallel run.

Parallel conductors: Single-cable ampacity exceeded — parallel conductors specified: main feeder 4× 300 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): For LV feeders above ~2500 A, a busway (母线槽) trunking system is recommended instead of parallel cables.

Prefabricated (box) substation: A factory-assembled box substation integrates the SF6 ring main unit, transformer and LV panel — compact, low-noise and quick to energize for urban sites (GB/T 17467).

Ring main network: The MV ring main unit (XGN15-12) keeps supply continuous: a fault on one feeder can be isolated while the ring feeds from the other side.

Load distribution: Dispersed load over a 800 m radius — 2 box substation node(s) keep LV feeders short and reduce cable loss.

EV charging: EV charging is a growing, highly intermittent urban load; size for simultaneous charging diversity and consider dedicated feeders.

Pole-mounted switchgear: For overhead MV sections, a pole-mounted vacuum load-break switch (ZW32/FZW28-12) provides line sectioning and fault isolation — priced at $1,183/unit (FOB reference).

计算过程说明

选型计算原理

接入负载 = 道路照明 + 隧道照明 + 桥梁/隧道 + 泵站 + EV 充电。需用负载 = 接入负载 × 同时系数（典型值 0.7）。在给定供电半径内分散的负载由多个箱式变电站节点供电，每个节点集成 SF6 环网柜、变压器和 LV 配电屏（GB/T 17467）。

适用标准

选型参考 GB 50052（供配电设计）、CJJ 45（城市道路照明设计）、GB 50054（低压配电设计）、GB/T 17467 和 IEC 62271（预装式变电站）。

常见问题

什么是预装式箱式变电站？何时使用？

箱式变电站把变压器、高低压开关柜集成在一个全天候外壳内，遵循 GB/T 17467 与 IEC 62271-202。城市基础设施（道路照明、隧道、泵站、充电）用它在土建变电站过贵或过大的场合。容量典型 100-1600 kVA、12/0.4 kV。

道路和隧道照明如何配电？

道路照明用 TT 或 TN-S 系统，由专用变压器或照明箱变供电，馈线可长达 1 km，压降按 CJJ 45 限 5%。隧道照明属安全负荷，需双电源或应急电源。计算器对分散负荷与馈线半径建模以选箱变。

什么是 SF6 环网柜？城市里为什么用它？

SF6 环网柜是采用 SF6 气体绝缘灭弧的紧凑密封型 12-24 kV 开关柜，维护量小、可装在小柜间内。城市在 10-12 kV 环网中用它给箱变供电，在密集区提供 N-1 供电。计算器包含城市馈线的环网柜选型。

EV 充电站给城市基础设施带来什么负荷特性？

EV 充电是陡峭且集中的负荷：一台 120 kW 直流快充可拉 120 kVA，10 桩站点峰值近 500-1200 kVA。充电时间高度相关、同时系数低，变压器选型须计入同时性。IEC 61851 与 GB/T 51313 规范安装；计算器把充电负荷纳入城市负荷组合。

城市 12 kV 配电用什么电缆？

城市 12 kV 网络用 XLPE 交联聚乙烯电缆（国内 YJV/YJV22，IEC 60502），截面 120-400 mm²，直埋或穿管。XLPE 取代油纸绝缘电缆，允许 90 ℃ 运行、维护更低。计算器选馈线电缆并校核载流量与压降。

城市隧道需要什么应急电源？

隧道属安全关键设施：照明、通风和消防需双电源，并加柴发或 EPS 供疏散（GB 50052 一级重要负荷）。应急照明须在 0.5-15 s 内恢复（GB 51309）。计算器对应急等级建模并为城市负荷配置备用回路。

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