接地故障回路阻抗计算器
在新西兰和澳大利亚，按 AS/NZS 3000 Table 8.1 中您的装置的最大值检查 Zs。
Reads AS/NZS 3008.1.2:2017 (NZ), AS/NZS 3008.1.1:2017 and 2025 (AU) and AS/NZS 3000:2018. Tables checked 27 Sept 2026.
尝试一个工程 7
每项工作都会预填示例数值。请替换为您自己的数值。
- Check disconnection timeThe loop impedance of a 32 A circuit on a 45 m run, against the maximum Zs.
- Check Zs on a socket circuitThe loop impedance of a 20 A circuit on 2.5 mm² over 30 m.
- Check Zs on a lighting circuitThe loop impedance of a 10 A circuit on 1.5 mm² over 40 m.
- Check Zs on a motor circuitThe loop impedance of a 25 A D‑curve circuit over 35 m.
- Check Zs on a shed submainThe loop impedance of a 63 A submain on 16 mm² over 60 m.
- Check Zs on a weak rural supplyThe loop impedance of a 20 A circuit with 0.8 Ω at the supply.
- Check Zs in AustraliaThe loop impedance of a 20 A circuit against the Australian tables.
输入
使用默认输入值的示例计算。
- 外部阻抗 Ze
- 0.35 Ω
- 电压
- 230 V
- 装置曲线
- C 型曲线
- 保护装置额定值
- 20 A
- 实测 Zs
- 0 Ω
- 标准
- NZ · AS/NZS 3008.1.2
- 敷设长度
- 30 m
- 有源导体规格
- 2.5 mm²
- 接地导体规格
- 取自 Table 5.1
- 材料
- 铜
- 绝缘
- PVC 75 °C
接地故障回路阻抗
0.89Ω
- 允许的最大 Zs
- 1.53Ω
- 预期短路电流
- 258.25A
- 接地导体
- 2.5mm²
- R1 + R2
- 0.54Ω
- Zs 下的最大长度
- 65.67m
此结果仅供设计参考。请对照现行标准进行核验。
计算步骤
- 接地导体规格2.5mm²
AS/NZS 3000:2018 Table 5.1
- 导体工作温度下每公里的 R1 + R218.02Ω/km
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- R1 + R20.54Ω
- 接地故障回路阻抗结果0.89Ω
- 允许的最大 Zs1.53Ω
AS/NZS 3000:2018 Table 8.1
- 预期故障电流258.25A
关于此计算器
How this is calculated
The tool works out the earth fault loop impedance of one circuit. It compares that impedance with the maximum for the protective device.
- Earth conductor. If you leave the earth size on From Table 5.1, the tool picks it from the active conductor size.
- R1 + R2. It reads the resistance of the active and the earth conductors at their operating temperature. The Standard select decides which part it reads. It reads AS/NZS 3008.1.2 for New Zealand or AS/NZS 3008.1.1 for Australia. It adds the two and multiplies by the run length.
- Zs. It adds the external impedance: Zs = Ze + (R1 + R2).
- Maximum Zs. It reads the maximum for the device curve and rating from AS/NZS 3000 Table 8.1. The circuit passes when Zs is at or below that maximum.
- Fault current. It divides the voltage by Zs to get the prospective fault current.
- Maximum length. It works out the run length at which Zs reaches the maximum.
Ze is a site value. Measure it, or ask the network operator for it. The tool warns when Ze alone takes 90 % or more of the limit. After you install the circuit, test it and compare the measured Zs with the calculated one.
| Step | Table or clause | What it decides |
|---|---|---|
| Earth conductor | AS/NZS 3000 Table 5.1 | The earth size when you do not name one |
| Conductor resistance | Tables 34 and 35 | R1 and R2 at the operating temperature |
| Maximum Zs | AS/NZS 3000 Table 8.1 | The limit for the device curve and rating |
| Disconnection time | AS/NZS 3000 Cl 5.7.2 | The times behind the Table 8.1 limits |
| Failed check | AS/NZS 3000 Cl 5.7.4 | The clause a circuit over the limit cites |
Tables without a standard named are in the part of AS/NZS 3008.1 you pick. The Table 8.1 guide explains why the B, C and D curve limits differ.
Common circuits, worked with the tool
Each line states its route. Every line uses copper cable with PVC insulation, a Ze of 0.35 Ω at 230 V and the New Zealand tables. The earth size comes from Table 5.1.
- Socket‑outlets, 16 A B curve over 30 m of 2.5 mm². Zs is 0.89 Ω against a maximum of 3.59 Ω. The prospective fault current is 258.25 A.
- Cooker, 32 A C curve over 25 m of 6 mm². Zs is 0.67 Ω against a maximum of 0.96 Ω. The earth conductor is 2.5 mm².
- The same cooker circuit over 40 m. Zs is 0.86 Ω against a maximum of 0.96 Ω. The run can reach 47.68 m.
- Motor, 20 A D curve over 50 m of 2.5 mm². Zs is 1.25 Ω against a maximum of 0.92 Ω, so it fails. The run can reach 31.63 m.
New Zealand and Australia
The Standard select picks the part of AS/NZS 3008.1 for the conductor resistance. Table 8.1 and Table 5.1 are in AS/NZS 3000, which is the same in both countries.
Keep the result
Every input sits in the page address, so the link in your browser reproduces the calculation. The PDF button prints the result with its steps and table references. Saving a calculation to a project needs a free account.
问题
结果仅供设计参考。请依据现行标准核对。
回路阻抗计算器有什么作用？
工具取线路上相线和接地导体的电阻，并加上外部阻抗 Ze。其和为 Zs，即接地故障回路阻抗。它将 Zs 与保护装置的最大值进行比较。它还报告预期短路电流以及仍能通过校核的最长线路。
哪些表格规定最大 Zs？
最大 Zs 取自 AS/NZS 3000:2018 Table 8.1，依据保护装置曲线和额定值。接地导体截面取自 Table 5.1。导体电阻取自 AS/NZS 3008.1.2:2017 Tables 34 至 35。校核不合格时，引用 AS/NZS 3000:2018 Clause 5.7.4。
什么对接地故障回路阻抗影响最大？
Ze、线路长度和相线截面对 Zs 影响最大。保护装置的曲线和额定值决定 Zs 所比较的限值。除非您自行输入，否则接地导体截面取自 Table 5.1。并联电缆只分担相线电阻，不分担接地导体电阻。
回路阻抗计算器是否测量 Ze？
否。Ze 为现场数值，工具不进行测量。当 Ze 单独占最大 Zs 的 90% 或以上时，将出现警告。预期短路电流按相对地电压计算，默认值为 230 V。输入值保存在页面地址中，便于分享。
计算示例
- Lighting circuit loop impedance, B curve 10 AA 60 m shop lighting circuit on 1.5 mm² cable with a B curve 10 A device, showing Zs, the maximum Zs, the fault current and the longest run that passes.
- A test sheet for a house boardA test sheet for a six-circuit New Zealand house board, with the tests in the AS/NZS 3017 order and the limit for each reading, then the Australian sheet.
- Max cable length for a 20 A C curve subcircuitA 20 A curve C socket circuit on 2.5 mm² runs 40 m. See the Zs the engine returns, the Table 8.1 limit and the maximum length before the circuit fails.
- Fault level at a sub‑board, 300 kVA transformerWork the prospective fault current at a sub‑board 45 m from a 300 kVA transformer, three‑phase and phase-earth, and check 6 kA and 10 kA breakers against it.
- AS/NZS 3000 Table 8.1: max Zs by curve and ratingTable 8.1 max Zs for a 16 A device, by curve. B allows 3.59 Ω, C allows 1.92 Ω and D allows 1.15 Ω. See why, with a 30 m circuit at 0.89 Ω.
- Earth fault loop impedance and maximum ZsWhat earth fault loop impedance measures, how the maximum Zs check works, and a 32 A circuit on 6 mm² over 25 m that lands on 0.67 ohms against a 0.96 limit.
背景
- MEN system: multiple earthed neutral explainedMEN means multiple earthed neutral. In NZ, earth and neutral join at the main switchboard. A fault on a 32 A C curve circuit then draws 343.8 A and clears.
- Checking an existing circuitThe five checks AmpSize runs on an installed circuit, from Iz and voltage drop to Zs and fault withstand, and what a site test adds that a calculation cannot.
- IB ≤ IN ≤ IZ: the overload rule on a 32 A circuitThe overload rule is IB ≤ IN ≤ IZ. A grouped 32 A circuit fails on 6 mm² and passes on 10 mm², with an IZ of 37.6 A. Why the order matters.
- IEC 60364 and the Wiring RulesIEC 60364 is the international series that AS/NZS 3000 stays aligned with. See how its parts are numbered, what TN-C-S, TT and IT mean, and where MEN fits.
- Loop impedance and disconnection timeZe, R1+R2, Zs and Ia, and the two disconnection times, worked on a 32 A curve C circuit over 30 m that returns 0.79 Ω against a 0.96 Ω limit.
- RCD types and where they are requiredType AC, A, F and B, what each one detects, and the clauses that place them. The fault path behind them, worked on a 20 A circuit over 25 m.
本工具读取的条款和表格
- AS/NZS 3000:2018 App B Para B5.2.2 Note 2Conductor temperature in the loop
- AS/NZS 3000:2018 Cl 5.7.4Earth fault loop impedance
- AS/NZS 3000:2018 Table 5.1Minimum earthing conductor size by active conductor size
- AS/NZS 3000:2018 Table 8.1Maximum earth fault loop impedance multipliers by MCB curve
- AS/NZS 3008.1.2:2017 Table 30, 34, 35Reactance at 50 Hz and a.c. resistance at 50 Hz
- AS/NZS 3008.1.1:2017 Table 30, 34, 35Reactance at 50 Hz and a.c. resistance at 50 Hz
- AS/NZS 3008.1.1:2025 Table 4.1(A), 4.1(B), 4.5(A), 4.5(B)Reactance at 50 Hz and a.c. resistance at 50 Hz
表格最后核对于 27 Sept 2026。
相关工具
- 电缆截面计算器Find the smallest cable size that passes each check.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- 测试结果检查器Check measured test results against Section 8 limits.AS/NZS 3000AS/NZS 3017Electricity (Safety) Regulations 2010
- 电缆短路耐受计算器Check that a conductor can withstand the fault current.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
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有问题，或数值看起来有误？联系我们。