电缆短路耐受计算器
适用于新西兰和澳大利亚的电缆短路耐受计算器。k 系数取自 AS/NZS 3008.1.2:2017，或取自 AS/NZS 3008.1.1:2025（可选择 2017 版）。
Reads AS/NZS 3008.1.2:2017 (NZ) and AS/NZS 3008.1.1:2017 and 2025 (AU). Tables checked 27 Sept 2026.
尝试一个工程 6
每项工作都会预填示例数值。请替换为您自己的数值。
- Check a conductor against fault currentWhether a 35 mm² XLPE conductor withstands 10 kA for 0.2 s.
- Check consumer mains against 6 kAWhether 16 mm² mains withstand 6 kA for 0.1 s.
- Check a final circuit against 3 kAWhether 2.5 mm² withstands 3 kA for 0.1 s.
- Check an aluminium feederWhether 95 mm² aluminium withstands 20 kA for 0.3 s.
- Check a one-second withstandWhether 120 mm² withstands 25 kA for 1 s.
- Check a cable with a soldered jointThe lower limit a soldered joint sets on a 25 mm² cable.
输入
使用默认输入值的示例计算。
- 预期短路电流
- 6 kA
- 切断时间
- 0.1 s
- 标准
- NZ · AS/NZS 3008.1.2
- 导体规格
- 25 mm²
- 材料
- 铜
- 绝缘
- PVC 75 °C
- 绝缘等级
- 来自电缆绝缘
- 敷设路径中的接头
- 无接头
最小导体规格
17.09mm²
- 所选规格
- 25mm²
- 耐受故障电流
- 8.78kA
- k 系数
- 111
- 温度限值
- 160°C
此结果仅供设计参考。请对照现行标准进行核验。
计算步骤
- 导体起始温度75°C
AS/NZS 3008.1.2:2017 Table 53
- 短路温度限值160°C
AS/NZS 3008.1.2:2017 Table 53
- k 系数×111.00
AS/NZS 3008.1.2:2017 Table 52 p.121
- 最小导体规格结果17.09mm²
AS/NZS 3008.1.2:2017 Cl 5.3
- 耐受故障电流8.78kA
AS/NZS 3008.1.2:2017 Cl 5.3
关于此计算器
How this is calculated
The tool checks that a conductor survives a fault current for the time the protective device takes to clear it. It uses the adiabatic equation, S = √(I²t) / k. It assumes that no heat leaves the conductor during the fault.
- Temperatures. It reads the start temperature and the short-circuit temperature limit for the insulation. The insulation class select can name a 110 °C cross-linked type. A joint in the run can set a lower limit than the insulation.
- k factor. It reads k from Table 52 for the conductor material and the two temperatures. A larger temperature rise gives a larger k.
- Minimum size. S = √(I²t) / k gives the smallest conductor, in mm², that stays within the limit. I is the fault current in amperes and t is the clearing time in seconds.
- Withstand. It turns the equation round for the size you pick: I = k × S / √t. That is the largest fault current the conductor survives for that time.
- Result. The size you pick passes when it is at or above the minimum.
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. Take the clearing time from the device curve at the fault current. A longer time needs a larger conductor.
| Step | Table or clause | What it decides |
|---|---|---|
| Temperatures | Table 53 | The start temperature and the limit for the insulation |
| Joint | Table 55 | A lower limit where the joint sets it |
| k factor | Table 52 | The k for the material and the two temperatures |
| Minimum size and withstand | Cl 5.3 | The adiabatic check itself |
Tables without a standard named are in the part of AS/NZS 3008.1 you pick.
Common faults, worked with the tool
Each line states its conductor. Every line uses copper and the New Zealand tables, with no joint unless the line names one.
- Submain, 6 kA for 0.1 s on 25 mm² PVC. The minimum size is 17.09 mm² with a k of 111. The 25 mm² cable withstands 8.78 kA.
- The same fault on 25 mm² XLPE. The minimum size is 13.27 mm² with a k of 143. The cable withstands 11.31 kA.
- 25 mm² XLPE with a soldered joint. The joint sets the limit at 160 °C. The minimum size is 18.99 mm² with a k of 99.9. The cable withstands 7.9 kA.
- 10 kA for 0.2 s on 16 mm² PVC. The minimum size is 40.29 mm² with a k of 111, so it fails. The 16 mm² cable withstands 3.97 kA.
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.
See also: Prospective fault current at a main switchboard, Arc flash incident energy at a 400 V switchboard and Short-circuit withstand and the k factor.
问题
结果仅供设计参考。请依据现行标准核对。
短路耐受计算器有什么作用？
工具对导体进行绝热校核。根据预期短路电流和切断时间，计算最小截面。它还会报告所输入截面在该时间内可耐受的故障电流。当安装截面不小于最小截面时，校核通过。
k 系数从哪里来？
k 系数取自 AS/NZS 3008.1.2:2017 Table 52，取决于导体材料和绝缘类型。校核不合格时，引用 AS/NZS 3008.1.2:2017 Clause 5.3，其中给出绝热方程 I²t = K²S²。更换材料或绝缘，k 系数随之改变。
什么决定故障时的最小电缆截面？
预期短路电流和切断时间决定最小截面。切断时间必须与切除故障的保护装置相匹配，而非下游保护装置。材料和绝缘决定 k 系数。并联电缆按合并截面的一根导体处理。
本检查不涵盖什么？
本工具不检查载流量、电压降或回路阻抗。请使用电缆截面工具进行这些检查。绝热法还假定故障期间导体不散热。输入值保存在页面地址中，因此链接可复现相同的检查。
导体截面或接头是否会改变 k 系数？
是的。AS/NZS 3008.1.2:2017 Table 53 将截面超过 300 mm² 时的热塑性材料温度限值由 160 °C 降至 140 °C。Table 55 将焊接接头的限值设为 160 °C。工具读取两者，然后从 Table 52 中取该起始温度与限值组合对应的 k 系数。
计算示例
- Switchboard fault rating at 25 kA for 1 sA 1 second withstand check at 25 kA on 185 mm² copper XLPE, returning a 174.83 mm² minimum size and a 26.46 kA withstand, with a thin margin explained.
- Consumer mains fault withstand for 16 mm² copperA domestic 6 kA fault cleared in 10 milliseconds against 16 mm² copper PVC mains, giving a 5.41 mm² minimum size and a 17.76 kA adiabatic withstand.
- 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 3008.1.2 Table 52: the k factorWhat Table 52 governs, how the adiabatic check uses k, and a 10 kA fault cleared in 0.1 s that needs 22.11 mm² against an installed 25 mm² conductor.
- AS/NZS 3008 vs BS 7671: cable sizing comparedHow BS 7671 and AS/NZS 3000 with AS/NZS 3008.1 size a cable, where they differ, and why a BS current rating never converts into an AS/NZS one.
- Prospective fault current at a main switchboardA 16 kA fault cleared in 0.1 s on 70 mm² copper XLPE, with the minimum conductor size, the withstand current and the k factor the adiabatic check returns.
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.
- Earthing conductor size: table or calculationHow the protective earthing conductor, the main earthing conductor and the bonding conductor are sized, worked on a 25 mm² active with a 3 kA fault.
- 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.
- Short-circuit withstand and the k factorThe adiabatic check in plain terms: prospective fault current, clearing time and k, worked on 25 mm² copper XLPE at 10 kA for 0.1 s.
- Arc flash basicsArcing current, incident energy, boundary and working distance explained, with three engine runs that show clearing time beating fault current every time.
- Industrial switchboards: fault rating, form, IPWhat the three ratings on an industrial switchboard or motor control centre mean, how each one is chosen, and which AmpSize tools feed the numbers behind them.
本工具读取的条款和表格
- AS/NZS 3008.1.2:2017 Cl 5.3Short-circuit performance
- AS/NZS 3008.1.2:2017 Cl 5.5.1Short-circuit duration
- AS/NZS 3008.1.2:2017 Table 52Values of constant K for determination of permissible short-circuit currents
- AS/NZS 3008.1.2:2017 Table 52, 53, 54, 55Short-circuit K values and temperature limits
- AS/NZS 3008.1.1:2017 Table 52Values of constant K for determination of permissible short-circuit currents
- AS/NZS 3008.1.1:2017 Table 52, 53, 54, 55Short-circuit K values and temperature limits
- AS/NZS 3008.1.1:2025 Table 5.1Values of constant K for determination of permissible short-circuit currents
- AS/NZS 3008.1.1:2025 Table 5.1, 5.2, 5.3, 5.4Short-circuit K values and temperature limits
表格最后核对于 27 Sept 2026。
相关工具
- 短路电流水平计算器Prospective fault current at a board from its source.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- 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
- 接地故障回路阻抗计算器Check earth fault loop impedance against the maximum Zs.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。