Tātaitai fault rating taura
Tātaitai fault rating taura mō Aotearoa me Ahitereiria. Ka ahu mai te k factor i AS/NZS 3008.1.2:2017, i AS/NZS 3008.1.1:2025 rānei me te 2017 ka kōwhiria.
Reads AS/NZS 3008.1.2:2017 (NZ) and AS/NZS 3008.1.1:2017 and 2025 (AU). Tables checked 27 Sept 2026.
Whakamātau mahi 6
Ka whakakī ia mahi i ngā uara tauira. Whakakapia ērā ki ō uara.
- 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.
Ngā whakauru
He tauira mahi me ngā whakauru taunoa.
- Iahiko hapa ka puta pea
- 6 kA
- Wā mukunga
- 0.1 s
- Paerewa
- NZ · AS/NZS 3008.1.2
- Rahi kaikawe
- 25 mm²
- Rauemi
- Parahi
- Insulation
- PVC 75 °C
- Karaehe whakamaherehanga
- Mai i te whakamaherehanga uaua
- Hono i te rerenga
- Kāore he hono
Rahi kaikawe iti rawa
17.09mm²
- Rahi kōwhiria
- 25mm²
- Te whakahaere i te au hapa
- 8.78kA
- k factor
- 111
- Rohe pāmahana
- 160°C
He āwhina hoahoa tēnei hua. Manatokohia ki te paerewa o nāianei.
Ngā hīkoi tātaitanga
- Te pāmahana tīmata o te kaikawe75°C
AS/NZS 3008.1.2:2017 Table 53
- Rohe pāmahana short-circuit160°C
AS/NZS 3008.1.2:2017 Table 53
- Tauwhāinga k×111.00
AS/NZS 3008.1.2:2017 Table 52 p.121
- Rahi kaikawe iti rawaHua17.09mm²
AS/NZS 3008.1.2:2017 Cl 5.3
- Au hapa e whakamanawa ana8.78kA
AS/NZS 3008.1.2:2017 Cl 5.3
Mō tēnei tātaitai
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.
Pātai
He āwhina hoahoa te hua. Manatokohia ki te paerewa o nāianei.
He aha te mahi a te tātaitai fault rating?
Ka whakamahi te taputapu i te tirotiro adiabatic ki tētahi kaikawe. Mai i te prospective fault current me te clearing time, ka tātaitia te rahi iti rawa. Ka pūrongo anō i te iahiko hapa ka taea e te rahi uruhia te ū ki mō taua wā. Ka pahi te tirotiro ina kāore te rahi kua whakauruhia i raro i te iti rawa.
Nō hea mai te k factor?
Ka ahu mai te k factor i AS/NZS 3008.1.2:2017 Table 52. Ka whakawirihia ki te rawa kaikawe me te momo insulation. Ka tohu tētahi arotake kore i AS/NZS 3008.1.2:2017 Clause 5.3, e hoatu ana i te whārite adiabatic I²t = K²S². Ina panonitia te rawa, te insulation rānei, ka panoni te k factor.
He aha e whakatau ana i te rahi taura iti rawa mō tētahi hapa?
Ko te prospective fault current me te clearing time e whakatau ana i te rahi iti rawa. Me ōrite te clearing time ki te taputapu e weto ana i te hapa, ehara i te taputapu o raro iho. Ko te rawa me te insulation e whakatau ana i te k factor. Ka whakaarohia ngā taura parallel hei kaikawe kotahi o te wāhi whakawhiti kua hono.
He aha ngā mea kāore e uru ana ki tēnei arotake?
Kāore e arotake i te reiti iahiko, i te heke voltage, i te loop impedance. Whakamahia te taputapu Rahi Taura mō aua arotake. Ka whakaaro anō te tikanga adiabatic kāore he wera e puta i te kaikawe i te wā hapa. Ka noho ngā uruhanga ki te wāhitau o te whārangi, nō reira ka whakaputa tētahi hononga i taua arotake ōrite.
Ka rerekē te k factor i te rahi kaikawe, i tētahi hono rānei?
Āe. Ka heke a AS/NZS 3008.1.2:2017 Table 53 i te tepe thermoplastic mai i te 160 ki te 140 degrees, i runga i te 300 mm². Ka whakaiti a Table 55 i tētahi hononga solder ki te 160 degrees. Ka pānui te taputapu i ngā mea e rua, kātahi ka tango i te k factor mō taua takirua tīmata me te tepe mai i Table 52.
Ngā tauira mahi
- 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.
Kōrero o muri
- 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.
- 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.
- Prospective fault current at a boardHow the fault current at a board comes from the source impedance and the submain, why the cold cable gives the maximum, and what to compare it with.
Ngā Clause me ngā Table e pānuitia ana e tēnei taputapu
- 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
Ia Clause me Table, me te pēhea i manatokotia ai ia tētahi
Ngā tūtohi i arotakehia whakamutunga i te 27 Sept 2026.
Ngā taputapu hononga
- Tātaitai taumata hapaProspective fault current at a board from its source.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Tātaitai rahi tauraFind the smallest cable size that passes each check.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Tātaitai earth fault loop impedanceCheck earth fault loop impedance against the maximum Zs.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
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