Tātaitai taumata hapa
Te iahiko hapa ka puta pea i tētahi papa mai i tōna puna.
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.
Whakamātau mahi 8
Ka whakakī ia mahi i ngā uara tauira. Whakakapia ērā ki ō uara.
- Find the fault level at a sub‑boardThe fault current at a board 45 m from a 300 kVA transformer, against 6 kA breakers.
- Check breakers beside a 1000 kVA transformerWhether 25 kA breakers suit a main board 20 m from a 1000 kVA transformer.
- Find the fault level at a house boardThe fault current at the end of 20 m of 16 mm² mains.
- Find the fault level at a shedThe fault current 60 m down a 16 mm² submain.
- Find the fault level at an MCCThe fault current 30 m from a 500 kVA transformer.
- Check 6 kA breakers at a tenancy boardWhether 6 kA devices suit the fault level at the board.
- Find the fault level on parallel feedersThe fault current with two cables per phase.
- Find fault level from a 10 kA serviceThe fault current at a board in Australia.
Ngā whakauru
He tauira mahi me ngā whakauru taunoa.
- Pūtake
- Transformer
- Whakatauhanga transformer
- 500 kVA
- Transformer impedance
- 4.5 %
- Voltage raina
- 400 V
- Paerewa
- NZ · AS/NZS 3008.1.2
- Roa o te matua-iti
- 30 m
- Rahi kaikawe
- 35 mm²
- Rauemi
- Parahi
- Insulation
- PVC 75 °C
- Ngā matua
- Multicore
- Ngā waea i te whakarite
- 1
- Kaha whakakore o te circuit-breaker
- 15 kA
Au hapa toru wāhanga i te poari
10.01kA
- Au hapa wāhanga–whenua, nui rawa
- 3.18kA
- Au hapa wāhanga–whenua, taura hot
- 2.63kA
- Impedance pūtake ia wāhanga
- 14.4mΩ
- Kaha wehe
- 15kA
He āwhina hoahoa tēnei hua. Manatokohia ki te paerewa o nāianei.
Ngā hīkoi tātaitanga
- Ārai whakawhiti ia wae, U² ÷ S × Z%0.01Ω
- Au hapa i te puna16.04kA
- Ōkiko wāhanga Submain i te pāmahana whakahaere0.02Ω
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- Ōkiko wāhanga Submain i te 20 °C0.02Ω
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- Reactance wāhanga Submain0Ω
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- Rahi kaikawe tiaki10mm²
AS/NZS 3000:2018 Table 5.1
- Ōkeroa kaikawe tiaki i te 20 °C0.06Ω
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- Au hapa toru-wae i te poari, U0 ÷ |Z|Hua10.01kA
- Au hapa wae-whenua i te poari, nui rawa3.18kA
- Au hapa wae-whenua, uaua i te pāmahana mahi2.63kA
- Āheinga whakawehe o te kaiwhakatere15kA
Mō tēnei tātaitai
How this is calculated
The tool finds the fault current at a board. The source is a transformer or a stated supply fault level. A submain then adds impedance. The tool compares the result with the breaking capacity of your device.
- Source impedance. For a transformer, the tool works Z = U² ÷ S × Z% per phase. It takes the source as all reactance. That gives the highest current for the size.
- Source current. It gives the fault current at the transformer terminals.
- Submain impedance. It reads the resistance and reactance of the submain for your size, length and material. The tables are Table 30 for reactance and Tables 34 and 35 for resistance. It scales the resistance to 20 °C for the maximum figure.
- Protective conductor. It reads the earth conductor size from Table 5.1 of AS/NZS 3000:2018. It adds that resistance to the earth loop.
- Fault currents. It gives the three‑phase current as U0 ÷ |Z|. It also gives the phase-earth current, maximum and with the cable hot.
- Breaking capacity. It compares the three‑phase current with the rating you enter.
| Step | Table or clause | What it decides |
|---|---|---|
| Submain reactance | AS/NZS 3008.1.2 Table 30 | The reactance of the submain |
| Submain resistance | AS/NZS 3008.1.2 Tables 34 and 35 | The resistance of the submain |
| Earth conductor | AS/NZS 3000 Table 5.1 | The size of the protective conductor |
Worked example
- 500 kVA transformer with a 30 m 35 mm² submain. The transformer has 4.5 % impedance. The three‑phase fault current at the board is 10.01 kA. The maximum phase-earth current is 3.18 kA. A 15 kA device passes.
Limits
- The tool works at nominal voltage. It does not apply the IEC 60909 voltage factors.
- It takes the network above the transformer as infinite. A real network lowers the current a little.
- It takes the phase-earth loop at the transformer as its phase impedance, as for a Dyn transformer.
- It does not add motor contribution. It does not grade devices. Use the IDMT tool for grading.
- The result is an estimate for sizing. Ask the network company for the supply fault level at the point of supply.
See also: Prospective fault current at a board, Fault level at a sub‑board on a 300 kVA transformer and Fault rating.
Pātai
He āwhina hoahoa te hua. Manatokohia ki te paerewa o nāianei.
Me pēhea te tātai a te taputapu taumata hapa i te iahiko?
Ka tāpiri ia i ngā impedance ia wāhanga. Ka hoatu te transformer i te U² ÷ S × Z%, ā, ka hoatu te puna hiko i te voltage wāhanga ki tōna iahiko hapa. Ka tāpiri te submain i tōna aukati me tōna reactance mai i ngā ripanga impedance AS/NZS 3008.1. Ko te voltage wāhanga ki te katoa te iahiko hapa wāhanga toru i te papa.
He aha ngā tauāhua phase-earth e rua?
Ko ngā ripanga e pupuri ana i te aukati i te pāmahana mahi o te kaikawe. Ko te taura makariri he iahiko teitei rawa, nō reira ka whakatika te aukati ki te 20 °C mō te nui rawa. Ko te uara wera he iti iho, mō ngā tirotiro wā disconnection i te taputapu loop impedance.
He aha tā te taputapu e whakapae ana mō te puna hiko?
Ka whakapae ia he reactance katoa te puna, ā, he mutunga kore te whatunga i runga ake i tētahi transformer. Mā ēnei e rua ka puta te iahiko teitei rawa mō ngā tauanga ka whakaurua e koe. Ka whakamahia te voltage ā-ingoa, kāore he tauwehe voltage IEC 60909. Mō tētahi puna hiko, me whai Ze i te takenga mō ngā tauanga wāhanga-whenua.
Me pēhea taku mahi i te hua?
Whakatairitea ki te kaha whati o ngā circuit-breaker i te papa. Kātahi kawea ki te taputapu fault rating, e arotake ana ka ū ngā taura ki te hapa mō te wā whakakore.
Ngā tauira mahi
- Starting a loaded conveyorA 22 kW conveyor that needs 120 % torque to break away. Why star-delta and a soft starter will not start it, and what a drive or autotransformer does.
- 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.
Kōrero o muri
Ngā Clause me ngā Table e pānuitia ana e tēnei taputapu
- AS/NZS 3000:2018 Table 5.1Minimum earthing conductor size by active conductor size
- 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
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 fault rating tauraCheck that a conductor can withstand the fault current.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 TransformerCalculate transformer full load current and impedance.Kāore he paerewa
He whai hua tēnei?
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