Design, verification and test reporting to IS 732:2019 · IS 3043:2018 · CEA (Safety) Regulations 2023 · NEC of India 2023 · IEC 60898-1/-2, IEC 60947-2, IEC 60269-1, IEC 60909-0, IEC 60287-1-1, IEC 61557-3
1 Project, Client & Test Details
2 System, Earthing Arrangement & Source
Earthing system and reference voltage
Cl. 4.2.11.4 / .5 / .6 of IS 732
Source — transformer or generator
%Z × kV² / (100 × MVA) — Eq. 7, IEC 60909-0
Splits Z into R and X for vector summation
TT / IT system — RCD condition (Cl. 4.2.11.5.3 of IS 732)
3 Fault Loop — Circuit Levels (source → final circuit)
How to use. Add one level for each protective device in the loop, in order, starting at the
main LV panel. There is no limit on the number of levels — use + Add level below on any level to
insert the next device downstream of it, or + Add level at the end to extend the cascade. Each level carries
its own OCPD (ACB, MCCB, MCB, HRC fuse or a relay with Ia entered directly), line conductor and protective
(PE) conductor. Impedances accumulate down the cascade exactly as in the fault loop. Enter measured values in
section 4 once the installation is tested.
Total operating uncertainty of a loop-impedance meter shall not exceed ±30 % of the
measured (fiducial) value — IEC 61557-3 with IEC 61557-1 Table 1. Enter the meter data sheet figures once;
they apply to every measurement below.
5 Results & Compliance Summary
Fault loop impedance build-up
Prerequisite compliance at each level
Recommendations
6 Client Report
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7 Reference Data & Basis of Calculation
Expressions used
Eq.
Expression
Source
1
Z ≤ U0 / Ia
Cl. 4.2.11.4.4, IS 732:2019
1A
RA × IΔn ≤ 50 V
Cl. 4.2.11.5.3, IS 732:2019
2
Zmax, allowable = ⅔ × Z
Cl. 6.2.3.6.2, Annex MM, IS 732:2019 — allowance for conductor temperature rise during the fault
3
Zsource = %Z × kV² / (100 × MVA)
Eq. 7, IEC 60909-0
4
R = ρ × L / A ; Rac ≈ 1.1 Rdc
Table 1, IEC 60287-1-1:2023
5
X = 2πf × 2×10−7 × [¼ + ln(D/r)] Ω/m
IEC 60909-4 — self + external inductance
6
Ib ≤ In ≤ Iz and I2 ≤ 1.45 Iz
Cl. 4.4.4.1, IS 732:2019
7
u = b(ρL/S·cosø + λL·sinø) Ib ; Δu% = 100u/U0
Annex Y, IS 732:2019
8
Smin = √(I²t) / k, for t ≤ 5 s
Cl. 4.4.5.5 and Cl. 5.4.3.1.2, IS 732:2019 (k from Table 11 and Annex EE Tables 58 to 62)
8A
Sp ≥ S for S ≤ 16 ; 16 for 16 < S ≤ 35 ; by calculation for S > 35
Table 12, Cl. 17.2.2.2, IS 3043:2018
8B
Separate PE ≥ 2.5 mm² with mechanical protection, ≥ 4 mm² without
Cl. 17.2.2.3, IS 3043:2018
7B
ρθ = ρ20 [1 + α20(θ − 20)]
Table 1, IEC 60287-1-1:2023 — temperature correction of conductor resistivity
9
B% = ±(B / fiducial value) × 100 ≤ 30 %
IEC 61557-3 with Table 1 of IEC 61557-1
Table 1 IS 732 — maximum disconnection timesConductor resistance and reactance (IS 8130 / manufacturer data)OCPD trip multiples — IEC 60898-1 / -2, IEC 60269-1, IEC 60947-2k values — Table 11 and Annex EE Tables 58 to 62 of IS 732Protective conductor sizing — Table 12 and Cl. 17.2.2.3 of IS 3043Transformer minimum %Z — Table 1 of IEC 60076-5Cable current ratings — Tables 20 and 21 of IS 732Line inductance — derivation behind Expression 5Engineering notes, assumptions and deviations from the source workbook
Foretec Electric India Pvt Ltd — Passion in Power Quality · Authorised Janitza Electronics GmbH Blue-Level Solution Partner
This tool assists the designer and the tester. It does not replace the judgement of a competent electrical engineer or the
requirements of the licensing authority. Standards are cited for guidance; always work from the current licensed text.
