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Technical articles on residential electrical installations, the I7 wiring regulations and good design practice.

I7-2011Deconectare automatăTabelul 4.1Cap.4.1

Protection by automatic disconnection: the principle and the disconnection condition

“I fitted a breaker, so I’m protected” — not quite. Fault protection doesn’t mean the breaker trips, it means it trips within the required time: 0,4 s at a 230 V socket-outlet in TN, 0,2 s in TT (Table 4.1, I7-2011). And whether you make that time depends on the fault-loop impedance — the condition Zs·Ia ≤ U0: a thin cable or an undersized PE can make a perfectly good breaker fail to trip in time.

30 iunie 2026·9 min readRead →
ReleuTensiuneFazeTablou Electric

The protection relay: types, principles and use in residential installations

The electromagnetic relay, the under/overvoltage relay, the three-phase monitoring relay, the thermal relay for motors and the digital multifunction relay — operating principles, what each one protects and concrete residential applications, with photographs and an internal cross-section.

8 iunie 2026·10 min readRead →
AFDDArc FaultPrevenire IncendiiIEC 62606I7 2023

How an AFDD works: the arc fault detection device and fire prevention

The arc fault — the hazard invisible to the MCB and the RCCB. Arc types (series, parallel), the HF signature, the DSP processor, the IEC 62606 disconnection times, false alarms and the requirements from the 2023 updates to I7.

3 iunie 2026·12 min readRead →
RCBODDRMCBTablou Electric

How an RCBO works: residual-current and overcurrent protection in a single module

The RCBO combines the RCCB toroid with the MCB mechanism. Dual mechanism, space advantages, selectivity limitations versus RCCB+MCB and a selection guide — with comparative diagrams.

2 iunie 2026·9 min readRead →
RCCBDDRProtecție DiferențialăIEC 61008

How an RCCB works: the toroidal core and residual current detection

The toroidal transformer, the I_L = I_N balance, what happens during an insulation fault, the 10/30/100/300mA sensitivities and types AC/A/F/B — with animations of the current through the core.

30 mai 2026·11 min readRead →
MCBTablou ElectricProtecțieIEC 60898-1

How an MCB miniature circuit breaker works: thermal, magnetic and arc extinction

The internal components of an MCB, the bimetallic mechanism for overloads, the electromagnet for short circuits, the arc-extinction chamber and the B/C/D tripping curves to IEC 60898-1 — with animations.

29 mai 2026·10 min readRead →

Does not apply directly to your standard (BS 7671)

These articles concern the Romanian I7 standard, not the standard of your country. You can read them automatically translated (Google Translate) — but machine translation can lose nuance; for normative quotations, consult the original.

More articles coming soon

Cable sizing, two-way switching diagrams, commissioning checklists and much more.

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