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The reference work for electrical work: Ohm's law, voltage drop, cable sizing and protection — explained so it can be used in practice.
Become an electricianGet started · 5 minThe electrician makes light, heat and power work in everything from detached houses to industry and charging points. It's a trade with high demand, pay during training, and a straight path from curious beginner to skilled tradesperson. Here's why you should consider the trade.Ohm's law and power in practiceBasic electrical engineering · 9 minU = R · I and P = U · I are the foundation of all electrical calculation. Here is the relationship between voltage, current, resistance and power — with practical examples and an explanation of what cos φ does to the power in AC.Voltage drop — why and how muchCables & sizing · 9 minWhen current flows through a conductor, the voltage drops along the conductor. Too large a voltage drop gives dim light, poorly performing motors and unnecessary energy loss. Here are the formula, the conductivity for copper and aluminium, and the indicative limits.Cable cross-section — the three requirementsCables & sizing · 15 minA conductor cross-section must simultaneously handle current-carrying capacity, voltage drop and short-circuit — the largest of the three requirements determines the cross-section. Here are the three requirements, and why the current-carrying capacity figures must always be looked up in the standard.Protection against electric shockProtection & safety · 12 minHow RCDs (HPFI/RCD), automatic disconnection and equipotential bonding together protect against electric shock. The protection rests on basic protection and fault protection — and the normative limits are always looked up in DS/HD 60364-4-41.Overcurrent protectionProtection & safety · 10 minThe difference between overload and short circuit, and how the tripping characteristic (B/C/D) of circuit breakers is chosen. Overcurrent covers two phenomena, both of which must be interrupted before the conductor is damaged.Power factor and three-phase powerBasic electrical engineering · 10 minActive, reactive and apparent power, the power triangle, and why cos φ matters in practice. A low power factor draws more current than the active power alone would require — and that costs you in cables and equipment.Standards and legislation for electriciansRules & standards · 10 minWhat laws and standards govern electrician work in Denmark, and what is the hierarchy? Here is the overview of the Electrical Safety Act, the Installation Regulation and the DS/HD 60364 series — with the most important changes in 2024 and 2026.Verification of electrical installationsQuality & documentation · 12 minVerification is not optional — it is a legal requirement that must be carried out by the authorised company before the installation is energised. Here are the sequence, the measurements and the documentation requirements to DS/HD 60364-6.RCD types and charging stations for electric vehiclesProtection & safety · 12 minThe choice of RCD type for a charging station is set out in law in DS/HD 60364-7-722 and depends on whether the charging box has approved DC residual current blocking. Type AC is prohibited — and it is not a matter of indifference whether you choose type A or type B.Grounding and grounding systemsProtection & safety · 12 minSoil spadeKLS and authorization as electrical installerRules & standards · 7 minThe Authorisation System and KLS Requirement (Quality Management System) are the Cornerstones of the Danish Electrical Installation Regime. Here are the Requirements, Documents and Consequences of Non-Compliance — with Precise References to BEK 722 and 725 from 2024.Common Regulations 2026Rules & standards · 6 minFrom 1 January 2026 the Common Regulation 2026 applies setting binding requirements for power factor phase asymmetry documentation and energy storage when connecting to the power grid. Here are the main requirements and what they mean for installations.Electrician training — new structure from August 2026.Education · 6 minElectrician training changes structure from August 1, 2026 with a new journeyman exam form, two specializations and stricter admission requirements for the main course. Here is an overview of the course, requirements and what's new.The history of the electrician trade in Denmark.The craft's history. · 7 minThe electrician trade emerged with electrification around 1900 and was gradually tied together by three things: a set of safety rules (the strong-current regulations), a licensing scheme and formal vocational training. Here is the long view — from the first installations through European harmonization to today's green transition.Sikkerhed ved el-arbejdeProtection & safety · 12 minEl er usynligt og kan dræbe. Før du rører et anlæg, gøres det spændingsløst efter de fem sikkerhedsregler — og kan det ikke, gælder de skrappe L-AUS-regler. Her er den livskritiske grunddisciplin: de fem regler, spændingsprøven, værnemidler, lysbue og førstehjælp.Solcelleanlæg (PV) — installation og DC-sikkerhedVedvarende energi · 13 minSolceller er en af de hurtigst voksende opgavetyper — og DC-siden opfører sig helt anderledes end den vekselstrøm, elektrikeren kender. Her er anlæggets opbygning, strengspændingen og dens temperaturafhængighed, DC-brydere, potentialudligning af moduler og det rigtige RCD-valg efter DS/HD 60364-7-712.Overspændings- og lynbeskyttelse (SPD)Protection & safety · 11 minTransiente overspændinger fra lyn og koblinger ødelægger følsom elektronik på mikrosekunder. Overspændingsbeskyttelse (SPD) er blevet et normativt krav i mange installationer. Her er SPD-typerne, placeringen, den kritiske 0,5 m-regel og samspillet med lynbeskyttelsen.Motorinstallation, motorværn og frekvensomformereAutomation & motorstyring · 15 minMotorstyring er kernehåndværk i industri- og automationsinstallationer. Her er de fire startmetoder (DOL, stjerne-trekant, softstart, frekvensomformer), motorværnets rette indstilling, frekvensomformerens EMC-kabling og lejestrømme, det rigtige RCD-valg — og maskinsikkerheden efter DS/EN 60204-1.Bygningsautomation og intelligente installationer (KNX)Automation & motorstyring · 11 minKNX er den åbne standard for intelligente bygningsinstallationer, hvor lys, varme, solafskærmning og persienner styres via ét bus-kabel i stedet for hver sin ledning. Her er forskellen på traditionel og bus-installation, KNX-topologien, bus-kablet og ETS-programmeringen.Tavlebygning og tavledokumentation (DS/EN 61439)Quality & documentation · 14 minAt bygge, mærke og dokumentere en tavle er dagligt håndværk — og det er styret af DS/EN 61439. Her er tavlestandarden, forskellen på original- og tavlefabrikant, de tre verifikationsmetoder, kapslingsgraderne IP/IK, temperaturstigning, samleskinnernes kortslutningsstyrke og kravene til mærkning og kursdiagrammer.Belysningsteknik og lysstyringLys & belysning · 13 minLys er et kerneområde i elektrikerfaget. Her er de lystekniske størrelser (lumen, lux, candela, luminans), farvetemperatur og farvegengivelse, blænding (UGR), belysningskravene efter DS/EN 12464-1, nødbelysning efter DS/EN 1838 og moderne lysstyring med DALI — plus lumenmetoden gennemregnet.Data-, tele- og netværksinstallationData & kommunikation · 13 minStruktureret kabling er kernehåndværk i moderne installationer. Her er parsnoet kabling Cat 5e/6/6A, 100 m-kanalen, skærmning, fiber, patchpaneler og stik, PoE efter IEEE 802.3, coax/antenne samt potentialudligning og adskillelse fra 230 V.El-diagrammer, symboler og referencebetegnelserQuality & documentation · 11 minAt læse og tegne el-diagrammer er grundforløbspensum. Her er diagramtyperne (kredsskema, hovedstrøm/styrestrøm, enstregs kontra flerstregs), de grafiske symboler efter DS/EN 60617 og referencebetegnelsessystemet (=anlæg / +placering / −komponent) efter IEC/EN 81346 — med et motorstartsdiagram læst trin for trin.Styringsteknik og PLCAutomation & motorstyring · 12 minStyrings- og reguleringsteknik er et speciale. Her er den hardwirede relælogik (AND/OR, selvhold, forrigling), PLC'ens opbygning og cyklus, programmeringssprogene efter IEC 61131-3 (ladder, FBD, ST) samt sensorer og aktuatorer — bindeleddet mellem diagram og virkelig maskine.Systematisk fejlfinding på installationer og styringerQuality & documentation · 11 minFejlfinding er en daglig kernekompetence og et selvstændigt bedømmelseskriterium. Her er metodikken: symptomanalyse, halvdelingsmetoden, systematisk indkredsning langs signalvejen, de fire klassiske fejltyper og hvordan man med multimeter og megger lokaliserer afbrud, kortslutning, jordfejl og dårlige samlinger — sikkert, efter DS/EN 50110-1.Brandtekniske installationer (ABA, ABDL og varsling)Protection & safety · 12 minAutomatiske brandalarmanlæg (ABA), branddørlukning (ABDL) og varslingsanlæg er en reel installationsopgave for certificerede elektrikere. Her er detektortyperne, centraludstyret, forskellen på konventionelle og adresserbare overvågede sløjfer, ABDL-magneterne og grænsefladen til de øvrige installationer — efter DBI-retningslinjerne og DS/EN 54-serien.