Matthias Surovcik
How international manufacturers can turn a process load list into a releasable electrical design, a testable installation and an operable factory
Your production date is fixed, and the new German factory must receive its first process equipment within months. Building services, utilities and manufacturing lines are still being designed by different suppliers. Transformer capacity appears sufficient and the main switchboards are ordered. From the programme meeting, the electrical design looks mature.
The site team may discover otherwise when the machines arrive. A load list describes demand, but it does not prove fault clearance, safe isolation, maintainability or verifiability. If those questions remain open until installation, the project has lost its least expensive opportunity to answer them.
Fix the interfaces before procurement fixes them for you
The point of connection, ownership of transformers and substations, supply arrangement, earthing concept, voltage levels and expected operating modes must be explicit. The design must also address maintenance, loss of a transformer, generator operation, uninterruptible supplies, islanded sections where applicable and restoration after a trip.
The maximum prospective short circuit current must be checked against equipment ratings. The minimum fault current matters as well, because protective devices still need to operate within the required time at the remote end of a circuit. Selectivity should be assessed against the operational consequence of a fault rather than promised by a generic statement. A process fault should not unnecessarily remove an entire production area, but absolute selectivity at every level may be neither possible nor justified. The decision needs calculations, device settings and an accepted protection philosophy.
Machine interfaces require equal discipline. IEC 60204 Part 1 starts the electrical equipment of a machine at its supply connection point. The site still needs to establish the supply characteristics, protective device, isolation arrangement, protective bonding, available fault current and any emergency or control interfaces. A machine declaration and CE marking do not verify the building circuit to which the machine is connected. It is you who need to take care for this in total.
Turn engineering questions into a design assurance gate
The current single line diagram defines the system in one controlled view. Short circuit and protection studies demonstrate equipment duty and fault clearance. Cable calculations address current carrying capacity, voltage drop, thermal withstand and installation conditions. The earthing and protective bonding design connects the supply concept with the protective measures. An isolation schedule shows whether equipment can be made safe for cleaning, fault finding and replacement.
Each result needs an owner, an input date and an acceptance criterion. For example, a supplier cannot select a machine incomer correctly without the available fault current and protective device characteristics. The site designer cannot complete protection coordination without the machine data.
The gate before purchase order release should confirm more than drawing status. It should confirm that interface data are issued, safety relevant assumptions are closed, required verification is specified and deviations have a named decision owner. If a temporary assumption must remain, the project should record its consequence and the last date on which it can be changed without rework.
Design the evidence before the inspection begins
German occupational safety duties reach the project before operation. Under the BetrSichV, the employer must assess hazards before work equipment is used, select suitable measures and verify their effectiveness. DGUV Regulation 3 requires electrical installations and equipment to be maintained in proper condition and addresses testing before commissioning and after modification or repair (§ 5). The applicable installation standards provide the technical verification methods, but they do not replace the employer decision that the factory can be used safely.
This makes the inspection concept a design input. Protective conductors and bonding connections must be identifiable. Circuits need stable references across drawings, labels and test records. The acceptance dossier should distinguish design evidence, installation verification, machine conformity, functional testing and the final operational release.
Taken early, these decisions produce a factory that can be tested, isolated, operated and changed. The operating team inherits controlled evidence rather than an unstructured collection of vendor files.
Conclusion
A factory becomes releasable when supply, protection, isolation and evidence are designed together before procurement. This keeps late vendor changes from becoming unsafe site improvisation. For the next stage, read “Mechanical Completion Is Not Permission to Operate”. Review your electrical interfaces before design freeze, we are happy to help (Click)
Frequently Asked Questions
Is a process load list enough to size the factory electrical system?
It is an essential input, but diversity, operating modes, starting currents, harmonics, future capacity, redundancy and fault conditions also affect the design. Equipment ratings and protective measures require short circuit and protection studies, not only a total connected load.
Who must provide the prospective short circuit current to a machine supplier?
The project must allocate that interface. The site electrical designer normally provides the maximum and minimum prospective short circuit current at the agreed connection point. The machine supplier confirms withstand ratings and protective requirements for those values.
Does CE marking cover the machine connection in the factory?
It covers the product conformity responsibilities applicable to the machine. It does not by itself verify the upstream site circuit, site protective measures, local installation work or the suitability of the complete operational interface.
When should the inspection concept be defined?
Before procurement and detailed installation. Required measurements, accessible test points, circuit identification, documentation formats and acceptance responsibilities can affect equipment specifications and layout.
Must every design deviation be closed before procurement?
Not necessarily. Safety critical parameters that determine ratings or protective measures should not remain undefined when equipment is ordered.
