Testing and commissioning electrical installations: a profession of its own

The last stage, and the most revealing

A substation, a switchboard or an industrial installation can be perfectly erected and still not behave as intended. A reversed wire, a wrong protection setting, a misconfigured automation: these faults only show up in testing. Finding them at energisation is costly. Finding them later, in operation, can cost far more.

Testing is therefore the moment when everything that was designed, manufactured and installed is verified. The test engineer, or commissioning engineer, is its guarantor.

The stages of a test campaign

Factory tests. Before delivery, the main equipment (transformers, switchgear, control cabinets) is tested at the manufacturer's, often with the client present. It is the first chance to catch a deviation from the specification.

Individual site tests. Once installed, each item is checked on its own: insulation measurements, winding resistance and turns ratio of a transformer, circuit breaker operating times, wiring continuity and labelling, earthing grid.

Functional tests. Next comes checking that the whole system behaves as intended: current and voltage injection into protection relays, tripping, interlocks, automation, signalling and exchanges with the control centre.

Energisation. It follows a programme approved with the operator and, where applicable, the grid operator. Progressive energisation, on-load checks, verification of measurements: every step is recorded.

What digital changes

With digital protection and control based on IEC 61850, some copper wiring is replaced by data exchanges over a network. RTE has begun deploying these systems in its substations.

For the test engineer, this shifts the work: less wiring verification, more checking of configuration files, messages exchanged between devices, time synchronisation and cybersecurity. Tools are changing, and skills with them.

Safety first

Testing takes place on installations moving from construction site to live asset. It is a sensitive period. In France, every intervention falls under the NF C 18-510 standard, which defines authorisations, including for testing operations, and isolation procedures. Rigorous procedures and clear responsibilities between construction and operations are essential.

The file matters as much as the test

A test campaign ends with a file: signed test reports, applied settings, updated drawings, the punch list and proof of its closure. This file is what allows the installation to be accepted, and the operator will rely on it for decades.

A sought-after profile

A test engineer combines knowledge of electrical engineering, grid protection and control systems, real methodological rigour and ease on site. With substation projects, industrial connections and data centers multiplying, and grid operators stepping up investment, this profile is increasingly in demand. Miles Group's current openings reflect it.