What Is Inspection?
Electrical installation inspection is the safety assessment of the whole installation by measurement. Visual examination alone is not enough: degraded insulation, an inadequate protective device or a high loop impedance come to light only through measurement.
Why Is It Done?
The aim is to prevent electric shock and electrically induced fire, and to verify that protective devices trip within the prescribed time when a fault occurs.
Which Equipment Is Covered?
- Industrial and commercial facility electrical installations
- Building interior wiring
- Construction sites and temporary installations
- Lighting and socket-outlet circuits
- Machine supply lines
Legal Basis and Interval
For electrical installations and protective systems the inspection interval follows the applicable electrical installation legislation and the risk class of the environment. In high-risk installations — explosive atmospheres, damp locations, construction sites — the interval is markedly shorter. Every substantial alteration to the installation calls for a new inspection.
Scope of Inspection
- Insulation resistance measurement (phase-phase, phase-neutral, phase-earth)
- Protective conductor continuity
- Fault-loop impedance and prospective short-circuit current
- Selectivity and adequacy of protective devices (fuses, circuit breakers)
- Tripping value and time of RCDs
- Phase sequence and voltage balance
- Cable cross-sections, load condition and voltage drop
- In-panel layout, labelling and touch safety
- Connection tightness and thermal condition
- Verification of the protection method suited to the installation type
Related Standards
- ISO/IEC 17020
- IEC 60364-6
- IEC 60364-4-41
- IEC 60364-5-52
- IEC 61557 series
Method and Equipment
- Multifunction installation tester
- Insulation resistance tester (megger)
- Loop impedance tester
- RCD test instrument
- Clamp meter and power analyser
- Thermal camera
Inspection Process
- 1Preliminary Information and PlanningThe single-line diagram, panel list, protective device data and installed capacity are collected; measurement points are defined.
- 2Visual InspectionPanel layout, conductor cross-sections, tightness of connections, labelling and protection against contact are checked visually.
- 3MeasurementsUsing instruments with traceable calibration, earth resistance, insulation resistance, continuity, loop impedance and residual-current device trip values are measured.
- 4Thermographic SurveyAbnormal heating at connections under load is surveyed with an infrared camera and graded against the reference temperature difference.
- 5AssessmentMeasured values are compared with the limits set by the relevant standard and by the design values of the installation.
- 6ReportingMeasurement tables, thermal images and the list of nonconformities are compiled into a report; corrective actions are proposed in order of priority.
Nonconformities
Insulation resistance below the minimum required by the standard, a loop impedance that does not meet the trip time of the protective device and a non-functioning residual current device are serious findings. They may require the relevant part of the installation to be taken out of service.
Inspection Report
- Details of the inspection body and the inspection personnel
- Identification of the installation and scope of inspection
- Measuring instruments used and their calibration data
- Tables of measurement points and measured values
- Thermal images and assessment of temperature difference
- Comparison with limit values
- List of nonconformities and their priority order
- Conclusion and the next inspection date
Accreditation
Inspection activities are carried out under ISO/IEC 17020, which requires the impartiality of the inspection body, the competence of its personnel and the validity of the inspection methods. Under the impartiality rule, a party that maintains or repairs an item of equipment cannot carry out the independent inspection of that same equipment. EUROLAB holds internationally recognised accreditation under ISO/IEC 17020, granted by accreditation bodies that are signatories to the ILAC mutual recognition arrangement; because accredited scope is defined per inspection type, it is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Inspections
Frequently Asked Questions
Does the insulation resistance measurement damage equipment?
Because the measurement is performed with a high DC voltage, electronic loads and sensitive equipment are disconnected from the circuit before it is taken. A measurement made without proper preparation both damages equipment and produces an incorrect result.
Why is thermography part of the installation inspection?
Loose or overloaded connections heat up before they fail. Thermal scanning catches these points before they turn into a fire; it is the only method that makes visible mechanical connection problems that cannot be found by measurement.
Why does the report state the calibration of the measuring instruments?
The result of an electrical inspection is not an observation but a measured value. For the measurement to be valid, the instrument must have been calibrated traceably; a measured value without calibration data cannot be defended.
Is the installation de-energised during the inspection?
Some measurements are made de-energised (insulation resistance, continuity) and others energised (loop impedance, residual current device, thermography). The inspection is therefore planned with both a short outage window and a period of operation under load.