Electrical pre-commissioning is performed by the commissioning team. Electrical testing typically involves more complex test setups and often requires specialized test equipment that only the commissioning team would have, or even a specialized team that’s brought in as a member of the commissioning team to perform electrical pre-commissioning.

At the end of pre-commissioning of a particular subsystem, the commissioning team confirms that all checklists are filled out and that all results are passing within tolerance. This confirms that pre-commissioning is complete and that all systems are contract compliant before we move into the next phase of commissioning.

The following types of routine test items for power transformers under the IEC standard:

IEC 60076-11, clause 11, complete list of tests

11.1 General requirements for tests

11.2 Routine tests

11.2.1 Measurement of winding resistance

11.2.2 Measurement of voltage ratio and check of phase displacement

11.2.3 Measurement of short-circuit impedance and load loss

11.2.4 Measurement of no-load loss and current

11.2.5 Applied voltage test (AV)

11.2.6 Induced voltage withstand test (IVW)

11.2.7 Partial discharge measurement

11.3 Type tests

11.3.1 Full-wave lightning impulse test (LI)

11.3.2 Temperature-rise test

11.4 Special tests

11.4.1 Partial discharge measurement for transformers operated under a single-phase line-to-earth fault condition

11.4.2 Measurement of sound level

11.4.3 Short-circuit test

11.4.4 Climatic tests

11.4.5 Environmental test

11.4.6 Fire behavior test

11.4.7 Seismic test

11.4.8 Special test for transformers equipped with amorphous core

Both the National Fire Protection Association (NFPA) and IEEE recommend a ground resistance value of 5.0 ohms or less.

It is strongly recommended that testing take the form of a comprehensive structured earthing survey comprising seven key steps. The first of these is a close visual inspection of the earthing installation. This should look for any signs of damage, for earthing conductors that have been broken, cut or have otherwise become disconnected, and for signs of corrosion, not only to the electrodes themselves but also at the connections between the electrodes and the earth conductors.