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Technical Bulletins

Tests after installation - IEC 60840

IEC 60840 ed 3: Power cables with extruded insulation and their accessories for rated voltages above 30 kV (Um = 36 kV)
Recommended voltage tests after laying, jointing and terminating of cables manufactured to this standard based Clause15.

Electrical tests after installation

Tests on new installations are carried out when the installation of the cable and its accessories has been completed.

A d.c. oversheath test according to A and/or an a.c. insulation test according to B is recommended. For installations where only the oversheath test according to A is carried out, quality assurance procedures during installation of accessories may, by agreement between the purchaser and contractor, replace the insulation test.

A. DC voltage test of the oversheath

A direct voltage of 4 kV/mm of specified thickness of extruded oversheath shall be applied with a maximum of 10 kV between metallic sheath and outer electrode (moist backfill or a graphite layer) for a period of 1 min to demonstrate the integrity of the cable oversheath after laying (Clause 5 of IEC 60229).

For the test to be effective, it is necessary that the ground make good contact with all of the outer surface of the oversheath. A conductive layer on the oversheath can assist in this respect.

B. AC voltage test of the insulation

The a.c. test voltage to be applied shall be subject to agreement between the purchaser and the contractor. The waveform shall be substantially sinusoidal and the frequency shall be between 20 Hz and 300 Hz. A voltage according to the table below shall be applied for 1 h.

Alternatively, a voltage of U0 may be applied for 24 h.

NOTE: For installations, which have been in use, lower voltages and/or shorter durations may be used. Values should be negotiated, taking into account the age, environment, history of breakdowns, and the purpose of carrying out the test.

DC testing of XLPE cables

DC testing of the insulation of XLPE cables is not recommended.