60831-2@IEC:2014 capacitors to be positioned in such a manner that these terminals or cables are just above the surfaceofthe liquid 17.2 Test sequence Before the test, the capacitance shall be measured as prescribed in 7.1 of IEC 60831-1:2014. Thetestsequence is in three parts as follows: a) The capacitor shall be energized at a voltage equal to 1,25 Un for 750 h. Taking the tolerances of the supply voltage into account, this test voltage shall be the average voltage for the whole test duration. b) The capacitor shall then be subjected to 1 0o0 discharge cycles consisting of: charging the capacitor to a d.c. voltage of 2 Un; discharging the capacitor through an inductance of: in which C is the measured capacitance in microfarads (μF) The cables used for the external circuit and the inductance shall have a cross-section appropriate to the maximum permissible current (see Clause 21 of IEC 60831-1:2014). The duration of each cycle shall be 30 s minimum. The connection for this part of the test shall be as described in Clause 16of IEC 60831- 1:2014. c) Repetition of item a). During the whole test sequence the temperature of the case shall be maintained equal to that indicated in 17.1.1. In the case of three-phase capacitors, the first and the third parts of the test sequence (items a) and c) shall be carried out with all the phases energized at 1,25 Un. This can be obtained either by using a three-phase source, or by using a monophase source and modifying the internal capacitor connections. Due to long duration of this test, voltage interruptions may occur unexpectedly. During these interruptions, the capacitor units shall remain in the same test setup and the test time is also the same starting conditions as described in 17.1.2 or 17.1.3. 17.3 Testrequirements During the test no permanent breakdown, open circuit orflashover shall occur. At the end of the test the capacitor shall cool down freely to the ambient temperature and the capacitance shall then be measured under the same conditions as before the test. The maximum permitted variation of capacitance compared to the values measured before the test shall be 3 % averaged over all thephases and 5 % on onephase. The voltage test between terminals and container shall be carried out with the same pro- cedures as prescribed in 10.1ofIEC 60831-1:2014. The sealingtest shall berepeated asprescribed in Clause 12 of IEC 60831-1:2014 - 8 - 60831-2@IEC:2014 18 Self-healing test This test may be carried out on a complete unit, or on a separate element or on a group of elements that are a part of the unit, provided the element or the elements under test are identical to those used in the unit and their conditions are similar to those they have in the unit. The choice is left to the manufacturer. The capacitor or element shall be subjected for 10 s to an a.c.voltage of 2,15 Un or to a d.c. voltage of 3,04 U (2,15 Un a.c.peak value). If fewer than five breakdowns occur during this time, the voltage shall be increased slowly until five breakdowns have occurred since the beginning of the test or until the voltage has reached 3,5 U in a.c or 4,95 U in d.c. If fewer than five breakdowns have occurred when the voltage has reached the above stated voltage limit for a time of 10 s, the test shall be finished, if at least one clearing has occurred. If no breakdown has occurred,the test may be continued until at least one breakdown is obtained or may be interrupted and repeated on another identical unit or element, at the choice of the manufacturer. Before and after the test, the capacitance and tan shall be measured. The following formula shall be checked: tan ≤1,1tan o+1× 10-4, (at 50 or 60 Hz) Where tan is the value after the test and tan So is the value before the test. NOTE 1 Breakdown during the test may be detected by an oscilloscope or by an acoustic or a high-frequency test method, In particular, self-healing breakdown test equipment as shown in Annex A could be used NOTE 2 The test carried