18(Houston/Norway)1
PROPOSAL FOR EXTENSION OF VOLTAGE LIMITS LEVELS
Background
1 In the course of drafting IEC 61892-1： "General requirements and conditions", the applicability of the standards to a.c. and d.c. voltages were discussed. TC 18 extended at the Kista-meeting the nominal system voltage from 11 up to and including 15 kV. However, today offshore units are powered from onshore or from neighbour units at voltages much higher than 15 kV, e.g. one in Norway (the Troll A) is powered from onshore at 45 kV.
2 The IEC 60038 (1983)： "IEC standard voltages" applies to a.c. transmission, distribution and utilization systems and equipment for use in such systems with standard frequencies 50 Hz and 60 Hz having a nominal voltage above 1000 V. The outcome of the discussion in WG 18 was that they should propose to TC 18 to apply the values given in this publication.
3 Looking at IEC 60038 (1983), it gives in Table III values for nominal system voltages above 1 kV and not exceeding 35 kV. In this table the 15 kV is put in parentheses ( ). In a note below the table it is indicated that values in parentheses should be considered as non-preferred values. Furthermore, the note indicates that these values should not be used for new systems to be constructed in future. There is no change in the matter in Amend. 1 (1994) or Amend. 2 (1997). For this reason, 15 kV should not be used in IEC 61892.
As far as we understand Table ill of IEC 60038 - Series I, the values for Nominal system voltage in kV are 3.3, 6.6, 11, 22. and 33 for50 Hz systems while 3, 6, 10, (15), 20 and 35 are for 60 Hz systems. Voltages for equipment in kV for both 50 and 60 Hz systems are 3.6, 7.2, 12, (17.5), 24, 36 and 40.5.
The IEC 60038 is dealt with by IEC/TC 8. In order to be sure that 3.3, 6.6, 11 ...... are for 50 Hz systems and 3,6,10 ..... are for 60 Hz systems, we contacted the Secretary of TC 8, Mr. G. Di Lembo, Italy, by telephone. He confirmed it to be correct.
4 In the CDV for IEC 61892-3： Part 3 Equipment, the following Normative references are listed：
IEC 60298： 1990, A.C metal - enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV
IEC 60466： 1987, A.C. insulation - enclosed switchgear and controlgear for rated voltage above 1 kV and up to and including 38 kV
This indicates that equipment for voltages higher than 15 kV already is included in IEC 61892.
5 It is agreed in WG 18 that they in IEC 61892-1, Part 1： "General requirements and conditions", under clause 4.3 will propose the following：
4.3 Applicability of the standards to a.c. and d.c.
Except where a specific statement is made to the contrary, the IEC 61892 series are equally applicable to equipment in all installations whether permanent, temporary, transportable or hand held, for a.c. installations up to and including 40 500 Volts and d.c.
Installations up to and including 1000 V. [IEC 60092-101,2.2 modified]
6 IEC 61892-2： "System design" contains clause 6： "Distribution systems" and clause 7： "Distributions system requirements". These clauses deal with voltages for transmission, distribution and utalization systems. WG 18 will here propose the value for 50 Hz nominal voltage systems to be 33 000 V and 35 000 V for 60 Hz systems, also in accordance with IEC 60038.
7 Norway ask the Plenary Meeting to consider the above and revoke the previous decision to limit the scope of work allocated to WG 24 and WG 25 to 15 kV
