IEC 60092-503-2021 pdf free download – Electrical installations in ships – Part 503: Special features – AC supply systems with voltages in the range of above 1 kV up to and including 36 kV.
4.9Divided system
Where a high impedance earthed system is divided into two or more sections,intended forseparate operation, means for neutral earthing shall be provided for each section.
lf it is possible to join two or more sections，the possibility of circulating currents shall beevaluated, and a proper plan or actions shall be taken into consideration (for example, leavingonly one point earthed).
5lnsulation
5.1Selection of insulation level
5.1.1General
The insulation level shall be chosen according to the established highest voltage for installationUm·
lnsulation coordination shall be in accordance with IEC 60071-1.
NOTE Due to the conditions on board ships, certain equipment requires an insulation level higher than that of thenominal voltage of the system in accordance with lEC 60071-1 and iEC 60071-2.
5.1.2 Lightning impulse withstand voltage
The earthing conditions (isolated or high impedance earthing)，for high-voltage ship-boardinstallations are listed in Table 1.
NOTE The values are on the basis of the higher values for the lightning impulse withstand voltage inIEC 61936-1:2021, Table 2.
5.1.3consideration of rated withstand voltages
Dielectric tests for equipment with lower clearances than shown in Table 1 shall be based onthe highest voltage Um for the installation.
5.2Verification of clearance and creepage distances5.2.1Clearance distance
Clearance and creepage distances for equipment are normally specified in the relevant productstandard.
Where no product standard is available, the following two options are available.
Option 1: Evidence that the minimum clearance distances based on Um of Table 1 are keptand performance of a short-duration power-frequency withstand voltage test in accordancewith lEC 60060-1.Test values shall be based on Um according to Table 1.
Option 2: lf the minimum clearances in air are not maintained for chosen insulation level(see 5.1), appropriate dielectric tests (i.e. short-duration power-frequency withstand voltagetests and lightning impulse withstand voltage test) in accordance with lEC 60060-1 shall beperformed.Test values shall be based on Umaccording to Table 1.
5.2.2 Creepage distance
All equipment shall have satisfactory creepage distances.
Unless otherwise specified, the minimum specific creepage distance of insulators shall comply with the recommendations of IEC TS 6081 5-1 , IEC TS 6081 5-2 and IEC TS 6081 5-3 for the level of pollution specified at the place of installation.
Where the level of pollution cannot be specified, the following values apply:
– 25 mm/kV in busbar systems;
– 1 6 mm/kV downstream, after circuit-breaker and fuses.
5.3 Voltage and frequency
Voltage and frequency shall be chosen in accordance with IEC 60038. The maximum nominal system voltage is 36 kV. The preferred values for nominal voltages for ship supply systems are stated in Table 2. If the system is intended to operate at variable frequency range, it shall be ensured that all affected equipment is designed to operate within entire range.
6 Electrical protection
6.1 General
In addition to the general requirements of IEC 60092-202, the requirements in 6.2 to 6.4 apply.
6.2 Voltage-transformer protection
Voltage-transformers for control and instrumentation with primary side connected between phases (line voltage) shall be protected against short circuit by fuses on the primary and on the secondary sides. Fuses may be omitted in circuits to voltage detectors in generator voltage regulators.IEC 60092-503 pdf download.