Three-Phase Submersible Distribution Transformers, Type ONAN
This Standard covers the features of three-phase submersible transformers. For other details, reference shall be made to CSA Standard C2, Single-Phase and Three-Phase Distribution Transformers Types ONAN and LNAN, which is hereinafter referred to as CSA Standard C2.
Included with this Standard is Appendix A, Recommendations for Corrosion Control of Submersible Transformer Installations, which covers handling and installation, cathodic protection, maintenance and records recommendations that the user should follow to ensure an acceptable service life.
The rated kV·A capacities at rated voltage shall be 75, 150, 225, 300, 500, 750, and 1000.
This Standard applies only to three-phase distribution transformer units intended for use in a ventilated vault or enclosure below grade level with all terminations and accessories cover mounted for operation from above grade. It does not apply to directly buried transformers in contact with the earth, to permanently submerged transformers, or to network type transformers.
The equipment covered by this Standard is primarily intended for operation by electric utilities on three-phase underground distribution systems having primary voltages as shown in Table 1.
When this equipment is intended for operation by other than an electric utility, it shall be the purchaser's responsibility to ensure that the unit meets the requirements of the appropriate electrical inspection authority.
The equipment covered by this Standard may have two HV bushings for each phase, designed for circuit loop feed within the transformer tank. High-voltage switching and fusing may be connected between these internal loop feed elements and the transformer high-voltage winding; they are not covered by this Standard and should be specified by the purchaser.