Errata and Comments to Bulletin 1728F-803

| Recently, RUS published Bulletin 1728F-803,    Specifications and Drawings for 24.9/14.4 kV Line Construction. We have identified    several errors in the first printing of 1728F-803, and we have received some comments that    are addressed below.

Errata to Bulletin 1728F-803

TABLE VII, Maximum Line Angles on Spool Insulator Assemblies, at the    beginning of Section "N", has the wrong value (*1,500 lbs./conductor*)    entered for the designated maximum transverse load for ANSI Class 53-4 spool insulators.    The correct value is 2,250 lbs./conductor, which is fifty percent of the mechanical    and electrical (M&E) strength for this class of insulators. Thus, all of the line    angles are incorrect; they are smaller than they need to be. The attached table (Exhibit    2) has the correct designated maximum transverse load value entered and the resulting    calculated line angles (which are greater), and are now correct. Please make copies of the    attached table and replace TABLE VII in each copy of Bulletin 1728F-803.

Assembly "VC2.51" should have 2 (two) pin type,    15 kV white insulators (item "a") listed in the QTY (quantity) column    instead of 1 (one) as shown.

The drawings of Assembly "VD1.81L" should show the outside    clamp type crossarm pins (item "f") 8 inches (20 cm) from the end    of the arm. On Assembly "VD1.83L," the clamp type crossarm pins should be    arranged the same as shown on the "VD2.91L" assembly drawing.

There may be other errors in the first printing of this bulletin.    Please contact us if you find errors or have questions or comments. RUS plans to publish    an errata sheet to this bulletin later this year.

Comments on Bulletin 1728F-803

The drawings for the transformer banks "VG2.1,"    "VG3.1," etc., show cutouts (item "af") and arresters    (item "ae") mounted next to each other on a crossarm. The drawings in old    Bulletin 50-5 show the use of a combination cutout/arrester    (item "ax"). Either method may be used. Also, either method may be used for    single-phase, conventional pole type transformers. However, RUS strongly recommends    that surge arresters be mounted directly on the transformer, thus shortening the    arrester lead length and providing maximum protection to the transformer.

Table 232-2 in the 1997 edition of the NESC requires 13.0 feet    (3.96 m) minimum ground clearance to platforms and equipment cases. This dimension is    shown for the platform mounted voltage regulators of assembly "VY1.3" in new    Bulletin 1728F-803. However, a 10.0 foot minimum (3.05 m) ground clearance is    shown for similar assemblies "VM7-1" and "VM7-3" in old    Bulletin 50-5 and "M7-11" in Bulletin 50-3, "Specifications and    Drawings for 12.5/7.2 kV line Construction." RUS requires that all new    construction comply with the most restrictive provisions of the most recent edition of the    NESC, RUS specifications, or other local regulating governmental authorities. Thus, for    these assemblies, the NESC clearance of 13.0 feet (3.96 m) minimum must be used    because it is more restrictive than the clearance shown in Bulletins 50–5 and    50-3. Please note, however, that the requirements of the NESC are not retroactive and only    apply to new construction.

If you have any information or questions, please call Jim Bohlk,    Electrical Engineer, Distribution Branch, at (202) 720-1967.
 

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