General Order 64

Detail Construction Requirements For Supply Lines

67    Transformers, Switches And Equipment.

(a)    Location of Transformers:  Where more than one transformer is installed on a pole, all transformers shall be hung on the same side of the pole, in order to give free access to all equipment on the pole.

(b)    Live Parts:  Current carrying parts of switches, automatic cutouts, etc., exceeding 300 volts to ground, when located below conductors, shall be enclosed or suitably guarded if less than 20 inches from pole center, except when located on or above the top cross arm.

Exception:  This shall not apply when switch or cutout is not to be worked on when alive.

(c)    Where Pole-top Line Switches are operated by all metal control mechanisms, such mechanisms must be grounded; when it is possible to operate such a switch while standing on the ground an insulated platform shall be provided.

(d)    Transformer Windings not exceeding 250 volts to ground (except those used exclusively for energizing signal and track circuits) shall be grounded as follows:  (See Appendix E, Fig. 21)

1.    Single Phase System:  In 2 wire (nominal 110 volt) systems one wire shall be grounded; 2 wire (nominal 220 volt) systems or 3 wire (nominal 110-220 volt) systems the neutral point of the winding shall be grounded.

2.    Two Phase Systems:  In 3 wire systems the neutral point of one transformer winding shall be grounded; in 4 wire independent systems the neutral point of each winding shall be grounded.

Note - In two phase 3 wire systems used exclusively for power service, the middle point of the transformer bank shall be grounded.

3.    Three Phase Systems:  In 3 wire delta systems the neutral point of one transformer winding shall be grounded; in 3 wire star and 3 wire T or Scott system the common point shall be grounded.

(e)    In single phase or polyphase supply systems, the earth or ground shall not be used as a return conductor; the grounding of the neutral in such single phase or polyphase systems is permitted only for the purpose of stabilizing the neutral of the system, and not for use as a return conductor.

(f)    Independent grounds shall be provided for the following:

1.    Lightning arresters.

2.    Low voltage power lighting circuits.

3.    The neutral wire of 4 wire, 3 phase systems where the line voltage exceeds 2500 volts.