ments. At strain points links of a certain length are inserted between the attachment to the structure and the top disc, the intention being to remove this link when the voltage is increased and not therefore being required to resag the conductors."

(Concurrence by: Kansas No. 20.)

California-No. 3:

"Where it is felt that the voltage of a transmission line will be raised to a higher value, provision is usually made during construction, by building the line for the higher voltage and operating it for the lower one until such time as the higher voltage becomes necessary. In case of a suspension type line a few units can be installed during construction and any additional discs, for the higher voltage, added at a later date."

(Concurrence by: California No. 5, Massachusetts No. 26, No. 24, Ohio No. 39, No. 46.)

Minnesota-No. 28:

"We believe the 'H' frame with suspension insulators is by far the best construction when building a line which is to be changed in the future to a higher voltage. In referring to higher voltage we mean any voltage over 66-KV., since up to that point single poles with wood crossarms will give excellent construction."

(Concurrence by: Texas No. 58.)

Pin Type Construction
Wisconsin-No. 63:

"The wood pole lines are of flat top construction, that is, the three conductors are supported on one 10 ft. crossarm, the ground wire is carried on a bayonet

Fig. 318. Method of Turning Corners Used by One Company

on Angles of 105°-165°.

Fig. 319. Method Used by Same Company on Angles

of 75°-105°.

directly above the pole, and the minimum distance between conductors is 3 ft. I am not at all sure that this is the best design for all purposes-in fact I am rather of the opinion that it is cheaper and better to place two shorter crossarms on the pole and place two of the conductors on one crossarm and the third on the other. I say this because it would be very difficult for us to raise the voltage of the lines which we have, due to the fact that it would require such a very long crossarm to give the proper separation be

tween the conductors."

Illinois No. 15:

"If the change of voltage is to come at an early date the line should be insulated for the ultimate operating voltage, otherwise the lower voltage insu

lators can be used, though I believe that the saving in expense as a rule will be found to be too small to justify the operating difficulties that will be found when the change must be made."

Pennsylvania-No. 51:

"Considering the problem, however, in a broad way, I believe that each company should very carefully study its territory and the best possible way of furnishing service to it. This will entail a definite decision as to what ultimate voltage can be employed

and, therefore, the corresponding space can be provided for on the supporting structures."

Minnesota-No. 29:

"On pin type construction our standard pole head is the same for 6,600 volts delta, 11,000 volts delta and 22,000 volts star. We have found that the difference in initial cost of construction is so small, and

the growth of the system so indefinite, that it does not pay to use separate types for this range of voltage."

Georgia-No. 12:

"It is our opinion that as a general rule the suspension insulator line spaced for its ultimate voltage and insulated for its present voltage is the most satisfactory line for raising to higher voltages. On pin type lines we often build a line spaced and insulated for its ultimate voltage, although operating it for the time being at the lower voltage."

(Concurrence by: Connecticut No. 8.)

Massachusetts-No. 25:

"The best design to permit of raising lines to higher voltages and to allow for live line work, such as changing and testing insulators, is to include sufficient spacing of insulators for the highest possible voltage desired. While in the past we have used various length crossarms on our 6,600 to 33,000 volt lines we have now practically standardized on the use of the 10 ft. four pin arm for all lines of this voltage range. When building one three-phase circuit we use the two pins on one side of the pole and the end pin on the other. When the second circuit is

Fig. 322. Turning Corner by Dead-Ending Conductors

on Crossarms.

Fig. 323. Corner on a 66-KV. "H" Frame Line.

added, the second crossarm is placed 3 ft. below the first arm and two wires of each circuit are carried on the top crossarm with one wire of each circuit at the extreme ends of the lower crossarm. This allows the maximum clearance for changing insulators and gives sufficient spacing up to 33,000 volts."

(Concurrence by: Illinois No. 14, Ohio No. 43.)

Ohio-No: 45:

"When building a new line where the ultimate voltage is expected to be considerably above the first operating voltage it is my opinion that the best type of a construction is the semi-triangular two arm arrangement, carrying one line wire and ground wire on the top arm, and two line wires on the lower arm. This will probably give greater spacing than necessary for the lower voltage, but by simply changing the insulators the line is suitable for operation at a higher voltage."

(Concurrence by: California No. 4, Oregon No. 49.)

Tennessee-No. 56:

"Our practice has been to design and construct transmission lines up to 44,000 volts of single wood poles, wood arms and pin type insulators without ground wire; using wood pole 'A' frames or 'H' frames to support long spans."

Fig. 324. Another Type of Corner Used on a 66-KV. Line.

Ohio-No. 40:

"We have never considered any method of convoltage. Our idea of raising to a higher voltage struction that would easily permit raising to a higher would be reconnection of our step-up transformers from delta to star. With this change, our limiting feature would be the rupturing capacity of the air and oil break switches, providing we grounded the neutral of our system."

Replies to the Committees' Question:

What Are the Relative Merits of the Delta and Star Connected Systems?

Star Connected Transformers California-No. 5:

"We are in favor of grounded star-connected transformers at least at one point in a transmission net work and if there is danger that this star-connected station may be disconnected with the line still in operation, it is essential that a second station be star-connected and grounded. We believe that even moderate voltage net works when they have grown. to a sufficient size require grounding for satisfactory operation; this is true even if the generator capacity is comparatively small, provided the system is rather extensive. As an example we would cite the case of an 11-kv. net work operating ungrounded delta. As this system gradually grew in size surges caused by arcing grounds, insulator failures, etc., became increasingly violent. Sets of multigap arrestors were frequently so shattered as to become useless. The surges appeared to travel from one end of the system to the other finding and breaking down all weak points. That these increasingly violent surges were due to increased electrostatic capacity rather than generating capacity was shown by the fact that no change had been made in the generator capacity over a considerable period and furthermore, when the system was later cut in half, the divisions being connected by a high voltage transmission line, the surges were very much less marked. We consider that the only satisfactory solution for a difficulty of this nature is grounding the neutral as has been borne out by the experiences of many companies."

Utah-No. 59:

"We believe in the use of delta-delta connected transformers throughout our system except at a single point at which the system is grounded through a star-star bank with a tertiary delta winding to stabilize the neutral. Our system was originally delta with no neutrals on the system anywhere. We had so many difficulties with secondary equipment breaking down, transformer and switch bushings flashing over, puncturing, etc., in cases of accidental grounds on the system that we concluded we should ground the neutral at one point in order to pre