Opinion ID: 2153271
Heading Depth: 1
Heading Rank: 4

Heading: Stabilizing Effect of DC Line on Supply System

Text: Square Butte does contend that the DC line will increase the reliability of the electrical supply system in North Dakota by reducing the frequency of phenomena known as low frequency oscillations. Whether or not low frequency oscillation will occur depends on the combination of the amount of generation in the area, the amount of transmission and the strength of that transmission. Professor Jack Krueger of the University of North Dakota further explained the phenomenon and its effect as follows: The oscillation process is aan actual displacement between the generation and the utilization point on electric power. A good example, one that is used in our classwork at the University, is to have two electrical machines, one is a generator, one is a load connected by a transmission line. And as the load is brought up to a particular level, the mechanical displacement between the rotating element of the motor that comprises the load versus the position of the rotating element of the machine, that is the generator, has a certain angular displacement. As you increase the load this angular displacement will increase still further. And above a certain point the angular displacement becomes so bad that they fall out of synchronism. And the generator then speeds up, the motor slows down and eventually would come to a stop. At that point . . . the system has collapsed. MP&L's manager of system planning testified that 68 low frequency undamped oscillations were recorded in North Dakota during 1972. He indicated that seven of those resulted in system collapses: The transmission system in North Dakota breaking up, the units tripping off the line, circuit breakers opening, et cetera. Since the power flow on a DC line is controllable by operator action, it can be modulated in exactly the right phase relationship with those low frequency oscillations to damp them or get them to reduce in magnitude and disappear from the system. The modulation would apparently occur at Center as the current is changed into DC. The generation will bypass the AC transmission system and the flow of AC power will be introduced at the eastern end of [the] system so that a return of energy to Square Butte will unload the existing facilities that are normally transferring power from west to east. In effect, the disturbance will be moved from North Dakota to Minnesota where the distances between the generating systems and the effective load center of the system are different enough so that the oscillation will not hinder operations on the receiving end. MP&L's employee was unable to specify the time or date of any system collapses in North Dakota, although he was aware that the Minnkota system had collapsed in 1972. He assumed that it took eight hours to get Minnkota's steam plant back on line, based on his experience with MP&L's plants of a similar size, but he did not know how long the outage lasted for the ultimate consumer. He testified that the length of such an outage would depend upon the availability of energy in other systems; under certain circumstances we could put it back together in a few minutes, under others it may take hours. Testimony at the trial included an averment that with the stabilizing effect of the DC line on the AC system the entire generating complex in the Bismarck area will be able to operate at a higher output level than currently exists. During his deposition, Professor Krueger indicated additional generation on the AC system with a stabilizing DC line . . . would not contribute to instability of the system, but without the line it would. MP&L chose the DC line after its studies indicated that various 345 KV AC transmission schemes totaling more than 950 miles of line would not be adequate to support the [generating] unit in North Dakota and deliver its output to the MP&L service area for the initial seven-year period. MP&L's manager of system planning concluded that the DC line will make the AC systems more reliable and increase the capability of loading those transmission lines that leave the generating complex in the Bismarck area. None of the trial court's findings of fact concern the effect of the DC line on low frequency oscillations. In his memorandum opinion, the trial judge observed, There has been testimony regarding the stabilization of the AC lines within the State of North Dakota which this Court finds is not persuasive enough to supply public use for condemnation purposes. By Rule 52(a), N.D.R.Civ.P., we may not set aside findings of fact in civil actions unless such findings are clearly erroneous. We explained that standard in In re Estate of Elmer, 210 N.W.2d 815 (N.D.1973): A finding is `clearly erroneous' only when, although there is some evidence to support it, the reviewing court on the entire evidence is left with a definite and firm conviction that a mistake has been made. [Citation omitted.] The mere fact that the appellate court might have viewed the facts differently, if we had been the initial trier of the case, does not entitle us to reverse the lower court. [Citations omitted.] Id. at 820; accord, Schumacher v. Schumacher, 242 N.W.2d 136 (N.D.1976); In re Estate of Blank, 219 N.W.2d 815 (N.D.1974) In light of the fact that the testimony asserting that the DC line will stabilize the existing AC generating and transmission systems in North Dakota was not disputed, it is possible that the trial court determined that the stabilizing effect is a benefit, but that such an influence is by itself insufficient to justify exercising the power of eminent domain. In any case we conclude that the trial court was clearly erroneous in not giving some effect to this influence. We think that the stabilizing influence is a factor that must be considered with other factors to determine whether there is a direct and substantial benefit to North Dakota.