Water-wheel Generators Research Articles

Erection of vertical water-wheel generators

THE TREND in the construction and erection of vertical water-wheel generators is to increasingly larger units as experience and materials permit. The machining tolerances called for become very remarkable as the sizes increase. The practices of the Canadian Westinghouse Company with approximately 9-million installed horsepower of generator experience can be used to illustrate modern construction and erection practices. (See Fig. 1.)

Production and Installation of Vertical Water-Wheel Generators [includes discussion

This paper deals with the shop work on Canadian Westinghouse water-wheel generators and with their installation at various hydroelectric stations. The mechanical aspects of such machines are important to the erection as well as in the production operations. The tolerances called for are remarkably close considering the size and weight of the components and the fact that large machines are erected on site. The remarks on design are confined to those concerning components.

Prevention of Babbitt Blisters in Thrust-Bearing Pads

Abstract Babbitt blisters were observed on water-wheel generator thrust-bearing pads. Investigation revealed that these blisters resulted from the accumulation of high-pressure hydrogen at the steel-babbitt interface. The hydrogen, it was found, came from the steel and was introduced during the manufacture of the steel. The maximum level of hydrogen content to insure freedom from blisters was determined. Processes to remove hydrogen from the steel were developed. The incorporation of these processes into the manufacture of thurst-bearing pads has resulted in the complete elimination of babbitt blistering.

Maximizing Income from Water-Wheel Generators [includes discussion

Maximizing Income from Water-Wheel Generators [includes discussion

Rotor Design of HiHh-Speed Water-Wheel Generator

Rotor Design of HiHh-Speed Water-Wheel Generator

The manufacture of a large waterwheel generator

The manufacture of a large waterwheel generator

Application of hydrostatic lubrication in vertical water wheel thrust bearings

Two systems are described for applying hydrostatic lubrication to pivoted-pad thrust bearings during starting of vertical water wheel generators. These are the externally pressurized system and the hydraulic lifting system. Current design features and practices of both systems are discussed.

Slot discharge detection in high-voltage generators during operation

Using frequency sensitive equipment across all or part of the neutral impedance, this modified slot discharge detection method permits tests without shutting down the machine or using auxiliary high-voltage equipment. Tests on eight large water wheel generators indicate that the method is generally applicable if there is a current transformer or other impedance in the generator neutral.

Application of Hydrostatic Lubrication to Vertical Water Wheel Generator Thrust Bearings [includes discussion

This paper presents a discussion of the application of hydrostatic lubrication to pivoted pad thrust bearings during the starting period. Two systems, the externally pressurized system and the hydraulic lifting system have been used to provide an oil film between the bearing surfaces prior to starting. Current design features and practices of both systems are described. It is hoped that, as a result, the present discussion will be of service in furthering the understanding of the purpose and use of hydrostatic starting lubrication.

Modern trends in the design of vertical water wheel generators

Progress in water wheel generator design is marked by improved reliability, greater compactness, and easier maintenance. Both umbrella-type and enclosed generators are still widely used, while underground and outdoor stations are becoming increasingly popular. Some design and construction problems of these generators are discussed.

Water wheel generator under construction for Seattle, Wash.

Water wheel generator under construction for Seattle, Wash.

Detection of Slot Discharges in High-Voltage Stator Windings During Operation

A modified slot discharge detection method, which permits tests without Shutting down the machine or using auxilliary high-voltage test equipment, was investigated. The method involves connection of frequency sensitive equipment across all or part of the ntral impedance. Tests on eight vertical water wheel generators in the range of 20,000- to 40,000-kva capacity indicate that the method is generally applicable when there is a current transformer or some other impedance in the generator neutral.

Vertical-shaft generators — Some problems and their solutions

A review of some of the problems involved in the design and construction of vertical water-wheel generators, and methods of solution

Generator Damper Windings at Wilson Dam

The majority of water-wheel generators now in service have been built without damper windings. Recent technical investigations and laboratory tests have indicated that, in addition to reducing oscillations and improving system stability, damper windings are very effective for reducing high-peak voltages during unbalanced short circuits. This applies particularly under switching conditions of clearing a fault when the load is disconnected from the distant end of a transmission line, and the charging current results in capacitive loading of the unfaulted phases. The existence of similar overvoltage conditions was recognized by the Wilson Dam operating staff and later confirmed by oscillograms during tests. This paper summarizes the studies and tests based on the observed overvoltage conditions and describes a method for adding damper windings to large water-wheel generators which are already installed. Short-circuit tests are extended to generators on a large scale which confirm the earlier theoretical and laboratory tests and demonstrate the advantages to be gained by adding damper windings to other water-wheel generators now in service. The tests show that damper windings in one generator when operated in parallel with another generator without dampers are effective in reducing high-peak voltages during unbalanced faults. Data are given to show the changes in machine reactances due to adding damper windings.

Unsymmetrical short circuits on water-wheel generators under capacitive loading

Unsymmetrical short circuits on water-wheel generators under capacitive loading

Unsymmetrical short circuits on water-wheel generators under capacitive loading

WATER-WHEEL GENERATORS without damper windings under capacitive load may have abnormally high voltages developed across their terminals at limes of unsymmetrical short circuits. These voltages are due to 2 causes. First, the difference in permeance of the magnetic circuit in the direct and quadrature axes produces, under unsymmetrical short circuits, distorted voltages which have high peak values even if there is no capacitance connected to the machine. Second, the capacitance of the line and the reactance of the machine resonate or partially resonate and produce still greater distortion of the voltages on the sound phase. The phenomenon associated with single-phase short circuits with no connected capacitive load, has been analyzed by Doherty and Nickle. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> The present paper is concerned with the effect of the capacitive load and an analysis of the factors involved in this phenomenon. Consideration is given to the system conditions under which these harmful voltages may arise and the remedial measures which may be applied for their elimination.

Calculation of generatorovervoltage

Following the sudden loss of load by an alternator speed and terminal voltage tend to increase rapidly. In the following article, a method is outlined for predetermining such overvoltage, with especial reference to waterwheel generators. Test results which have been obtained on an actual machine prove that the curve of overvoltage which may be calculated by this method closely follows that secured in practise.

Damper Windings for Water-Wheel Generators

The severity of unsymmetrical system faults is affected by the negative sequence impedance of the connected machines. These impedances in turn depend largely upon the character of damper windings. The paper discusses the effect of amortisseur or damper windings upon both the real and reactive components of the negative sequence impedance. Machines without damper windings possess the highest negative sequence reactance and from this viewpoint are the most desirable, but machines with high-resistance damper windings possess the highest negative sequence resistance. Calculations show that combining the effect of resistance and reactance, the high-resistance damper is more desirable. In the event of system oscillations low-resistance copper damper windings produce the greatest damping of the mechanical movement. However, this effect is unimportant during and following a system fault except in the exceptional, rather rare case in which the system is so constituted that pull-out takes place as a result of compound oscillations following a disturbance. Consideration is also given to a special type of double deck damper winding.

Starting Performance of Salient-Pole Synchronous Motors

This paper presents an analysis of the sub-synchro-nous speed phenomena of a salient pole synchronous motor in which formulas and equivalent circuits are developed, making it possible to calculate the torque and current for a broad range of Conditions. Equations in terms of the impedances of the direct and quadrature axes are first derived from the revolving field point of view. The equivalent circuits for the two axes are then set up and expressions for the separate impedances of the circuit elements established. Adequate means of taking into account the combined effects of salient poles, incomplete amortisseur windings, and open or closed field windings are presented. The results obtained are illustrated by a comparison of the predicted performance and test data for a large 60-pole motor. The calculated distribution of current between the amortisseur bars of the same motor is shown by curves. Other curves show the calculated performance of the motor with and without continuous end rings between the poles and with the field winding open and closed. A final example shows the theoretical effects of changing the positions of the bars in the poles of a large waterwheel generator.

Abridgment of starting performance of salient-pole synchronous motors

This paper presents an analysis of the sub-synchronous speed phenomena of a salient-pole synchronous motor in which formulas and equivalent circuits are developed making it possible to calculate the torque and current for a broad range of conditions. Equations in terms of the impedances of the direct and quadrature axes are first derived from the revolving field point of view. The equivalent circuits for the two axes are then set up and expressions for the separate impedances of the circuit elements established. Adequate means of taking into account the combined effects of salient poles, incomplete amortisseur windings, and open or closed field windings are presented. The results obtained are illustrated by a comparison of the predicted performance and test data for a large 60-pole motor. The calculated distribution of current between the amortisseur bars of the same motor is shown by curves. Other curves show the calculated performance of the motor with and without continuous end rings between the poles and with the field winding open and closed. A final example shows the theoretical effects of changing the positions of the bars in the poles of a large waterwheel generator.