Artificial representation of power systems

Abstract

The size and complexity of present day power systems have increased to the point where the prediction of the behavior of the system by analytical methods is more and more difficult. The solution of commercial networks by Kirchhoff's Laws or by cut and try methods, even with the help of star-delta transformations, leads to such involved equations that the need for simpler methods is keenly felt. Increasing attention has been given to various methods of representing power systems in miniature so that an experimental solution may be substituted for an algebraic one. The d-c. short circuit calculating table is a satisfactory and relatively simple means of determining short circuit currents in networks, but is too inaccurate to give satisfactory solution under normal operating conditions. An a-c. artificial representation of power networks in miniature has been developed by O. R. Schurig of the General Electric Company who used 3.75-kw. 110-volt three-phase generators as power stations. Actual transformers are used, while lines and loads are made up of conveniently arranged lumped units of inductance, capacity, and resistance. This apparatus has been in satisfactory operation for several years. Evans and Bergvall of the Westinghouse Electric and Manufacturing Company used a test floor setup to check experimentally the theory of long line stability. Powers of about 500 kv-a. were used. The present paper presents a method of artificial representation on a laboratory scale, decreasing the size of the apparatus and increasing the precision of the results. All rotating apparatus has been eliminated. Generators are represented by phase shifting transformers; transformers by their equivalent circuits, and lines by lumped constants. A description of the apparatus used by the writers is presented, together with the results which were obtained by its use in the solution of several typical problems. An analytical check on one of the examples is given, showing a precision of better than 1 per cent.