High-voltage Bus Research Articles

Impact of residential photovoltaic power systems on the electric utility in Cairo, Egypt

The impact of utility-interactive residential photovoltaic (PV) power systems on the electric utility was studied. Power flow analyses were performed before and after the introduction of PV, on a subtransmission and distribution network model of an actual residential utility feeder serving a suburban area of Helwan in Cairo, Egypt. The changes in bus voltages and utility power factor were used to assess the impacts caused by the PV introduction. PV systems were examined at different penetration levels and were introduced in the low- and high-voltage buses of the distribution circuit. PV power factors as low as 0·7 were used to account for various power conditioner designs. PV-utility interconnection at the high-voltage distribution level is recommended since it results in acceptable voltage regulation throughout the network as well as a good utility power factor.

Load Response Coefficients Monitoring System : Theory and Field Experience

The active and reactive powers, at a high voltage bus level, have generally been modelled either as functions of the time of the day or as load response functions of voltage and frequency changes (at a given time). The study of the dependence of these load response coefficients on time and weather has not been possible until now, since the determination of these coefficients required test perturbations. A mobile mini-computer based load response coefficient monitoring system has been conceived and tested, based on an estimation procedure requiring no test perturbations. Results, including the load response coefficients at about 6-minute intervals, from the operation of the system, at two Hydro-Quebec 120 kV substations, are also presented.

Electronic simulation of electrical power system loads

A discussion of various approaches to modelling the bulk load as seen at a high voltage bus of an electric power system leads to a mathematical model and an analogue representation suitable for an Electronic Power System Simulator. The load is represented as real and reactive power as a non-linear function of voltage, a linear function of frequency and a real power component to represent mechanical inertia. The model features a novel amplitude detector and phase-locked loops to measure the frequency at the load terminals. Application of the load model to an example transient stability study shows the considerable effect that load characteristics may have on critical clearing times and system oscillation damping.

Trenton Channel 9 - A Change in Philosophy of Design of Supplies to Auxiliaries

The engineering of the electrical auxiliary system for Trenton Channel 9 is based on a major change in the philosophy of designing auxiliary electrical systems. A single transformer connected to the unit high-voltage bus will supply the major auxiliaries for the unit. Major features of the auxiliary system are described.

Analog Computer Studies or System Overvoltages Following Load Rejections

The purpose of this paper is to report analog computer studies which were made to determine the magnitudes and durations of fundamental frequency overvoltages appearing at the generator terminals and transformer high-voltage bus following certain types of load rejections.

138-kv isolated-phase bus and switching structure

A DEFINITE TREND has been indicated toward higher subtransmission voltages to meet increasing load demands in certain metropolitan areas. High-voltage metal-enclosed isolated-phase bus structures offer a practical and economical solution to the bus and switching needs at these higher voltages and have many advantages such as simplification of arrangement, greater flexibility, and greater safety. Following this trend, the Consolidated Edison Company of New York installed a 138-kv metal-enclosed isolated-phase bus and switching structure at their East River plant. The bus structure provides for four 138-kv incoming circuits and six 69-kv circuits. Limited space made it necessary to mount the equipment at several levels (Fig. 1).

H-V impulse tests on lines and substations

SINCE AUGUST of 1952 high-voltage surge studies have been in progress at the 500-kv test project sponsored by the American Gas and Electric Company. The test project is located adjacent to the Tidd power plant near Brilliant, Ohio. The surge studies were conducted as a co-operative program between the Westinghouse Electric Corporation and the American Gas and Electric Service Corporation. Westinghouse supplied the surge generator and all necessary measuring equipment; American Gas and Electric erected the high-voltage bus, surge generator, and control building in addition to making the transmission lines available for the tests.

Measuring equipment and techniques used for high-voltage impulse tests on lines and substations [includes discussion

Since August 1952, high-voltage surge studies have been in progress at the 500-kv test project sponsored by the American Gas and Electric Company. The 500-kv test project is located adjacent to the Tidd power plant near Brilliant, Ohio. The surge studies were conducted as a co-operative program between the Westinghouse Electric Corporation and the American Gas and Electric Service Corporation. Westinghouse supplied the surge generator and all necessary measuring equipment; American Gas and Electric erected the high-voltage bus, surge generator, and control building, in addition to making the transmission lines available for the tests. The surge studies were divided into two principal sections: line attenuation and substation characteristics. Companion papers discuss each of these groups. The purpose of this paper is to describe the surge generating and measuring equipment used, and the techniques involved.

Ground relaying of generators in unit connection

A-C GENERATORS in modern power plants usually are operated in unit connection directly on high-voltage bus bars, that is, alternator and transformer form one unit so that the circuit breaker at generator voltage is eliminated. A preferred method of ground protection for such units has been indirect high-resistance neutral grounding by connecting the primary winding of a distribution transformer between generator neutral and ground, and by loading the secondary of this transformer with a resistance of such magnitude that the resulting primary ground current for a solid ground fault at machine terminals becomes 10 to 20 amperes. This grounding method was first suggested <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> in this country by L. F. Hunt as a means of minimizing fault damage within generators. The sensitivity of this scheme of protection depends on the lowest permissible pickup current of a relay activated by the current through the resistance. This pickup current indicates the parts of the machine windings which are protected. The straight line in Figure 1 shows that the assumed relay setting would lead to relay operation for faults anywhere between machine terminal (100) and location a, whereas ground faults between the neutral (0) and a would lie in the unprotected or dead zone.

Sensitive Ground Relaying of A-C Generators [includes discussion

Increased use has been made recently of high resistance neutral grounding of generators which operate in unit connection on high-voltage bus bars. High resistance grounding is achieved by connecting a constant resistance between the secondaries of a distribution transformer, the primaries of which are connected to the generator neutral and to ground. Replacing this resistance by one of nonlinear characteristic improves the protection by reducing the dead zone. Ground protection of the complete winding, including the neutral, may be achieved by introducing permanent neutral displacement by means of a small distribution transformer.

The Fundamentals of Industrial Distribution Systems

The intensive manufacturing activity accompanying the present defense program has stimulated interest in industrial electric power distribution. The ultimate objective is one of effectively satisfying electric power requirements with reasonable first cost consistent with a fair standard of safety and service reliability. This paper presents the fundamental aspects of industrial power distribution, with particular reference to low-voltage power supply to distributed electrical machinery, and compares various basic system designs, including large concentrated substations and distributed load-center substations with radial and secondary network modifications, as to safety, service reliability, simplicity, and so on, relative to estimated installed cost. The comparative analysis comprehends the complete electrical system between high-voltage supply bus and utilization terminal of low-voltage feeders. The ideal size of unit substation as influenced by operating voltage and load density is covered. Principles of system design here disclosed are applicable not only to new plant construction but to expansion or modernization of existing plants as well.

Accelerated Aging Tests on High Voltage Cable, and Their Correlation With Service Records

Experience in recent years with underground cable for the higher operating voltages has developed the fact that specifications for the insulation were incomplete and inadequate, because some of its properties which were of slight importance for the lower operating voltages became of vital importance in cable for the higher voltages. Tests on impregnated paper insulation of the ordinary type as made at the factory heretofore have determined the quality of the insulation at the time of making the tests, but gave little indication of the rate or extent of the deterioration that might occur in service. When the Commonwealth Edison Company, Chicago, Ill., adopted 66-kv cable for tie lines between generating stations so that the cable practically formed a high voltage bus, it became very important that the cable should be reasonably free from failures in service. Unfortunately the cable included in thefirst installation in 1926 fell below this requirement, and some of it had to be replaced within a few years. A careful comparison of test and service records of the four makes of cable installed in 1926 showed that the cable had a wide range in quality. A marked difference was noted in the behavior of practically identical cable on a line heavily loaded and on a line moderately loaded. Accordingly, a series of tests was undertaken with the object of developing in a short time the deterioration which had been found in the several cables in service.

Accelerated aging tests on high voltage cables and their correlation with service records

Experience in recent years with underground cable for the higher operating voltages has developed the fact that specifications for the insulation were incomplete and inadequate, because some of its properties which were of slight importance for the lower operating voltages became of vital importance in cable for the higher voltages. Tests on impregnated paper insulation of the ordinary type as made at the factory heretofore have determined the quality of the insulation at the time of making the tests, but gave little indication of the rate or extent of the deterioration that might occur in service. When the Commonwealth Edison Company, Chicago, Ill., adopted 66-kv cable for tie lines between generating stations so that the cable practically formed a high voltage bus, it became very important that the cable should be reasonably free from failures in service. Unfortunately the cable included in thefirst installation in 1926 fell below this requirement, and some of it had to be replaced within a few years. A careful comparison of test and service records of the four makes of cable installed in 1926 showed that the cable had a wide range in quality. A marked difference was noted in the behavior of practically identical cable on a line heavily loaded and on a line moderately loaded. Accordingly, a series of tests was undertaken with the object of developing in a short time the deterioration which had been found in the several cables in service.

Safe Harbor-Westport 230-kv transmission line

SAFE HARBOR development will have an ultimate capacity of 510,000 hp, a large portion of which will be available for Baltimore. During certain periods Baltimore will be dependent primarily upon this Safe Harbor power; therefore, reliability of transmission is of the utmost importance. The selection of the operating voltage was made only after a thorough investigation of the relative economic and reliability factors involved, the possibility of future interconnections, and system stability. Studies made in conjunction with the engineers of the Consolidated Gas Electric Light and Power Company of Baltimore covered a comparison of 2 23-kv circuits with 6 110-kv circuits. These studies also included investigation of such problems as terminal location, 2-point versus single-point supply, the use or omission of high voltage buses, and amount of synchronous condenser capacity required. An a-c calculating board was employed to cheqk the results obtained by analytical methods.