US1755060A - Automatic voltage-regulating means - Google Patents

Description

F W. GAY

April 15, 1930.

AUTOMATIC VOLTAGE REGULATING MEANS Filed May 6, 1927 2 Sheets-Sheet l INVENTOR. fia zazfl ra April 15, 1930. w GAY 1,755,060

- AUTOMATIC VOLTAGE REGULATING MEANS Filed May 6, 1927 2 SheetsSheet 2 IN V ENTOR.

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Patented Apr. 15, 1 930 UNITED. STATES PATENT; OFFICE FRAZER GAY, OF NEWARK, NEW JERSEY, ASSTGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK AUTOMATIC VOLTAGE-REGULATIING MEANS Application filed May 6, 1927. Serial No. 189,241.

' This invention relates to improvements in voltage regulating means for power circuits; and the same has reference, more particularly, to a simple magnetic means adapted for 5 substantially instantaneous automatic operation whereby the voltage transmitted through power lines is eflicientlyregulated under wide variations of load.

Heretofore voltage regulation in connection with power circuits as been usually at tained by means of motor operated induction regulators controlled by contact-making voltmeters, or by synchronous condensers either hand operated or controlled by automatic voltage regulators. .Certain objections to the usual forms of induction regulators have been noticed; for example, the same are slow in operation; expensive to maintain, since they require more or less frequent repair, for which reason it is generally necessary to locate the same in substations where the may be subject to periodical inspection an overhauling; furthermore, such induction regulators are very noisy and for this reason can not be located in a residential district unless enclosed in sound-proof housing. Synchronous condensers are fairly well adapted to serve long transmission lines for carrying heavy power, but such electrical devices are generally very large and are usually slow acting, requiring an appreciable time (running into several seconds) to effect large increases or decreases of the machine magnetism.- Furthermore, under sudden and large variations in load there are correspond ing sudden and great variations in voltage. In the event the load is suddenly decreased, as, for'example, by the opening of a circuit breaker following a short circuit, the voltage at the end of a long transmission line may rise to a very high value due to the slow operation of the automatic electromechanical means connected with transformers and regu-- lating devices ordinaril included in the line, and which operate to alance line drops in volta e caused by variations in load. "When the a ove effects are coupled with the effects of a heavy charging current normally existing in a long transmission line, and which is also immediately operative on decrease in load to raise voltage both at the generator station as well as at the distant end of such long transmission line, the very hi h resultant voltage, especially at the end of the long line, may reach a dangerous value. In the event the transmission line is operating at a very heavy load and an additional heavv load of low power factor comes on, such, for example, as is caused by a feeder short circuit through reactors, then the voltage will suddenly fall, and the resulting disturbance coupled with low voltage may be sulficient to upset the stability of the entire system, and cause the falling out of step of synchronous apparatus with consequentinterruption to normal power service. 1

The instant invention has for its principal object to provide a novel and simple means for voltage regulation which will overcome the above noted and other difficulties, the same comprising a quick and automatically operative regulator device in the form of a reactor or transformer having a core constructed to provide a magnetic circuit adapted to saturate at a predetermined induced volt age value, preferably in combination with a condenser of suflicient capacity to more or less neutralize the magnetizing current of the reactor or transformer at approximately normal voltage; all whereby the core of the reactor possesses a saturated section to absorb, large watt-less magnetizing kilovolt-amperes at normal voltage, which magnetizing kilovolt-amperes will greatly increase upon a slight increase in voltage and almost disappear upon a slight decrease in voltage. The resultant wide variation in magnetizing current largely offsets load variations, so that there is very little change in voltage under such load variations. Thus the novel regulating means of this invention may be employed alone, or as an auxiliary to the ordinary electro-mechanical regulating devices commonly included in long transmission lines so that the former instantaneously operate in maintaining the normal line voltage pending the operation of said slower acting electromechanical devices.

Various embodiments of my present invention are illustrated in the drawings, in which Figure 1 shows a simple form of my novel magnetic voltage regulator device connected across a power circuit, the core of the device having a portion of reduced cross section to provide a magnetic circuit having the desired saturated section;

Figure 2 is a diagram showing a saturation curve taken on the magnetic voltage regulator device;

Figure 3 shows the novel magnetic voltage regulator device having a static condenser connected in multiple therewith;

Figure 4 shows the novel magnetic regulator device as in incorporated part of a transformer Figure 5 shows the magnetic regulator device with a modified form of reduced core section to provide the magnetic circuit with the desired saturated section; and

Figure 6 is a diagrammatic view showing the novel voltage regulator means incorporated in a generator fed three phase transformer at the station end of a transmission line, and in a three phase transmission trans former feeding a local three phase distribution circuit at the distant end of'the same transmission line.

Similar characters of reference are employed in the above described views, to indicate corresponding parts.

accompanying Referring to Figure 1, I have shown there- 7 in my novel magnetic voltage regulator in a simple form, comprising a coil D connected across the power circuit L and L said coil being wound on a magnetic core M. The core M is provided with a portion of reduced cross section N to provide a saturated section in themagnetic circuit of said core. A load Q, is indicated at the end of the single phase power circuit L and L. In Figure 2 I have shown a saturation curve taken on the magnetic voltage regulator of Figure 1, in which OE indicates normal voltage, and 0A indicates the value of the magnetizing current at normal voltage. If in the operation of the power circuit, the voltage increases, for example, to five per cent above normal, indicated by 0E it will follow that the magnetizing current will greatly increase, being substantially doubled, attaining 'a value indicated by OB. If in the operation of the power circuit, the voltage decreases, for example, to five per cent below normal, indicated by 0B,, the magnetizing current will greatly diminish, attaining a value indicated by 00. From this it will be evident that a wide variation of magnetizing current accompanies tendencies to voltage fluctuation, so that variations of load on the power circuit are automatically off set and consequently the voltage of the power circuit is automatically regulated or stabilized.

In Figure 3 I have shown in combination with the novel magnetic voltage regulator, a static condenser C connected in multiple therewith. The capacity of this condenser is so rated as to more or less neutralize the magnetizing current in the voltage regulator at approximately normal voltage of the power circuit, thus rendering the regulator more sensitive to voltage fluctuationsin circuit. Now it will be readily understood that when the magnetizing current taken by the coil D is exactly equal to the charging current taken by the condenser C at normal voltage, the condenser and regulating device will be in resonance, and the charging current will lead the voltage 90 while the magnetizing current lags the voltage 90, consequently the two currents will substantially neutralize each other so far as the transmission line is concerned, and at normal voltage the current taken from the line will be only that corresponding to losses'in the regulating device plus harmonic currents due to the magnetization of the iron. and D will circulate around the local circuit CD only. Referring to the diagram in Figure 2, If, however, the voltage of the line drops to a value corresponding to DE approximately 95% of normal, then the magnetizing current takenby the coil D will be reduced in the ratio 8 or to about 25% of the normal voltage value, while the charging current in C will bereduced in the ratio or to about 95% of normal voltage value. It is therefore evident that a charging current of about 95% minus about 25% equals approximately of the normal voltage of charging current which will be available for flow in the transmission line, thus greatly improving the line power factor and tending to increase voltage at the terminals of the device. On the other hand if the voltage rises to approximately 105%, or to DB then the charging current will rise to 105 of normal but the magnetizing current will rise to a value proportional to OB or approximately 200% of normal voltage value. The magnetizing current flowing in the line will therefore be approximately 200% minus 105% of the power The heavycurrents in O the normal voltage current taken by the coil D. This magnetizing current will operate to cause a low lagging power factor in the tend to hold down transmission line, and'will 7 connection of the circuit L and L across windings having taps T,, T and T so that saturation of the core M may be made to Like place at any desired terminal voltage within the range of availabletaps by mak ing the desired selected tap connections. The

magnetic core M is provided with suitably disposed saturation sections N of reduced cross section. The secondary coils D feed the low voltage power circuit L an'd'L and a condenser 0 is connected across the low voltage terminals of the transformer to more or less neutralize the magnetizing current in the core M at the 'normalvoltage deliveredto the ower circuit L and L In" i ure 5 I have shown my novel magnetic vo tage regulator providedwith a modified form of core M wherein the saturation sections of reduced cross section are obtained by providing groups of perforations H arranged to provide such saturation sections at a plurality of points in the magnetic circuit of the core. The modified core structure thus provided-possesses several important advantages. The small sections of iron between the perforations H in each group of the latter saturate normally at a high flux density at normal voltage and hence have a high loss per pound of material. But since it is desirable to reduce as much as possible the weight of iron in the core sections so satu rated that losses caused by high densities will be reduced to a minimum, the provision of several groups of perforations tends to distribute the losses, and at the same time provides a maximum of accessibility to the centers of heat formed by the small iron sections between the perforations whereby the cooling oil, in which transformers are usually immersed, may be most eiiiciently applied to the hot spots.

In Figure 6 I have shown my novel magnetic voltage regulator means in combination with transformers in a connected three phase transmission circuit and three phase power distribution circuit. In this embodiment of my invention, G indicates a three phase generator having an excitation circuit E and a regulator R and feeding a long high voltage transmission line F F and F through a three phase transformer B, the primary coils D of which receive the current from the generator G, and the secnndary coils S of which feed through the line F F and F the primary coils of three phase thre. wind ';.:g transformer 13,. The latter transformer B is provided with tertiary coils or windings Y connected to a synchronous condenser C having an excitation circuit E and a regulator R and with secondary coils S feeding a local three phase distribution circuit L 6 and L The magnetic sections or cores M and M of the respective transformers B and B are provided with the restricted saturation sections provided by the portions of reduced cross section between the members of the groups of perforations with which the cores are furnished, -'whereby, at normal voltage, the magneticcircuitsiequire a considerable fractiongof the output of the generator'G and condenser. O for their magnetization. It will be obvious, inthe event the load on the distributi'on-"ci'rcuit L5, L5 and L,- is suddenly dropped, that the voltage both at the transformer Bi' and the transformer B will rise,

and that theexce'ssiv'e magnetic density there by 'produced'in the saturation sections of the cores of these transformers will absorb all the excess capacity of the generator G and condenser C until the voltage regulators R;

"and R of these machines have brought the voltages at the transformers back to normal, and consequently an excessive voltage rise in the transmission circuits Will'be prevented. If, on theother hand, a'lieavy lowv power factor load comes on the distribution circuit L Lg; and L then the voltage at all points on the transmission system will fall slightly, and the magnetizing current of both transformers B and B will be greatly reduced, so that thegenera tor and condenser capacity released by the reduction of magnetizing current will be'inst'antly available to compensate for theincreased load and thus serve to prevent a further drop ,in voltage in' the transmission system until the voltage regulator's H and It on the generator and synchronouscondenser have time to bring the line voltage back to normal.

It will be obvious that the saturation points desired in the magnetic circuit of my novel regulator device may be obtained by other means than the provision of the portions of restricted cross section; as, for example, by providingthe core with a section of magnetic material adapted to saturate at a density relatively low with respect to the saturation density'throughout the remainder of the core-body. 1

As many other changes could also be made in the constructions above described and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, I, therefore, aim in the appended claims to cover all such changes-and modifications as fall within the true spiritand scope of my invention.

WhatI claim, as new and desire to secure by ilietters Patent of the United States is 1. In. combination, a-transformer having a magnetic core arranged to be saturated substantiallyabove the knee of its saturation curve at its normal operating voltage, an inducing w indin I on said core, an induced winding on sai core,- a tertiary winding on said core, and asynchronous condenser connectedtosaidtertiary winding for neutralizing the magnetizing current of said transformer at its normal operating voltage.

2. In. combination, an electric circuit, a

transformer connected thereto, a synchronous condenser connected to said transformer, and an automatic voltage regulator for said synchronous condense1- to maintain normal volt age .on said transformer, said transformer having a saturated section in its magnetic core a apted greatly to increase 1ts magnetizing current with a rise in voltage above normal and greatly to decrease its magnetizing current upon a drop in voltage below normal to prevent a substantial change in the voltage of said transformer during the period required for said voltage regulator to become effective.

3. In combination, a power transmission line, a magnetic device including a winding in circuit with said transmission line, said magnetic device having a magnetic core with a porton thereof arranged to saturate at normal line voltage, and a condenser connected to said magnetic device for neutralizing the lagging component of current thereof at normal line voltage while permitting the lagging component of current of said magnetic devlce to predominate substantially when said line voltage increases slightly above normal and the leading component of said condenser to predominate substantially when said line voltage decreases slightly below normal. v

4. In combination with a generator feeding its energy to a power circuit through a transformer, said transformer having a portion of its magnetic circuit adapted to be saturated substantially above the knee of its saturation curve at normal generator voltage whereby said transformer absorbs a large part of the capacity of said generator as magnetizing current upon a rise in generator voltage but reduces its magnetizing current to a very small value upon a drop in said generator voltage.

5. In an electrical power transmission system, the combination of a synchronous alternating current generator, a transmission line connected to said generator, a magnetic device including a winding connected to said transmission line and having a core portion arranged to be saturated substantially above the knee of its saturation curve at the normal operatin voltage of said line, a capacitance connecte to said magnetic device and arranged to neutralize the lagging reactive power thereof at the normal operating voltage of said line, and a regulator for automatically regulatin the field excitation of said generator, sai magnetic device being so saturated that upon variation in said line voltage from sald normal value reactive power of sufficient magnitude is added in the lnterval required for said regulator to function to prevent said line voltage from changing to a value at which the line is unstable.

6. In an electrical power transmission system, the combination of a source of alternating current supply, a. receiving circuit, a transmission line connecting said source of supply and said receiving circuit, a transformer in said transmission line arranged to be saturated substantially above the knee of its saturation curve at the normal operating 7 voltage of said line, a synchronous condenser connected to said transformer and arranged to neutralize the laggingcurre'ntof said '7 ulator for automatically regu- "7 -1 transformer, at said normal operating volt} age, and a re lating the fie d excitation of said generator and said condenser, said transformer being so saturated that upon change of load and consequent change. in line voltage reactive power of sufficient magnitude is added to the system to prevent a material change'in voltage during the interval required for the regulater to. function to restore said line voltage to its normal value.

In testimon that I claim the invention set forth above I have hereunto set'iny hand this 3rd day of May, 1927. I FRAZER W. GAY.

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