US1234916A - Electric regulating system. - Google Patents

Description

P. M. LINCOLN.

ELECTRIC REGULATING SYSTEM.

APPLICATION FILED MAY 14, I915.

Patented July 31, 1917.

INVENTQIR /40/ M L/hm/fi ATTYORNEYL WITNESSES: 2

UNTTED STATES PATENT GFFTQEJ PAUL M. LINCOLN, 9F PITTSBURGH, PENNSYLVANIA, ASSIGNOR, TO WESTINGHOUSE ELECTRIC AND MANUFACTURING CQIXIPANY, A GOBPOBATION OF PENNSYLVANIA.

ELECTRIC BEGULATING SYSTEM.

Application filed May 14, 1915.

To all whom it may 0011061 12 Be it known that 1, PAUL M. LINCOLN, a citizen of the United States, and a resident of Pittsburgh, in the county of Alle I gheny and State of Pennsylvania, have inthe excitation of the generators in accordance with the voltage at the remote end of the distributing circuit and also in such a manner as to prevent cross-currents between the generators.

The object of my invention is to provide means for correcting the inaccuracies, or

eliminating the errors, in regulation that have pertained to previous systems of the character indicated when the power factors of the systems depart from unity or 100%.

In electrical distributing systems in which several generators may be connected in parallel to supply current to a common transmission line, it has heretofore been proposed to employ Mershon compensators for causing regulators of the vibratory-contact type to so regulate the generators as to maintain a substantially uniform voltage at the distant end of the transmission line. It has also been proposed to so regulate the parallel-connected generators as to prevent flow of cross-currents between them, thereby causing the generators to divide the load properly. This is accomplished by reducing the excitation of the over-excited generator and increasing that of the under excited generator. The means employed comprises an auxiliary coil for each regulator that cooperates with its main voltage coil and receives current proportional to the current supplied by the generator with which that particular regulator is associated, the currentin the auxiliary coil being displaced 90 in phase with respect to that in the main voltage coil when the system has a power factor of 100%. The auxiliary coil has no effect upon the regulation when the power factor of the system is 100%, unless there is a tendency toward a circulation of current between the generators, in which case there is a departure from the quadrature relation Specification of Letters Patent.

Patented July 31, 1917.

Serial No. 28,035.

of the currents in the main and auxiliary coils followed by a correction by the regulators of the cause for the departure.

However, if the power factor of the system as a whole varies, or is other than 100%, the auxiliary coils upon the regulators detrimentally aifect the regulation from this cause, resulting in an error that is dependent, in value, upon the degree of departure of the power factor from 100% and upon the relation of the ampere-turns in the auxihary coil to those in the main coil.

According to the present invention, this error is eliminated or compensated for in a manner that will now be disclosed.

In the single figure of the accompanying drawing which diagrammatically illustrates an electrical system embodying my invention, current is supplied from a plurality of generators 1 and 2 to bus- bars 3, 4L and 5 to which is connected a transmission line or distributing circuit 789, switches 10 and 11 being employed for controlling the connections of the generators to the bus-bars. lVhile, for the sake of simplicity, the system, as shown, comprises only two generators, it will be understood that the invention may be employed with any other number of generators. Current is supplied to field-magnet windings 12 and 13 of the generators from the armatures l-land 15 of two exciters having field magnet windings 16 and 17, respectively, in circuit with which are resistors 18 and 19. The voltages of the generators are regulated by controlling the effective values of the resistors 18 and 19 by means of two regulators 20 and 21 that are similar in construction and mode of operation.

The eifective value of the resistor 18 is governed by rapidly opening and closing a circuit in shunt thereto by means of a pair of cooperating contact terminals 28 and 24: of a relay that is provided with an actuating magnet winding 25, the circuit of which is controlled by means of another pair of cooperating contact terminals 26 and 27 that constitute parts of the main control element of the regulator. The contact terminal 26 is adapted to be actuated by means of two levers 28 and 29, the former of which is in the form of a bell crank and is provided with a stationary fulcrum at 30, and the latter of which is fulcrumed upon the lo er endof the vertical of the ie er The lever 28 is actuated, in opposition to the tension of a spring 31, by means of an electroma-n'net having a winding 32 that re'- ceives current from the bus-bars 345, a switch 33 being employed for closing the circuit of the winding when the switch 10 is closed for the purpose of connecting the generator 1 to the bus bars. The degree of energization of the winding 32 is caused to vary by repeatedly opening and closing the circuit in shunt to a resistor 34 that is included in circuit therewith, a relay, having contact terminals 35 and 36,being employed for this purpose. The relay is also provided with an actuating winding 37 that is connected in parallel with the relay winding 25, the circuit of which is controlled simultaneously therewith by the contact terminals 26 and 27 The movements of the lever 28 are preferably somewhat retarded by means of a dash pot 38. Because of the varying degree of energiz'ation of the winding 32, the contact terminal 26 is vibrated into and out of engagement with the terminal 27 thereby causing opening and clos ing ofthe circuits in shunt to the resistors 18' and 34.

The lever 29 is so actuated as to vary the position of the contact terminal 26 with respect to the terminal 27 by means of an electromagnet having a main winding 41 and an auxiliary winding 42, movements of the lever being. preferably somewhat retarded by means of a dash pot 43. The main winding 41 is adapted to receive current, through what is commonly known as a Mershon compensator, that is proportional to the voltage at a remote point on the transmission lines 78-9, a switch 44 being employed for connecting the winding to the compensator. The compensator comprises two seriestransformers 46 and 47 the primary windings of which are respectively in circuit with the conductors 7 and 9 of the transmission line, and the secondary windings of which are cross-connected for the purpose of producing a resultant current in phase with the voltage between the conductors 7 and 9. Included in the secondary circuit of the series transformers are a noninductive resistance 48 and a main inductive resistance 49, which have heretofore been commonly employed in such compensators and, in addition, two-auxiliary reactances 50 and. 51 that are adapted to be connected in parallel to each other and in series with the resistance 48 and the reactance 49 by means of switches 52 and 53. The said'switches are preferably actuated simultaneously with the switches 10 and 11, respectively, though, if desired, they may be operated independently of the generator switches. The ar rangement is such that only one of the auxiliary reactances is employed when a single generator is connected to the bus-bars and both of them are employed when two generators are connected to the bus-bars. If more than two generators are employed in the system, as many auxiliary reactances should be used as there are generators.

The voltage applied to the winding 41 of the regulator is derived mainly from the bus-bars3 and 5 through a voltage transformer 55, the secondary circuit of which includes suitable portions of the resistance 48 and the reactance 49, and also as many of the auxiliary reactances 50 and 51 as there are generators in use. The values of the resistance 48 and the reactance 49 are adjusted correspondingly, in the usual manner, to bear the same relation to each other that the values of the resistance and reactance of the transmission line between the bus bars and some predetermined remote point upon the line bear to each other, and the connections are such that the secondary voltage of the transformer 55 is reduced in proportion to the drop in voltage between the bus bars and the selected remote point.

on the transmission line. In this manner,

the voltage applied to the winding 41 is caused to correspond to the volta e at the remote point on the transmission line, and the voltages of the generators are regulated in accordance therewith. w

The auxiliary winding 42 of the regulator 20 is supplied with current that is proportional to that flowing between the generator 1 and the bus-bar 4,. which current is in quadrature relation to the voltage between the bus bars 3 and 5 when there are no crosscurrents flowingbetween the generators, and.

the power factor of the system is unity or 100%. The corresponding coil of the regulator 21 also receives current that is proportional to that flowing between the generator 2 and'the bus bar 4. The winding 42 has, at full load on the' generator, only a small percentage of the ampere turns of the winding 41, say from 3% to 5% thereof.

Since, when no cross-currents are flowing. between the generators and the power factor of the system is unity, the current in the coil 42 is in quadrature relation to that in the coil 41, it will be seen that the coil 42 has no appreciable effect upon the regulation, under these conditions. However, if there is a tendency for the How of cross-currents between the generators, there will be a departure from the quadrature relation of the currents in the said windings, with the result that the winding 42 will affect the regulation in proportion to the" degree of departure from the quadrature relation and 1 and the bus-bar 4, the winding 42 will assist or supplement the winding 41 and tend to cause the contact terminal 26 to move away from the terminal 27, thereby causing a decrease in the excitation and voltage of the generator 1. At the same time that the current flowing between the generator 1 and the bus bar 4 lags, as a result of the flow of cross currents between the generators, the current flowing between the generator 2 and the bus-bar 4 is leading, and the coil 42 of the regulator 21 then opposes the main winding 41 of the said regulator and causes the excitation and voltage of the generator 2 to be increased. The effect of the regulators, therefore, is to cause a decrease of the excitation and voltage of the generator that is over-excited and an increase of the excitation and voltage of the generator that is under-excited. In other words, a lagging current flowing between one of the generators and the bus-bars 4 acts through the regulator the same as an increase of the bus-bar volt-age, while a leading current acts the same as a decrease of the bus-bar voltage.

Since the currents flowing between the generators 1 and 2 and the bus-bar 4 may be caused to either lag or lead as a result of a departure of the power factor of the system, as a whole, from unity or 100%, as well. as by the flow of crosscurrents between the generators, it is obvious that the auxiliary coils 42 will affect the regulation detrimentally when the power factor of the system changes, thus causing inaccuracies or errors in the regulation. In order to compensate for, and eliminate, the said inaccuracies and errors, the auxiliary reactances 50 and 51 are employed as parts of the compensator. The auxiliary reactances are of such value that the drop of potential over each of them bears the same ratio to, or is the same percentage of, the total drop produced in the secondary circuit of the transformer 55 by the compensator as the ampere turns in the auxiliary coils 42 of the regulators bear to the ampere turns in the main windings 41.

The function of the auxiliary reactances will be understood when it is considered that the currents in the windings 42 bear a 90 degree phase relation to the voltages applied to the windings 41 when the power factor of the system is 100% or unity, and that the drop of voltage in the auxiliary reactances also bears a 90 degree phase relation to the voltage applied to the windings 41 at 100% or unity power factor. Consequently, the currents in the windings 42 and the drop of voltage in the auxiliary reactances 50 and 51 are in phase and the efiect of one exactly cancels the eifect of the other, thereby neutralizing the error that would otherwise occur in the regulating effect of the regulator.

Only one of the auxiliary reactances is employed when only one generator is connected to the bus-bars because, in that case, all of the current in the auxiliary coil of the one regulator in operation is excited in proportion to the total current flowing in the transmission line. When two generators are connected to the bus-bars, the auxiliary coil 42 of each regulator is supplied with current proportional to only one-half of the total current flowing in the transmission line, and, consequently, the tendency toward error is only one-half as great as when one generator alone is in operation. Accordingly, the auxiliary reactance should be of only one-half the value employed with one generator, and, for that reason, the two reactances are connected in parallel for the operation of two generators. For the sake of convenience, the connections of the reactances may be controlled simultaneously with the opening and closing of the switches for connecting the generators to the busbars, but, obviously, other means for making the connections may be employed if desired.

I claim as my invention:

1. In an electrical system, the combination with a distributing circuit, a plurality of generators for supplying current thereto, and a regulator associated with each generator, of a compensator for causing the regulators to control the generators in accordance with an electrical condition at a predetermined point on the distributing circuit and comprising reactance and means for adjusting the value of said reactance in accordance with the niunber of generators in use.

2. In an electrical system, the combination with a distributing circuit, a plurality of generators for supplying current thereto, and a regulator associated with each generator, of a compensator for causing the regulators to control the generators in accordance with an electrical condition at a predetermined point on the distributing circuit and comprising reactance and means for adjusting the value of said reactance to correspond both with the reactance of thedistributing circuit and the number of generators in use.

3. In an electrical system, the combination with a distributing circuit, a plurality of generators for supplying current thereto, and a regulator associated with each generator having a main actuating winding that receives current proportional to an electrical condition of the distributing circuit, and an auxiliary winding that cooperates with said main winding and receives current proportional to an electrical condition of the generator with which its regulator is associated and in approximate quadrature relation to that in the main winding, of a compensator interposed between the distributing circuit and the main winding of the regulator comprising a resistance and a main reactance connected in series,auxiliary reactances that are adapted to be connected in parallel with each other and in series with the main reactance and means for controlling the connections of the said auxiliary reactances.

4. In an electrical system, the combination with a distributing circuit, a plurality of generators for supplying current thereto, and a regulator associated with each generator having a main actuating winding that receives current proportional to the voltage of the distributing circuit, and an auxiliary winding. that cooperates with said main winding and receives current proportional to the current supplied: by the gen orator with. which its regulator is associated and in approximate quadrature relation to that in the main Winding, of a compensator interposed between the distributing circuit and the main Winding of the regulator comprising a resistance and a main reactance connected in series, auxiliary reactances that are adapted to be connected in parallel with each other and in series with the main reactance and means for controlling the connections of the said auxiliary reactances.

5. In an electrical system, the combination 7 with a. distributing circuit, a plurality of generators for supplying current thereto, and a regulator associated with each generator having a main actuating winding that receives current proportional to an electrical condition of the distributing circuit, and an auxiliary winding that cooperates with said main winding and receives current parallel with each other and in series with the main reactance, the drop of potential over each auxiliary reactance bearing the same ratio to the total drop of potential produced by the compensator in the circuit of the main winding of the regulator as the ampere turns of the auxiliary regulator winding bears to the ampere turns of the main regulator winding and means for con-v trolling the connections of the said auxiliary reactances.

In testimony whereof, I have hereunto subscribed my name this 24th day of April 1915.

PAUL M. LINCOLN.

Copiesof this patent may be obtained for five cents each, by addressing the Commissioner of Patents.

Washington, I), 0'.

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