US2023084A - Regulating system - Google Patents

Description

Dec. 3, 1935. J. F. KOVALSKY REGULATING SYSTEM Filed Aug. 15, 1934 INVENTOR J0 h E K qlsky I Patented Dec. 3, 1935 UNITED STATES PATENT OFFICE REGULATING SYSTEM assignor Company, East Pittsburgh, Pa, a corporation of Pennsylv Application August 15, 1934, Serial No. 739,917

4 Claims. (01. 171-312) My invention relates to regulating systems and it has particular relation to means for increasing the eiiectiveness of automatic voltage regulators utilized in applications in which rapidity of response is of prime importance.

One such application is in connection with electrical power systems involving interconnecting synchronous machines. Upon the. occurrence of system disturbances which demand a quick response on the part of the regulator to increase themachine excitation it is desirable, in the interests of maintaining system stability and high power-transmitting capacity, to initiate this increase at the earliest possible moment. Regulatorssuitable for such applications frequently utilize voltage-responsive control elements havingone or more sets of mechanically separable contact members which, upon engagement, initiate operationof suitable machine-excitation or other voltage adjusting means.

I The necessity of mechanical movement of these contact members before a corrective operation can be efl'ected introduces an appreciable time lag which, while relatively small, is nevertheless highly objectionable in synchronous-synchronous power systems and other comparable applications. While some reduction of this inherent delay may result from a closer positioning of the contact members, such reduction is definitely limited by operating considerations, it having been found that unless complicated notching and anti-hunting arrangements are used, an appreciable spacing of the contacts must be maintained to allow the regulator to satisfactorily settle the voltage after correctively adjusting it. Regulators of this type have, therefore, an inherent delay in their response.

My invention is directed to simple and enective means for correcting the named inherently delayed response of automatic voltage regulators.

Generally stated, it is an object of my invention to provide means for accelerating the response of voltage regulator control elements.

Another object of my invention is to supplement the conventional contact-making-voltmeter control means utilizedin automatic regulators by electronic tube devices capable of substantially instantaneous response and arranged to function during the time required to effect the necessary mechanical movement of the controldevice contacts.

A further object of my invention is to so apply such supplemental control means as to permit the power limits of electrical circuits connecting alternating current systems involving regulator controlled synchronous machines to be materially increased.

My invention itself, together with additional objects and advantages thereof, will best be understood through the following description of a 5 specific embodiment when taken in conjunction with the accompanying drawing, in which the single figure is a diagrammatic view of apparatus and circuits illustrating one preferred form of my invention applied to an automatic voltage regulator. 1

Since my invention is particularly applicable to regulators which control synchronous machines forming a part of alternating current power systems, I have in the drawing represented it in such an application- This representation will, however, be understood to be illustrative rather than restrictive. I

Referring to the drawing, I have there illus-'- trated what will be assumed to be the generator end only of a power transmission system, the equipment depicted including an alternating current generator l0 shown as having armature windings it directly connectedwith the conductors of a three-phase power transmission circuit IS. The generator is provided with a field winding 24 which in the system shown is energized from an exciter generator 25. This main exciter is provided with a field winding 21, shown as being of. the parallel-path type to reduce inductive lag, 'which may be energized by any suitable source of substantially constant direct potential such as an auxiliary or pilot exciter 28.

To control the voltage of the regulated generator it, a motor-operated rheostat 30 is con- The mentioned relays are controlled by means of a contact-makingvoltmeter or primary relay 31 that is responsive to the potential impressed upon an operating winding 38 thereof. This winding is energized by the terminal voltage of machine l0 through equipment, illustrated as comprising a pair of potential transformers 39 and sixrectifier units 40, which functions to supply to the winding a uni-directional voltage which at all times is proportional to the average oi the three single-phase voltages acting in the u of contactors 2 three-phase circuit it. In operation of device 31 an increase in the voltage thus impressed thereon increases the upwardly acting magnetic pull circuiting from and for inserting in the field control circuit relatively large blocks of resistance. Contactor 41, for example, when in its normal circuit closing, position illustrated, establishes a shunt connection around a resistor 58. Likewise, contactor 48 is disposed to'short circuit the rheostat 30 and the resistor 59 when the contactoris actuated to its circuit-closing position.

In the illustrated system relay device 31 is provided with two separate sets of contacts. One set comprises members L, 44 and R and is responsive to small voltage changes while a second set, comprising members L, and R, is responsive to and adapted to eifect large changes in the regulated voltage. The small-change responsive contacts function to control the motor control relays 34 and 35, and the large change responsive contacts control the actuation of the resistor shunting contactors 41 and 43. The control circuits for these devices are illustrated as bein energized from a source of direct current potential shown in the form of a battery 50.

Considering first that operation of the described regulating system which results from small deviations in regulated voltage, a decrease in the voltage of machine Ill causes the contact member 44 of the primary relay 31 to be lowered into engagement with the stationary member R. and thereby completes a circuit from battery which efiects an actuation of the relay 34. In moving its contact members upwardly, this relay completes, through member =32, a circuit for so energizing, from a battery 63, the rheostat operating motor 32 that the motor is caused to operate the rheostat 33 inthe resistance lowering direction. This eifects an increase in the excitation of machine III which in turn raises the machine voltage back to its desired value.

- Similarly, a small increase in the voltage of machine It causes the primary relay 31 to move the contact member 44 thereof upwardly into engagement with the stationary member L, thereby completing an actuating circuit for the relay 35. This relay moves its contact members'upwardly completing, through member 34, a circuit for so energizing the motor 32- that it adjusts rheostat 33 in the resistance increasing direction andv thereby effects a corrective reduction in the excitation and voltage of machine I 3.

Considering next that operation which results from deviations in the regulated voltage which are sufllciently large to engage the second-named sets of primary relay contact members, in the event that the machine voltage thus drops to an abnormally low value, there is completed through contact members 45 and R of the relay 21 an actuating circuit for contactor 43. This contactor then actuates to establish a shunt connec-,

tion around rheostat 30 and resistor 59 and thereby causes the voltage applied to the field windings 21 of the exciter 25 to be rapidly increased. This fast excitation build up continues until such time as the voltage of nnichine ID has tactors '41 and risen above the predeterminedly low value necessary to hold contact member 45 in engagement with member R, at which time the members separate and interrupt the actuating circuit of contactor 41, thereby restoring the excitation 5 control to the motor operated rheostat 3D.

In a similar manner, anunusually large rise in the voltage of the machine ill completes through contact members 45 and L of device 31 an actuating circuit for contactor 41, which contactor \0 functions to remove a normally maintained shunt connection around resistor 58, and thus allows this resistor to become effective in the excitation control circuit to reduce the current supplied to exciter windings 21. The resulting rapid reduc- 15 tion in machine excitation continues until the machine voltage has been reduced below the predeterminedly large value necessary to hold contact member 45 in engagement with member L,

at which time the excitation control is restored to go the motor operated rheostat 30.

For the purpose of preventing hunting during the operation of the regulator, auxiliary resistor sections 52 and 53 are preferably disposed in the energizing circuit of the contact making volt- 25 meter 31. Normally, section 52 is shunted from the circuit by means of an auxiliary contact member 55 carried by motor control relay 35, while the resistor 53 is shunted from the circuit by an auxiliary contact member 56 only upon so the actuation of the motor control relay 34. By thus anticipating the voltage changes at the terminals of machine iii which are eilected by ad- Justing operations of rheostat 30, these antihunting resistors cause the operations to be dis- 85 continued somewhat before the voltage correction has completely reached the desired value,

' and in this manner prevent overshooting of the corrective action. c

My invention, as applied to the regulating sys- 4o tem just described, resides in the provision of means for substantially instantaneously actuating one or the other of the ileld forcing con- 48 immediately. upon the occurrence of a predeterminedly rapid change in the 45 voltage of the regulated circuit. By thus eliminating the appreciable time required for the contact members of primary relay 31 to be moved into engagementwith one or the other of the 7 associated stationary members, the eii'ective reso spouse of the regulating system is materially raised,'and operation of the regulat0r in this respect is greatly improved. Although in the application just described and considered, there usually exists a mental control means only in connection with the excitation raising contactor 48, there are situations in which such special control may advantageously be applied also to the excitation lowering contactor 41, and hence I have illustrated the 60 control means of my invention as being applied to both of the named field forcing contactor devices.

To effect this desired special control, I utilize in association with each of the rapid-excitation 63 change contactors an electronic tube represented distinct need for such suppie- 5t conductive it similarly will complete an actuating circuit for contactor l'l. Suitable direct current energizing potential for the tubes and the contactor actuating circuits in which they are positioned is represented as being supplied from the previously referred to battery 80. It will be noted that the connections are such as to maintain the tube anodes at a positive potential with respect to the cathode elements.

These electronic tubes 18 and I2 are preferably of the grid controlled gas-filled variety, each comprising an anode element 18, a cathode element II and a control grid element 16. As long as the potential of the grid with respect to that of the cathode is maintained below a certain critical value, the tube functions as an insulator and is capable of passing no current from the anode to the cathode. However, when the grid potential is raised to or above this critical value, a glow discharge is initiated between the grid and cathode, which discharge is immediately transferred to the tube anode to produce a break down of the internal insulation characteristics and a passage of current through ,the tube. Once started, conduction continues until the tube is shunted by a low resistance or its anode circuit is interrupted;

To increase the sensitivity of tube control, I prefer to normally maintain the grid element of each of the tubes at a potential slightly below the critical or tube break-down value. For such purpose, I preferably connect these grid elements I. to a point 82 which is common to a pair of capacitors l8 and 80 which are connected in series in an auxiliary circuit upon which is impressed the uni-directional voltage of the control source ill. The relative electrical dimensions of these condenser devices are such that after having been charged to the equilibrium value by the voltage of battery 88, the potential appearing across the capacitor 88 is slightly below the critical voltage required to render the tube devices 18 and I2 conductive. Under such conditions only a small increase in grid potential is required to convert the tube from an insulator to a conductor.

For the purpose of allowing sudden changes in the regulated voltage to produce such increases, I interpose between the grid element 16 of each of the tubes and the common point 82 in the capacitor circuit the secondary winding 88 of a transformer. Such a transformer is represented at 84 in association with tube I and at 86 in association with tub 12. The primary windings of these two transformers, which preferably are of a rather high step-up ratio, are, in turn, acted upon by a direct current voltage which is at all times proportional to the potential acting in the regulated circuit It.

In the illustrated connection, this transformer energizing voltage is derived from the output terminals of the before described rectiflers 40 which supply a uni-directional potential having therein small pulsations or ripples the frequency of which varies directly with that of the voltage of circuit l8. Changes in the magnitude of the voltage of circuit l8 thus directly appear as changes in the average or effective magnitude of the direct current voltage which is impressed upon the transformers 88 and 86. When of sufllcient rapidity and depending upon their direction, these changes selectively render conductive one or the other of the tube devices Iii and 12 to, in turn, quickly eil'ect actuation of one or the other of excitation changing contactors 81 and 48.

. effect upon the excitation control of the regu- In operation of the supplemental control means of my invention Just described, as long as the regulated voltage remains constant the uni-d1,- rectional current flowing in the primary windings of transformer 84 and 88 is substantially unvary- 5 ing, and as a result insuilicient voltage is induced in the secondary windings of these transformers to raise the tube grid potential above the critical value. Consequently, both of the tubes HI and I! are maintained in their nonconductive state. Similarly, changes in the regulated voltage which are relatively gradual, or of but normal or usual rapidity cause the transformer energizing currents to change at asimilarly slow rate which is insuiiicient to induce in the secondary winding of either the potential necessary to raise the grid voltage of either of the electronic tubes to the critical value, and in such case, the control of the machine excitation is effected solely by the contact making voltmeter 81 in the usual or normal manner.

However, in the event that the regulated voltage changes are of high or abnormal rapidity, there is induced in the transformer secondary windings a potential which is sumcient to cause the break down of. one ofthe tube devices to thereby efl'ect immediate actuation of its associated excitation control contactor. For a given direction of voltage change, the polarities of the transformed-induced potentials which results are '80 respectively such that the grid voltage of one of the two tubes Iii and 12 is raised while that of the other tube is correspondingly lowered. Selective conduction thereby results.

Thus, assuming that the voltage of regulated 85 circuit I suddenly drops at or above a predeterminedly high rate, there will be induced in the secondary winding of transformer 84 a direct cur-' rent voltage which adds to that appearing across capacitor 80 and thereby raises the potential impressed upon the grid of tube 10 to above the critical value. This tube, accordingly breaks down and allows to flow from its anode to cathode a current which is of sunicient magnitude to actuate the excitation increasing contactor 88, and 85 thereby immediately initiate the desired corrective action. Conduction through the tube having once started, it continues even though the grid potential may decrease below the critical value, and thereby assures that the contactor 88 will remain actuated until the primary relay 8! of the regulating system has had time to bring contact member 48 into engagement with member R; Upon such engagement, the tube device 10 is short circuited so that the glow discharge therethrough immediately discontinues. From that point on the tube has no further effect upon theexcitation control, further corrective adjustments being determined by the contact making voltmeter 81 in the usual manner.

Similarly, in the event of an abnormally fast rise in the regulated voltage circuit there will be induced inthe secondary winding of transformer 86 a direct current voltage which adds to that of capacitor 80 and thereby raises the grid potential of tube I2 above the critical value; The resulting breakdown of the tube allows to pass from the anode to the cathode element thereof suflicient current to actuate the excitation lowering contactor 41. Such actuation is maintained until the primary relay 31 has time to move contact member 45 into engagement with member L. From that point on the tube I2 has no further lated machine. 76

' more of these ripples is given a high peak in the direction of the change, which peak may be. depended upon to confer conduction to the tube.

- In which case the before-referred to margin may be made much larger than otherwise and in some 1 instances the supplemental or constant bias on the tube grid may completely be dispensed with.

E[t will thus be seen thatI have provided a system which permits inherently sluggish regulating devices to be made practically instantaneous in their response, which system 'may be applied very readily to known forms of regulators which are in such extensive applications at the present time. My invention therefore, is one of Y high utility, it is not being relatively simple and inexpensive, but exceedingly positive and reliable in its operation.

Although I have shown and described a certain specific embodiment of my invention, I am fully aware that many modifications thereof are possible. My invention therefore, is not to herestricted exceptinsofar as is necessitated by the prior art and by the scope of the appended claims.

I claim as my invention:

1. In a regulating system comprising an electrical circuit, means for adjusting the voltage thereof, a contactor for efiecting operation of said means and a circuitvoltage-responsive device having contact members adapted to control actuation of said contactor, the combination of an electronic tube connected inparallel-circuit relation with said contact members, and controlmeans' adapted to render said tube conductive upon the occurrence of a predeterminedly sudden change in the voltage of said circuit.

2. In a regulating systemcomprising an elec- 5 trica1 circuit, means for adjusting the voltage thereof, a relay for eiiecting operation of said means and a circuit voltage-responsive device having contact members adapted to control actuation of said relay, the combination or an electronic tube adapted also to effect an actuation of said relay, control means responsive to changes of predetermined suddenness in the voltage of said circuit for rendering said tube conductive, and means for discontinuing said conductivity upon an engagement of the contact members of said circuit-voltage-responsive device.

'3. In combination with an electrical circuit, voltage-adjusting means therefor, and a circuitvoltage responsive device having contact members adapted to control operation of said means, an electronic tube adapted to initiate, operation of said means, said tube being normally non-conductive, control means responsive to changes of predetermined suddenness in the voltage of said I circuit for rendering said tube conductive, and

means for causing the conductive state of said tube, when once initiated, to persist until an engagement of the contact members of said circuitvolta'ge responsive-device is effected.

4. Apparatus for acceleratingv the response of a voltage regulator incorporating a contact-making control device comprising, in combination, an electronic tube connected in parallel-circuit relation with the contacts of said device and means for rendering said tube conductive upon the occasion of changes in the regulated voltage which proceed with predetermined suddenness.

. JOSEPH F. KOVALSKY.

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