US1734239A - Synchronizing relay system - Google Patents

Description

INVENTOR ATTORNEY 3 Sheets-Sheet l P. THOMAS Filed Sept. 23, 1927 D I HZ Fig.

SYNCHRONIZING RELAY SYSTEM 7 m I I 2 3 O A AA 2 II II I 26 I I II I 1 Nov. 5, 1929.

F'Jg. 3.

LVVVW Phillips Thomas.

Nov. 5, 1929. THOMAS 1,734,239

SYNCHRONI Z ING RELAY SYSTEM Filed Sept. 23. 192'? a Sheets-Sheet 2 INVENTOR Phil/1P6 777 027705.

Nov. 5, 1929.

P. THOMAS SYNCHRONIZING RELAY SYSTEM Filed Sept. 25, 1927 3Sheets-Sheet 5 INVENTOR Phi/lips Thomas.

, ATTORNEY 5 The principal object of this invention is to Patented Nov. 5, 1929 ATENT. oFFICE PHILLIPS THOMAS, or EnoEwoon-riiimsYnvAmA, ASSIGNOR mo 'wnsr'menousn ELECTRIC & MANUFACTURING comrANY, A CORPORATION or PENNSYLVANIA svivcnnonizme RELAY SYSTEM Application filed September 23, 1927.- Serial No. 221,490.

This invention relates to automatic s nchronizing relay systems, the general ob ect of which is to parallel alternating circuits when conditions therein are suitable.

provide a synchronizing relay system which shall be inexpensive to manufacture and which shall be positive and reliable in operation.

vide a control device withoutmoving parts, having a variable time element in its operation, whereby its response is delayed for an adjustable time interval after the occurrence of conditions to which it responds.

A further object of my invention, is to utilize the above described control device in a system for paralleling alternating current circuits when properly synchronized.

0 A still further object of my invention is to employ the aforementioned control device to initiate the closing of the paralleling breaker when the voltages of the circuits to be paralleled are within a predetermined angle and are approaching synchronism at a predetermined rate, regardless of which voltage is momentarily leading, so that the paralleling switch is finely closed precisely at the instant of exact synchronism.

A further object of this invention is to arrange the paralleling system, so that operation of the paralleling breaker will be positively prevented when the voltages of the circuits are in synchronism and going out of phase, thereby preventing closure of the breaker when the voltages are out of synchronism.

A further object is to incorporate in the above described paralleling relay system, means for compensating for a decrease in the voltage of one or both of the circuits whereby paralleling takes place at a wider angle of phase difference between the voltages if one or both of them be below normal, than if both are at their normal value.

In my copending application, Serial No. 215,377 filed, Aug. 25, 1927 I have described a system for paralleling alternating current -circuits which depends for its operation upon the characteristics of a thermionic discharge Another object of this invention is to protube." In another copending' ap lication,

Serial No. 227,461, filed Oct. 20, 192 I have tem in which provision is made for energizing the closing coil of the paralleling breaker at a time in advance of the occurrence of exact synchronism, which is suflicient to permitthe switch to close exactly at synchronism. In that application, I have also described means for compensating for a decrease in voltage of one or both of the circuits, whereb less exact agreement in phase is required of t e voltages of the circuits if one of them is below its normal value, or if both are below normal.

The invention disclosed in the present application is a further improvement on the systems described in the applications referred to, and involves the use of a magnetic relay controlling device having an adjustable time element in its operation. The invention may be more clearly understood by reference to the accompanying drawings in which identical elements arereferred to in the various figures by the same reference numeral.

Figure l is a diagrammatic representation of the magnetic relay controlling device of my invention.

Fig. 2 is a diagram illustrating the magnetic conditions in the control device.

Fig. 3 shows the application of my relay controlling device to a simple paralleling system.

Fig. 4 shows how the relay controlling device of my invention maybe combined with the means for securing energization of the closing coil of the paralleling breaker in advance of exact synchronism.

Fig. 5 illustrates a system including means for compensating for the variations in the ygltage of either of the circuits to be paral- Fig. 6 is the diagram of a system which makes possible advance energization of the paralleling breaker closing coil regardless of which circuit has the higher frequency. Fig. 7 is similar to Fig. 6, except that it includes also means for positively preventing the operation of the paralleling breaker when the voltages of the circuits are in phase and departing from that condifirm Fig. 8 is a vector diagram showing the re'- lation of the voltages of the two circuits in the paralleling system of Fig. 7.

It is well known that the superposition of a unidirectional flux upon an alternating flux such as exis in the core of a transformer will tend to decrease the reactance of the winding inducing the alternating flux. I make use of this principle in obtaining a delayed energization of any suitable voltage responsive device. The means by which I accomplish this result are indicated in Figure 1.

In Figure 1, I show a transformer core 1 having three vertical legs. Primary and secondary windings 2 and 3 respectively are located on two of these legs, and a direct current winding 4 and a damping winding 5 are disposed on the central leg. The primary and secondary windings 2 and 3 are equally dividedon the outer legs of the core. This arrangement of the windings causes the net alternating flux in the center leg to be zero, so that there is no alternating voltage induced in the windings thereon. The primary winding 2 of the transformer 1 is energized from a constant potential alternating current source 6. A variable impedance 7 which I have illustrated as a resistor may be employed to control the energization of winding 2. The secondary winding 3 is connected to a voltage responsive device 12 which may be of any desired type but which generally takes the form ofa relay. As shown, the device 12 is energized by alternating current but if it is desirable to use a direct-current device, a rectifier may be inserted between the secondary 3 and the relay 12. The direct-current winding 4 is energized from a source 8 which I have shown as a battery and the energization of coil 4 may be controlled by a rheostat 9 and a switch 10 in series therewith. The winding 5 which is the damping winding is connected to a variable resistor 11.

The operation of the control device of Figure 1 is as follows:

Assuming the switch 10 to be open, the alternating current 6 will supply current to the primary winding 2 and the impedance 7. The voltage of the source 6 will be divided between the winding 2 and the impedance 7 in accordance with the design constants of these elements. A voltage proportional to that across winding 2 will be induced in the winding 3 and will be impressed on the voltage responsive device 12. If the switch 10 be now closed, direct current will circulate in the winding 4 with the result that the reactance of the transformer will be decreased or, in other words, its magnetizing current will be increased. As a result of this change, the voltage drop in the impedance 7 will be increased and that across the winding 2 decreased. A corresponding decrease occurs in the voltage induced in the-winding 3. By varying the strength of the direct current in winding 4, the variation in the voltage across secondary winding 3 may be made of the proper value. The winding 5 exerts a damping effect which tends to delay any change in the condition of the magnetic circuit and by adjustment of the rheostat 11, the time interval between the establishment of a direct current in winding 4 and the resulting change in the voltage induced in winding 3 may be varied as desired.

As stated above, flow of direct current in winding 4 has the effect of reducing the voltage induced in winding 3. This voltage may be restored to its original value by opening switch 10 to interrupt the flow of direct current in winding 4. The winding 5, due to its self inductance, tends to prevent a decrease in the flux through the central le of the transformer, but this flux is reduced to zero after a time interval depending upon the setting of rheostat 11. The reactance of the transformer is thereupon restored to its normal value and the voltage induced in the winding 3 is also restored to its original value.

It is obvious that by properselection of circuit constants and by suitably designing the transformer, the variations in the voltage of the secondary winding 3, resulting from variations of the current in the directcurrent winding 4 may be made to operate the voltage responsive device 12. i In Fig. 2, I have illustrated graphically the effect upon the voltage of the secondary winding 3 of the superposition of the unidirectional flux due to direct-current wind-,

ing 4. In Fig. 2, I have shown at BOOAC, the magnetization curve of the core of transformer 1. At BXAY, I have indicated the hysteresis loop of the transformer core when operating under normal conditions. Now, if a uni-directional flux of the value 00' is superposed upon the alternating flux, the result will be that the axis of ordinates will be shifted to the position 0'0" and the transformer will operate on hysteresis loop CYDX. As a result; of this shift of the axis, the secondary voltage of the transformer will be proportional to CD instead of to AB' as is the case when the transformer is operating normally. It is evident, therefore, that the superpost'l flux due to the direct current winding has the effect of reducing the voltage induced in the transformer windings. The amount of this reduction in voltage may, of course, be controlled by varying the value of the direct current which excites the superposed flux.

In Fig. 3, I have shown how the phenomenon described above may be utilized to control the paralleling of two alternating current-circuits. To accomplish this result, 1 control the energization of the paralleling switch or of a paralleling relay by rectifying the resultant of the voltages of the circuits and supplying this rectified voltage 7 legged transformer such as shown in Figure ing current source which ma The a generator.

1 output of rectifier. 33. 3c 7 1. This transformer has an appropriate time delay adjustment to prevent paralleling upon the occurrence of momentary synchronism.

In' Fig. 3, -21 represents an alternating current circuit which'maybe a transmission line or bus and 22-23 a second alternat- Lines 20-22 are connected y conductor 24 and across the lines 21 fand 23 is connected the primary of the transformer 32,the sec ondary of which supplies a rectifier 33 which may be of any sultable type, but which I have illustrated as of the copper oxidetype. At 25, I have, indicated a 'transformersimilar to that above described, havinga primary winding 26 connected through impedance 27 to the lines 22 and 23 leading to the genera tor. The secondary-winding 28 supplies a rectifier 34, the ,output. of which. energizes the closing coil of a switch35 to cause engagementof the contacts 36. The switch 35 may be a relay or the parallelin switch itself. .The damping winding is s own at 30 and its controlling resistance at 31; Direct-current winding 29 on the central leg of the transformer 'is energized by the The operation of the system shown in Figure 3 will now be described. Assuming that the voltage and frequency on the line 20-21 are normal and that the generator connected to lines 22 and 23. is being brought to synchronous speed, and is developing normal voltage, the resultant of the voltage of the two circuits willbe impressed on the primary of transformer 32. By means of the rectifier 33, a direct current will be supplied to winding 29 which will be proportional to the resultant of the circuit voltages. As long as this resultant has a value sufficient to send a predetermined current through the winding 29, the voltage of the secondary 28 will be reduced to a value insufiicient to operate the paralleling switch 35. As the resultantvaries periodically, however, the direct ourrent through winding 29 varies proportionally and the voltage *of the winding 28 will be increased sufficiently to cause the operation of the switch 35, when thefrequencies of the two circuits are nearly equal, so that the delay between the decrease in the D. C. and the increase in ,A. C. voltage, caused by the damping winding is insufficient to prevent the A. C. voltage from reaching its maximum value.

The damping winding prevents the voltage across the winding 28 from reaching a value suflicient to operate the relay 35 until a predetermined time after the occurrence of synchronism. This time lag is introduced to prevent paralleling upon the occurrence of momentary synchronism when the difference in the frequencies of the two circuits tem which permits the closing coil of the paralleling breaker to be energized in advance of the occurrence of synchronism. In systems where large paralleling breakers are necessary, the time required for their operation may be sufficient to cause parallelingwhen the voltages are considerably out of phase if the operation of 'the breaker is initiated in response to exact synchronism. For this reason, I make arrangements whereby the closing of the breaker may be started in advance of exact synchronism by a time suflicient to permit operation of the breaker, so that the circuits will be finally paralleled exactly at synchronism. The system by which this may be accomplished is described in my copending application Serial No. 227,461, above referred to and briefly it is as follows:

"The device controlling the operation of the paralleling breaker is made to respond to synchronism between a voltage in phase with that of one of the circuits and a voltage out of phase with that of the other circuit. In this way, the operation of a paralleling breaker may be started when the voltages of the two circuits are at a predetermined angle and are approaching synchronism at a predetermined ra e.

As in Fig. 3, 20-21and 22-23 may be the line and machine leads respectively- Across the machine leads, I connect a phase splitter 37 comprising a resistor and a reactor, and across the resistor of the phase splitter I connect the primary of a transformer 39. Transformer 38 is connected directly to the conductors 20-21 of the line. The secondaries of the transformers38 and 39 are connected inseries with the primary of the trans former 32 which will obviously be subject to the resultant of the voltage of the line and that of the phase splitter 37. The secondary of transformer 32 is connected as in Fig. 3 to rectifier 33 which supplies direct current to the winding 29 of a transformer 25. In other respects. the circuit of Fig. 4 is the same as that of Figure 3. Instead of the three transformers 32, 38 and 39, I may use a single transformer connected between the line conductor 21 and the junction point of the phase splitter 37, the conductors 20 and 22 being connected by a conductor 24 as in Fig. 3.

Upon the occurrence of synchronism between the line voltage and the voltage in phase With the current in the phase splitter 37, the voltage on transformer 32 may by proper design of the circuit be made to equal zero. In this case, of course, the current in the winding 29 will be reduced to zero and after a predetermined time interval depending upon the adjustment of the damping circuit 30-31, the voltage of the secondary 28 will be increased sufiiciently to operate the switch 35 as in Fig. 3. By properly designing and adjusting the constants of the phase splitter 37, synchronism of the line voltage and that in phase withthe phase splitter current may be made to occur when the voltages of the l ne and machine are approaching each other and are at a given angular displacement.- This system obviously makes it possible to energize the closing coil of a paralleling switch, which requires a definite time for its operation, in advance of the occurrence of exact synchronism by the time required for the operation of the switch.

In Figure 5, I have illustrated a circuit providing for compensation for variations in the voltage of one ofthe circuits and which utilizes the magnetic relay controlling device of Figure 1 to control the paralleling operation. The means provided for voltage compensation are fully described and claimed in my copending application Serial No. 227,461 herembefore referred to, but the description 18 repeated here for clearness.

As in the preceding systems, 20-21 and 2223 represent the line andmachine leads. Across the line is connected a transformer 40 operating a rectifier 41 and connected -be tween the line and machine is the transformer 32 on which is impressed the resultant of the line and machine voltages as in Fig. 3. Transformer 32 operates a rectifier 33 which is connected in series with the rectifier 41. A battery 42 is connected to a potentiometer 43 so as to oppose the combined voltages of rectifiers 33 and 41. The direct current winding 29 of a transformer 25 is so connected as to be energized by current resulting from the difference between the potentiometer voltage and that of the two rectifiers in series. As in Fig. 3, the primary 26 of transformer 25 is connected to the machine leads through impedance 27 and the damping winding'lO is also provided on the central leg of the trans former. The relay '35 is operated in the same manner as in preceding circuits.

The object of the voltage compensation means is to permit paralleling to take place with less regard for phase conditions when the voltage of one circuit is below normal. As/a general rule, the voltage of the line will vary between normal voltage and zero, while that of the incoming generator may be made substantially constant at its normal value. \Vhen the line voltage drops, it is desirable that the incoming generator be placed on the line as promptly as possible to boost the drooping line'voltage and it is for this reason that phase agreement between the voltage of the source becomes of secondary importance under such conditions.

The operation of the voltage compensator in connection with the magnetic controlling means will now be described Assuming first that the line and machine voltages are normal and out of phase, a current proportional to the resultant of'the line be reduced sufliciently to cause operation of the relay switch 35 when the voltages of the circuits are at a predetermined angle. Now, assuming that after synchronism has been attained, the line voltage decreases the result will be a decrease in the voltage of transformer 40 and a corresponding increase in the voltage of transformer 32, so that the net result is that conditions in the local circuit including the rectifiers is unchanged. This means that when the line voltage is below normal, paralleling will take-place at relatively wider angles of phase difference than when both line and machine voltages are normal. Without my compensating arrangement a decrease in line voltage would require a closer agreement in phase before the resultant of line and machine voltages would be reduced sufliciently to cause paralleling.

It may be noted in connection with Fig. 4

that operation of the paralleling switch will be initiated in advance of the occurrence of synchronism only when the frequencies of the two circuits have a. definite relative value; i. e., when the line voltage has the higher frequency. It is desirable, of course, to have the operation of the paralleling breaker initiated in advance of synchronism regardless of which frequency is the higher. This result may be accomplished by the system shown in Fig. 6 in which I employ a phase splitter in both the line and machine circuits. Synchronism of the voltage of one circuit and that of the phase splitter in the other circuit is utilized to produce energization of the breaker closing coil. In F ig. 6, the line leads are presented by 5051 and the machine leads by 5253. Leads 50 and 52 are connected by conductor 54. Phase splitters 55 and 56 are connected across the line and machine leads respectively. Connected to the line leads is a transformer 57. A transformer 60 is similarly connected to the machine leads. Transformers 58 and 59 are energized by the voltage in phase with the current throughthe phase splitters 55 and 56. Transformers 57 and 60 energize rectifiers 61 and64 which are connected in series with the rectifiers 62 and'63 grouped in parallel. Opposing the combined voltages of the rectifiers is that of the potentiometer 70 supplied by battery '69. Obviously, the battery 69. may be replaced by an additional trans former and rectifier, or any convenient source of constant D. C. potential. Rectifiers 62 and 63 energize direct current windings 65 and 66 on the center legs of transformers 69 and 77 similar to those shown in the previous figures. The primary windings 71 and 78 are energized from the generator leads 5253 and are in series With impedances 78 and 73" respectively. Damping windings are shown at 67 and 67 The secondaries 72 and 79 of transformers 69 and 77 are connected to rectifiers 74 and 74. which siipply direct current to switches 75 and 75, the contacts 76 and 76 of which are connected in parallel, and may serve to parallel the line and generator circuits directly, or to complete a local paralleling circuit.

The potentiometer is so adjusted that when the voltage of one circuit and that of the phase splitter in the other circuit are in synchronism, the potentiometer voltage is equal to that of the corresponding rectifiers, so'that as a result, the current in one of' the windings 65 and 66 is reduced to zero, and the voltage of one of the secondaries 72 and 79 is increased suiiiciently to cause energization of the closing coil of switch 75. As long as the circuit and phase splitter voltages are out of phase, current will flow through the windings 65 and 66 due to the fact that the potentiometer voltage is higher than the sum of the rectifier voltages. When, however, the voltage of one line and that of the phase splitter in the other circuit are synchronized,

the sumof the two rectified voltages is sufiicient to oppose the voltage of the potentiometer 7 0, so that the current in the direct current coil on the center leg of one of the transformers is reduced to zero, With the result described above.

By the provision of a phase splitter in each of the circuits, it is, therefore, possible to cause energization of a paralleling switch in advance of the occurrence of actual synchronism regardless of which of the voltages has a higher frequency. By referring to Figure 8, this may be made more clear. In this figure, I have indicated at OL and OM the line and machine voltages, at 0L and OM? the corresponding transformer voltages,

' and at OL" and OM, the voltages of the phase splitters in the line and machine circuits. As above stated, whenever synchronism of the voltage of one circuit and that of the phase splitter in the other circuit occurs, the paralleling switch will be energized. Assuming that in Figure 8, the frequency of the vector OL is normal and that the machine is being brought up to synchronous s eed, the vector OL will overtake the vector M with a relative speedfdependent upon the frequencies of the two circuits. As 0L approaches OM, 0L and OM" will coincide when OL andOM are at the angle MOM" and energization of the closing coil of the paralleling breaker will occur at that time, sothat by the time QL "coincides-withjOM, the switch will be closed. I I

Assuming on the other hand that the frequency of the machine voltage is greater than that of the line, the vector OM will overtake the vector OL and as it does so, OM will coincide with OL" resulting in the energization of the closing coil of the paralleling breaker. Thus, it is obvious that regardless of which circuit has the higher frequency, the system shown in Fig. 6 will cause the closing of the paralleling breaker to be initiated prior to the occurrence of synchronism.

In Fig. is shown a system similar to.

that of Fig. 6, except that in the system of Fig. 7, I provide means for positively preventing energization of the closing coil of the paralleling breaker when the voltages of the circuits are exactly in synchronism and going out of phase. To accomplish this'object, I add to the circuit of Fig. 6 a transformer 80 connected so as to be subject to the resultant of the line and machine voltages. This transformer supplies a rectifier 81 which in series with rectifiers 64 and 61 energizes the direct current winding 82 of a third threelegged transformer 83 having a. primary winding 84 connected in parallel with the primary windings of transformers 69 and 77. The secondary winding 85 of transformer 83 is connected to a rectifier 86 which supplies direct current to the operating coil of a relay 87. The resistance 86' in series with the primary winding 84 serves the same purpose as the impedance 7 of Figure 1. The .relay 87 when de-energized closes the circuits from secondaries 72 and 79 to rectifiers 74c and 74'.

The operation of the system shown in Fig. 7 is identical with that shown in Fig. 6, except that upon the occurrence of synchronism between the voltages of the line and generator circuits of Fig. 7, the voltage of the transformer 80 becomes zero and the direct current in Winding 82 likewise decreases to zero because the voltage of potentiometer 70 is equal to that of rectifiers 64 and 61 in series, with the result that the voltageof secondary winding 85 is increased as explained in connection with Figure 1, so that the relay 87 is operated to open the contacts 88. These contacts connect the secondaries 72 and 79 to rectifiers 74 and 74' and thereby, when open, prevent operation of the switches 75 and 7 5' to parallel the circuits when the voltages thereof are in synchronism and passing away from that condition.

The successful operation of the system of Fig. 7 depends on the characteristics of the relays 75, 75 and 87. These relavs'will pick up their armatures at a definite voltage but will not release them until the voltage has fallen considerably below the pick-up value. For this reason, the relays 75 and 75 will not be energized by the. coincidence of OM and ()L when 0L is passing awayfrom OMQ-since relay 87 will maintain the contacts 88 disengaged for an appreciable period after the coincidence of OL and OM, so that the operating circuits of relays 75 and 75 are open during this aeriod.

The circuit of ig. 7 also incorporates the voltage compensation scheme described above and shown in Fig. 5. I

Although I have shown the primary windings of the three-legged transformers con nected to the generator terminals, if this system is utilized to parallel circuits the voltage of both of which is variable, it is necessary to provide a separate source of constant potential alternating current for exciting these windings. I

I claim as my invention: x

1., In a system for automatically connecting alternating-current circuits, a switch for connecting said circuits, a solenoid for closing said switch, a-transformer connected to one of said circuits for energizing said coil, said transformer having a winding for reducing the secondary voltage,when energized, :1 rec tifier supplying direct-current to said winding in proportion to the resultant of the voltages of said circuits and a damping winding on said transformer for postponing variations in secondary voltage for a time interval after the corresponding variations of said resultant.

2. An automatic paralleling system for two alternating-current circuits comprising a switch for connecting said circuits and means for controlling said switch including a threelimbed reactor having a primary winding, an impedance connected in series therewith across an alternating-current source, said reactor also having a secondary winding, a saturating winding, and a damping winding,

means responsive to the voltage induced in' said secondary winding for closing said switch and means for supplying direct cur rent to said saturating winding proportional to the vector resultant of the voltages of said circuits, whereby the voltage induced in said secondary winding is maintained below the operative value of said switch-closing means as long as said voltages are out of phase by more than a predetermined angle. 7 3. A paralleling system for two alternating-current circuits comprising a paralleling switch and closing means therefor, a trans former having a primary winding connected ary windings, means to one of said circuits and a secondary winding, means for energizing said switch-closin means in accordance with the voltage induced in said secondary winding, a saturating winding on said transformer for controlling the voltages induced in the rimary and secondor energizing said saturating winding in proportion to the instantaneous resultant of the voltages of said circuits, and a damping winding on said transformer to delay the changes in the induced voltages caused by changes in. said resultant.

4. The combination with two alternatingcurrent circuits, a switch for connecting said circuits, closing means for said switch and a t 'ansformer for supplying energy to the closing means, of means forcontrolling said switch including saturating means on said transformer for controlling the voltage induced in the winding thereof, means responsive to the resultant of the voltages of said circuits for energizing said saturating means to control the closing of said switch, and a damping winding on said transformer to preclude the effective energization of said switch-closin g means as long as the frequency of said resultant is above a predetermined value.

5. The combination with two alternatingcurrent circuits, a switch for connecting said circuits, closing means for said switch and a transformer for supplying energy to the closing means, of means for controlling said switch including saturating means on said transformer for controlling the voltages induced in the windings thereof, and means responsive to the resultant of the voltages of said circuits for energizing said saturating means to control the closing of said switch.

In testimony whereof, I have hereunto subscribed my name this 12th day of September, 1927.

PHILLIPS THOMAS.

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