US2426033A - Distance type product responsive relay - Google Patents

Description

Aug. 19, 1947.

B. E. LENEHAN DISTANCE TYPE, PRODUCT RESPONSIVE RELAY.

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ATTORN EY INVENTOR Patented Aug. 19, 1947 DISTANCE TYPE PRODUCT RESPONSIVE. RELAY Bernard E. Lenehan, Bloomfield, N. J assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 16, 1945, Serial No. 578,161

9 Claims.

My present invention relates to a new protective relay for alternating-current lines, the principal novel characteristic feature of the relay being that it has a distance-responsive characteristic, or a modified impedance characteristic which can be readily adjusted. My invention relates more particularly to a novelly energized wattmetric or product-responsive element which has readily adjustable characteristics so that its impedance-circle can be separately adjusted as to center-placement and circle-radius.

An object of my invention is to energize the two windings of a wattmetric relay with a current-compensated voltage, with such adjustments as to be able to completely adjust the character'- istic circle-response of the relay. The currentcompensated line-voltage is equal to the vectorial sum of an alternating-current function of a linederived voltage, plus the product of an alternating-current function of a line-derived current times an impedance. Throughout the specification, when I refer to a wattmetric element or relay, I mean any product-responsive element which develops a torque equal to the product of its two energized quantities times a function of the angle between them, whether that angleiunction is a sine or a cosine or any intermediate function.

In the accompanying drawing, Figure 1 is a characteristic response-circle diagram which will be referred to in the explanation of my invention, and Figs. 2:, 3, 4 and 5 are diagrammatic views of circuits and apparatus illustrating my invention in four difierent forms of embodiment.

If a cosine-responsive product-type relay is energized with two complex quantities, which may be two diverse alternating magnetic fiuxes 1=E-df (1) and it will produce a torque which is the absolute value of the algebraic sum of the products of the respective terms, or

At the balance-point of the relay, the torque T will be zero. Dividing Equation 3 by I and put- I ting the equation equal to zero, the conditions for the balance-point of the relay will be found to be 0=ez --z'(ac'+5) +di) (5) This is the equation of a circle, as will be seen from Fig. 1, where the circle 1 represents any circle, plotted on rectangular coordinates in terms of the line-resistance R and the line-reactance X, with the center C of the circle at the impedance 56:20, and with a circle-radius C' P=Qo, where P is any point in the circle. Then the locus of the line-impedance :2, or the locus of all values of the line-impedance which termihate in the circle, is the locus of the vector-sum ZU+QO=Z (6) Comparing Equations 5 and 8 and equating equal powers of Z,

a a e. -cc; elem-1 1 and a diameter 2Qo equal to the difference (tb).

If we put where 0 is the angle by which the line-current i lags the line-voltage E, R is the line-resistance 3 up to the fault, and X is the inductive linereactance up to the fault, then This is the equation for a circle with a radius The slope of the circle-center impedance Z is a+Rl The displacement Z0 of the circle-center from the origin is A cosine relay, responding to negative values of the torque T, and energized as set forth in Equations 1 to 25, will respond for all values of the line-impedance Z falling inside of the circle I, and will hold back against its back-stop for all values of the line-impedance Z falling outside of the circle.

If the angle of maximum response of the relay has any value 951- other than zero, so that response to the two energizing-quantities (p1 and Q52 is a maximum when 1 lags $2 by an angle 1, then if the lagging angle of 1 with respect to 2 is rather than 11 the relay-torque will be However, the Torque- Equations 3 and 20 are valid only for a cosine-relay, or a relay having a critical angle r 0. In order to make Equations 3 and 20 valid for a relay having a critical angle (Pr, it will be necessary to replace the energizing-quantity 1 of Equations 1 and 18 with another quantity 1o which leads 1 by the respouse-angle 1- of the relay, as shown by the equation For example, if the response-angle of the relay is (1:90, the relay will be a sine-responsive relay, responding to the product of its exciting quantities multiplied by the sine of the phaseangle between them, as shown by the torqueequation,

Equation 21 shows that we are interested only in the sum and difierence of Ra and Rb, and in the sum and difference of Xu and Xb, and that the difference-quantities (Ra-Rb) and (Xa--Xb) afiect only the circle-radius Q0, and not the center-position (R0, X0). It will sometimes be convenient, therefore, to make either (Ra-Rb) or (Xa-Xb) equal to zero.

Fig. 2 shows a form of embodiment of my invention in which Ra=Rb=R1 (30) Xa=X1+M4 (31) and Xb=X1-M4 (32) Then the circle-radius will be Qo=M4 (33) the coordinates of the center will be at Ru==R1 (34) Xn=X1 (35) the slope of the center-line will be a & otan 1 R1 (36) and the center-displacement Will be ZO=VWXF=Z1 Still more generically, we know that we are interested only in the vector value of (cl-H3) and the absolute value of [d-b], as shown in Equations 10 and 11. We may write, therefore, the general equations where Z3 and Z4 are any impedances. These reand a circle-radius Q0 expressed by the absolute value of Z4 as shown by the equation The absolute value of the impedance-component Za in Equation 40 expresses the ohms (or distance) displacement Z0 of the circle-center C from the origin, while the phase-angle of the impedance-component Z3 expresses the slope o of the circle-center line Zo.

Equation 41 shows that the phase-angle of the impedance-component Z4 is quite immaterial. This impedance-component Z4 may be pure'resistance, pure reactance, or any combination of the two.

There are man form in which these principles may be embodied.

Fig. 3 shows a form of embodiment of my invention in which the center-placement component Z3 is separated into two factors, a variable scalar quantity or absolute value Z3, and a variable phase-angle 3, and the illustration is in tended to be symbolic of any means to that end. The angle-changing element is shown in the form of a compensator-impedance Z5 which is variable in phase-angle without changing its magnitude; and the displacement-changing element is hown in the form of a variable ratio or factor K, which affects the magnitude of the current Ki which is circulated through the compensator-impedance Z from the source of line-derived current I.

In Fig. 3, therefore,

The particular form of impedance Z5 in Fig. 3 is convenient for changing the center-line angle o of the response-circle between an upper limit of 90, or coincidence with the +X axis, corresponding to R5= or open-circuited, or an upper limit of 85 if the maximum Value of R5 is (45.8)M, and a lower limit dependent upon the minimum practicable limit of R5 commensurate with an acceptable burden on the source of linederived current I, or a lower limit of 50 if the minimum value of R5 is (4.3)M, for example.

In Fig. 3, I have also illustrated the application of my invention to a sine-type relay W having two force-reacting elements glue and oz, and producing a force proportional to wz sin as discussed in connection with Equations 26 to 29. In order to make my invention applicable to such a relay, it is necessary to make the exciting-current in 1o lead the exciting-current in 2 by 90 when the same voltage is impressed on both 9510 and m. This may be approximated by including a capacitor C in series with the winding 1o and properly choosing the relative numbers of turns in 1o and 52 to produce substantially the same flux in each, when the impressed voltage is the same.

In general, if the characteristic phase-angle of the relay is r so that its maximum torque is produced when the angle between its two cooperating fluxes 1 and (#2 is r, then the relay-torque T is 12 cos (r), and it is necessary to cause the voltage-responsive excitation-components of the two fluxes to be dephased by (Pr, and to cause the corresponding current-responsive excitationcomponents of the two fluxes to be likewise dephased by r. In Fig. 3, a sine-responsive relay W is presupposed, and hence the angle r is 90". In the other figures, a cosine-reponsive relay W is presupposed, and hence the characteristic relay-angle r is zero.

In Fig. 4, I have shown a further form of the phase-changing means, in the form of an imped- 6 ance 2a which has different practical limits of angle-variation.

Thus, in Fig. 4, if X6 is varied and Rs held constant, the circle-center angle o may be changed, for example, from which is 240, corresponding to Xs=(1.15)Rs, to 60, or 3-00, corresponding to Xe: (3.46) Re.

In all of the foregoing derivations, it has been assumed that the relay-current, 1'1-=f 1+1"2, or IT=I'1o+I'2, is negligibly small with respect to the compensator-current I, within acceptable limits of error.

It will further be noted, from Equation 10, that the center-line angle #10 of the response-circle l of the relay is the same as the phase-angle of the average value, Zo:(d+b)/2, of the coefiicients a and b of the line-current response of the relay. Furthermore, the voltage-responsive coefficient c in Equation 2 must be unity, as shown in Equation 9. Taking into consideration, also, the relations shown in Equations 41 and 4'7 to 49, we may write the quantities to be multiplied, thus:

Then the circle-center displacement will be Zo=KZe (59) and the circle-center angle will be L (60) and the circle-radius will be or the absolute value of Z7, regardless of its phaseangle.

Since the phase-angle of Z7 is immaterial, the

impedance-component Z7 may be replaced by Z"1=Z a L 56 (62) yielding, from Equations 5'7 and 58,

1=E (KZ6+Z:8) 1:41pm; (63) 2=E- (KZ6Z8)IA6 (64) instead of e=sin wt. In other words, the angle s in Equations 63 and 64 is in effect the relative angle between the current-responsive excitationcomponent and the voltage-responsive excitation- It will be seen, therefore, that the circle-center angle (pm is the difference between the phase-angle (4)6-(lm) of the current-responsive coefiicient, and the phase-angle ('e) of the voltage-responsive coefiicient, at unity power-factor. Thus, instead of rotating the current-responsive terms through an angle s to obtain a center-line angle o=c, it would be possible to leave the phase-angle of the current-responsive term equal to zero, by putting /)G= /)e, and to obtain the desired center-line angle 0 c by rotating the response of the relay to the line-voltage El through a leading angle (e) while keeping the current-responsive terms in phase with the line-current i. Or both the current and voltage responses may be rotated, yielding qbo: (6-(/)e) Many phase-shifting networks are known.

In Fig. 5, I have shown a voltage-shifting network 9 of a type which is described and claimed in an application of H. J. Carlin, Serial No. 583,926, filed March 21, 1945, and assigned to the Westinghouse Electric Corporation. By a decrease of a secondary resistance R9 from infinity to a certain large value, with either position of the reversing-switch 3, the voltage E ma be shifted through any angle 9 up to 30, in either direction, without materially changing its mag nitude, within acceptable limits of error.

In Fig. 5, the circuit is such that It is believed that the various circuits and parts shown in Figs. 2 to 5 will be clear from the foregoing description. These figures may be briefly type windings 4n and m, and having a relaycontact I which closes when the relay responds. The details of the relay circuit 8 which is controlled by the contact 1 are not indicated, as my invention relates to the means for obtaining the contact-closin response at 1, rather than the use which i made of that response in the controlled relaying circuits 8.

In Fig. 2, a potential transformer |0 serves as a source of the line-voltage E, which is applied acros the terminals II and 12 of the relay. A line-current transformer |3 serves as a source of line-current l, which is applied across the relay-terminals l4 and I5. The relaying current l is circulated through a circuit including the compensator-resistance R1, the compensator inductance X1, and the primary winding of a mutual reactor 2M4, all of these values being adjustable. The mutual reactor 2M4. is provided with a secondary winding 23 having a mid-tap 2|.

In Fig. 2, the currentresponsive voltage-drop which appears across the resistor R1 and the reactor X1 is added to the line-derived voltage E, either directly, or through a suitable coupling transformer 24 having any appropriate turnratio. The relay-terminal II i connected to one end of each of the relay-windings 1 and m. The other ends Olf the windings 51 and 2 are connected to the terminals of the secondary winding 20 of the mutual impedance element 2M4. The mid-tap 2| of this secondary winding 20 is connected to the other voltage-terminal |2 of the relay through the secondary winding of the compensator-transformer 24. The response of the apparatus shown in Fig. 2 has already been discussed, and need not be further reviewed.

In Fig. 3, a sine-responsive wattmetric element W is utilized, as already discussed, necessitating the inclusion of the capacitor C10 in series with the relay-winding (m, as already explained. The current-responsive circuit, which is connected to the relay-terminals M and IS in Fig. 3, includes the primary winding 25 of a variable-ratio transformer K, as well as the primary winding of the previously described mutual reactor 2M4. The secondary winding of the transformer K circulates the current Kl through the impedance Z5, which consists of a variable resistance R5 in series with the primary winding of a fixed mutual reactance M. The resistance R5 is shunted by the primary winding of a fixed mutual reactance 2M. The two mutual reactors 2M and M have secondary windings 21 and 2B which are serially connected, in opposite polarities, between the voltage-terminal l2 and the mid-point 2|. The characteristics of this circuit, as shown in Fig. 3, have already been discussed.

In Fig. 4, the same variable transformer K is utilized, but the mutual reactance 2M4 is re-- placed by a variable resistance 2R4, the voltage of which is applied to the relay-windings l and (in through a transformer 29 having a secondary winding 30 which is provided with a mid-tap 3|. The mid-tap 3| is connected to the voltageterminal l2 through two resistors R6 and His. The resistor R6 is shunted by the secondary winding 32 of a transformer 33, which also has a primary winding 34. The resistor 2R6 is shunted by a variable inductance Xs. The secondary winding 26 of the variable transformer K supplies the current Ki to the parallelcircuit combination 2R6 and X6, in series with the transformer-winding 34, the latter being connected in reversed polarity so as to send the current Kl in the reversed direction through the resistor R6. These circuits of Fig. 4 have also been analyzed in the preceding mathematical discussion, and need no further comment.

terminals II and I2 of the relay. The phasechanging network 9 consists of a transformer 4|! having a primary winding 4| which is connected in series circuit relation between the potential transformer H) and the relay-terminal H. The transformer 40 also has a secondary winding 42 which is connected, through the reversing switch 3, between the relay-terminal l2 and the variable resistor R9. The other terminal of the variable resistor R9 is connected to the same potential-transformer terminal which is connected to the primary winding 4|;

The current-responsive circuit |4-|5in Fig, 5 contains the primary winding 25 of the variable transformer K, and'the primary winding of the mutual reactor 2M4, thesame as in Fig. 3.

The

secondary winding 26 of the variable transformer K circulates the current Kl through the inductance X3 which is connected between the voltageterminal l2 and the mid-tap 2|. The efiect of the circuit-connection shown in Fig. 5 has already been discussed and needs no further explanation.

In all of the embodiments of my invention, it will be observed that I have provided means for independently-adjusting the radius Q0 and the position of the center C of the response-circle I. The center-position C can be fixed either by separately adjusting its coordinates R0 and X0, or by separately adjusting its center-line slope 60 and its displacement Z0.

While I have illustrated and explained my invention in connection with four different forms of embodiment, I wish it to be understood that there are many different forms of embodiment, as many variations may be made, without departing from the essential features of my invention. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language and the prior art.

I claim as my invention:

1. An adjustable distance-type productresponsive relay having two diverse cooperating alternating magnetic fluxes, means for so utilizin said fluxes as to produce a torque in response to the product of said fluxes, multiplied by cos (T) where i the angle between said two cooperating fluxes and (Pr is the characteristic phase-angle of the relay, and two diverse fluxproducing mean for producing the respective fluxes, characterized by each of said flux-producing means comprising means for producing a voltage-responsive excitation-component in response to a line-derived voltage, and means for producing two current-responsive excitationcomponents in response to a line-derived current, said two current-responsive excitation-components being added, one to the other, in one flux, and subtracted, one from the other, in the other flux, a first adjustment-means for jointly varying a, first one of the two current-responsive excitation-components of both fluxes, and a second adjustment-means for jointly varying the second one of the two current-responsive excitation-components of both fluxes, said two fluxproducing means including circuit-connection means for causing a phase-angle of substantially (,br to exist between each of the corresponding excitation-components of the two cooperating fluxes.

2. An adjustable distance-type product-responsive relay having two diverse cooperating alter nating magnetic fluxes, means for so utilizing said fluxes as to produce a torque in response to the produce of said fluxes, multiplied by cos r) where o i the angle between said two cooperating fluxes, and r is the characteristic phase-angle of the relay, and two diverse fluxproducing means for producing the respective fluxes, characterized by each of said flux-producing means comprising :means for producing a voltage-responsive excitation-component in response to a line-derived voltage, and means for producing two current-responsive excitationcomponents which are out of phase with each other in response to a line-derived current, and means for separately adjustin said currentresponsive excitation-components, said two fluxproducing means including circuit-connection means for causing a phase-angle of substantially 10 r to exist between each of the corresponding excitation-components of the two cooperating fluxes.

3. The invention as defined in claim 1, characterized by said first adjustment-means being a compensator-means comprising a variable resistance and a variable reactance traversed by a line-derived current.

4. The invention as defined in claim 1, characterized by said first adjustment-means comprising means ior varying the magnitude, without substantially varying the phase-angle, of said first one of the two current-responsive excitation-components of both fluxes, in combination with an adjustable phase-shifter means for varying the relative phase-angle between the voltageresponsive excitation-component and the first current-responsive excitation-component in each flux without substantially varyin their magnitudes.

5. An adjustable distance-type product-responsive relay having two diverse cooperating alternating magnetic fluxes, mean for so utilizing said fluxes as to produce a torque in response to the product of said fluxes, multiplied by cos (T), where is the angle between said two cooperating fluxes, and r is the characteristic phase-angle of the relay, and two diverse fluxproducing means for producing the respective fluxes, characterized by each of said flux-producing means comprising means for producing a voltage-responsive excitation-component in response to aline-derived Voltage, and means cfor producing a current-responsive excitation-component in response to a line-derived current, a first adjustment-means for causing substantially identical quantities to be added to the two current-responsive excitation-components of the two fluxes whereby the sum of thetwo currentresponses of the two fluxes is varied without substantially changing their difference, and a secondadjustment-means for causing substantially identical quantities to be added, in one case, and subtracted, in the other case, from the respective current-responsive excitation-components of the two fluxes whereby the magnitude of the difference of the two current-responses of the two fluxes is varied without substantially changing their sum, said two flux-producing means including circuit-connection means for causing a phase-angle of substantially r to exist between each of the corresponding excitation-components of the two cooperating fluxes.

6. The invention as defined in claim 5, characterized by said first adjustment-means being a compensator-means comprising a variable resistance and a variable reactance traversed by a line-derived current.

7. An adjustable distance-type product-responsive relay having two diverse cooperating alternating magnetic fluxes, means for so utilizing said fluxes as to produce a torque in response to the product of said fluxes, multiplied by cos (r), where the angle between said two cooperating fluxes, and r is the characteristic phase-angle of the relay, a first flux-producing means for producing a first one of said cooperating fluxes in response to the vectorial sum of a voltage-responsive excitation-component in response to a line-derived voltage, plus a first current-responsive excitation-component in response to a line-derived current, plus a second currentresponsive excitation-component in response to a line-derived current, a second flux-producing means for producing the second one of said cooperating fluxes in response to the vectorial sum of the same voltage-responsive excitation-component, plus the same first current-responsive excitation-component, minus the second currentresponsive excitation-component, and separate adjustment-means for separately varying the first and. second current-responsive excitationcomponents.

8. The invention as defined in claim 7, characterized by the means for adjusting said first current-responsive excitation-component being a compensator-means comprising a variable resistance and a variable reactance traversed by a line-derived current.

9. An adjustable distance-type product-responsive relay having two diverse cooperating alterhating magnetic fluxes, means for so utilizing said fluxes as to produce a torque in response to the product of said fluxes, multiplied by cos (-r), where is the angle between said two cooperating fluxes, and 1- is the characteristic phase-angle of the relay, a first flux-producing means for producing a first one of said cooperating fluxesin response to the vectorial sum of a voltage-responsive excitation-component in response to a line-derived voltage, plus a first current-responsive excitation-component in response to a line-derived current, plus a second current-responsive excitation-component in response to a line-derived current, a, second fluxproducing means for producing the second one of said cooperating fluxes in response to the vectorial sum of the same voltage-responsive excitation-component, plus the same first currentresponsive excitation-component, minus the sec-- ond current-responsive excitation-component, a first adjustment-means for varyin the relative phase-angle between the voltage-responsive excitation-component and the first current-responsive excitation-component without substantially varying their magnitudes, a second adjustmentmeans for varying the magnitude of the first current-responsive excitation-component without substantially varying its phase-angle, and a third adjustment-means for varying the magnitude of the second current-responsive excitationcomponent.

BERNARD E. LENEI-IAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,000,803 Van C. Warrington May 7, 1935 2,115,597 Traver Apr. 26, 1938

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