US2393983A - Relay - Google Patents

Description

\ Feb. 5, 1946.

S. L. GOLDSBOROUGH RELAY Filed Aug. 1, 1944 INVENTOR Shirley L. Goldsborouyb.

WITNESSES:

\IZM

ATTORNEY Patented Feb. 5, 1946 RELAY Shirley L. Goldsborough, Basking Ridge, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsyl- Vania Application August 1, 1944, Serial No. 547,561

Claims.

My present invention relates to a new protectlve relay for alternating-current lines, the principal novel characteristic feature of the relay being that it has a distance-response characteristic which can be readily and conveniently shifted or molded to fit different line-conditions.

This application is a cOntinuatiOn-in-part of my applications, Serial No. 504,695, filed October 2, 1943, for Long-line fault-detectors and relaylug-systems, and Serial No. 513,356, filed Decem ber 8, 1943, fo Modified-impedance carrier relays, with additional details relative to means for making three substantially independent adjustments on the relay, so that the user of the relay may readily and independently make any one or the three adjustments, without substantially disturbing either one of the others. A first adjust ment-means enables the user to adjust the radius of the response-locus circle of the relay, when the locus of the line-impedance at the balance-point of the relay is plotted on ectangular coordinates of resistance and reactance. A second adjustment gives the user of the relay a choice as to the angle along which the center of the circle is displaced from the origin, thereby choosing the phase-angle at which the relay has preferential directional characteristics. A third adjustment enables the user to preselect the amount by which the circle-center is displaced from the origin along the preselected center-axis or angle, thus predetermining the amount of di rectional response which is superimposed upon an impedance-response. These three adjustments are preferably calibrated in ohms and angles, as the case may be.

Distance-type transmission-line relays, and reactance-relays, and combined impedance and reactance relays, or combined impedance and di rectlonal relays, have heretofore been used very successfully. It has been possible to design such relays, either on the balanced-beam principle or on various kinds of watt-response principles, so that any possible desired type of response-circle could be obtained with any possible circle-radius, and any possible position of the center of the circle. However, the relay-design has been a matter of calculation, or fixed predetermination, without the provision of means whereby the three above-mentioned circle-characteristics could be independently changed at will, changing any one of the characteristics without disturbing the setting of the relay as to the other two characteristics.

Many different types of directional distance relays have been known, with different combinatlons of current and voltage on the operatingcoil side and on the restraint-coil side of a balanced-beam relay, and in the two fluxes which are to be multiplied in an induction-disk relay, an induction-loop relay, or other type of wattmetric relay. Of all these types of current-voltage energizations of different kinds of directional impedance relays, however, there is only one, which I have thus far been able to discover, in which these three independent adjustments may readily be made, in a manner which can be precalibrated because each adjustment is substantially independent of either one of the other two adjustments.

A particular object of my invention, therefore, is to provide a beam-type relay having an operating coil which is responsive only to the linecurrent, and having a restraint-coil which is responsive to the vectorial sum of a line-v oltage plus a function of a line-current, in conjunction with adjustment-means for making the three substantially independent adjustments heretofore mentioned. By a beam-type relay, I means to include any relay having an operating force which is responsive to the square of any flux or field-strength, which I may call the operatingcoil field-strength, and a restraining force which is responsive to the square of another flux or field-strength, which I may call the restraintcoil field-strength.

With the foregoing and other objects in view, my invention, as claimed in this application, consists in the circuits, systems. combinations, methods, apparatus, and parts, hereinafter described and claimed, and illustrated in the accompanying drawing, wherein:

Figure 1 is an impedance-curve diagram, illustrative of my invention and of its application in transmission-line protection, and

Fig. 2 is a diagrammatic view of circuits and apparatus embodying my invention in an illustrative form of embodiment.

Fig. 1 is an impedance-diagram, in which I have shown some of the difficult conditions which distance-type protective-relays must handle, particularly on the more heavily loaded and longer transmission lines, in which it is becoming increasingly diflicult for the relays to distinguish between fault-conditions and load-conditions, or to distinguish between momentary load-swings or synchronizing-surges from which the system has the ability to recover or stay in step, and those swings or surges which develop into a definite out-of-step condition. In Fig. 1, the apparent line-impedance, or the quotient of line-voltage divided by line-current, is plotted on rectangular coordinates representing the line-resistance R and the line-resistance yX.

In Fig. 1, it is easy to plot the fault-ohms, because the resistance-ohms and the reactanceohms of the transmission-line are readily available. Thus, in Fig. l, the line OEcLr is the line on which all of the impedance-ohms of the transmission-line will fall, and the point Ln represents the ohms for a solid fault at the far bus of the protected line-section. The vector Lra represents the apparent impedance-value when the arc-resistance of a fault is included, or added to the impedance of the line-conductors. It is easy to plot these two impedance vectors LF and LFR.

It is generally much more diflicult, however, to plot the impedance-values representing momentary load-swings and synchronizing-surges. Exact methods for accurately and laboriously calculating these swings and surges are known, and form no part of my present invention. An approximate idea of the manner in which the impedance-vector for a synchr-onizing-surgemay shift can be gained by locating the point Ea, along the line Ls, which representsthe distance. in ohms, of the electrical center of the transmission system, as measured from the relaylocation. The surge-impedance vector, such as Is in Fig. 1, will terminate approximately in a straight line SS.ESS which is approximately at right angles to the fault-chm vector Lr at the point Es corresponding to the distance of the electrical center. The more severe the swingcondition, the closer this vectorIs will approach the fault-line Lr. Some particular maximum approach to the line Ls will represent the divi ing-line between the ability of the system to stay in step, or to develop into a definite out-of-step condition. The particular vector Is which is shown in Fig. 1 represents approximately the maximum position of the synchronizing-surge ohms from which the system can recover.

Generally, it is desirable to permit tripping for all surge-conditions from which the system cannot recover, that is, for surge-ohms terminating in the region EcIS in Fig. l, but to prevent tripping for all load-conditions and surges up to this non-recovering point Is. This means that the relay response-characteristic, when plotted on the Pv-X diagram, as shown at Z2 in 1, must properly encircle the'entire vector Lea, representing line-fault ohms including fault-resistance, but it must not encircle the swing-ohms, in the region IsSS, from which recovery is possible.

In many or most transmission-lines, particularly the longer ones, the minimum synchronizing-surge ohms Is for which it is not desired to have a relay-response, or a circuit-breaker tripping-action, may fall quite close to the faultohm line LR. Moreover, each transmission-line is diiierent, each havin its own individual characteristic, and the characteristics may even change particularly as to the position of the electrical centerEc of the system, during difierent system-conditions. -My new relay is designed for the purpose of making it possible for the user of the relay to make calibrated adjustments of each one of the three characteristics which determine the size and the position of the impedance-circle, such as the ircle Z2 in Fig. I.

In Fig. 2, I have illustrated my invention as applied to the protective relaying of one phase of a three-phase transmission-line 3, which is connected to a three-phase bus 4. The several phases, or phase-conductors, are distinguished by the letters A, B, and C. The relay is diagrammatically represented as a centrally pivoted beam 5, shown in its non-energized position, or nonresponsive position, having make-contacts 6 at one end. The front or contact-carrying end of the beam 5 is operated upon by a diagrammatically indicated operating-coil T, which develops an operating-force F0 tending to close the relay-contacts S. The back end of the beam 5 is acted upon by one or more restraint-windings or coils, as diagrammatically indicated at 8.

A relaying-current I is derived from the line 3 through 1ine-current transformers l0, and applied to the operating-coil l, and to the primary winding ll of an auxiliary current-transformer 12. A relaying-voltage E is derived from the line, by a potential-transformer I3, and this voltage E is applied to the restraint-coil 8 through a voltage-shifter I4. The auxiliary current-transformer I2 has a secondary winding l5 which feeds current into a current-type phase-shifter I 6 of any suitable type, the same being illustrated as an inductance l1 shunted by a resistance I8, which is so connected as to add a current-responsive voltage-component to the voltage E in the energizing-circuit of the restraint-coil B, as will be subsequently described.

In the following derivations, we will regard lagging phase-angles as positive, and leading phase-angles as negative, so that lagging linereactance X will be positive.

The operating-coil flux or field-strength may be written and the restraint-coil field-strength may be written Hr=hml (0+M) -hnE4N (2) where g, h, m, and n are any scalar-value constants; 0 is the power-factor angle of the line, counted positive for lagging power-factors; U, M, and N are phase-shifter angles, counted positive for lagging phase-shifts; U is immaterial; N is the angle by which the voltage-responsive voltagecomponent applied to the restraint-coil 8 lags behind the line-derived voltage E; and M is the angle by which the current-responsive voltagecomponent applied to the restraint-coil 8 lags behind the line-derived current I if I is in phase with E at unity power-factor, so that, in any event, regardless of the relative phases of I and E at unity power-factor, (0+M) is the angle by which the current-responsive restraint-coil energizing-component lags behind the line-derived voltage E, taken as a reference-base.

The operating force of the relay is responsive to the square of the operating-coil flux Ho. It is therefore The restraining force of the relay is responsive to the square of the restraint-coil flux Hr. It is therefore F =h m l +h n E 2h3mnlE cos (N-.-M0) (4) If the operating and restraining forces had been proportional to the first power, rather than the square, of the flux, the result would have been the same, using the square-root sign on each side of Equation 5, which could be instantly'cleared by squaring both sides.

Dividing Equation 5 through by I, and transposing one of the terms, and remembering that cos O=R (6) sin =X and that cos (N-M-o)=cos (NM) cos 0+sin (NM) sin 0 Equation may be rewritten as It hn 0, we may divide through by h n without changing the inequality-sign in Equation 7, obtaining an expression for the relay-response whenever When the apparent line-resistance R and the apparent line-reactance X are plotted, as abscissas and ordinates, respectively, of a system of rec- 4 tangular coordinates, the locus of the balancepoint of the relay is thus a circle, as shown, for example, at Z2 in Fig. 1. If the relay is to operate, the apparent or measured line-impedance must fall inside of this circle.

The coordinates of the center Co of the circle, expressed in ohms, are

R g-:- cos (N M) X0 sin (N M) 10 The radius of the circle, in ohms, is

l Qo- (11) sn= (N M) 1.2

The displacement 0C0 of the center of the circle,

measured in ohms from the origin along the line at the angle So to the R-axis, is found from Equations 9 and 10 to be Examination of Equations 11, 12, and 13, for these three variations of the circle-characteristics, will show that the constants or controllable variables g and h occur only in Equation 11, the angle (N -M occurs only in Equation 12, and the constant or controllable variable m occurs only in Equation 13. The variables g and h are the response-ratio factors dependent upon the effective number of turns and the effective magnetic reluctance (or airgap-setting) of the operatingcoil 1 and the restraint-coil 8, respectively. Usually it is more convenient to vary only one of these factors 9 or h, usually h, and to calibrate the adjustment of the circle-radius Q0 in ohms, as, for example, by turn-adjustment taps 19 on the operating-coil 1 of the relay, as shown in Fig. 2.

The angle, -M, is the angle by which the current-responsive voltage-component of the restraint-coil energization Hr leads the line-derived current I, if I is in phase with the line-derived voltage E at unity power-factor, the negative sign indicating that the angle is leading. If I is not in phase with E at unity power-factor, but lags it by some angle Mo, as because of some stardelta transformation, then (M M o) is the angle by which the current-responsive Hr component lags behind the line-derived current I. The angle N is the angle by which the voltage-responsive voltage-component of the restraint-coil energization Hr lags behind the line-derived voltage E. The angle (N M is the angle by which the voltage-responsive Hr component lags behind the current-responsive Hr component at unity powerfactor. At any power-factor angle 8, the voltageresponsive Hr component leads the current-responsive Hr component by an angle (0+M-N).

In terms of the circle-diagram, plotted on R,X coordinates, as shown in Fig. 1, the angle, -M,' represents the angle DeoOR by which the currentresponsive phase-shifter l6 causes the line DD" of circle-center displacement to shift, in a leading direction or counter-clockwise, with respect to abscissa-axis or R-axis; and the angle N represents the angle DODso by which the voltage-responsive phase-shifter l4 causes said line DD of circle-center displacement to shift, in a leading direction or counter-clockwise, with respect to the abscissa-axis of R-axis. The angle (NM) is the total angle So between the line DD of circlecenter displacement and the R-axis. This total displacement-angle S0=(NM) of the responsecircle can be varied, without varying either of the other circle-characteristics Q0 or Do, by varying either N or M, or both, without varying the magnitude-ratios n or m. Usually it is more convenient to vary only the voltage-circuit phaseshifter 14 so as to change the angle N, and to suitably calibrate the adjustment in degrees.

A feature of my invention is to provide an adaptable impedance-circle relay in which the angle So of the displacement of the circle-center Go from the origin 0 may be independently adjusted through any desired range, specifically through a range between 30 to the right or left of the ordinate-axis or the y-axis along which lagging line-reactances X are plotted. Thus, the

angle So=(N- M) is varied, through a 60 range,

from Sc=60 to :120", leading with respect to the R-axis or abscissa-axis.

To this end, it is convenient to produce the non-variable 60 part DsoOR of the variable angle So by the current-circuit phase-shifter I6, by assigning such values to the inductance I! and the resistance l8 that the current in the resistance I8 leads the impressed current Iby 60, corresponding to M=-60. Any amount of the resistor-voltage of i8 is tapped off at 2!, and connected in series between the voltage-source E and the restraint-coil 8, to provide the current-responsive component of the energization Hr.

Any suitable voltage-circuit phase-shifter I4 is then used, to shift the impressed voltage E by a variable amount from to 60 in the lagging direction, corresponding to N: anywhere between and 60. Since the voltage-responsive com ponent of the energizing-current in the restraincoil 8 lags the impressed voltage by almost 90, or by any convenient angle between say, 60 and 84, I have shown a voltage-circuit phase-shifter 14 of a form invented by Herbert J. Carlin, as described and claimed in his application Serial No. 583,925, filed March 21, 1945, said phaseshifter comprising a mutual reactor 22 having a primary winding 23 which is connected in series with the restraint-coil 3, and a secondary winding 24 which is connected across the voltagesource E through a variable resistor 25, the value of which may be adjusted, as by a tap or taps 26, from open-circuit or infinity, down to a suitable amount, calibrated according to the corresponding phase-shift angle N, or calibrated according to the corresponding center-shifts slope in degrees, as the center-axis DD is shifted between the limits D60 and D120 in Fig. 1.

This simple type of voltage-circuit phaseshifter 14 shifts the phase-angle N of the applied voltage without substantially varying the magnitude 11 of the response, and is quite sufficient where as much as a or percent variation (or other variation) in the radius R0 and the displacement D0 is within tolerable limits of accuracy. I wish it to be understood, however, that I am not limited to any specific kind of either current-type or voltage-type phase-shifter H5 or i 4.

The constant or controllable variable m, which affects only the center-displacement D0, without affecting either of the other circle-characteristics Q0 or So, is a magnitude-ratio or response-ratio which is controlled by primary or secondary taps 21 on the restraint-energizing current-transformer l2, which may be calibrated directly in ohms of the displacement-distance Do between the circle-center C0 (Fig. 1) and the origin 0.

Fine adjustments. for values between transformer-taps 27, may be provided by the resistortaps 2| on the output of the current-circuit phase-shifter 16. 'When this current-transformer I2 is out out of the current-circuit, the currentresponsive restraint-component is zero, and the center C0 of the circle is at the origin, corresponding to a pure impedance-response of the relay, without any directional discrimination.

If the circle is to pass through the origin, for a directional response, the center-displacement Do must equal the radius Q0, and Equations 11 and 13 show that, under such circumstances, the current-responsive operating-force r1 1 must exactly equal the current-responsive restraint-force h m I when the voltage-source E is unenergized. For larger displacements of the circle-center Co from the origin, hm must be larger than 9. For smaller displacements, hm must be less than 9, producing an impedance-characteristic with a sense of direction, so that the response to lineimpedance is greater in some directions than others.

The center C0 of the circle can thus be shifted up the slope-line DD at the angle So=(NM), by increasing the current-responsive restraintcoefiicient m, in any amount, which may be done by adjustment of the current-transformer taps 21, or the resistor-taps 2|, or both. The circle-center Co can be shifted in the opposite direction, or down from the origin, by reversing the polarity of either the current or the voltage on the restraintside of the relay. None of these center-displacement adjustments has any efiect upon either the radius Q0 of the circle or the angle So along which its center Co is displaced.

In the particular embodiment shown in Fig. 2, I have shown a preferred choice of line-derived current I and line-derived current E, but I Wish it to be understood that my invention is perfectly general, and my relay may be energized in response to any single-phase current I derived from the line, and any single-phase voltage E derived from the line, or voltage otherwise having the same frequency as the current. There is less difference in the response of the relay, between phase-to-phase faults and three-phase faults, if I use the delta line-current and the same phase of delta line-voltage, defining the delta line-current as (IAIB), or the difference between the line-current IA in phase-A, and the line-current In in phase-B. The delta voltage EAB is the voltage across the two line-conductors A and B. However, other combination of line-derived current and line-derived voltage may be utilized, pro-' vided that care is taken. to make allowance for the phase-angle M0 by which the derived current lags behind the derived voltage at unity-powerfactor line-conditions, as previously explained.

In the foregoing explanation of my invention, I have designated the relay-coil 1 as an operatingcOil which tends to close the make-contacts 6, and I have designated the other coil 8 as a restraintcoil. I have adopted this notation as a convenience of description, in accordance with the usual practice of having a distance-relay connected so that it remains in its non-energized position until the occurrence of the fault-conditions to which the relay is designed to respond. I wish it to be understood, however, that my invention is ob viously just as applicable to the type of relay which responds when there is no fault and which drops out during fault-conditions; in other words, a relay having an ohm-characteristic rather than an impedance-characteristic, so that it responds to all impedance-values lying outside of the circle Z2 in 1, and drops out for all impedancevalues inside of said circle, instead of the other way around, as previously explained. Thus, if the force F0 of Equation 3 were a restraining force rather than an operating force, and if the force Fr of Equation 4 were an operating force rather than a restraining force, then the inequali y signs of Equations 5, 7. and 8 would be reversed, indicating an impedance-response for impedancevalues outside of the circle, rather than inside of the same, and necessitating back-contacts rather than the make-contacts 8 of Fig. 2.

While I have indicated my invention in but a single form of embodiment, which I at present prefer, I wish it to be understood, therefore, that the previously outlined changes, and other departures, may be made in the ezrazt details of embodiment Without departing from the essential spirit of my invention, the broad of which is to provide a distance-type relay having a relay-characteristic which can be readily molded to best fit the conditions any particular line. and specifically having separate and independent adjustments for the diameter of the relay-cir is. the slope of the displacement-ee ie of relay-center, and the amount of displacement of the relay-center from the origin of the system of RX coordinates. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language.

I claim as my invention:

1. An adjustable distance-type relay having an operating-circuit magnetizing-means, for producing an operating flux and an operating force responsive to the operating flux; a restraint-circuit magnetizing-means, for producing a restraining flux and a restraining force responsive to the restraining flux; energizing-circuit means,

, for energizing the operating-circuit magnetizingmeans so as to be exclusively responsive to a line-derived current; two restraint-circuit energizing-circuit means for energizing the restraintcircuit magnetizing-means, one in response to a line-derived current and the other in response to a line-derived voltage; and means for making a substantially independent adjustment in each one of any pair selected from the three following constants, to wit: (1) the ratio of the response-ratios of the operating flux and the restraining flux, each of these response-ratios being dependent upon the effective number of fluxproducing turns and the effective reluctance of the magnetic flux-path; (2) the angle between the voltage-responsive component of the restraining fiux and the current-responsive component of the restraining flux at unity powerfactor of the line; and (3) the response-ratio determining the magnitude of the current-responsive component of the restraining flux with reference to the line-derived current which pro-f duces it.

2. An adjustable distance-type relay having an operating-circuit magnetizing-means, for producing an operating flux and an operating force responsive to the operating flux; a restraintcircuit magnetizing-means, for producing a restraining flux and a restraining force responsive to the restrainingfiux; energizing-circuit means, for energizing the operating-circuit magnetizing-means so as to be exclusively responsive to a line-derived current; two restraint-circuit energizing-circuit means, for energizing the restraint-circuit magnetizing-means, one in response to a line-derived current and the other in response to a line-derived voltage; and means for making a substantially independent adjustment in each one of the two immediately following constants, to wit: (1) the ratio of the response-ratios of the operating flux and the restraining flux, each of these response-ratios being dependent upon the effective number of flux-producing turns and the effective reluctance of the magnetic flux path; and (2) the angle between the voltage-responsive component of the restraining flux and the current-responsive component of the restraining flux at unity powerfactor of the line; each adjustment effecting substantially its own constant, without any substantial effect upon the other constant or upon (3) the response-ratio determining the magni tude of the current-responsive component of the restraining flux with reference to the line-derived current which produces it.

3. An adjustable distance-type relay having an operating-circuit magnetizing-means, for producing an operating flux and an operating force responsive to the operating flux; a restraint-circuit magnetizing-means, for producing a restraining flux and a restraining force responsive to the restraining flux; energizing-circuit means,

for energizing the operating-circuit magnetizing-means so as to be exclusively responsive to a line-derived current; two restraint-circuit energizing-circuit means, for energizing the restraint-circuit magnetizing-means, one in response to a line-derived current and the other in response to a line-derived voltage; and means for making a substantially independent adjustment in each one of the two immediately following constants, to wit: (1) the ratio of the response-ratios of the operating flux and the restraining flux, each of these response-ratios being dependent upon the efiective number of flux-producing turns and the efiective reluctance of the magnetic flux-path; and' (2) the responseratio determining the magnitude of the currentresponsive component of the restraining flux with reference to the line-derived current which produces it; each adjustment affecting substantially its own constant, without any substantial effect upon the other constant or upon (3) the angle between the voltage-responsive component of the restraining flux and the current-responsive component of the restraining flux at unity powerfactor of the line.

4. An adjustable distance-type relay having an operating-circuit magnetizing-means, for producing an operating flux and an operating force responsive to the operating flux; a restraint-circuit magnetizing-means, for producing a restraining flux and a restraining force responsive to the restraining flux; energizing-circuit means, for energizing the operating-circuit magnetizing-means so as to be exclusively responsive to straint-circuit magnetizing-means, one in response to a line-derived current and the other in response to a line-derived voltage; and means for making a substantially independent adjustment in each one of the three following constants, to wit: (1) the ratio of the response-ratios 0f the operating flux and the restraining flux, each of these response-ratios being dependent upon the effective number of flux-producing turns and the effective reluctance of the magnetic flux-path; (2) the angle between the voltage-responsive component of the restraining flux and the current-responsive component of the restraining flux at unity power-factor of the line; and (3) the response-ratio determining the magnitude of the current-responsive component of the restraining flux with reference to the line-derived current which produces it.

5. An adjustable directional impedance relay, comprising triply adjustable line-energized relay-means responding to a line-derived voltage and a line-derived current, for producing two separate relay-fluxes and a relay-response to line-impedance values lying within a responsecircle, when the locus of all line-impedance values at the balance-point of the relay is plotted on rectangular coordinates of the line-resistance R and the line-reactance X, said line-energized relay-means having three separate adjustmentmeans, for separately and substantially independently adjusting each of the respective quantities, Q), So and D0, which determine said re-

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