Separate earth fault relay provided makes earth fault protection faster and more sensitive. See U.S. Pat. The output signal of function generator 22, developed at output terminal 31, is supplied to an integrator 46 which preferably comprises a time dial 47 and an integrating operational amplifier 48. 2 illustrates a protective relay circuit embodying my invention and having the extremely inverse time-overcurrent characteristics shown in FIG. The diodes 32 and 33 when used are poled so as to serve the purpose of preventing a positive voltage from appearing at the output terminal 37 of the function generator whenever the inverting input of the amplifier 24 is negative due to the magnitude of the input signal being less than that of the bias signal. The particular curves 1A-10A of the family shown in FIG. Another resistor 131 is connected between the source 129 and the juncture of resistor 128b and diode 130. Another approach that has heretofore been proposed in the static overcurrent relay art is to use log and antilog function generators ahead of an integrator. Static over current relays • The output of this summation C.T is fed to an auxiliary C.T. The inverting input is connected to rectifier 14 via an input resistor 61, and the output is connected to integrator 46 through a diode 62. Referring now specifically to the drawings, the family of curves A shown in FIG. A pickup level detector and reset circuit 45 keeps the integrator 38 inoperative until the average value of the rectified input signal is above a preselected value which indicates that excessive current is flowing in protected line 10. A fourth and lowest gain likewise becomes effective when the input rises beyond the maximum limit of the third range, at which point diode 42a begins to conduct. In an over current relay or o/c relay the actuating quantity is only current. The closing of contact 70 activates tripping circuit 71 to open a circuit breaker 72 in protected line 10. The output of operational amplifier 127 is connected to the output terminal 138 of function generator 120 through a diode 135. The gain of function generator 22 changes depending on the magnitude of the input signal. Generally, inverse time-overcurrent protective relays respond to the magnitude of a circuit quantity, such as alternating current or its negative phase sequence component for example, becoming excessive. If function generator 22 were not present, the relay's time-overcurrent characteristic would have a slope of approximately -1 throughout its range. As there are multiple kinds of relays, these devices will have applications in various industries across electrical, aeronautical, medical, space, and others. For this reason, small signals take a relatively longer time to produce a trip signal than do larger signals. The output of function generator 22 developed at the output terminal 37 is applied to an integrator 38 comprising a "time dial" 39 and an integrating operational amplifier 40. • Definite time overcurrent relays • Inverse-time overcurrent relays with definite minimum time (IDMT) • Directional overcurrent relays Static Overcurrent Relay • A. Static Instantaneous Overcurrent relay • The current derived from the CT is fed to the input transformer which gives a proportional output voltage. This happens so as the CT saturation occurs at a later stage but as soon as CT saturation occur there will not be any flux change and hence the current output of CT will become zero and hence the time of operation will nearly become constant. Similar to the first embodiment, the gain of the function generator 120 varies with the magnitude of the modified input signal applied to terminal 118. 2 which is used to produce a relay having an "inverse" characteristic. It is still another object of my invention to provide an inverse time-overcurrent relay which is operable over an extremely wide range of input currents and operating times. By substituting the function generator 22a for the function generator 22, the relay shown in FIG. The particular curves of family C represent I2 t operating characteristics for different K factors, K being determined by the particular machine being protected. 1 is a chart of operating time plotted against multiples of overcurrent used to illustrate the operating characteristic of an "extremely inverse" time-overcurrent relay constructed in accordance with a first form of the present invention. Type 49/50/51 overload relays The Type 49/50/51 overload relay provides three important functions for the protection of a motor Packaged in one case, the three functions are individually adjustable, allowing optimum protection without compromising the various elements. The static relay consumes very less power because of which the burden on the measuring instruments decreases and their accuracy increases. A comparison of the curves 1A and 1B will reveal that the operation of my relay has been slowed by the function generator at low overcurrents (e.g., less than two times pick-up) but hastened at higher overcurrents (e.g., between 2 and 8 times pick-up) compared to the hypothetical relay. This input signal is supplied to a non-linear function generator composed of an operational amplifier with an appropriate feed-back loop. Model overcurrent overcurrent or earthfault boards size † inst † inst † inst MCGG 22 14 MCGG 42 26 MCGG 52 38 MCGG 53 28 MCGG 62 36 MCGG 63 16 MCGG 82 48 Application The relay can be used in applications where time graded overcurrent and earth fault protection is required. Overcurrent Coordination Page 3 Qual-Tech Engineers, Inc. 8. If the modified input signal continues to increase from the magnitude it resumed when the input signal has reached its range-changing value, the second, third and fourth gains may again become effective. The shapes of these characteristic curves are very similar to those of the electro-mechanical counterparts of the present invention. While electromechanical relays have performed well for many years, improved solid state varieties are now becoming more popular. 3a) whose instantaneous magnitude is proportional to the instantaneous magnitude of alternating current in the protected line 14. ACR Types ACR11B, ACR11C, & ACR11E Reclosing Relay – ACR ALPS Type ALPS Advanced Line Protection System – alpsman B-30 Type BS30 Bus Differential Relay UR Series – b30man When the modified input signal increases to about 7 volts the potential at this junction becomes positive with respect to ground, the diode 130 will begin to conduct, and when this occurs the input resistance of the operational amplifier 127 decreases because of the parallel combination of resistors 128a and 128b. The reset time of the relay is very less. The input signal after emerging from buffer amplifier 169 is applied to a level detector comprising operational amplifier 172 whose non-inverting input is connected to common by resistor 174 and also to its output by resistor 174a. When applied to the function generator 22 this signal causes the gain to switch to its second constant value during part of each half cycle. In accordance with my invention, the feedback loop of operational amplifier 24 includes an additional branch, in parallel with resistor 21, comprising a second operational amplifier 34 which is connected at its inverting input to the output terminal 31 of the function generator by resistor 35a and at its output to the inverting input of operational amplifier 24 through resistor 35 and diode 43. Since the rate of integration of the integrator 38 is proportional to the average value of the output signal produced by the function generator, the length of time required to produce the trip signal is inversely proportional to the magnitude of the function generator output. Instantaneous, Definite Time, Inverse-Time OverCurrent Relays Static relays are mainly made with semiconductor switches like thyristor. Preferably the resistance values of feedback resistors 124 and 125 and input resistor 122 are selected such that amplifier circuit 116 has a gain of a first predetermined amount (e.g., 5) when contact 126 is open and a second predetermined amount (e.g., 1) when the contact is closed and resistor 124 is shorted. The value of the bias due to source 177 is chosen so that the contacts close at an input signal and therefore at an overcurrent higher than that which causes the fourth gain of function generator 120 to become effective. FIG. To illustrate the effect of the multiple gains of my function generator 22, I have shown in FIG. 3b shows a larger input signal 104 whose peak magnitude exceeds the breakpoint magnitude 101. This scheme eliminates the leading problems mentioned above. The alternating current output of signal sensor 12 is rectified by a full wave rectifier 14 and fed through resistors 16 and 18 to derive a unipolar voltage input signal of variable amplitude representative of the current in the protected line 10. All rights reserved. 3a . Static overcurrent relay is made in the form of a single unit in which diodes, transistors, resistors, capacitors etc. Positive peak 108 would be produced in output signal 102 were it not for the presence of blocking diodes 32 and 33, which prevent the output from going above zero. Relay contact 70, which is normally in an open position, closes as a result of current in coil 69. This gives a much better approximation to the desired relay characteristics by slowing relay operation for current values at or near pick-up. The static relay gives the quick response, long life, high reliability and accuracy and it is shockproof. The input signal is supplied to the input terminal 20 of a function generator 22, with the polarity of this terminal being positive relative to a common potential bus (shown as ground). The value of the input signal at which range changing means 168 operates is illustrated by vertical line 6 in FIG. FIG. 1. This scheme has the disadvantage that it requires relatively large input signals and it imposes a relatively high burden on the instrument current transformers. The instantaneous and time delayed overcurrent protections with RXIG are … This relationship may be expressed by the formula In t=k where I is the circuit quantity being monitored, n is an appropriate power determined by the relay's eventual application, t is the response time of the relay, and k is a constant. For increasing values of I2 within this range, the operating time of a relay which is adjusted so that K = 2 will decrease from 250 seconds to approximately 5 seconds. The definition is: Activating the contact unit using electromagnetic attraction, which is produced when electric current exceeding the specified value flows to the electromagnet; the voltage and current (input signal) applied to the coil opens or shuts the contact. Resistor 128b initially has no effect on the gain for the reason that diode 130 is not conducting because the potential of its anode is then relatively negative with respect to its cathode which is held at virtual ground. The overcurrent detection circuit will operate as soon as overcurrent is detected and the (X) relay will operate less than 0.5 s later. These developments have produced changes in the way they are applied from electromechanical (EM) relays and, further, offer many new features to provide greater utilization than previously possible. 2 will operate with characteristics closely approximating those of an inverse electro-mechanical overcurrent relay, as is illustrated by family of curves A in FIG. As mentioned above, the rate of integration of integrator 38 is proportional to the average value of the output signal of function generator 22. US3942074A US05/509,879 US50987974A US3942074A US 3942074 A US3942074 A US 3942074A US 50987974 A US50987974 A US 50987974A US 3942074 A US3942074 A US 3942074A Authority US United States Prior art keywords current protective relay magnitude capacitor The illustrated integrator 46 includes operational amplifier 48 having capacitive feed-back (via integrating capacitor 50 in parallel with diode 51), but an RC circuit or other integrating means could be substituted as is well known in the art. Generally, circuit protective overcurrent relays are classified by the slope of this curve as either "inverse", "very inverse" or "extremely inverse". 2). This device is used for the protection of generators from overheating caused by negative phase sequence currents due to unbalanced faults or loads. The reset time of the relay is very less. The reference level is selected such that the average magnitude of the input signal will equal or exceed it whenever the current in protected line 10 rises to at least a certain percent higher than normal. In Conference Paper CP62-1091, presented to the American Institute of Electrical Engineers in June 1962, E. W. Kimbark disclosed a static inverse timeovercurrent relay including a function generator, or voltage modifying circuit, consisting of a network of diodes and resistors which alter the d.c. voltage applied to an integrating RC circuit as a function of the amount of overcurrent in the protected line. The trip signal turns on transistor 63 thus energizing a relay coil 69. When the level of the reference signal is exceeded, a trip signal is emitted which may be used to activate an appropriate warning device or to trip a circuit breaker in the protected line. 1 is a chart of operating time plotted against multiples of overcurrent used to illustrate the operating characteristics of relays constructed in accordance with the present invention. Delay in operation: Easily provided Fig. Historically inverse time-overcurrent protective relays were of the electro-mechanical type. 2 illustrates the first embodiment of my invention and shows an alternating current circuit or line 10 to which signal sensor 12 of my relay is coupled. 4 is a schematic circuit diagram of the negative phase sequence overcurrent relay embodying my invention. The inverting input is connected to rectifier 18 via an input resistor 52, and the output of the amplifier 46 is connected to integrator 38 by a diode 53 and resistor 53a. The term ‘ static ’ implies that the relay has no moving mechanical parts in it. In order to achieve the very inverse curves B shown in FIG. 2 is a schematic circuit diagram of the extremely inverse relay embodying my invention. If you are having trouble finding the instruction manual you are looking for then please reach out! Operational amplifier 24a is also supplied with a bias signal induced by a relatively small negative voltage source 28a. 3a and FIG. © 2004-2021 FreePatentsOnline.com. The JEM 1357 standard (Inductive and Static Protective Relays for Three-phase Inductive Motors) stipulates that the must operate value should fall between 105% and 125% The function generator 22 is composed of a first operational amplifier 24 having its non-inverting input connected to the common potential bus by resistor 25. The time dial consists of a series of resistors R1 - R10 accessed by a rotary switch 49. d. integrating means having an input terminal to which said output signal is supplied and being operative whenever said quantity becomes excessive for producing an integrated output signal which increased in magnitude at a rate dependent upon the value of said integrating means; This invention relates to the protection of electric circuits and apparatus from dangerous overcurrents, and more particularly, it relates to relays which offer this protection using solid state components. B. If the input signal exceeds this maximum value and enters a second predetermined range, function generator 22 will have a second gain which is less than the first because the branch of the feed-back loop containing resistor 29 and zener diode 30 then becomes effective and the total resistance of the loop decreases (e.g., to about 20K ohms). Privacy Policy No. 200 millivolts) when the current in the protected line is normal. The resistance value of resistor 174a is selected such that contacts 126 and 149 once closed will remain closed until the average magnitude of the input signal drops more than 10 percent below that value (e.g., 2 volts) which is required to cause range changing means 168 to become effective. A current sensor well suited for this purpose is described in the copending application of Little (supra), although other sensors could be used and other circuit quantities could be responded to if desired. The curves are plotted on a log-log scale with the ordinate representing the log of the time of operation of the relay and the abscissa representing the log of multiples of pick-up current, i.e., multiples of the minimum current which will cause the relay to respond. In digital relays there are two states i.e., ON and OFF which can be referred to 1 and 0 state. generation, <- Previous Patent (Ground fault detecto...). Voltage source 46a is typically set at 15 volts with respect to common. This factor is the nth power (n = 2 for the illustrated function generator) of the ratio of the amounts of amplifier 116 gain before and after the range is changed, and it prevents any discontinuity in the operating characteristic at the relay when the modified input signal decreases due to the reduced amount of gain. 1 correspond to different "time-dial" settings as will be more fully explained below. a. means for deriving from said circuit a unipolar input signal of variable amplitude representative of said quantity; b. means for providing a predetermined bias signal of relatively low magnitude; c. function generating means to which said input signal and said bias signal are supplied in polarity opposition, said function generating means being operative to produce an output signal which varies as a non-linear function of the sum of said signals, d. means connected to said function generating means and operative whenever the value of said circuit quantity becomes excessive for integrating said output signal in order to produce an integrated output signal; and. A solid state protective device is disclosed which monitors an electric quantity such as current in a protected circuit and which responds to abnormal conditions by activating a circuit breaker or warning device after a period of time which is related by a non-linear inverse function to the magnitude of the circuit quantity being monitored. An overcurrent relay responsive to the negative phase sequence component of line current and having an I22 t=k operating characteristic over a wide range of current values (e.g., 35:1) would ideally provide the required protection in this application. Since the bias is of opposite polarity to the unipolar voltage input signal and since the bias is a significantly higher percentage of a small signal than of a larger one, the bias even further retards the rate of integration for small signals while having little effect on larger signals. FIG. Furthermore, this approach will not match the operating characteristic of extremely inverse relays at high current values, since the slope in this region must decrease as mentioned above. The function generator 22 is composed of an operational amplifier 24 whose non-inverting input is connected to the common potential bus through a resistor 26 and whose output is connected to an output terminal 37 of the function generator via diode 33. In one case, as is shown in FIG. The output signal of the function generator is integrated by an operational amplifier having capacitive feed-back, and this integrated output signal is compared to an appropriate reference signal by an operational amplifier used as a level detector. Static relays offer the advantage of higher sensitivity than purely electromechanical relays, because power to operate output contacts is derived from a separate supply, not from the signal circuits. Functions: 1 relay can perform various functions. This invention will be more fully understood and its various objects and advantages will be more fully appreciated from the following description taken in conjunction with the accompanying drawings in which: FIG. It is contemplated, therefore, by the claims which conclude this specification to cover all such modifications as fall within the true spirit and scope of the invention. In carrying out my invention in one form, I provide a suitable signal sensing mechanism, for example a current transformer used to monitor alternating current in a protected circuit, and full wave rectification means to provide a unipolar voltage input signal proportional to the monitored circuit quantity. "Electronic Trip Control For A Low Voltage, High Current Breaker," David Little, 1968 - Thesis submitted to Faculty of The Moore School of E.E. 100 ABB ITE-47H Analog - Static Undervoltage Relay ITE-47H ITE-47H 101 ABB ITE-50H Analog - Static Instantaneous Overcurrent CAPE_IOC_1 PFD+GFD CAPE_IOC_1 102 ABB ITE-51I Analog - Static Overcurrent I CAPE_TOC CAPE_TOC 103 ABB ITE-51Y Analog - Static Overcurrent VI CAPE_TOC_IOC CAPE_TOC_IOC IPS v1.00 Printed: 07/06/2017 6:00:13 PM Page 4 of 597 The family of solid line curves A is characteristic of the inverse relay (FIG. 4 shows an alternative function generator 22a that can be used in a second embodiment of my invention to produce a relay having an inverse time-overcurrent operating characteristic. 1 depict the operating characteristics of an extremely inverse overcurrent relay embodying my invention in one form. The position of the switch determines the number of resistors in series between output terminal 31 and the non-inverting input of operational amplifier 48, thus determining the time constant of integrator 46. What I claim as new and desire to secure by Voltage Relays, Timers, Annunciators, Earth Fault & Overcurrent Relays, Frequency Relays, AMF & Synchronising relays, Generator control & safety units, Static Relays, Motor control Relays The relay consists mainly of a input current transformer (for isolation), filter circuits, microprocessor, However, in order to achieve relay coordination in electric power delivery and distribution systems, it is desirable that these new solid state relays have operating characteristics similar to those of the older electro-mechanical models. When the input signal subsequently falls below its pick-up level, due to the protective operation of the relay or to prior subsidence of the disturbance causing excessive negative sequence current, it is essential that the relay not be completely reset until the generator rotor has time to cool down. The integrated signal provided by the integrator 38 is fed to a level detector 54 which preferably comprises an operational amplifier 55 whose non-inverting input is connected to the common potential bus through resistor 56 and whose inverting input receives a signal from summing point 57. See U.S. Pat. 3, use of my novel range changing feature will almost double the operating range of my device by producing the straight line portion 9 of the K = 2 characteristic curve for overcurrents greater than 0.7 per unit, shown by vertical line 6. If the quantity being monitored increases above a predetermined pick-up level, the output voltage of the function generator is integrated, and after a delay determined by the time required for the integrated voltage to reach a preset reference level, a trigger circuit is energized and the required protective action will be effected (e.g., a circuit breaker is opened or an alarm is sounded). Particular "time dial" settings, as determined by rotary switch 49, correspond to particular curves in the family of characteristic curves A shown in FIG. Based on Characteristics some … Accordingly, it is the purpose of the reset control circuit 162 to delay the discharge of the integrating capacitor 151 whenever the pick-up circuit 153 drops out, and this feature of the illustrated relay is the subject matter of my copending application Ser. 9. 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