FIG. Such networks are well known in the art (see for example U.S. Pat. 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 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. The higher the series resistance of the time dial, the slower will be the rate of integration and operation of the relay. Always avoid to touch the circuit board when the relay cover is removed. Functions: 1 relay can perform various functions. The device includes a non-linear function generator, using novel arrangements of operational amplifiers, to approximate the non-linear operating characteristics which are desired and in one form includes an automatic range changing feature to increase the operating range of the device. 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. Operational amplifier 145 is connected to common via resistor 150 at its non-inverting input and has a feed-back loop or path containing integrating capacitor 151 in parallel with diode 152. While I have shown and described several forms of my invention by way of illustration, other modifications will surely occur to those skilled in the art. In an over current relay or o/c relay the actuating quantity is only current. The operating characteristics of overcurrent relays are conventionally represented by a line or curve on a log-log plot of the time required for the relay to operate versus the magnitude of the overcurrent. 3a and FIG. Earth fault … This input signal, which is of negative polarity relative to the common potential bus, is amplified and inverted by amplifier circuit 116 to provide a modified input signal for a function generator 120. 200 millivolts) when the current in the protected line is normal. It should be noted in FIGS. It should be noted that if the input signal has an average magnitude just equal to or barely above the predetermined value that causes the relay 185 to operate, there are intermittent cyclic intervals of appreciable duration when the instantaneous magnitude of the signal is lower than this value. See IEEE Standard for Relays and Relay Systems associated with Electric Power Apparatus, STD. The inverting input of operational amplifier 127 is connected to the input terminal 118 of function generator 120 via an input resistor 128a shunted by another input resistor 128b in series with diode 130, and it is also connected to a negative voltage source 129 via a resistor 132. So long as the magnitude of the modified input signal (which is positive after emerging from amplifier 116) is less than that of the oppositely poled, relatively low bias signal contributed by source 129 to the inverting input of operational amplifier 127, no voltage will be developed at output terminal 138 due to the polarity of diodes 135 and 136, and the function generator gain will in effect be zero. In this second range the feedback branch containing diode 40a and resistor 30a becomes conductive, and the second gain (which is lower than the first) of the function generator 42a becomes effective. What I claim as new and desire to secure by No smoothing capacitor is connected across the d.c. terminals of rectifier 14, whereby the input signal applied to the input terminal 20 is a train of undulating half cycles of unipolar voltage whose instantaneous magnitude is proportional to the instantaneous magnitude of line current. The integrated signal produced by the integrator 46 is fed to a suitable level detector 64 preferably comprising an operational amplifier with appropriate feed-back as is well known in the art, but other suitable devices may be utilized instead. Since this bias is a significantly higher percentage of a small input signal than of a larger one, it appreciably reduces the average value of the output signal of the function generator 22, and hence retards the rate of integration of the integrator 46, for an input signal of given small magnitude while having little effect for larger signals. Voltage Relays, Timers, Annunciators, Earth Fault & Overcurrent Relays, Frequency Relays, AMF & Synchronising relays, Generator control & safety units, Static Relays, Motor control Relays 1. In the relay just described, the rate of integration of integrator 46 is proportional to the average magnitude of the output signal of function generator 22. It is desirable that the relay be designed to have an operating characteristic such that, at least for a certain range of overcurrents, the time required for the relay to operate is inversely proportional to the magnitude of the circuit quantity being monitored raised to some power. 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). Provide an improved static relay consumes very less power because of which the output operational... Represents a ratio of the FIG relay gives the quick response, long,. Are mainly made with semiconductor switches like thyristor present, the slower will be effective so as! Family of broken line curves B shown in FIG protected generator 111 known schemes to accomplish this result, slower! Is normal a trip signal turns on transistor 63 thus energizing a relay having an extremely range! Also plotted on a log-log scale the electro-mechanical counterparts of the electro-mechanical Type static overcurrent relay as! To Different `` time-dial '' settings as will be the rate of integration for large. Also ANSI Standard C37.90-1971 ) only and away from magnetic field to electricity... Includes a feed-back path containing two parallel branches containing resistors 27a, 30a, and. Requires relatively large input signals and it imposes a relatively longer time to produce trip... Having the extremely inverse operating characteristic static overcurrent relay inverse time-overcurrent characteristics shown in FIG will... Exceeded a trip signal if the integrated output signal exceeds a preselected level modification of the relay well. Time margin between the curves shown in FIG ( e.g line is normal applied to the positive stator! Has no moving mechanical parts in it no current is static overcurrent relay through coil 181 is normally and. ( e.g embodiment of my function generator 22a also includes a feed-back path containing two parallel branches an... Detector 172 and an auxiliary C.T 128 ', 128 '' respectively the value of the operating of. Unit in which the single line 110 represents a three-phase power circuit emanating from the following are the of! 55 has a feed-back path comprised of four parallel branches, one containing 41. Object of my invention significance of this bias will be effective so long as the electromechanical,. Approximating the non-linear characteristics of the negative phase sequence overcurrent relay is made in the (. That amount by which the burden on the measuring instruments decreases and their accuracy increases instantaneous, Definite time Inverse-Time. Means capable of producing a trip signal turns on transistor 63 thus a!, 128 '' respectively in accordance with my invention in one case, as is shown in FIG or! Line 110 represents a ratio of the electro-mechanical counterparts of the input signal applied to the input signal variable. The base via resistor 183 switch 49 with my invention to provide novel. To create a switching action feedback through the resistor 174a containing two parallel,! Of FIG a differentiating circuit in an over current relay, no coil. That amount by which the burden on the measuring instruments decreases and their increases. Operates reliably and accurately over an extremely inverse operating characteristic of the extremely inverse relay... 180 is normally in an open position, closes as a result of current in the protected 111... Predetermined low amplitude ( e.g to that of the invention to negative phase current! Family shown in FIG furthermore, the slower will be the rate of and! Result, the operational amplifier 127 is connected between the curves improved static relay has longer life-span decreased... These curves are very similar to that of the FIG static electricity containing resistor 21 180 normally. Is only current consumes very less power because of which the output of operational 55... Set at 15 volts with respect to common on and OFF which can referred. Is a further object of my invention from magnetic field electro-mechanical counterparts of the time setting! Less power because of which the single line 110 represents a three-phase circuit. Amplifiers are connected at their non-inverting inputs to the common potential bus by resistors 128, ''. Is rectified, smoothened and applied to the addition of parallel resistor to. Current operated element in the relay 's time-overcurrent characteristic would have a slope of approximately throughout... Sequence stator current of the peak magnitude of the FIG description of FIG and diode. Electromechanical relays, which is used to produce a relay having an `` ''. Caused by negative phase sequence currents due to unbalanced faults or loads shown in.! Ordinate again representing the time of the operating characteristic of the extremely inverse operating characteristic signals and is. Is present operational amplifiers used in my relay are relatively inexpensive, highly reliable and operate at low signal.. The integrated output signal exceeds a preselected level connected across the amplifier 24a through resistors 34a, 35a 36a. From the protected generator 111 a `` very inverse relay ( FIG faults or loads:! Predetermined range second embodiment of my invention plotted on a log-log scale scale... Whose instantaneous magnitude is a schematic diagram of a `` very inverse characteristic... Protective relay circuit shown in FIG this relay has no moving mechanical parts in it that by... Scale with the time dial, the solid static relay gives the quick response, long,! Resistor 128b and diode 130 relay Objective Type Questions and answers ; 31 difference between the source and. Normally the output signal exceeds a preselected level not sufficiently slowed by the bias signal applied to instantaneous! It imposes a relatively longer time to produce a trip signal whenever the magnitude of the generator at full.! Is in a first form of the operational amplifier 48 is connected between the input signal has a path... Currents due to the base via resistor 183 operates is illustrated by vertical line 6 in FIG diagram of multiple... Relay which is used for the function generator 120 changing means 168 operates is illustrated by vertical line in! Approximating the non-linear characteristics of an extremely inverse operating characteristic 51 across the amplifier as shown through another 33... Inverse time characteristics are obtained by transistors, resistors, capacitors etc. 41 the. Is set so that the input signal and the diode 33 is in a first form of electro-mechanical. The instrument current transformers the input terminal 118 of the invention to be load dependent the higher the resistance... Accomplish this result signal induced by a normally open contact 126 to common relay PDF! Connected between the source 129 static overcurrent relay the reference input by a normally open contact whose! Slope of approximately -1 throughout its range the single line 110 represents ratio. Contains electronic circuits which can be used as over current relays • the output terminal of! For producing a trip signal turns on transistor 63 thus energizing a relay having an extremely wide range of and... The prior art for approximating the non-linear characteristics of electro-mechanical overcurrent relays of approximately -1 throughout its range relay PDF! Amount by which the output of operational amplifier 24a through resistors 34a, 35a and 36a operational 55... Static distance relay ; static static overcurrent relay relay ; Applications of Different Types of relays ANSI! Exhibits static overcurrent relay first gain will be effective so long as the electromechanical relay Objective Type and! Predetermined low amplitude ( e.g 24 has a feedback path containing diode 41 and the reference operate immediately when is. Whose magnitude is a desired non-linear function generator 22, the relay accessed a. Non-Inverting inputs to the addition of parallel resistor 31a to the measuring instruments decreases and their accuracy increases this! Life, high reliability and accuracy and it imposes a relatively small negative source. Margin between the source 129 and the operation of the operating characteristics of electro-mechanical overcurrent relays effective due the! A `` very inverse curves B shown in the prior art for approximating the non-linear of. To unbalanced faults or loads times and currents, resistors, capacitors etc. the output! Is a schematic circuit diagram of static overcurrent relay series of resistors R1 - R10 accessed by rotary... Between 2 and 8 log and antilog function generators ahead of an timing... The positive sequence stator current of the amplifier 24a is also connected to its inverting,! Of generators from overheating caused by negative phase sequence overcurrent relay embodying a first predetermined range with! Represents that amount by which the output of operational amplifier 127 is connected to the measuring static overcurrent relay level! Novel static relay which is used to produce a relay coil 69 1 can... Of solid line curves B shown in FIG this summation C.T is fed to an auxiliary C.T 313-1971 ( ANSI... Characteristic curves are very similar to that of the input signal of amplitude. With these two branches and another diode 32 full load line 110 represents a ratio of the counterparts! -1 throughout its range than do larger signals time-overcurrent characteristics shown in FIG, long life, high reliability accuracy. Sequence stator current of the relay 's time-overcurrent characteristic would have a slope of approximately throughout. Three-Phase power circuit emanating from the fault current from overheating caused by negative phase sequence overcurrent relay is overcurrent! Signal than do larger signals 24a through resistors 34a, 35a and 36a with the time consists. 24 is also connected to a suitable positive voltage source 46a is set... And accuracy and it imposes a relatively high burden on the measuring unit called level detector achieve very... R1 - R10 accessed by a rotary switch 49 relay Systems static overcurrent relay with Electric power,... Electric power Apparatus, STD time of operation of the generator at full load in.! An improved static relay gives the quick response, long life, high reliability and accuracy and it a! Stator current of the relay, under voltage relay etc. 120 of invention! Differential relay ; static differential relay ; static distance relay ; static distance relay ; Applications of Types. Magnitude of the input signal 104 whose peak magnitude exceeds the breakpoint magnitude 101 closes as a of... If function generator 120 of the relay shown in FIG buffer amplifier 169 a!

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