A protective relay adapted to be coupled to a polyphase a-c circuit including electrical apparatus in order to protect said apparatus from overheating comprising: a. means for deriving from said circuit an electric input signal representative of the heating effect which a current in said circuit has on said apparatus; b. an accumulator having a quiescent state and a trip state, said accumulator being supplied with said input signal and being operative to change from said quiescent state to said trip state at a rate determined by said input signal, whereby the operating time of said accumlator varies inversely with the heating effect of said current; and. 1 shows block diagram of the directional static overcurrent relay. 6. 0000001168 00000 n Directional time-overcurrent relay 1MRK 509 025-WEN Version 2.1 Replaces - 1MRK 509 025-WEN Page 2 ABB Network Partner AB Version 2.1 SETTINGS: All settings can be changed while the relay is in normal service. 8. If the input signal again increases above its pick-up level prior to the voltage output of integrator 22 reaching its quiescent magnitude, the resetting action will terminate, and the residual charge then remaining on capacitor 30 will be proportional to the heat remaining in the protected generator. In this option, the secondary device must be rated no more than 125% of rated current of the transformer and the primary no more than 250%. The operating time of high-speed relays is usually expressed in cycles based on the power-system frequency; for example, "one cycle" would be 1/60second in a 60-cycle system. 3. Thus, it has a adjustable time setting as well as a pick up adjustment. A protective relay as defined in claim 1 in which said integrating means comprises a capacitor, the charge on which determines the magnitude of said output signal, and in which said control means comprises a discharge path including a constant current source effective whenever said resetting action occurs to remove said charge from said capacitor at said substantially linear rate. Index. 4.1, where there is a high impedance unit such as a transformer which makes the fault much less for faults beyond the transformer. Electromechanical relays are the oldest generation of relay and have been in use for a long time, they started to be used from 1900 until 1963. A protective relay as defined in claim 1 in which said integrating means comprises a first operational amplifier across which is connected a feed-back loop capacitor. Abstract: The technology of static overcurrent relays has developed very rapidly in the past few years. By way of example, the means 1 could derive an input signal comprising a train of intermittent pulses whose frequency and amplitude both vary with current, as is taught in U.S. Pat. In a typical application the over current relay is used for over current protection, connected to a current transformer and calibrated to operate at or above a specific current level. This relay has to be installed straight only and away from magnetic field. overcurrent relays should be used over a limited length in the 3 feeder sections. 108: OVERCURRENT RELAYS . The modified input signal derived by the condition responsive means 1 is supplied to the input terminal 19 of the accumulator 2 which is operative to change from a normal quiescent state to a trip state at a rate determined by its input signal, whereby the operating time of the accumulator will vary inversely with the square of the signal 17 and thus with the heating effect of the negative phase sequence current in the circuit 10. Static Relays : Development and classification of static relays, Different types of phase and amplitude capacitors, Basic static relays used in protective scheme, Elementary idea about digital & numerical protection. The device includes a novel reset feature such that the time required for the device to take protective action after an overcurrent is detected is reduced by a period of time which is a linear function of the heat remaining in the protected apparatus due to any prior overcurrents. Over the past decades, static relays were used, while nowadays microprocessor relays are used. Low Voltage Breaker - Fuse coordination requires a minimum 0.1 second time margin between the … The electrostatic discharges mean sudden flows of electrons between the charged objects. Title Page. Depending on the time of operation the overcurrent relay is categorized into following types. [AU/Nov/Dec/09/11] It refers to the current or voltage which is used to activate the relay into operation. In an over current relay or o/c relay the actuating quantity is only current.There is only one current operated element in the relay, no voltage coil etc. 71 0 obj << /Linearized 1 /O 73 /H [ 599 187 ] /L 471989 /E 8875 /N 14 /T 470451 >> endobj xref 71 9 0000000016 00000 n 2. No. In the illustrated embodiment of my invention, the function generator 18 approximates a squaring function and produces at a terminal 19 a relatively negative modified input signal which is proportional in magnitude to approximately the square of the signal 17. The scale constant I s is equal to the rated current Ir times the sum of the set value of the switches S1:1, S1:2 and S1:3 plus 0,1. 617,417). 3,262,017), the accumulator 2 could be either an analog RC integrator as shown or a digital counter as is suggested in U.S. Pat. The illustrated pick-up control circuit 32 is comprised of an operational amplifier 34 whose inverting input is connected to resistor 33 and whose non-inverting input is connected to a suitable negative voltage source 35 by resistors 36, 38 and 40. Static overcurrent relay Download PDF Info Publication number US3942074A. In this relay, a symmetrical component segregating network derives a voltage signal proportional to the negative phase sequence current in the stator windings of the protected generator, and this signal is rectified and applied to the input of a non-linear function generator which produces an output signal, the magnitude of which varies approximately with the square of the input signal. This p roduces a retarding effect on motion of the rotor in either di rection. These over-current relays need to coordinate with each other such that the relay nearest fault operates first. Static relay circuit (using analog and digital ic’s) for over current: The Solid State Relay (Static Relay): History of Relay: The static relay are next generation relays .The Solid Static relays was first introduced in 1960’s. 78: TIMER RELAYS AND VOLTAGE RELAYS . d. means connected to said integrating means capable of producing a trip signal when said output signal exceeds a preselected magnitude. Working Principle of Over Current Relay. 4. 10. It is contemplated therefore, by the claims which conclude this specification to cover this and other such modifications as fall within the true spirit and scope of the invention. Gravitational force can affect the relay. For feeder protection, there would be more than one over-current relay to protect different sections of the feeder. Selected pages. The components used by the static relay are very sensitive to the electrostatic discharges. Thus, it can be observed that curve 1 represents a static instantaneous over-current relay with a generally undesirably high transient overreach percentage while curve 2 represents one form of static instantaneous overcurrent relay of the present invention having a reduced transient over-reach percentage. It protects the equipment of the power system from the fault current. 15.2Types of Overcurrent Relay Time delayed Definite Time Relay: A definite time over-current relay can be adjusted to issue a trip output after a specified delay when the relay picks up (PSM>1). This linear reset rate is selected to correspond to the cooling rate of the protected generator 12. If negative phase sequence current increases to a value at which the input signal 17 exceeds the pick-up level, the output of pick-up control circuit 32 will become positive, diode 46 will be forward biased, and there will be a net flow of current into the inverting input of the operational amplifier 50. Under these conditions, the total current at the inverting input of operational amplifier 50 will flow through resistor 53 to the negative terminal 54, the output of reset control circuit 48 will be positive, the diode 57 will block, and the diode 56 will conduct. 1. In cases where the load is fixed and current exceeding the rated value clearly is an abnormal condition for the load, then failure to shut down the motor immediately when overcurrent is supplied will damage the load and the damage may spread through the system. In this case, the negative phase sequence component (I2) of current in the stator of the machine sets up a counter-rotating flux field which causes double-frequency currents to flow in the rotor iron and slot wedges, thereby overheating the rotor. 0000000786 00000 n A protective relay as defined in claim 1 in which said linear rate corresponds to the cooling rate of the apparatus being protected. An improved static relay using solid-state components and having an I2 2 t = K operational characteristic has been developed to furnish the desired protection. In other words, once the relay has responded and the overcurrent causing this response subsides, the amount of time required for the relay to take protective action for any subsequent overcurrents must be decreased by an amount proportional to the heat remaining in the apparatus. 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. using thermal images, Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions, Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors. Define energizing quantity. 1: COMPARATORS AND ASSOCIATED ELEMENTS . So long as the average magnitude of the input signal 17 applied to the same amplifier is less than a pick-up level established by this reference signal, the output of pick-up control circuit 32 will be negative with respect to ground and the diode 46 will block since its cathode potential is fixed at virtual ground. The current derived from the CT is fed to the input transformer which gives a proportional output voltage. 317/27R ... E. W. Kimbark disclosed a static overcurrent relay including a non-linear voltage modifying circuit using zener diodes or the like for modifying the DC voltage applied to a series RC circuit as a function of the amount of overcurrent. In these prior art devices the rate of capacitor discharge is non-linear or exponential which is undesirable for certain applications. No. While I have shown and described one form of my invention, modifications will surely occur to those skilled in the art. 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. Pick-up control circuit 32 will keep the integrator 22 inoperative until the negative phase sequence current exceeds a predetermined critical pick-up level. As is indicated in the drawing, the aforesaid input signal 17 in addition to being supplied to the function generator 18 is also supplied to an input resistor 33 of the pick-up control circuit 32. Fuse - Relay coordination requires a minimum 0.3 second time margin between the curves. When this occurs the output of amplifier 50 will be slightly negative with respect to ground, diode 56 will block, and no current will flow through either resistor 55 or resistor 58. Define operating time of a relay. (a) When the input current to the level detector is less than the threshold value or set value, the output of the level detector is zero. Thus signal 17 is a train of undulating half cycles the amplitude of which is proportional to the negative phase sequence current. relays. 9. 3,413,496-Baude and British Pat. To study and test static overcurrent relay at different current settings and plot the characteristics. A protective relay as defined in claim 3 in which said electrical apparatus comprises a generator and said current is a negative phase sequence current. Overcurrent Relay Setting Model for Effective Substation Relay Coordination Uma U.Uma, I.K.Onwuka Akanu Ibiam Federal Polytechnic Unwana Micheal Okpara University Umudike Abstract: - Relay protection setting of substation plays a very vital role for power system safe operation. Thus it requires to serve the system voltage as well as the system current. This invention relates to the protection of electrical apparatus from dangerous overcurrents and thermal damage caused thereby, and, more particularly, it relates to relays which provide this protection using solid state components. 00 directional overcurrent relay The RXPE 40 is a static, single-phase, voltage- polarized ac directional overcurrent relay mo- dule which measures the component of current that has a phase angle equal to the designed characteristic angle. Over the past decades, static relays were used, while nowadays microprocessor relays are used. Over-current relays can be used to protect practically any power system elements, i.e. 7. 0000000599 00000 n g`b`�� �� 06��c��x\b��+w��wܙ=����,�ya�z-~9$�X���A����@���Ao@� ��� endstream endobj 79 0 obj 83 endobj 73 0 obj << /Type /Page /MediaBox [ 0 0 614.39999 792 ] /Parent 69 0 R /Resources << /XObject << /Im1 77 0 R >> /ProcSet [ /PDF /ImageB ] >> /Contents 74 0 R /CropBox [ 0 0 614.39999 792 ] /Rotate 0 >> endobj 74 0 obj << /Filter /FlateDecode /Length 75 0 R >> stream @��. 91: DIRECTIONAL RELAYS . In many applications it is also desirable that the relay quickly reset after the overcurrent subsides in order that it be in a position to freshly respond to any subsequent overcurrents. Under these conditions the magnitude of the output voltage of the operational amplifier 24 can increase with time in a positive sense with respect to ground, the capacitor 30 begins to charge, and the integrator 22 is enabled to integrate the modified input signal which is produced at terminal 19. The output of pick-up control circuit 32 is supplied through a resistor 44 and a diode 46 to the reset control circuit 48. transmission lines, transformers, generators, or motors. STATIC RELAYS A Static Relay Is A Relay Which Uses Solid State Components Like Transistors, Diodes Etc. Position of relay: Relay can be installed at any location and at any position. relays that operate in a minimum time of approximately 0.1 second. Table of Contents. The Output Signal Is Turned Operated A Tripping Device Which May Be … ... For example, an overcurrent protective relay may have an AC to DC power supply for the input circuit, a level detector circuit and an RC time delay circuit. Fig: 1 Directional static overcurrent relay . 9. H�*��234�31P AsK#=39��K�3�P�%��+�� � ��� endstream endobj 75 0 obj 44 endobj 76 0 obj 7217 endobj 77 0 obj << /Type /XObject /Subtype /Image /Name /Im1 /Width 2560 /Height 3300 /BitsPerComponent 1 /Decode [ 1 0 ] /Filter /CCITTFaxDecode /DecodeParms << /K -1 /Columns 2560 /Rows 3300 /BlackIs1 true >> /ColorSpace /DeviceGray /Length 76 0 R >> stream It is used for short Others have heretofore suggested that the reset action of overcurrent relays be delayed for various reasons. are required to construct this protective relay.. Thus special maintenance is provided to the components so that it does … For example, the quiescent magnitude of the voltage across the integrating capacitor can be selected to be that voltage at which the capacitor is fully charged, and the level detector could be designed to be activated at a predetermined low magnitude of the integrator ouput voltage (e.g., near zero volts). While early comparators used discrete transistor circuits, modern designs use operational amplifiers. The preferred embodiment of such a function generator is more fully described in my copending application mentioned above. Since the discharge current is of a constant magnitude, the value of which is determined by the output voltage of reset control circuit 48 and the ohmic value of resistor 58, proper selection of these parameters will provide a desired linear rate of discharge of capacitor 30. LA PUNTIMATIC S.n.c. 11. time current characteristics of static over current relay, components of instantaneous over current relay, instantaneous over current relays. Integrating means 22 is normally reset, in which state the charge on capacitor 30 has a quiescent magnitude near zero volts which is determined by the forward drop of diode 28. Microcontroller based overcurrent relay, VPL – 01 THEORY: Static relays are those relays which consist of electronic circuitry to develop all those characteristics achieved by moving parts in an electro-magnetic relay. The term ‘static’ implies that the relay has no moving mechanical parts in it. A protective relay adapted to be coupled to an electric current circuit including electrical apparatus in order to protect said apparatus from overheating comprising: a. means for deriving from said circuit an input signal representative of the heating effect which a current in said circuit has on said apparatus; b. normally reset integrating means having an input terminal to which said input signal is suplied and an output terminal at which is developed an output signal having a magnitude that increases with time when the integrating means is operative; c. control means for enabling said integrating means to operate whenever the magnitude of said current exceeds a predetermined pick-up level, and for resetting said integrating means in delayed response to said current subsiding below said pick-up level, the time delay resetting action reducing said output signal at a predetermined substantially linear rate toward a quiescent magnitude near zero; and, thereby approximating the cooling characteristic of said electrical apparatus. The only discharge current path is through resistor 58, and since the inverting input of operational amplifier 24 remains at virtual ground the magnitude of this discharge current is the same as was flowing through resistor 58 prior to pick-up. This relay is described and claimed in my copending application Ser. This relay has to be installed straight only and away from magnetic field. 18 FUNDAMENTAL RELAY-OPERATING PRINCIPLES AND CHARACTERISTICS Time delay is obtained in induction-type relays by a "drag magnet," which is a permanent magnet arranged so that the relay rotor cuts the flux between the poles of the magnet, as shown in Fig. The resetting action of my relay is designed to approximate the cooling curve of the generator rotor which in this case has been estimated to be a linear function of time, and consequently the decrease in the operating time for a subsequent overcurrent will be proportional to heat remaining in the rotor. In electrical systems, a static relay is a type of relay, an electrically operated switch, that has no moving parts. Preferably the reset control circuit 48 consists of an operational amplifier 50 whose non-inverting input is connected to common by resistor 52 and whose inverting input is connected to pick-up control circuit 32 via the resistor 44 and the diode 46 and to a suitable negative voltage source 54 by a resistor 53. ����i⏖��������i'Q�e�k�,�}W~��w�ֿ����������u��׿������ؘ�t#!\��$5��tC�����F��;@а�(�!��[Ap���Ak���N!� N�!+ pD0����MUv��߅� ޽�^�_N�?�����������U����M{�����~R*!��kԇ�k��%�(?�B�������ؿ�! 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 drawing, the single FIGURE of which is a schematic circuit diagram of a relay embodying a preferred form of the present invention. Static overcurrent relay is made in the form of a single unit in which diodes, transistors, resistors, capacitors etc., are arranged on printed board and are bolted with epoxy resin. SGC12A/B Static Negative Sequence Time Overcurrent Relay for Generator Protection Author: GE Multilin Subject: Instruction Manual Keywords: SGC, SGC12A, … For The Measurement Or Comparison Of Electrical Quantities. A protective relay as defined in claim 6 in which said control means comprises second and third operational amplifiers connected in series with one another, said third operational amplifier being connected to said feed-back loop capacitor. For LRG systems, the pickup for the relay on the main breaker is generally at 10% of the maximum single line-to-ground fault current. A solid state protective device is disclosed which protects electrical apparatus from heat damage due to overcurrents, particularly one which protects electrical generators from damage caused by heat due to excessive negative phase sequence currents. In the accumulator 2, the output voltage of integrator 22 is monitored by the level detector 60, and when this voltage has increased to a predetermined magnitude a trip signal 62 will be emitted which causes the trigger circuit 64 to produce an appropriate response signal 65 which may be used to open a circuit breaker or activate an alarm or warning device (not shown). These relays have earned a … APPARATUS REQUIRED: Microcontroller based overcurrent relay, VPL 01 THEORY: Static relays are those relays which consist of electronic circuitry to develop all those characteristics achieved by moving parts in an electro-magnetic relay. 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