time current characteristics of static over current relay, components of instantaneous over current relay, instantaneous over current relays. Whenever the input signal 17 subsequently subsides below a predetermined level which ordinarily is the same as the pick-up level, the output of the reset control circuit 48 becomes positive again and the capacitor 30 begins to discharge. Delay in operation: Easily provided 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 A protective relay as defined in claim 10 in which said control means is effective in response to said current subsiding below said pick-up level for discharging said capacitor at said substantially linear rate. 8. This p roduces a retarding effect on motion of the rotor in either di rection. 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. 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 An "Over Current Relay" is a type of protective relay which operates when the load current exceeds a preset value. Where this is so, a current magnitude device can be used, such as a fuse or an instantaneous relay or trip device and selectivity can be obtained by grading current. A protective relay as defined in claim 1 in which the resetting action of said control means is terminated in the event said current again exceeds said pick-up level prior to said output signal being reduced to its quiescent magnitude. Functions: 1 relay can perform various functions. di Musiani Franco & C. Siemens Ag, 1000 Berlin Und 8000 Muenchen, De. The preferred embodiment of such a function generator is more fully described in my copending application mentioned above. The term "high speed" connotes operation in less than approximately 0.1 second and usually in 0.05 second or less. The second option is to install overcurrent devices in both the primary and secondary circuits of the transformer. 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. The static relay can easily operate in earthquake-prone areas because they have high resistance to shock. SGC12A/B Static Negative Sequence Time Overcurrent Relay for Generator Protection Author: GE Multilin Subject: Instruction Manual Keywords: SGC, SGC12A, SGC12B, SGC12 … GENERAL INTRODUCTION TO STATIC RELAYS . 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. While early comparators used discrete transistor circuits, modern designs use operational amplifiers. 15.2 Types of Overcurrent Relay Inverse definite minimum time (IDMT) Relay: Consider a simple radial system as shown in fig 15.5. Operational amplifier 24 has a feedback path between output terminal 21 and its inverting input consisting of two parallel branches, the first containing diode 28 and the second containing capacitor 30. Diodes 56 and 57 are poled as shown. Position of relay: Relay can be installed at any location and at any position. 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). 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. As the name implies, these relays do not contain any moving parts. 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 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. 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. 6. 3. 44: SOLID STATE POWER SUPPLY CIRCUIT . In this case the relay would be reset by a constant charging current, rather than by a constant discharging current. 4. This linear reset rate is selected to correspond to the cooling rate of the protected generator 12. The current derived from the CT is fed to the input transformer which gives a proportional output voltage. 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. 0000001126 00000 n H�b```e`` 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. Now, if we use a definite time relay to coordinate R 1 with fuse, the coordination. 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. overcurrent relays should be used over a limited length in the 3 feeder sections. 1: COMPARATORS AND ASSOCIATED ELEMENTS . 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. )��A�T{���ֺ{������n��|?_����!�����ߵ�|��|�M���[�������u�w���?���6���_}M��߯��}�����v����Z��w ��\�)e����N��W}�w����p�g���}��*�I]�q�x����I�����} �c�<5�+�X0��K����UW�~��?a��{�� k�����������o��{�N����ޠ�m��\Ewz�����A�$�kݭ�;�" [��m���Wj������K����f���c�#��Ta0�`���S�D�`�DDB"�`��� �‚E�X�%SD� `�A�� 0~ �� `xn? This current may be expressed by the relationship I = V/R58 , where V is the output voltage of the reset control circuit 48 (e.g., + 0.2 volts) and R58 is the ohmic value of resistor 58 (e.g., 1 megohm). The general equation for time characteristic is given as – I n t = K … (4.5) The Output Signal Is Turned Operated A Tripping Device Which May Be … 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. It is used for short 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. The operation of pick-up and reset control circuits 32 and 48 of the control means 3 will now be summarized. 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. 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. Depending on the time of operation the overcurrent relay is categorized into following types. Title: SLC 51E Static Overcurrent Relay Author: GE Multilin Subject: Instruction Manual Created Date: 3/7/2003 9:25:13 AM The term ‘static’ implies that the relay has no moving mechanical parts in it. No. 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. Thus signal 17 is a train of undulating half cycles the amplitude of which is proportional to the negative phase sequence current. Index. Testing and maintenance of protective gear, Protection against surge … The illustrated integrating means 22 is comprised of an operational amplifier 24 whose non-inverting input is connected to the common potential bus by resistor 26 and whose inverting input is connected to the input terminal 19 by a resistor 20. 50 Instantaneous Overcurrent Relays. 9. The means 1 of my relay includes more specifically a signal sensor 14 which is coupled to the line 10 and which typically comprises a symmetrical component segregating network capable of producing a voltage proportional to the negative phase sequence current in the stator windings of the protected generator. 1. ����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�! 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. @��. 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. 3,018,416. Thus in the protection of generators from negative phase sequence overcurrents, if one unbalanced current condition occurs and then subsides, my relay will operate more quickly in response to any subsequent unbalanced condition occuring before the machine rotor has recovered to its normal temperature. 7. 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. Accordingly, it is an object of my invention to provide an improved static overcurrent relay having a linear reset characteristic which matches an approximately linear cooling curve of the electrical apparatus to be protected. relays. 0000000526 00000 n This delay is fixed and it is independent of PSM value. 108: OVERCURRENT RELAYS . To study and test static overcurrent relay at different current settings and plot the characteristics. It protects the equipment of the power system from the fault current. 0000001146 00000 n The reset control means includes a source of constant current for discharging, at a linear rate, the energy storage element (usually a capacitor) which comprises the integrator of the relay. c. control means responsive to said current exceeding a predetermined pick-up level for enabling said accumulator to operate and responsive to said current subsiding below said pick-up level for returning said accumulator to said quiescent state at a substantially time delayed linear rate thereby approximating the cooling characteristic of said electrical apparatus. No. No. If a second overcurrent condition were to occur while the delayed resetting action is still in progress, the integrating action will resume with a residual charge on the energy storage element, whereby a relatively shorter time is required for the integrated voltage to reach the same reference level at which the trigger circuit is energized. No. Setting of the scale-constant Is. 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. 4.1, where there is a high impedance unit such as a transformer which makes the fault much less for faults beyond the transformer. This quiescent state is maintained by the action of the associated control means 3 which will next be described. The control means 3 comprises a pick-up control circuit 32 in combination with a reset control circuit 48. The output of reset control circuit 48 is supplied via resistor 58 to the inverting input of operational amplifier 24 of the integrating means 22. 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 This operational amplifier has a feed-back path containing capacitor 42. 0000001004 00000 n 0000000766 00000 n 2. Abstract: The technology of static overcurrent relays has developed very rapidly in the past few years. These over-current relays need to coordinate with each other such that the relay nearest fault operates first. Static overcurrent relay Download PDF Info Publication number US3942074A. For The Measurement Or Comparison Of Electrical Quantities. For feeder protection, there would be more than one over-current relay to protect different sections of the feeder. 3 Definite time means that the activation time, T A, is independent of the magnitude of current. 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). 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. 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. 4. Define operating time of a relay. These relays have earned a … Over the past decades, static relays were used, while nowadays microprocessor relays are used. The components used by the static relay are very sensitive to the electrostatic discharges. 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. When an overcurrent subsides, the capacitor proceeds to discharge through the parallel resistor (see U.S. Pat. LA PUNTIMATIC S.n.c. 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. Table of Contents. A typical case where current grading can be used is shown in fig. data:image/svg+xml;base64,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, data:image/svg+xml;base64,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, GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER, EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS, Emergency protective circuit arrangements responsive to undesired changes from normal non-electric working conditions using simulators of the apparatus being protected, e.g. Static over current relays • The output of this summation C.T is fed to an auxiliary C.T. 3. Operational amplifier 50 has a feed-back path between its output terminal and its inverting input terminal consisting of a first branch containing resistor 55 in series with diode 56 and a second parallel branch containing diode 57. Thus it requires to serve the system voltage as well as the system current. 0000000786 00000 n 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. User Review - Flag as inappropriate. This is the aforesaid "trip state" of the accumulator 2, and the rate at which it is attained varies with the average magnitude of the signal at the input terminal 19. 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. whose output is rectified, smoothened and applied to the measuring unit called level detector. chosen for electromechanical relays and 0.30 seconds for static relays to allow coordination with the motor relays that are typically set with a 0.05 second delay. 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. However, if the relay is used to protect electrical apparatus having thermal inertia, it may be desirable that there be a delay in the reset action while any heat stored in the apparatus is dissipating. 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. These relays have earned a … CO Circuit Opening Overcurrent Relay The overcurrent unit contacts are in the contactor switch coil circuit and when they close, the solenoid plunger moves upward to open the de-ion contacts which normally short circuit the trip coil. In some prior art disclosures of static overcurrent relays, a reset delay is inherently obtained because of the connection of a leakage resistor in parallel relationship with the timing capacitor of the relay. Gravitational force can affect the relay. The block schematic diagram of the static instantaneous Overcurrent relay is shown in the figure. 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