Features and Benefits Develop SELogic control equations using ac SELE r ato r QuickSet Software. Sir kindly share manual of 7sj over current relay manula my email. Thank you. The phasor diagram of a meter test on the Directional Overcurrent 67 relay connected to Circuit Breaker 4 would look like the following. Or they can also be set to trip for faults behind the relay in the reverse direction. The primary coil is connected to the secondary of CT through tapping in it. advantages of directional overcurrent relay. The disc of this element rotates and the moving contact attached to it closes the trip circuit. Therefore, the latter element cannot start to operate until its secondary circuit is completed. 3. 5. If we reversed the source and load, you could swap the phasor diagrams above for each relay. The fault current is lagging in nature. Compact in size — The size of a single three-phase overcurrent relay may be about one-fourth of three electromagnetic relays. transmission lines, transformers, generators, or … It is to be noticed that the directional over current operation is different for phase and earth faults. Its zone is clearly demarcated by the CTs which provide the boundary. You could also perform a test in either direction first and see what direction the relay is set to trip. Directional overcurrent protection schemes were replaced with line impedance relays 21 to prevent a situation like this from occurring. This paper presents hybrid genetic algorithm (GA) - nonlinear programming (NLP) approach for determination of optimum values of TMS and PS of OCRs. Negative sequence voltage can be simplified to mean unbalanced voltage You can get more information in the Sequence Components section of The Relay Testing Handbook: Principles and Practice. The technique of overcurrent relaying is still widely used as a means of fault detection on distribution system and on transmission lines supplied from one end. The relay is designated to develop maximum torque when the relay current leads the voltage by 45 o. DIRECTIONAL OVERCURRENT RELAY When short circuit current can go in both directions through the protection relay location, it may be required to make the response of the protection relay directional by the initiation of a directional control device. To illustrate the principle let us consider that current rating of primary winding is A and secondary winding is A. The relay will not operate when the value of current is less than the pick value. The characteristic curve for the relay is shown in the figure below. The characteristic angle is the phase angle by which reference or polarising voltage is adjusted such that the directional relay operates with maximum sensitivity. Simpler to co-ordinate. The proposed overcurrent relay can be employed to protect feeders of distribution systems for overcurrent and earth fault protection. When the directional unit operates, it closes the open contacts of the secondary winding of the relay may be either wattmeter or shaded pole type.In this post operation of Directional current relay along with its settings explained. The trip contacts 1 and 2 of the directional element are connected in series with the secondary circuit of the overcurrent element. Most electro-mechanical relays, and GE relays like the one from The Relay Testing Handbook example, use the phase-phase voltage from the two un-faulted phases as a polarizing signal. Inverse Time overcurrent Relay, Inverse De_nite Minimum Time overcurrent Relay, Very Inverse Relays and Extremely Inverse Relay are presented in [2]. I used to occasionally run into problems when testing Directional Overcurrent 67 elements using traditional testing techniques.CSV Jul 14, Jul 14, Pin it. Each phase current is compared with the voltage between other two phases. It starts operating instantly when the value of current is more than the relay setting. The instantaneous overcurrent relay is placed in the outgoing feeder. It may be noted that plug-setting bridge is also provided in the relay for current setting but has been omitted in the figure for clarity and simplicity. Conventionally denotes that forward direction refers to power flow away from the busbar towards the protected zonewhile reverse direction refers to power flowing towards the busbar. RELAY: A Relay is a protection device that senses the fault in the circuit and gives a trip signal to the Circuit Breaker to isolate the faulty circuit. Uses and Benefits; Hands on Testing of Relays. The directional over current relay recognizes the direction in which fault occurs, relative to the location of the relay. If we reversed the source and load, you could swap the phasor diagrams above for each relay. However in case of fault in the line segment AB, we get:. The typical region for a fault in the forward direction occurs in the green shaded area for both relays. Normally, the conventional over current relay non-direction will act for fault current in any direction. Join your peers on the Internet's largest technical engineering professional community. Or they can also be set to trip for … Directional element: It is essentially a directional power relay which operates when power flows in a specific direction. Some relays use the negative sequence voltage as the polarizing signal. You can tell by graphically adding the three voltages together, or with the negative sequence formula. The quick short circuit clearance time helps to decrease damage at the short circuit location. The voltage of faulty phase drops and other phases remain healthy.I used electro-mechanical directional relays as an example, which may have been a mistake. Already a member? The impedance relay trips if the magnitude of the impedance is within the circular region. However, for faults in feeder AY, the circuit Breaker CB y trips, due to direction feature of the relays, set to act in the direction AY. What is out-of-step condition; How does a relay detect out-of-step condition; Hands-on Relays Testing Introduction. Both fault currents flow into the transmission line, so the directional overcurrent relays connected to Circuit Breakers 3 and 4 will see the current in the forward direction because the current flows into both CT polarity marks. Overcurrent relays are also employed in conjunction with distance relays to provide backup protection. The first protection devices based on microprocessors were employed in 1985. For Example consider a phase fault occurs at angle of o. Conventionally denotes that forward direction refers to power flow away from the busbar towards the protected zonewhile reverse direction refers to power flowing towards the busbar. It'll be easier to answer the questions if I or others have a better understanding of the question. Therefore, for faults in feeder AX, the circuit breaker CB ydoes not trip unnecessarily. The spindle of this disc carries a moving contact which bridges two fixed contacts when the disc rotates through an angle, which is adjustable between 0 o to o. Join Eng-Tips Forums! Now our Directional Overcurrent 67 test plan looks like the following drawing where we start with the raw currents and voltages, calculate the non-faulted phase-to-phase voltage, and plot the operating current and polarizing signal, which in this case is VBC. This means that it is a coin toss whether the relay will operate or not. Overcurrent relays are the most common protective relay in an electrical system. I hope this helps clear up the definitions of forward and reverse for Directional Overcurrent 67 relays. At this line relay current is in phase with the reference or polarising voltage. One important thing to be noted here is that the connection of the star points of both the C.T. Always ask the engineer what they intended if there is any doubt. My name is Daniel Pecsoy and my email add is dpecsoy yahoo. In this case, from the magnitude of the current seen by the relay R 2it is not possible to distinguish whether the fault is in the section AB or BC. Neither did I Davidbeach However it shows that the 50GS having a dedicated ground relay feeding the relay as shown in the figure on page The 50N does not refer to figure on page 20 of the manual. Any current flowing into the polarity mark is considered to be the forward direction. Since faults in section AB are not in its jurisdiction, it should not trip. Overcurrent Relay Benefits. We added the B-C phase-phase voltage to the drawing, which is the polarizing voltage this style of relay uses. A directional over current relay operates when the current exceeds a specified value in a specified direction. The phasor diagram for this situation might look like the following. The spindle of this disc carries a moving contact which bridges two fixed contacts when the disc rotates through an angle, which is adjustable between 0 o to o. Both the graph theoretic and functional dependency approaches provide a solution which is the best setting, but not necessarily an optimal solution. The various advantages of the distance relays are: 1. There are no physical moving parts involved in the design of solid state relay. They are more complicated in static form as compared to their electromagnetic counterparts. Extremely inverse overcurrent relays are used for the fuse coordination and thermal protection of transformers and induction motors. Differential protection can be used for tapped lines multiterminal lines where boundary conditions are defined as follows:. directional element is added with the over-current relay in order to minimize the outage area [13, 14]. This is the voltage taken from Potential Transformers. When the input to measuring unit is less than the threshold value, the output of the level detector is zero. HelloThe endeavour behind presenting this website for we Electrical protection Engineers is really awesome. Overcurrent relaying is well suited to distribution-system protection for several reasons. Thank you very much. These voltages are available only during earth fault conditions. That is, each of the current elements is directionalised by a voltage derived from the other two phases. Log In. This operates the circuit breaker which isolates the faulty section. The current flows into the polarity mark of the CT on Breaker 3, and into the Directional Overcurrent 67 Relay using the same direction. The directional over current relay recognizes the direction in which fault occurs, relative to the location of the relay. Now if an internal fault occurs within the device like interturn short etc.The directional power relay is unsuitable for use as a directional protective relay under short-circuit conditions. If the power flow is in the opposite direction, the relay will not operate. This is because the induction disc characteristics of the overcurrent relays inverse characteristics are not amenable to simple mathematical analysis. Both fault currents flow into the transmission line, so the directional overcurrent relays connected to Circuit Breakers 3 and 4 will see the current in the forward direction because the current flows into both CT polarity marks. However, when a short-circuit occurs, there is a tendency for the current or power to flow in the reverse direction. Differential protection tends to be extremely accurate. secondary’s and relay windings by a neutral conductor should be made. Healthy phase magnitudes and angles not changed. The reference voltage is called polarising voltage. For directional unit, the secondary winding of the over current relay unit is kept open AB. Reverse power flow relays with directional features, not only senses the direction flow, but also measures magnitude of power flow. Transformer Differential; Volts per Hertz; PMU Testing Overcurrent Protection Fundamentals and Fundamentals and Improvements for Directional Relays has been sent to your email. Already a Member? This ratio also indicates the distance of the fault from the relay. However, static overcurrent relays offer several advantages over the electromagnetic form:. You can choose a good fault angle using one of these methods:. Please send me the PDF on aforementioned documents as announced. Therefore, Induction Type Directional Overcurrent Relay upper element does not operate, thereby keeping the overcurrent element lower element unenergised. Characteristic Angle is also called Directional angle as it decides the direction of operation of the relay. If the system is resistance grounded in the range of 25 to amps, then a zero sequence window CT feeding a ground relay is more appropriate. Abstract: The time of operation of overcurrent relays (OCRs) can be reduced, and at the same time, the coordination can be maintained, by selecting the optimum values of time multiplier setting (TMS) and plug setting (PS) of OCRs. We start with the raw currents and voltages, then calculate the negative sequence voltage, and then plot the operating current and polarizing signal V2. Close this window and log in. The most significant advantage of the instantaneous relay is that it has low operating time. This allows a decrease in the operating time at high short circuit levels possible. The potential coil of this element is connected through a potential transformer P. The current coil of the element is energised through a C. This winding is carried over the upper magnet of the non-directional element. 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