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asked Jun 23 by anonymous. If there is a fault at F1, Equivalent source impedance Zs = 10×10/20 = 5 Ω. Impedance up to the point of Fault = 5+4 = 9 Ω. The relay is operated in three zones with the required delay based on impedance. It provides a low impedance […] Application of Differential relays: They have been compiled using information from the IEEE and the National Association of Relay Manufacturers. If an impedance-relay characteristic is offset, so as to make it a modified relay, it can be made to resemble either a reactance relay or a mho relay but it will always require a separate directional unit. The major relays that we have used in different applications are reactance, simple impedance, and Mho relay. systems. In the figure above, R1 is an over current relay which is used for the protection of Transmission Line. 71 views 1 answer. The relay continuously measures voltages and currents which are used in the calculation of the ‘apparent impedance’. Stabilizing Resistor in High Impedance Differential Protection is used to prevent the operation of Relay in case of through fault. For the impedance elements of a distance relay, the quantities being compared are the voltage and current measured by the relay. The most important feature of the relay is their speed of operation. I THINK IT IS A BECAUSE FOR PHASE FAULTS WE ARE USING IMPEDANCE RELAY. 1). This is the characteristic of the mho element used in the GCY relay. Impedance relay can be used for? 3. The relay pickup setting should be low enough to trip in response to the minimum sustainable generator contribution (i.e., synchronous current E/Xd), but should not trip unnecessarily due to normal overloads. An impedance being non-directional in characteristic, will trip for a fault lying within the R-X circle, irrespective, will trip of the fact that fault point lies either in the forward direction or in the reverse direction. It is directional and more sensitive to fault currents lagging 60-85 degree than to loads that are near 0-30 degree lagging. This type of impedance relay has several settings: trip setting Z trip, Ohm; offset setting Z offset, Ом; angle of maximum sensitivity φ, degrees; the return coefficient k res, which determines the return of the relay to an idle state (characteristic indicated by a dashed line in Fig. For remote zone 3 protection, use an impedance relay offset into the first quadrant. Share. use a balance-beam magnetic-attraction structure or an induction-cup or double-loop structure. A) Audio transformers B) Oil filled power transformers C) Air core transformer D) None of these thumb_up_alt 0 like thumb_down_alt 0 dislike. 87 F2 F1 Fig. Actually, there is much overlapping of these areas. Relay | Protective Relay Objective Type Questions and answers; 6. With this combination, the impedance relay responds only to the measured impedances which are in the shaded portion of this diagram. That kit used for this purpose is Vinytics VMC 8506 which has an inbuilt ADC interface based on ADC0809 chip and also some relays which can be turned on or off by providing simple 8085 instructions. Tweet. Another option is to use a modified impedance relay (mho relay) which is obtained by offsetting the impedance circle and placing it in the origin. 1 Answer. Add blinders to the characteristic to limit reach along the real axis. The DTOC relay has been used extensively in the United Kingdom but its inherent issue of operating slower for faults closer to the source led to the development of the IDMT relay. In this paper the implementation of an impedance relay using 8085 microprocessor is described. Earthing transformer is generally used in a power system is delta connected. This is because the reactance relay is practically unaffected by arc resistance which may be large compared with the line impedance, as described elsewhere in this chapter. The impedance ‘ Z’ is designated as the impedance of the line with ‘ mZ ‘ representing a section of the line and where ‘ m ‘ is the per-unit distance to the fault, e.g. the distance to the fault in kilometers divided by the total line length in kilometers. Bookmark Like 0 Dislike 0 ⚐ Report. Through fault is a fault outside the zone of protection. The relay protects the system from earth fault and also used for protecting the system from circulating current. Previous question Next question. The impedance relay is mainly used as a minimum relay. This paper describes the technique used to model an impedance relay using the RTDS software and hardware. This paper describes the technique used to model an impedance relay using the RTDS software and hardware. Lets us assume that High Impedance Differential protection is used to protect a Bus bar as shown in figure. A relay is an electrically operated switch.It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. They function even if the short circuit current is relatively low. A Mho relay is also called the admittance relay and it is a high-speed relay. 4. 5. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.. Used for Protection: 1: Impedance Relay (Z) Current (I) Voltage (V) Phase faults in medium length lines: 2: Reactance Relay (X) Current (I2) Voltage – Current SinΦ ( V – I sin Φ) Ground faults in short lines: 3: Admittance Relay (Y) VI Cos (Φ – α) V: Phase faults in long Lines: CSV Aug 15, 2016 SHARES. Use minimum C value and β of 0.25 Equation 2 - For applied sinusoidal currents:- Vpeak 1.09 C Irmsß Use maximum C value and β of 0.25 Operating conditions for the majority of high impedance relays offered by M&I Materials Ltd are given within this leaflet. However, the relay uses the unfaulted phase voltages for directional comparison, thereby blocking operation for faults in the opposite direction. impedance bus differential relay can provide protection for a single phase, two phases, or all three phases, depending on the number of relay current inputs. All values of fault impedance which will cause the relay to close its contacts lie in the shaded areas of these curves. Figure 12. The maximum fault distance (corresponding to the maximum fault impedance or minimum fault current) that triggers the relay in a certain impedance zone, or in a certain time instant (depending on the configuration), characterizes the reach of an impedance relay [33]. This “false” differential current decreases in magnitude and pulse width as the primary current waveform ap-proaches a sinusoidal steady state value since concurrently the fault CT saturates for less of each succeeding negative primary current half cycle. Priya said: (Tue, Jun 5, 2018 04:40:59 PM IST) Impedance relay is a widely used protective scheme for the protection of high or an extra high voltage transmission lines. use in the relay industry. There are numerous techniques available for performing the comparison, depending on the technology used. Buchholz relay is used as a safety device with respect to which of the following? 4. B. Impedance relay. Mho type distance relays are the most common type of distance elements used in transmission and distribution. Figure 3 – Operating characteristics of impedance and offset impedance … The relay used for phase fault protection of short transmission lines is . OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments . The major factors that needed to be considered for the relay selection in transmission lines are:- 1. Therefore the setting of over current Relay should be more than 14113.5 A. For a quadrilateral characteristic, reset the relay. A. Reactance relay . Yes D is right ...bkos long line Mho relay is used.... Jitendra Singh Said on 2018-01-03 09:25:39. 3, and the reactance element, plotted in Fig. Medium Length Lines: For medium length transmission lines Impedance relays are used. Question is ⇒ Which of the following statements is incorrect?, Options are ⇒ (A) Station batteries are used to operate relay only, (B) The lightning arresters are basically surge diverters, (C) An impedance relay has maximum fault current when fault occurs near the relay, (D) A high speed relay has an operation of 1 to 2 cycles, (E) , Leave your comments or Download question paper. Enable the load encroachment function of the relay. C. Mho relay. Where your condition requirements are not covered, M&I Materials are pleased to A typical wiring diagram for a low-voltage impedance relay is shown in Figure 6-38. In a similar manner, we can simplify the equa-tions for the impedance element, plotted in Fig. 2. Shaikh aarif Said on 2018-01-05 04:29:35. It will be observed that the elements of Fig. Since an impedance relay responds to measurements in all quadrants, a directional unit is generally used to limit the reach to the line side of the relay, as is shown in this figure. In instances where different terms are used synonymously, one has been defined and others have been cross-referenced to it. Pin it. Mho relays are used for these lines as they occupy the least space in R-X diagrams compared to other relays. 6. False Example 3. D. IDMT relay In this example, we have a 2-terminal system with some export load flow and an A-B fault behind the relay. 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