Modelling and simulation of mho type distance relay for high voltage transmission line protection using matlab software. Abstract mho elements constitute the main component of transmission line protection in. A forward offset mho relay is a mho relay with the center. The ceb52a relay a threephase, high speed, single zone directional rnho distance phaserelay with. Understanding the dynamic mho distance characteristic. A forward offset mho characteristic can provide good backup protection for remote forward resistive faults, without the load encroachment problems of a mho element with no forward offset.
As has been previously stated the most positive and reliable type of protection compares the current entering the circuit with the current leaving it. Cfe generator protection guidelines for setting 40 and 64g. Abstractdistance relays rely on accurate voltage and current signals to correctly determine if a fault is within their zone of. Pdf mho relay for protection of series compensated.
Gcy12 mho distance relays ge grid solutions online store. It is based on the logic diagram of flag signals, which. On closer examination it turns out that the microprocessorbased relay is a small computer in. Understanding the dynamic mho distance characteristic donald d. In this relay operating torque is obtained by the voltamperes element and the controlling element is developed due to the voltage element. This relay consists of two units an overcurrent element and a currentvoltage directional element. Distance protection is a nonunit system of protection, which measures the impedance between the relay location and the point where the fault is incident and compares it with the set value. A mho relay is a highspeed relay and is also known as the admittance relay. Mho type relays are best suited for phase fault relaying for long lines and particularly where a severe synchronising power surge may occur. The question arises if the microprocessorbased protection device is a relay in the full sense of the word. If the measured impedance is less than the set value, the relay operates and isolates the faulty section. Modern electrical protection relays are mainly micro processor based, but still electromagnetic relay holds its place.
Distance protection highspeed numerical distance relay providing up to 5 zones of lfzr r4117 modular for extra high protection and a choice of scheme options. The operating input, iz r, is the line current multiplied by the replica impedance z r v. Typical reach and time settings for a 3zone distance protection are shown in figure 11. Hence this relay is called a voltage controlled directional relay. Thus, a directional relay is commonly used together with the impedance relay, and a mho relay is used as a starting unit for the. A simple form of mho relay admittance or angle admittance relay shown in the figure below. This analysis refers to one relay unit of a threephase mho distance relay, for example the ab phase pair unit. A simple mho distance function, with a reach of z ohms, is shown in figure 1. Provides mho phase fault voltage transmission characteristics with a choice of shaped mho or quadrilateral earth fault systems characteristics. Offset mho zone and phase packaged directionaldistance relays ge protective relays description type ceb relays are highspeed, singlezone mho directional distance phase relays with provisions for offsetting the characteristic. Relays are the primary protection as well as switching devices in most of the control processes or equipment regardless of whether they are electronic or electromechanical.
All points on the bolted fault locus between the relay reach point and the origin are enclosed within the area of operation. No attempt will be made here to describe the effect of all types of crosspolarization. Digital and numerical distance relays may have up to five zones, some set to measure in the reverse direction. This paper describes a novel idea for fast protection of parallel seriescompensated transmission lines operating in various configurations. Philosophy of protection, nature, causes and consequences of faults, zone of protection, requirements of a protective scheme, basic terminology components of protection scheme. The transient overreach characteristic is such that these relays are suitable for 2nd or 3rd zone applications. Protection systems of such generators have also become more stringent required to reduce the outage period to a minimum achieved by rapid discriminative clearance of all fault.
More specifically, the relay operates depending upon the impedance between the point of fault and the point where relay is installed. Offset mhozone and phase packaged directionaldistance. The mho relay has an inherent directional characteristic. Negativeoffset mho elements the normal setting for the offset mho relay in the impedance plane has two circles with a diameter of saturated direct axis transient reactance x d and a negative offset of x d. Fundamentals and improvements for directional relays. Modelling and simulation of mho type distance relay for. Figure 15 shows a forward offset mho relay used in conjunction with a mho element. These relays are known as distance relay or impedance relay. Ihr krankenhausaufenthalt macht es erforderlich, zu. Till date all the theoretical performance evaluation of distance relay in presence of upfc incorporated transmission line has been done using mho relay.
It is an electromagnetic induction cup type mho relay. So before going through detail of protection relay system we. The mho relay is reliable because it combines both the directional and distance measuring functions in one unit. All distance relays compare voltages and currents to create impedanceplane and directional. The directional element is so designed to give maximum torque angle mtarca of 90 degree. In this application it is used in conjunction with mho measuring units as a fault detector andor zone 3 measuring unit. Generator protection introduction size of individual generating unit 30 mw to 500 mw loss of even a single unit is a serious problem consequence. Transmission lines are an important part of a power system. This implies that reactance relay is an overcurrent relay with directional restraint. Switchgear and protective devices 310 modulei 10 hours protective devices. Schweitzer, iii, and jeff roberts schweitzer engineering laboratories, inc. A forward offset mho relay is a mho relay with the center of the circle offset away from the origin.
Abstractin order to retain dependability and security in cases of closein faults when the loop voltage is zero, mho distance elements use crossphase andor memory polarization. Distance relay or impedance relay working principle types. Performance comparison between mho elements and incremental quantitybased distance elements gabriel benmouyal, normann fischer, and brian smyth, schweitzer engineering laboratories, inc. So, with the reverse reach arranged to extend into the busbar zone, as shown in figure 4, it will provide backup protection for busbar. The mho relay model is tested with this system using the emtprv simulation package. Transmission lines have high power transmission capacity and they are prone to faults of larger magnitudes.
They are most sensitive of all the distance relays. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Relay classification, principle of different types of electromagnetic relay. All the relays respond to one or more electrical quantities like voltage or current such that they open or close the contacts or circuits. Thus, distance relays activate when relay s apparent impedance. Frequency relay contacts must remain closed if sensing voltage goes to zero voltage balance relay 60 protects against loss of sensing time delay relay 62 protects against sudden application of nominal voltage during inadvertent energization, allowing overcurrent to trip lockout relay 86 lockout relay must be manually reset. Electromagnetic relay working types of electromagnetic. Principles and characteristics of distance protection. Zertifizierungsqualitatsbericht 2014 download pdf ca. Phase distance relays normally use linetoline voltage, vab, and odelta currents,o ia n ib, so that the reach is the same in positive sequence ohms for phasetophase or threephase fauits. Transmission line distance protection explained in detail. A mho impedance relay generally has an operating characteristic which is a circle passing through the origin. Principles and characteristics of distance protection these relays may sometimes be set based in percentages of the line impedances, for example a typical setting for zone 1 is 80% of the impedance of the line in order to not reach the remote end, the zone 2 can be set at 120% of the impedance of the line in order to dependably overreach the. Applications such as the protection of seriescompensated lines.
Since the operation of the impedance relay is practically or actually independent of the phase angle between v and i, the operating characteristic is a circle with its. On the other hand, the impedance and the reactance relays see faults in all directions. Istance relays perationdepend on the agnitude of the current or ltage of the circuit. There is one type of relay which functions depending upon the distance of fault in the line. Offset mhozone and phase packaged directionaldistance relays. Reactance relay mho relay is a distance relay with inherent directional element. The mhotype relays have a maximum reach along an angle that typically is close to the angle of the transmission line impedance. The distance relay also known as impedance relay determines the. The transmission lines are 40% compensated with fixed series capacitors, installed at the remote end of the lines. Actually, all modern mho impedance relays for phase, ground and 3phase protection have an expanded characteristic that includes the origin. The current element developed positive torque and a currentvoltage developed directional element which opposes the current element depending on the phase angle between current and voltage. Different relay characteristics like mho and quadrilateral are used for protecting high voltage long and medium transmission lines in different scenarios. It will take much longer time to replace all electromagnetic relays by micro processor based static relays.
Zertifizierungs qualitatsbericht 2011 download pdf ca. Eight most important distance relay characteristics based. Protection against loss of excitation in generators. The residual current compensation algorithm is used to compensate. The mho function uses the current and voltage measured at the relay to determine if the apparent impedance plots within the mho. Basic distance protection will comprise instantaneous directional zone 1 protection and one or more timedelayed zones. Protective relays, associated communication systems, voltage and current sensing.
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