Transmission lines have high power transmission capacity and they are prone to faults of larger magnitudes. Fundamentals and improvements for directional relays. Published in the sel journal of reliable power, volume 1, number 1, july 2010 previously presented at the. Modern electrical protection relays are mainly micro processor based, but still electromagnetic relay holds its place. A simple form of mho relay admittance or angle admittance relay shown in the figure below. Protection against loss of excitation in generators. This implies that reactance relay is an overcurrent relay with directional restraint. The ceb52a relay a threephase, high speed, single zone directional rnho distance phaserelay with. Zertifizierungs qualitatsbericht 2011 download pdf ca. Actually, all modern mho impedance relays for phase, ground and 3phase protection have an expanded characteristic that includes the origin. Offset mhozone and phase packaged directionaldistance. Modelling and simulation of mho type distance relay for high voltage transmission line protection using matlab software. Figure 15 shows a forward offset mho relay used in conjunction with a mho element.
Applications such as the protection of seriescompensated lines. The mho relay model is tested with this system using the emtprv simulation package. This paper presents the design of a mho relay model for the protection of two parallel 500 kv, 280 km long transmis sion lines. 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. A forward offset mho relay is a mho relay with the center of the circle offset away from the origin. The distance relay also known as impedance relay determines the. So, with the reverse reach arranged to extend into the busbar zone, as shown in figure 4, it will provide backup protection for busbar. Pdf mho relay for protection of series compensated. Understanding the dynamic mho distance characteristic. In this application it is used in conjunction with mho measuring units as a fault detector andor zone 3 measuring unit. Schweitzer, iii, and jeff roberts schweitzer engineering laboratories, inc. The mhotype relays have a maximum reach along an angle that typically is close to the angle of the transmission line impedance. No attempt will be made here to describe the effect of all types of crosspolarization.
Ccvt failures and their effects on distance relays sophie gray, centerpoint energy derrick haas and ryan mcdaniel, schweitzer engineering laboratories, inc. Offset mhozone and phase packaged directionaldistance relays. Electromagnetic relays are those relays which are operated by electromagnetic action. Switchgear and protective devices 310 modulei 10 hours protective devices. The transient overreach characteristic is such that these relays are suitable for 2nd or 3rd zone applications. Abstract mho elements constitute the main component of transmission line protection in. All the relays respond to one or more electrical quantities like voltage or current such that they open or close the contacts or circuits. 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.
Mho type relays are best suited for phase fault relaying for long lines and particularly where a severe synchronising power surge may occur. 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. Abstractdistance relays rely on accurate voltage and current signals to correctly determine if a fault is within their zone of. The operating input, iz r, is the line current multiplied by the replica impedance z r v. 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. Cfe generator protection guidelines for setting 40 and 64g. Zertifizierungsqualitatsbericht 2014 download pdf ca. Thus, distance relays activate when relay s apparent impedance. Generator protection introduction size of individual generating unit 30 mw to 500 mw loss of even a single unit is a serious problem consequence. 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. So before going through detail of protection relay system we. On the other hand, the impedance and the reactance relays see faults in all directions. 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.
Hence this relay is called a voltage controlled directional relay. Gcy12 mho distance relays ge grid solutions online store. A forward offset mho relay is a mho relay with the center. It is based on the logic diagram of flag signals, which. Modelling and simulation of mho type distance relay for. Istance relays perationdepend on the agnitude of the current or ltage of the circuit. Basic distance protection will comprise instantaneous directional zone 1 protection and one or more timedelayed zones.
Reactance relay mho relay is a distance relay with inherent directional element. All points on the bolted fault locus between the relay reach point and the origin are enclosed within the area of operation. This diagram is exactly equal to an rx diagram except that all of the impedance vectors have been operated on by the current i. This analysis refers to one relay unit of a threephase mho distance relay, for example the ab phase pair unit. Electromagnetic relay working types of electromagnetic. Distance relay element design schweitzer engineering. On closer examination it turns out that the microprocessorbased relay is a small computer in. The mho function uses the current and voltage measured at the relay to determine if the apparent impedance plots within the mho. Till date all the theoretical performance evaluation of distance relay in presence of upfc incorporated transmission line has been done using mho relay. Different relay characteristics like mho and quadrilateral are used for protecting high voltage long and medium transmission lines in different scenarios. 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.
Eight most important distance relay characteristics based. More specifically, the relay operates depending upon the impedance between the point of fault and the point where relay is installed. Principles and characteristics of distance protection. 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. A mho impedance relay generally has an operating characteristic which is a circle passing through the origin. Relay classification, principle of different types of electromagnetic relay. There is one type of relay which functions depending upon the distance of fault in the line. The directional element is so designed to give maximum torque angle mtarca of 90 degree. 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. Understanding the dynamic mho distance characteristic donald d. Transmission line distance protection explained in detail. Provides mho phase fault voltage transmission characteristics with a choice of shaped mho or quadrilateral earth fault systems characteristics. This relay consists of two units an overcurrent element and a currentvoltage directional element. The residual current compensation algorithm is used to compensate.
Ihr krankenhausaufenthalt macht es erforderlich, zu. In this relay operating torque is obtained by the voltamperes element and the controlling element is developed due to the voltage element. Transmission lines are an important part of a power system. 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. 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. Performance comparison between mho elements and incremental quantitybased distance elements gabriel benmouyal, normann fischer, and brian smyth, schweitzer engineering laboratories, inc. Typical reach and time settings for a 3zone distance protection are shown in figure 11. Philosophy of protection, nature, causes and consequences of faults, zone of protection, requirements of a protective scheme, basic terminology components of protection scheme. If the measured impedance is less than the set value, the relay operates and isolates the faulty section. 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. Distance relay or impedance relay working principle types. This paper describes a novel idea for fast protection of parallel seriescompensated transmission lines operating in various configurations.
Protective relays, associated communication systems, voltage and current sensing. It is an electromagnetic induction cup type mho relay. These relays are known as distance relay or impedance relay. 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. In reactance relay the operating torque is obtained from the current and the restraining torque by the current and voltage of the directional element. Mho relay admittance or angle admittance relay my tech.
They are most sensitive of all the distance relays. All distance relays compare voltages and currents to create impedanceplane and directional. A simple mho distance function, with a reach of z ohms, is shown in figure 1. The mho relay has an inherent directional characteristic. 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. The mho relay is reliable because it combines both the directional and distance measuring functions in one unit. Abstractphase and ground directional elements are relied on for fast and secure protection throughout the power system. The transmission lines are 40% compensated with fixed series capacitors, installed at the remote end of the lines. It will take much longer time to replace all electromagnetic relays by micro processor based static relays. As has been previously stated the most positive and reliable type of protection compares the current entering the circuit with the current leaving it. A mho relay is a highspeed relay and is also known as the admittance relay. Digital and numerical distance relays may have up to five zones, some set to measure in the reverse direction.