There are different types of protective relays available now. All the relays consist of one or more elements which get energized and actuated by the electrical quantities of the circuit. The art and science of protective relaying ge grid solutions. The operating characteristics of the more commonly used protective relays are described in this section. Testing and maintenance of protective gear, protection against surgesurge absorber, surgediverter. At this point, the problem has occurred and caused damage. Types of protection relays are mainly based on their characteristic, logic, on actuating parameter and operation mechanism. Protective relays detect the abnormal conditions in the electrical circuits by constantly measuring the electrical quantities which are different under normal and fault conditions. Abb network partner ab generator protection 1mrk 502 003aen page 7 4 protective relays for generators and generatortransformer units fig. Relays can have many independent contacts, some no and others nc, and each contact can be used in a different circuit for a different task. Protective relays, associated communication systems, voltage and current sensing devices, station batteries and dc control circuitry. Ot trip oil temperature trip wt trip winding temperature trip bearing temp trip etc. The presence of tapped transformers on a line, or reactive compensation devices such as series capacitor banks or shunt reactors, also influences the choice of protection system, and the actual protection device settings. This impedance or corresponding distance is called the reach of relay.
What are different types of principles of operation of electromechaical relays. Types of relays the relay may be defined as an electrical device interposed between the main circuit and the circuit breaker in such a manner that any abnormality in the circuit acts on the relay, which in turn if the fault is dangerous then it causes the circuit breaker to isolate and so to remove the faulty element. Basically, types of protective relays are analoguebinary signal converters with measuring functions. Most of the relays used are electromechanical type which work on the principles of electromagnetic attraction and electromagnetic induction. In this article, the different types of relays like overload protection relay, solid state relay, solid state contactor relay, buchholz relay, mercury wetted relay and many more are explained with diagrams. Different types of relays power system protection youtube.
A power system consists of various electrical components like generator. The variables such as current, voltage, phase angle or frequency and derived values obtained by differentiation, integration or other arithmetical operations, appear always as analogue signals at the input of the measuring unit. Overcurrent relays overunder voltage relays directional relays distance relays differential relays. Also this paper highlights the significant role played by the fuses in providing protection from shortcircuit damages. Electromechanical relays can be classified into several different types as. Power system protection part power system protection lecture. Different types of relayss like overload protection relay, solid state and contactor relay etc. A big difference between conventional electromechanical and static relays is how the relays are wired. Event reporting is a standard feature in most microprocessorbased protective relays. Numerical relays are based on the use of microprocessors. On the other hand, the impedance and the reactance relays see faults in all directions. Different types of protective relays editorial team january 24, 2018 0.
Numerical relays protection and control products for. Attracted armature solid computerized state digital relays plunger type magnetic induction electromagnetic numerical relays magnetic attraction others. Activating the contact unit using electromagnetic attraction, which is produced when electric current exceeding the. Overcurrent relays are also employed in conjunction with distance relays to provide backup protection. In addition to having different operating types, relays can have their contacts arranged in various configurations depending on the use. Unit i introduction of relays a relay comprises of an electromagnet and a contact unit.
These are operated to open or close the load contacts in response to one or more electrical quantities like voltage and current. The most common types of protective relays include. Origi nally, all protective relays were of the electromechanical type. Use time, current and a combination of both time and current are three ways to discriminate adjacent overcurrent relays. Relay classification, principle of different types of electromagnetic relay. Electromagnetic attraction type induction type solid state relays numericalmicroprocessor based relays insulation monitoring relays gas. Ieee guide for protective relay applications to power transformers. Distance relays are designed to respond change in current, voltage, and the phase angle between.
Protection relay or protective relay is a device designed to trip a circuit breaker when a fault is detected as matter of fact it is designe to protect power system. In my earlier post i have alreaady explained the working of relays, and their design and construction. Power system protection relays can be categorized into different types of relays. Protective relays can also be classified by the type of measurement they make 92 a protective relay may respond to the magnitude of a quantity such as voltage or current. Different types of relays used in protection system and. When the coil is energized, all no contacts belonging to that relay close, whereas all nc contacts open. The electrical quantities which may change under fault conditions are voltage, current, frequency, and phase angle.
Types of electrical protection relays or protective relays. Types of relays there are different ways to classify relays. Understanding and analyzing event report information. Induction relays can respond to the product of two quantities in two field coils, which could for example represent the power in a circuit. The mho relay has an inherent directional characteristic. General equation of phase and magnitude comparators, duality of comparators, electromagnetic relays, over current relays directional relays, distance relay impedance, reactance and mho type, differential relays. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker. Types of protective relays basic construction different. The relays are connected to the power system through the current transformer ct or potential transformer pt.
There are several types of distance relays, including impedance, reactance, and mho relays. The factors affecting the choice of protection are type and rating of equipment, location of the equipment, types of funks, abnormal conditions and cost. When the power surges too high it can create a fire hazard. Power devices in power plants must have protective relays to operate. Various curve types, including inverse, very inverse, extremely. Types of relaysoverload protection relay,solid state. Sel introduced the worlds first digital relay in 1984, revolutionizing the power protection industry by offering fault locating and other features for a fraction of the cost of earlier systems. White paper on different types of relays the relay is an automatic protective and switching device which is capable of sensing abnormal conditions in electrical circuits. Comparison between the different generations of protective relays. Based on operation mechanism protection relay can be categorized as electromagnetic relay, static relay and mechanical.
I believe the types of relays are classified according applications and how they are triggered or controlled electromagnetics are controlled by a coil actuated contacts, and depending on the applications comes in many different size and package. Implementation of out of step relays to protect generators 3. Nc, the term normally refers to the state in which the coil is not energized. Table 1 compares the salient features and characteristics of the five types of relays. Power system protection part power system protection. When two different materials are joined together it forms into a bimetallic strip. Types of relay based on the principle of operation. Protective relays work in concert with sensing and control devices to accomplish their function. The main features of a good protective relaying are its reliability, sensitivity, simplicity, speed, and economy. Different types of relays used in protection system and their. For electromagnetic relays, this was a main design characteristic. Electromechanical relays can be classified into several different types as follows. Based on operation mechanism protection relay can be categorized as electromagnetic relay, static relay and mechanical relay. Protective relaying is a crucial part of electric power systems.
All the relays react to voltage or current with the end goal that they open or close the contacts or circuits. Understanding and analyzing event report information david costello schweitzer engineering laboratories, inc. Voltage restraint over current relay b based on logic. Some large industrial fuses have replaceable wire elements, to reduce the. Overcurrent protective relays overcurrent relays overcurrent relaying is the simplest and cheapest type of protection used for protection of lines, transformers, generators and motor. Relays are used in many type of industrial applications. As in any craft, an intimate knowledge of the characteristics and capabilities of the available tools is essential to their most effective use. Different types of relays, their construction, operation.
Power system protection relays can be categorized into different types of. Transmission lines can be protected by several types of relays, however the most common. The icw51a and icw51b relays are singlephase induction disk devices with inherent time delay. Faults relays instrument transformers correlation to drawings one lines ac schematics dc schematics other types of protection coordination of relays protect personnel. Definition of protective relay a relay is automatic device which senses an abnormal condition of electrical circuit and closes its contacts. Fuses are rated in terms of their voltage capacity as well as the current level at which they will blow. Different types of protective relays and monitors can reduce or eliminate damage because they detect problems in advance of traditional devices. Relays are the electrical protection mechanisms that sense an increase in the power supply and trip the circuit breakers. The protective relay is the device that responds to signals from the transducers by quickly initiating or allowing a control action to be implemented in order to prevent damage to the faulted equipment and to restore service as soon as possible. The protective relays do not eliminate the possibility of fault occurrence on the power system rather their circuit actions start only after the fault has occurred on the system. Electrical relays are used in many types of technological systems from cars and appliances to medical equipment and aircraft.
Protective relays introduction protective relaying is one of the several features of the power system design. Faults instrument transformers correlation to drawings other. In the years since, we have grown and developed a complete line of products and services for the protection, monitoring, control, automation, and metering of electric power systems. Nonpolarized relays nonpolarized relays do not use a permanent magnet in their. These relays are constructed with electrical, mechanical and magnetic components, and have operating coil and.
Relay type feature electromechanical solid state digital. Concept and working of different types of fuses protection. Types of relays the main types of protective relays are summaries in the following diagram. The following groupings will be used in this technical guide. Under normal power system operation, a protective relay remains idle and serves no active function.
The data and information saved in these reports are valuable for testing, measuring performance, analyzing problems, and identifying deficiencies before they cause future misoperations. Types of electromagnets relays are classified into the following types, depending on whether or not they have a permanent magnet. These overcurrent relays need to coordinate with each other such that the relay nearest fault operates first. This course introduces the student to various applications of protective relays bus protection, line protection, transformer protection as well as types of protective relays instantaneous overcurrent, time overcurrent, undervoltage, electromechanical, digital. Switchgear and protective devices 310 modulei 10 hours protective devices. Temperature pressure wattmetric type induction cup shaded pole types of relay. Classification or the types of relays depend on the function for which they are used. General equation of phase and magnitude comparators, duality of comparators. A recommended minimum of relays for different types and sizes of generators is given under section protective relay schemes. The protective relays are either single actuating quantity relays such as overcurrent, undervoltage, earth fault relay or double actuating quantity relays such as distance relays, differential relays. Some of the categories include protective, reclosing, regulating, auxiliary and.
What are some of the common types of protective relays. There are four common types of relays that we briefly discuss each of these relays has only solenoid coil, but a varying number of power contacts. Faults instrument transformers correlation to drawings. Electromechanical and static relays have fixed wiring and the setting is manual. Overcurrent relays types based on operating time characteristics, normally defined by the time vs. For feeder protection, there would be more than one overcurrent relay to protect different sections of the feeder. Other than the electromagnetic relay there are many other types of relays which work on different principles. Types of protection relays are mainly a based on characteristic. Protective relays continuously monitor these parameters. The ability to quickly and accurately analyze event data can save money.
But when fault or undesirable condition arrives relay must be operated and function correctly. Relays prevent that by breaking the circuit through the use of breakers. Mv system coordination doesnt have to be complicated, as long as you know the types of protective relays available, their function, and how they work. Apr 25, 2016 how relays are connected in the power system. Protective relays, associated communication systems, voltage and current sensing devices. Types and revolution of electrical relays introduction. Jun 08, 2019 power system protection relays can be categorized into different types of relays. Recently, solidstate electronic relays, just like the solidstate trip unit shown at the right, have become more popular. Power relays application guide ge power management. Mohammed tawfeeq 11 1 ct or vt, 2 relay 3 tc 4 cb 5 dc supply. Philosophy of protection, nature, causes and consequences of faults, zone of protection, requirements of a protective scheme, basic terminology components of protection scheme. Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and intolerable conditions.
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