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What is the benifis of harmonics analisys in protection relays?
Wiki User
∙ 15y ago
inrush uses 2nd order 100 % staror protection in generator protection uses 3rd order overexcitation uses 5th order thanks
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∙ 15y ago
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What are the Relays in transformer?
There are many types of protection relays used in transformers depend upon its construction, size, use etc. They are 1. Buchholz relay for incipient faults like short ciruit, winding temparature protection, oil temparature protection, oil level protection, oil pressure protection, Pressure relief valve (for oil filled transformers) 2. Differential protection 3. Thermal Protection 4. Earth fault protection 5. Over current protection 6. Over excitation protection(where OLTC is used) etc
What is difference between reverse power relay and directional relay in electrical protection?
A reverse power relay is a directional overcurrent relay. Directional relays are relays that sense power flow in one direction, and include (directional) overcurrent relays, reverse power, and impedance based relays. So a reverse power relay is a directional relay, but a directional relay is not necessarily a reverse power relay.
What are protective relays?
A protective relay is a device designed to trip a circuit breaker when a fault is detected. The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, over-voltage, reverse power flow, over- and under- frequency. Microprocessor-based digital protection relays now emulate the original devices, as well as providing types of protection and supervision impractical with electromechanical relays. In many cases a single microprocessor relay provides functions that would take two or more electromechanical devices. By combining several functions in one case, numerical relays also save capital cost and maintenance cost over electromechanical relays. However, due to their very long life span, tens of thousands of these "silent sentinels" are still protecting transmission lines and electrical apparatus all over the world. An important transmission line or generator unit will have cubicles dedicated to protection, with many individual electromechanical devices, or one or two microprocessor relays.
What is directional protection relay and how is it works?
Directionalized relays are relays that use a polarizing circuit to determine which "direction" (in the zone of protection, or out of the zone protection) a fault is. There are many different types and different polarizing methods - ground polarizing, voltage polarizing, zero sequence voltage polarizing, negative sequence polarizing, etc. The basic operation of this relay is just like any nondirectional relay, but with an added torque control - the directionalizing element. This element allows the relay to operate when it is satisfied that the fault is within the zone of protection (ie not behind where the relay is looking).
What is the difference between directional and non directional over current protection?
The directional part. Directional relays will operate for events "in front of" them, but will not operate for events "behind" them. Typically directional relays are used in non radial situations such as on the bulk electric system. Non-directional overcurrents are commonly used on radial lines.
What are disadvantages of harmonics?
harmonics increase heating of motors ,transformers and capacitors .Power system protecting relays may operate falsly, meters give inaccurate readings,interference with telephone lines may also occur. Moreover resonance due to harmonics also causes problems
How can you interfere same lcd display for number of numerical protection relays?
electron
Why percentage differential relays do not normally need to be coordinated with the action of any other relay?
Differential relays should only operate for faults within the zone of protection, so there is no coordination issue. The reason to coordinate relays is for backup protection (a relay at a remote substation sees faults that should be cleared by another relay, for example). A differential will not see this fault, since it is external to it's zone of protection.
When shall you use class x CT?
in substation protection To be connected to unit protection relays (i.e. differential, REF, Dist., etc.)
What are the Relays in transformer?
There are many types of protection relays used in transformers depend upon its construction, size, use etc. They are 1. Buchholz relay for incipient faults like short ciruit, winding temparature protection, oil temparature protection, oil level protection, oil pressure protection, Pressure relief valve (for oil filled transformers) 2. Differential protection 3. Thermal Protection 4. Earth fault protection 5. Over current protection 6. Over excitation protection(where OLTC is used) etc
What type of protection is used on power transformers?
Depending on the size of the transformer, it can be protected by fuses, thermal elements, or by a full relay protection package, which could include overcurrent relays, differential relays, and distance relays.
What is Numerical Relays?
These are microprocessor-based relays in contrast to other relays that are electromechanically controlled. These relays provide great precision and convenience in application in the sophisticated electronic products. By combining several functions in one case, numerical relays also save capital cost and maintenance cost over electromechanical relays. The first protection devices based on microprocessors were employed in 1985. The widespread acceptance of numerical technology by the customer and the experiences of the user helped in developing the second generation numerical relays in 1990. Modern power system protection devices are built with integrated functions. Multi-functions like protection, control, monitoring and measuring are available today in numeric power system protection devices. Also, the communication capability of these devices facilitates remote control, monitoring and data transfer. Traditionally, electromechanical and static protection relays offered single-function, single characteristics, whereas modern numeric protection offers multi-function and multiple characteristics. Some protections also offer adaptable characteristics, which dynamically change the protection characteristic under different system conditions by monitoring the input parameters. The measuring principles and techniques of conventional relays (electromechanical and static) are fewer than those of the numerical technique, which can differ in many aspects like the type of protection algorithm used, sampling, signal processing, hardware selection, software discipline, etc. First generation numerical relays were mainly designed to meet the static relay protection characteristic, whereas modern numeric protection devices are capable of providing complete protection with added functions like control and monitoring. Numerical protection devices offer several advantages in terms of protection, reliability, and trouble shooting and fault information. Numerical protection devices are available for generation, transmission and distribution systems. The following sections cover relay hardware, relay software, multiple protection characteristics, adaptive protection characteristics, data storage, instrumentation feature, self-check feature, communication capability, additional functions, size and cost-effectiveness.
About bus bar protection ques and ans?
Protection of busbars is mainly done using differential relays. These relays sense current flowing into the bus and current flowing out of the bus. If current in != current flowing out, the relay assumes there is a fault on the bus and trips breakers to isolate the bus.
How does a transformer protect an appliance?
Normally current transformers are used for two things . For measuring and protection. Whenever the CT is a protection CT it will be connected with the protection relays and there will be setting in the relays based on our requirement. when the current pass through the relays are more than the setting range then relay will send the tripping signal to the breaker available in the system to isolate the fault section. Finally the CT is not protecting the system. it will transfer the high primary current from the system to relay as small secondary current.
What is unit protection?
Unit protection is one whereby the power network system is divided into discrete zones of protection. Each zone is provided with relays and circuit breakers to allow for the detection and isolation of its own internal faults. Example of zones of protection by Unit protection schemes are Generator protection, Busbar protection, Feeder protection, Transformer protection and Motor protection.By Makenote Tshuma
Which types of relay is use in power transformer?
A 'power transformer' is a category of transformer used within electricity transmission and primary distribution systems. Relays are widely used with power transformers to provide various types of protection that will act to disconnect the transformer in the event of a fault. Examples of these relays include Buchholz relays, earth-fault relays, and differential relays. Relays are also used to operate a power transformer's automatic tap-changing mechanism in order to compensate for changes in load.
What are the Application of electromagnetic relay?
1) protection of various ac and dc components 2)it can be used for differential protection 3)used as auxiliary relays in contact systems of protective relaying schemes
