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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.
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Difference between relay and solid state relay?
All solid state relays are relays, but not all relays are solid state relays. There are three basic kinds of (protective) relays I know of: electromechanical (rely on induced voltages and currents to spin disks or energize solenoids), solid state (built with solid state parts - basically prerequisites to microprocessors), and microprocessor based relays (fancy computers).
What is an instrument transformer?
An 'instrument transformer' is a category of transformer used to supply measuring instruments or protective relays. There are two types of instrument transformer: a 'voltage transformer' (known as 'potential transformer' in North America), and a 'current transformer'. They are used with high-voltage systems, where it is hazardous to connect instruments directly to such systems.Voltage tranformers are used to reduce high-voltages down to a level that can be safely applied to voltmeters, or to the voltage-coils of wattmeters or energy meters, or to protective relays, while electrically-isolating those instruments (and personnel) from the high-voltage supply.Current tranformersare used to reduce high-voltage currents down to a level that can be safely applied to ammeters, or to the current-coils of wattmeters or energy meters, or to protective relays, while electrically-isolating those instrument (and personnel) from the high-voltage supply.
Why earthing is use in transformer?
Earthing of a transformer is done to 1:reduce the sensitivity of protective relays. 2:reduce the damage due to fault current. 3:get rid of great loss of equipment and money in case of any earth fault.
How are substations protected?
Almost all of the equipment inside of a substation is used for the purpose of protection. The circuit breakers and power transformers in the substation are equipped with current transformers (CTs) that step down the current passing through the equipment to a level that can be read by protective relays. These protective relays can cause the breakers to trip upon many different events including under/overvoltage, current spikes, frequency issues, transformer/bus differential, etc. The breakers in a substation are placed strategically so that different pieces of equipment or sections of a circuit can be isolated without loss of service to the customer.
What is PU in electrical engineering?
"PU" can stand for multiple things, depending on what part of "electrical engineering" you're interested in. In the power world (power generation, transmission, distribution) "PU" may stand for per unit, or pickup if related to protective equipment like relays.
What has the author Victor H Todd written?
Victor H. Todd has written: 'Protective relays' -- subject(s): Electric relays
What is the function of auxiliary relay in power station protection?
Auxiliary relay is a relay which will repeat the operations of protective relay such as tripping, time lag, breaking of trip circuit current, giving alarms and showing flags etc..Protective relay contacts are delicate and light weight hence it will not capable of carrying a large amount of current for a long period.protective relays do not have enough contacts to perform all the operations of protective scheme.Therefore auxiliary relays, auxiliary switches and repeat contacts are used to assist protective relays.
Why current transformers are required in protective relaying scheme?
Current transformers (CTs) are used to monitor the current (or lack of) in high-voltage systems, and their secondary outputs controls the behaviour of protection-system relays. The CTs (1) reduce the current to values that match the current ratings of the protective relays, and (2) electrically-isolate the relays from the high-voltage system.
Difference between relay and solid state relay?
All solid state relays are relays, but not all relays are solid state relays. There are three basic kinds of (protective) relays I know of: electromechanical (rely on induced voltages and currents to spin disks or energize solenoids), solid state (built with solid state parts - basically prerequisites to microprocessors), and microprocessor based relays (fancy computers).
Why you use dc supply in generator protection panel?
The DC supply may supply power to trip breakers, or to power the protective relays.
What has the author Heinz Clemens written?
Heinz Clemens has written: 'Relaisschutztechnik in Elektroenergiesystemen' -- subject(s): Electric power systems, Protection, Protective relays
What is protective relaying?
A protective relay is a complex electromechanical apparatus, often with more than one coil, designed to calculate operating conditions on an electrical circuit and trip circuit breakers when a fault was found. Unlike switching type relays with fixed and usually ill-defined operating voltage thresholds and operating times, protective relays had well-established, selectable, time/current (or other operating parameter) curves. Such relays were very elaborate, using arrays of induction disks, shaded-pole magnets, operating and restraint coils, solenoid-type operators, telephone-relay style contacts, and phase-shifting networks to allow the relay to respond to such conditions as over-current, over-voltage, reverse power flow, over- and under- frequency, and even distance relays that would trip for faults up to a certain distance away from a substation but not beyond that point. An important transmission line or generator unit would have had cubicles dedicated to protection, with a score of individual electromechanical devices. The various protective functions available on a given relay are denoted by standard ANSI Device Numbers. For example, a relay including function 51 would be a timed overcurrent protective relay. These protective relays provide various types of electrical protection by detecting abnormal conditions and isolating them from the rest of the electrical system by circuit breaker operation. Such relays may be located at the service entrance or at major load centers. http://en.wikipedia.org/wiki/Relay
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
Where is diagnostic port in a 1986 e 150 ford van?
Under the hood. Not sure which side but it is where all the relays and electrical stuff is. It may be snapped into a protective cover so it is not in plain view.
How many types of relays?
relays are two type 1. Electromagnetic attraction relays. 2. Electromagnetic induction relays.
What is an instrument transformer?
An 'instrument transformer' is a category of transformer used to supply measuring instruments or protective relays. There are two types of instrument transformer: a 'voltage transformer' (known as 'potential transformer' in North America), and a 'current transformer'. They are used with high-voltage systems, where it is hazardous to connect instruments directly to such systems.Voltage tranformers are used to reduce high-voltages down to a level that can be safely applied to voltmeters, or to the voltage-coils of wattmeters or energy meters, or to protective relays, while electrically-isolating those instruments (and personnel) from the high-voltage supply.Current tranformersare used to reduce high-voltage currents down to a level that can be safely applied to ammeters, or to the current-coils of wattmeters or energy meters, or to protective relays, while electrically-isolating those instrument (and personnel) from the high-voltage supply.
When was Kansas Relays created?
Kansas Relays was created in 1923.
