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because the distance is propotional to the impedance of the line ,so the operation of the impedance relay comes into picture when the impedance seen by the relay is less than the pre-setting value.When a fault occurs ,the current increases to a high value and so the Impedence decreases and the relay actuates
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What is an impedance relay?
Impedance relays are used whenever over-current relays do not provide adequate protection. They function even if the short circuit current is relatively low. The speed of operation is independent of current magnitude. Impedance relays monitor the impedance between the relay location and the fault. If the impedance falls within the relay setting, the relay will operate. The basic construction for impedance relays on which the principle of operation is easily explained is the balanced beam.
How does a distance protective relay work?
The distance relay trips when a fault occurs at a distant or a remote place in the electric transmission line. There is a mechanism based on the impedance calculation of the distance of the transmission line after which it is accurately known where the fault has taken place. Thus the distance protective relay can trip the circuit & prevent the fault to be carried further and also can indicate the location of the fault.
Which is better high input impedance or low input impedance and why?
That depends on the output impedance. In electronic we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance. An input impedance is called also a load impedance or an external impedance. An output impedance is called also a source impedance or an internal impedance.
Input impedance is greater than to load impedance?
In electronic gears we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.
How to distinguish between characteristic impedance and input impedance?
The characteristic impedance or surge impedance belongs to uniform transmission lines.In electronic gears we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.
What is function of mho relay?
OFFSET IMPEDANCE RELAYOffset impedance relay is also known under names ADMITTANCE RELAY or MHO RELAY
How does distance protection Relay work?
Well any type of relay protection is extremely complicated any many people will spend their whole career learning about protection and control. But a distance relay essentialy looks at the impedance of the circuit to be protected. When a fault occurs the impedance of the circuit will change. It then calculates this new impedance to determine where the fault has occurred. By knowing where the fault is it can trip appropriate CB's to isolate the faulted section.
What is an impedance relay?
Impedance relays are used whenever over-current relays do not provide adequate protection. They function even if the short circuit current is relatively low. The speed of operation is independent of current magnitude. Impedance relays monitor the impedance between the relay location and the fault. If the impedance falls within the relay setting, the relay will operate. The basic construction for impedance relays on which the principle of operation is easily explained is the balanced beam.
How can we make the distance relay to operate in 3 zones?
as distance relay is an impedance relay & measures impedance interms of current & voltage. first zone : 85% of the selected ist portion's impedance interms of resistance & reactance. normally we use 85% to 90% of ist portion to avoid any human & other CT & PT's instruments errors. secound zone: selected zone ist + 50% of the secound selected portions. Third ZOne: selected zone ist + zone 2nd + 20% of the thrid selected portions. Distance relay is CT & PT operated relay & give us exact location of the fault after measuring the level of the fault current & voltage.
What is instantaneous over current relay?
Instantaneous over current relay, which operates very fast with no intentional time delay and the operating time of these relay can be as low as 0.01sec . These relay operates only when the impedance between the relay and the source zsis very small compared to the impedance to the impedance of the protected section zl .
What is distance really?
The most common form of protection on high voltage transmission systems is distance relay protection. Power lines have set impedance per kilometre and using this value and comparing voltage and current the distance to a fault can be determined. The ANSI standard device number for a distance relay is 21
How does a distance protective relay work?
The distance relay trips when a fault occurs at a distant or a remote place in the electric transmission line. There is a mechanism based on the impedance calculation of the distance of the transmission line after which it is accurately known where the fault has taken place. Thus the distance protective relay can trip the circuit & prevent the fault to be carried further and also can indicate the location of the fault.
Which is better high input impedance or low input impedance and why?
That depends on the output impedance. In electronic we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance. An input impedance is called also a load impedance or an external impedance. An output impedance is called also a source impedance or an internal impedance.
What is the distance called that each person runs in a relay race?
Each segment of the relay is referred to as a leg.
Input impedance is greater than to load impedance?
In electronic gears we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.
How to distinguish between characteristic impedance and input impedance?
The characteristic impedance or surge impedance belongs to uniform transmission lines.In electronic gears we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.
What is analog audio impedance?
To get all the audio voltage from a source to a target without loss you need voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is at least ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.
