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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.
What else can I help you with?
Why impedance relay is called as distance relay?
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
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.
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.
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.
Why is output impedance kept low?
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.
What is function of mho relay?
OFFSET IMPEDANCE RELAYOffset impedance relay is also known under names ADMITTANCE RELAY or MHO RELAY
Why impedance relay is called as distance relay?
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
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 .
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 difference between high impedance busbar protection scheme and low impedance busbar protection scheme?
high impedance circit provides a varistor unit which has stabilising resistor which ll protect the relay from being operating for maloperations like through fault, CT faults whereas this varistor unit is provided internally in an numerical relay where the CT of class 5P can be used.
How does a standby earth fault relay work?
As per my openion standby earth fault relay work on zero impedance measurement, when earth fault occures than zero
What is purpose of ct supervision relay in high impedance bus bar protection?
A high impedance bus bar relay uses summed CTs from multiple breakers into a high resistance to determine a fault condition. Since all CTs connect to a single input on the relay, the relay cannot determine if a valid fault condition has occured, or one of the CTs is disconnected (open circuited). External CT supervision must be supplied to confirm.
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 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 is metrosil?
Metrosil is a non linear resistor and used with high impedance differential protection.During an internal fault ,the voltage developed across the relay can be very high and the metrosil limits the voltage across the relay ,thus protecting the relay and the wiring from any damage
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.
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.
