0
High impedance fault can occur on fail or low maintenance insulators (e.g. near coastal area) or wet vegetation area (in canyon), and highly loaded industrial area (high harmornics). It all depends on the ground moist level.
Wiki User
∙ 11y ago
Add your answer:
Earn +20 pts
What is the Difference between low and high impedance relays?
It depends on the resistance level in that area if the soil have low resistance then they will use high impedance system and vice versa..so reason behind this have to reduce fault current.
Why short circuit and accidental ground is the most dangerous faults?
These are the most dangerous faults because you will be dealing with very high fault levels. Phase to phase will have very little to limit the impedance of the fault current. And phase to ground faults can be high since most systems are solidly grounded. Arching faults and faults through an impedance will be lower and cause less electrical and mechanical stress on the system.
What are the importance of impedance matching in amplifiers?
Two reasons. 1...When impedance of source and destination match, power transfer is maximum. 2...If a long transmission line is involved, the characteristic impedance of the line must match the destination impedance, or reflections will occur on the line.
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
Why emitter follower preferred to transforms as a impedance matching?
because it has high input impedance and low output impedance
What is the Difference between low and high impedance relays?
It depends on the resistance level in that area if the soil have low resistance then they will use high impedance system and vice versa..so reason behind this have to reduce fault current.
Why fault current can be extremely high?
Because the impedance to current flow is very low.
More the transformer impedance less the fault current... so is a high value of transformer impedance good for it?
It depends a lot on the application, i would go with low impedance transformers if am using the transformers for distribution as it will really increase the the maximum fault current. If am using the transformers as step up specially for generators or to charge capacitors, using a high impedance transformer is a good idea as it will decrease the inrush current of the system. you have to see your application and decide what fit that best. Mohammad Jaradat Power Generation Project Manager
Why short circuit and accidental ground is the most dangerous faults?
These are the most dangerous faults because you will be dealing with very high fault levels. Phase to phase will have very little to limit the impedance of the fault current. And phase to ground faults can be high since most systems are solidly grounded. Arching faults and faults through an impedance will be lower and cause less electrical and mechanical stress on the system.
What are the importance of impedance matching in amplifiers?
Two reasons. 1...When impedance of source and destination match, power transfer is maximum. 2...If a long transmission line is involved, the characteristic impedance of the line must match the destination impedance, or reflections will occur on the line.
In a multistage amplifier input impedance is high and output impedance is low justify the statement?
no. input impedance is low & output impedance is high
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
Why emitter follower preferred to transforms as a impedance matching?
because it has high input impedance and low output impedance
Definition of low impedance medium impedance and high impedance?
For instance: A microphone rated at 150 ohms to 300 ohms is considered low impedance. About 600 to 2 000 ohms is medium impedance, and 10 000 ohms or more is high impedance.
When does ALE float to its high-impedance state?
These pins are not at their high-impedance stateduring a hold acknowledge.
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.
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.
