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.
how the apfc relay work
reactance relay is used for distance protection of the transmission line....
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
They're completely different, used for different applications (usually). A distance relay uses both current and voltage. A differential relay uses only current. A differential relay usually has harmonic restraint capability, while distance relays ideally track system frequency. Differential relays require fast operation, while distance relays may not be required to operate as quickly. Distance relays have more issues with operating for out of zone problems than differential relays. There are many more, but this gives an idea.
They seem to be the same thing. Such a device is a protective relay. It uses a microprocessor to analyze power system voltages, currents or other process quantities for the purpose of detecting faults in an industrial process system.
basic circuit of electrical protective relay
kutria
Power Transformer
It has a display distance of 2 meaters.
distance relay..........
how the apfc relay work
reactance relay is used for distance protection of the transmission line....
How Negative phase sequence relay work
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
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
Each segment of the relay is referred to as a leg.
They're completely different, used for different applications (usually). A distance relay uses both current and voltage. A differential relay uses only current. A differential relay usually has harmonic restraint capability, while distance relays ideally track system frequency. Differential relays require fast operation, while distance relays may not be required to operate as quickly. Distance relays have more issues with operating for out of zone problems than differential relays. There are many more, but this gives an idea.