what are the differences between directional and non directional relay. I want to get information about relay. can anyone provide me any site address for this?
It sounds like directional relays are just relays that only turn on when the voltage/current are the right polarity and magnitude, whereas a regular relays just turns on if magnitude is large enough.
Maybe these were used before semiconductors were widespread? You'd just stick a diode in series with the coil of a regular relay nowadays.
But they seem pretty complicated compared to normal relays. The directional DC relays sound like they use magnetic elements (either field windings or permanent magnet) on the switch (rather than just steel that always gets attracted to any polarity magnetic field) so that only the right coil polarity move the switch on the correct direction to activate the relay. And then it talks about relays that use multi-tap transformers for their coils which allows you to make relays that activate on current imbalances between multiple wires, or relays that activate based on AC phase-shifts and current polarity.
Directional and nondirectional could mean DC verses AC. In that case the AC relay has a copper slug around its core that acts like a shorted winding. This allows it to stay energized while the power reverses.
The other possible meaning is that you are talking about a Polar Relay. It has a permanent magnet and multiple windings. It is energized by a specific amount of current in one direction only and remains energized until the current drops below another specific value. For instance, it might require 35ma to pull in but will not release until the current drops below 18ma. The pull-in and drop currents are adjustable. Telephone MF receivers and central office trunks used then in cross-bar offices.
what are the differences between directional and non directional relay. I want to get information about relay. can anyone provide me any site address for this?
Guys Directional and non directional relays are over voltage protection devices. They are used to protect the power system under faulty condition.
The directional relays are the one which operates under the direction of flow of fault current. See the following quote
Directional relay senses direction of power flow by means of phase angle between V and I, When the phase angle between V and I exceeds certain predetermined value, the directional relay operates with a condition that the current is above the pickup value. Thus directional relay is a double actuating quantity relay with one input as current I from CT and the other input V from PT.
Its provided by our college dude. Actually its not a text book. its study material for us. I have that paper in this semester. But if i found the correct source means i'll let you know.