08-05-2009, 07:18 AM
Dear PJW
many thanks for your explanation.
I think you are have commented on what I was asking, exactly.
I got the values of the margines, from an indian book. in setting the regulating resistance in DC TCs, it was mentioned that a 2.5 times PU voltage is considered. this is to make sure that the relay voltage does not go beyound that. (perhaps to prevent the relay from overvoltage)
VR <= PUV when Rb (the ballast resistance) is infinity and feed is in maximum value.
the checking for the reliability is considered to be:
VR >= 1.25 PUV , this should ensure that the relay is in pick up condition in worst case, when the feed is in minimum and Rb also in minimum.
and the last checkin, as you said for safety,
VR <= 0.85 DAV, this should ensure the safety, since ensures dropping of the relay when the track is occupied. in the maximum value of the feed and the ballasat resistance.
are these values true for the network rail as well or they depend on the design and situation?
and my main question was that do we need to consider similr values for the AC TCs as well?
If these calculations are not valid for the AC circuits, is there any reference to use?
I think it should be a bit more coplicated when impedance bond is added to the circuit,
Mirabadi
many thanks for your explanation.
I think you are have commented on what I was asking, exactly.
I got the values of the margines, from an indian book. in setting the regulating resistance in DC TCs, it was mentioned that a 2.5 times PU voltage is considered. this is to make sure that the relay voltage does not go beyound that. (perhaps to prevent the relay from overvoltage)
VR <= PUV when Rb (the ballast resistance) is infinity and feed is in maximum value.
the checking for the reliability is considered to be:
VR >= 1.25 PUV , this should ensure that the relay is in pick up condition in worst case, when the feed is in minimum and Rb also in minimum.
and the last checkin, as you said for safety,
VR <= 0.85 DAV, this should ensure the safety, since ensures dropping of the relay when the track is occupied. in the maximum value of the feed and the ballasat resistance.
are these values true for the network rail as well or they depend on the design and situation?
and my main question was that do we need to consider similr values for the AC TCs as well?
If these calculations are not valid for the AC circuits, is there any reference to use?
I think it should be a bit more coplicated when impedance bond is added to the circuit,
Mirabadi