Overcurrent Relays - Tap Setting vs. Tap Range
Overcurrent Relays - Tap Setting vs. Tap Range
(OP)
Hi Everybody,
I have a simple question regarding 50/51 overcurrent relays.
I understand that these relays have both a tap range and a tap setting within that range. Some of these ranges however overlap, i.e. Tap range 1.5-6.0 & 4.0-16. My question is if I have a tap setting of 5, does it matter which Tap range I choose? Are the characteristics of either range different given that my tap setting is 5 for both?
I searched the forums and I read one posting that the range is related to short circuit current. Is this range supposed to be a max withstand rating of the relay?
Thank you in advance for your help!
I have a simple question regarding 50/51 overcurrent relays.
I understand that these relays have both a tap range and a tap setting within that range. Some of these ranges however overlap, i.e. Tap range 1.5-6.0 & 4.0-16. My question is if I have a tap setting of 5, does it matter which Tap range I choose? Are the characteristics of either range different given that my tap setting is 5 for both?
I searched the forums and I read one posting that the range is related to short circuit current. Is this range supposed to be a max withstand rating of the relay?
Thank you in advance for your help!






RE: Overcurrent Relays - Tap Setting vs. Tap Range
So you have to select the tap range the relay has and then select a tap setting (pickup) within that range.
RE: Overcurrent Relays - Tap Setting vs. Tap Range
All that being said - in this day and age, I would expect you to be purchasing a numerical protection relay, with range so wide it's not an issue (actually, I don't recall every having to specify a range for a numerical relay, other than choosing between 1A and 5A CT secondaries).
RE: Overcurrent Relays - Tap Setting vs. Tap Range
For the older style relays where several tap ranges are available, is there a difference in the characteristics (curves) of the same relay with different selected tap ranges? Or do they overlap over the values that the range is the same?
I ask because I'm conducting a short circuit study and the tap range for relays in the software do not match exactly those of the actual relay. Therefore, I'd like to know whether the pickup range will have an effect on the coordination curves of the relay.
I'm wondering if anyone can shed some light on that.
RE: Overcurrent Relays - Tap Setting vs. Tap Range
If there is a difference, it is within the same +/-% range as the normal variation in actual performance among a group of "identical" relays. Not something to worry about for your purposes. (If you are worried, you are measuring with a micrometer and cutting with an axe.)
RE: Overcurrent Relays - Tap Setting vs. Tap Range