I Want to Program ABB Make IRXM Protection Relay for 4000/1A CT. Maximum Current Allowed for Tripping 320A

Could you not find the following document? I just searched for "ABB IRXM relay" on internet....the document front page has IRXm.

https://library.e.abb.com/public/65cfeba9aff29009c12577ec0055e89d/IRXM.pdf?x-sign=wKw/l40KNPEMggX4MqaquOEjbp1iRUWsGWh83pTpY1ylvLN2rKFjb6B27Phre0zE

320 amps is 320/4000 = 0.080 ≡ 8.0% of relay nominal full scale of 1 amp ≡ 80 mA

It would appear you must set a range switch behind the front plate for each unit of front panel switch K to be 0.5% or 5%. I have no idea what B positions are.

Using 1 amp input terminals each K switch unit can be 5 mA - no good 5 mA x 10 = 50 mA or, high range; 50 mA (k=1) ; 100 mA (k=2).

Alternatively, using 5 amp input terminals, each K switch unit can be 25 mA - giving a choice of 75 mA (k=3) or 100 mA (k=4).

So you cannot get a setting of 320 amps. As an old work colleague remarked, when deserved, " What dead-head designed this".

Maybe there is an "interposing transfo" installed between CT and relay - ratio e.g. 80/75 = 1.067 - possible 1.05 to 1 ratio available as standard part. Possibly a resistor of burden 7% of the relay burden could be paralleled with relay CT input.

I would suppose that circuit/wiring diagram should show interposing CT and if relay input is on 1 amp or 5 amp terminals - but check real connection back of relay!

I would set 75 mA - safe against "under-protection" [maybe risk of unwanted operation on fault outside relay zone] - till you get a reply to your "rocket" to the design engineer.

67model

Help me...till the time I get interposing CT I would set it on 400Amp.

Then what will be the calculations and position of K switch and switch behind the front panel.

400 amps primary is 10% [0.1 x In] of CT primary rating 4000 amp.

At secondary, 10% of 1 amp is 100 mA (0.1 x In, where In = 1 amp).

1. If the CT input terminals are 1 & 2 (relay 1 amp nominal) then range switch at 5% and K switch at 2 will give 2 x 5% = 10% setting [400 amp at primary, 1 amp x 0.10 = 0.1 amp secondary].
2. If the CT input terminals are 5 & 6 (relay 5 amp nominal) then range switch at 0.5% and K switch at 4 will give 4 x 0.5 = 2% setting [400 amp at primary, 5 amp x 0.02 = 0.1 amp secondary].

You asked for a maximum setting of 320 amp, so a smaller setting of 300 amp - as option 2, but K switch at 3 would be OK. With 1 amp CT, there is no danger of overloading relay at 5 amp nominal.

Having noted that, the usual design limit for Restricted Earth fault & similar relays is the unbalance due to CT current mismatch at the highest external fault current (fault outside the zone protected by this relay) - which gives the minimum setting avoiding spurious trips. Theoretically, there is zero relay current for an external fault and the lowest possible relay setting would be used, but practical [iron core] CTs saturate causing significant error.

67model

The relay IRXm is meant for High impedance circulating current differential protection. This has current setting and the stabilising resistor and metrosil are externally mounted. When you say 320A current, I presume it is Effective primary operating current for the protection and not the relay current setting itself (which will have to be lower than 320A).

The effective primary operating current adds the estimated CT magnetising current (at the relay operating voltage) to the relay set current. This is part of the protection setting calculation including Stability voltage Vs, Stabilising Resistor Rst and Effective Primary Operating Current as well as the Metrosil requirement.

The calculation requires parameters and excitation characteristic curves for all CTs involved, in addition to through fault current (for which the relay is expected to be stable).

It is all too common for this protection to maloperate (i.e. operate for out-of-zone faults) if the calculation is not done correctly and the stabilising resistor is not correctly set or if the CT parameters are inadequate.