Substation Breaker Relay Settings Calculations

[gobblerhuntr]

In setting a breaker relay (ABB DPU 2000r) for the 51p element our relay is set for a ickup of 5 with a 600:5 ct ratio, this means at 600 amps the relay will pickup and operate. The time dial is 1. On the 51p-1 element the pickup is set at 7.3, what is the calculation for this element's pickup, is it the 7.3 times the ct ratio or is there another factor involved?

Our 51N element is 1.2 and time dial of 6. I assume that this will start picking up at 1.2 times ct ratio, with a tardiness of 6 based on the time dial. Is this correct?
Then the 51N-1 element has a pickup of 20, so does this calculation go 20 times the ct ratio also?

 

[stevenal]

I see no 51P-1 or 51N-1 settings for a 2000R. They do have 50P-1 and 50N-1 settings, though. The pickup for these elements are expressed as multiples of the respective 51 pickups. Suggest you RTFM.

 

[gobblerhuntr]

I am sorry it was a typo, the element are 50P-1 and 50N-1. So you say that the pickups for the 50P-1 are the 51P element pickup which would be 600 amps times 7.3 which equals 4380 amps. And the same calc for the 50N-1?

 

[stevenal]

Yes, same calc for the 50N-1, 50N-2, and 50N-3 elements; they are all expressed as a multiple of the 51N pickup. This is one of the things I dislike about ABB. Adjusting a time overcurrent setting forces you to also adjust the associated instantaneous/definite time elements if you don't want their pickup values to change. And the range of possible 50 pickup values is limited by your 51 selection.

 

[switchgearman]

The only multipliers on the DPU2000R are the points of the time/current curve you selected. With 600:5 ct's, that's 120:1 51P-1 set at 7.3 the primary current would be 7.3*1.2=876 amps. The 50N-1 with pickup set at 1 would be primary 120 amps, if it was 20, that would be 2400 primary amps. The only time a multiplier would be used if your testing the relay and inject some function of current to make certain the relay is operating according the manufactures curves.

 

[gobblerhuntr]

Sitchgearman are you sure about your calculation on the 50P-1 set for 7.3 amps, I have a relay that fault data shows the 51P-1 element didn't operate at 3600 amps. I thought the 7.3 was a multiple of the 51P.

 

[stevenal]

Switchgearman,

I stand by my previous posts. DPU2000R, DPU2000, Circuit Shield DPU all work this way. Take a look at WinECP, and you'll see the 50 element settings are called "pickup X." The X means your entry is not in secondary amps, but a multiple of the time overcurrent setting. Testing also confirms this. You may also wish to RTFM and review your settings.

http://library.abb.com/GLOBAL/SCOT/...6E5400409172/$File/IB7.11.1.7-4e add v5.4.pdf

]

 

[gobblerhuntr]

I am sorry for the typos in my previous post it should have read as follows.



Switchgearman are you sure about your calculation on the 50P-1 set for 7.3 amps, I have a relay that fault data shows the 50P-1 element didn't operate at 3600 amps. I thought the 7.3 was a multiple of the 51P.

 

[RalphChristie]

I agree with stevenal. All the ABB-relays (even the old ASEA-relays) I've used, use that type of operation.

http://library.abb.com/GLOBAL/SCOT/...CA004D8C49/$File/DB41-219m DPU2000R .pdf

[red](copy and paste whole address)[/red]





Read through the manual especially on pg 2.

instantaneous Overcurrent Function: 50 (I>>)
- Pickup: 0.5 to 40 x 51P (3I>) and 51N (IN>) pickup setting

Regards
Ralph

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