Cold Load Pickup Scheme Timers - typical settings?

[kxw]

Hi all,

I am interested in typical values for the timers in a cold load pickip scheme. Specifically the loss of diversity timer and the timer that retstors the normal protection after restoration.

Thanks!

 

[dpc]

These are implemented a bit differently depending on the device in question. What relay are you working with?

Often, the CLPU scheme is asserted after any lock out trip. With older recloser controls it is done manually. I think the last Form 6 I looked at had a 20 second duration setting.

 

[kxw]

It's a SEL 351R on a 630A line recloser.

 

[cranky108]

This should be the setting in the 79 function called the reset timer, which if I recall, also controls the insertion of the fast curves.
I.E. shot 0, and 1 (?) torque control the first set of 51 settings.

 

[ppaya]

we set 51 element to be higher then 2xMAX load on the feeder + to be sensitive to see all faults to the end of the protected feeder. Instantaneous element 50 will be generally set to the same value (50PU=51PU) , CLPU scheme blocks 50 element for 10 sec after closing of the breaker (manual). This is sufficient time for load that lost deversity to come back to "normal" (note relay is set always 2-ce as high as max load among other things to accomodate for CLPU that may take up to 15 minutes with this 200% magnitude)
I hope this helps

 

[bacon4life]

Some our substation just have a push button that the operators use if they expect cold load pickup that will raise the neutral pickup.

I have only seen one actual recording of cold load pickup, but was very surprised that the load actually continued to rise for several minutes.

 

[apowerengr]

I'd use 60-180 seconds at 2.8X the normal pickup value however I'd not affect the ground settings for a 4 wire wye grounded distribution system. This gives you enough margin so you don't have to set the normal pickup too high and yet if cold load is an issue you won't have to sectionalize the feeder to restore power.

 

[bacon4life]

Check out the following application guide Cold Load Pickup Scheme Using the SEL-551 Relay

https://customer.selinc.com/metadot...ld_name=item_attachment_file&op=download_file

Unfortunately you will have to register to get access to it.