T1 Line Communication Rate adequate for Differential Protection 1

[Thriggen]

The question says it all. I am in the process of determining whether a T1 line will be adequate for differential line relay (SEL 311L) communication. The plan is to have the relay use a fiber input to a MUX which will output to a T1 line to the other substation. Reverse on the other end. Fiber to the other substation is too expensive right now and the 4 wire lease lines from our current telco provider is being phased out so a tone relay, which is primarily what we use, is not an option.

Is this something that I need to get with the providor to make sure they can provide what we need?

Typically how many cycles are needed from the time of fault detection to the time the breaker needs to open?

Any other insight on this topic would be greatly appreiciated.
Happy Halloween.

 

[DTR2011]

I would recommend contacting SEL. They provide excellent customer support.

 

[eryp]

You would have to measure the latency in the network. I have a similar circuit using a combination of T1 and fiber across 2 networks. However, this is not being used for differential protection. The latency on this circuit is less than 5ms or 0.3 cycles. I'm not a transmission engineer but I believe this latency would be acceptable for trip purposes. I'm not sure what SEL's requirment would be.

Attached is an example of what the message rate is using SEL's mirrored bits. This may not apply to the Differential comm ports.

SEL's own media converter has a data delay of 200ms: (They may have meant 200us)

http://www.sel-com.com/sel-3094.htm

In the end - it all comes down to measuring actual latency with similar packet/frame rates to the actual data that will be passed. smallgreek has it right. Contact SEL.

 

[stevenal]

http://www.selinc.com/WorkArea/DownloadAsset.aspx?id=10631

 

[zer0sequence]

Contact SEL, then post back with your findings!!

 

[JG2828]

Here is some good reading from SEL.

http://www2.selinc.com/techpprs/SEL_Fodero_Rosselli_ApplyingDigitalCurrent_6186.pdf