Clarification on DOs to be used for Arc-Flash protection function with Easergy P5x30

[GiuliaMorandi]

Hi there,

I'm writing to call out P5 users/experts part of the community for a clarification about DOs to be associated to Arc stages in P5x30 Arc-Flash protection.

Useful information on this topic from the User's manual are:

Characteristics of the Arc-Flash protection function (as per table 68, screenshot attached here)
  -> according to this table high speed operation can be obtained with high speed,high break contacts

Technical characteristics of relay DOs (as per table 4, meaningful parts again attached here)
  -> according to this table there's no high speed DO in P5x30 Arc-Flash module

Given the above info:

- Should Arc stages be associated to high speed,high-break control output relays only?
- What operating time can be obtained by associating Arc stages to normal non-high speed,high-break control output relays instead? Still in the range compatible with arc mitigation?

Thanks in advance for support,

[Rudolf_Simon · Accepted solution]

Using the high speed, high-break relay output provides best operation of arc-flash protection, hence it is recommended to use it.

Worth to notice that this output is designed for CB trip command application, so circuit wear is no issue.

Using any other command rated P5 relay output introduces a typical operation delay of 6 to 7 ms (due to the mechanical inertia of the output contact). 

Whether arc flash protection operation then is still acceptable depends on local requirements/ user expectations/ ...