4160 vac, 2000A switchgear shunt current testing 2

[eng1561]

What is the difference between full load shunt current testing and current injection testing? Is one method more suited for a given situation than the other? Do they both accomplish the same thing? I could use a nice overview if anyone can help. Thanks.

 

[candu6]

If I understand you question correctly: Current injection testing or "primary current injection" means injecting current through a breaker at the levels of the breaker trip settings to test the entire trip circuit (CTs and trip mechanism). Shunt current injection bypasses the CTs and injects lower current values (that would appear on the secondary of the CTs) to test the trip circuit. Many switchgear manufacturers have tripping test boxes that plug into the breaker's trip unit (ex. Westinghouse Amptector) to perform this type of testing.

 

[PWR]

4160V breakers have the protection devices physically separate from the breaker itself. For routine testing, the protective relays would be tested with test current representative of what flows in the secondary of the associated current transformers.

Breakers at 600V and below generally have all the protective devices contained on the breaker itself. The most thorough test of those devices is to inject primary current equivalent to what actually flows through the breaker during an overload or fault (except that the test current is driven by a much lower voltage level than the "real life" operating voltage).

 

[eng1561]

Thanks much to PWR and candu6! This helps alot!

 

[busbar]

 
Consider asking the originator of the work request to define the terms, and cite national-consensus electrical standards that reference them.