procedure for testing REF scheme?

[RIYAZAHAMED]

hello people....
I am an assistant engineer in TESTING AND COMISSIONING. I have tested REF relay and the full scheme in HIGH IMPEDANCE method. I heard that there are some other methods too for REF scheme testing. The method which i use to check is like

FOR STABILITY
i used a primary current injection set and made current to flow through two CT's(one phase and another neutral CT) and no spill current is observed.

FOR SENSITIVITY
made primary current to flow through only one CT(each phase CT's and neutral CT's) and the spill current is observed in relay and followed by trip.

some other method i heared is like shorting one winding(ex star secondary in DYn TRX) and injecting voltage on the other winding(ex delta primary). Am not sure of this method and will be helpfull if any one give an answer for this in some detailed manner.I just need the testing procedure alone. (for distribution DYn TRANSFORMER,1500kva,11/0.415 KV) Thanks in advance.

 

[DTR2011]

The paper named Lessons Learned Commissioning on the Schweitzer website, located @

http://www.selinc.com/search/SearchPage.aspx?searchtext=commissioning

gives a detailed explanation of using the power transformer, short circuited as a current source. The description is in Appendix A.

I have used this method (Primary Injection Testing) extensively for years as a final test, after all other elements of commissioning have been performed. It does not take long to do and when dealing with transformers with bushing CT's (ANSI world) is the only way to really prove things 100%. It is also very useful when commissioning generator protection.

Alstom also has a description for this in the MFAC relay manual.

http://www.alstom.com/Global/Grid/R...on/Technical manuals/MFAC 14_34 Manual GB.pdf

PLEASE NOTE: You will need something like 110V, not 415. Your calculations will determine some reasonable voltage - you want a reduced voltage short circuit. It is necessary to perform the calculations for expected secondary current and phase angle prior to conducting the tests. I recommend making a spreadsheet with calculated and measured values. If all other parts of the protection system have been properly checked, your primary injection tests should only take as much time as required to confirm and document your measured results.