As Yohjo above. The powder is probably there to absorb humidity. Of course you've cleaned the wires thoroughly before connecting.
As a side issue, you can leave the wires as is. You'll have to clean them from time to time (the oxides) and you can use some chemicals that promise to slow down oxidising (Kontact and others).
As a side issue, you can leave the wires as is. You'll have to clean them from time to time (the oxides) and you can use some chemicals that promise to slow down oxidising (Kontact and others).