In 19th and 20th century, the typical orchestra musical instruments were restricted to a group of 4 musical instruments which are: the brass, wood, string and percussion instruments but as time passed, other musical instruments have been introduced to the orchestra and electric instruments are part of the instruments introduced.
Most large orchestras now use electric instruments like the keyboard, piano and electric guitar. Keep in mind that they are electric violins, saxophone and other electric version of typical orchestra instruments now.
To give you a more direct answer, I will say that electric instruments were not used in orchestra before but they are now used in orchestra.