stv11a

This relay is generally used to sense the overexcitation of a Generator. Overexcitation occurs when their is a sudden drop in load, the prime mover loses control, or the control system sends the prime mover information that is contrary to actual conditions. The relay monitors the voltage and frequency to determine if the power is within acceptable limits. As long as the voltage and frequency are close to fundamental and rated voltage, this relay will not operate. For instance, a STV Relay attached to a 60hz 4160V Generator would trip when the frequency goes to 61 Hz and 4263V if set at the 2.5 setting.

In order to test this relay you must have a variable voltage and frequency test source such as a MultiAMP EPOCH-30. Most Modern computer operated test sets also have this capability. Check the specifications on your test set to determine if it is capable of changing both voltage and frequencey