Generator control relay continuous built-in test circuit

An apparatus for performing a continuous built-in test for a generator control relay (GCR) switch, the apparatus comprising:

• a controller configured to periodically generate a continuous built-in test (CBIT) control signal at a first logic level to initiate the CBIT for the GCR switch;
• a GCR switch control circuit configured to generate a GCR switch control signal to open the GCR switch responsive to (i) the CBIT control signal from the controller, (ii) an exciter drive control signal from a generator control circuit, (iii) a GCR control signal that can open the GCR switch, and (iv) a CBIT completion status signal that disables the GCR switch control circuit from opening the GCR switch after it has already opened one time for a given test iteration;
• a first latch circuit configured to latch a test completion status signal to one of a first logic state indicating a test is incomplete and a second logic state indicating the test is complete, wherein the first latch circuit is cleared responsive to the CBIT control signal from the controller going to a second logic level;
• a voltage sensing circuit configured to sense a voltage across the GCR switch and to generate a voltage sense signal;
• a comparator configured to compare the voltage sense signal with a reference voltage and generate a first logic signal to indicate the GCR switch has passed the continuous built-in test or a second logic signal to indicate the GCR switch has failed the continuous built-in test;
• and
• a second latch circuit configured to latch an output to the first logic signal responsive to the first logic signal from the comparator or latch the output to the second logic signal responsive to the second logic signal from the comparator.

A method for performing a continuous built-in test for a generator control relay (GCR) switch, the method comprising:

• periodically generating a control signal at a first logic level to initiate the continuous built-in test for the GCR switch using a controller;
• determining when the GCR switch will not have a current flowing therethrough using a GCR switch control circuit;
• generating a GCR switch control signal to open the GCR switch responsive to the control signal from the controller using a GCR switch control circuit when the GCR switch does not have the current flowing therethrough;
• monitoring a voltage across the GCR switch when the GCR switch is opened using a voltage monitoring circuit;
• comparing the monitored voltage to a threshold value using the voltage monitoring circuit;
• and
• generating a first output value indicating the GCR switch has passed the continuous built-in test responsive to a first comparison result or a second output value indicating the GCR switch has failed the continuous built-in test responsive to a second comparison result.