Sensing and control electronics for a power grid protection system

A system for detecting harmonics in a transformer signal or on a power line, the system comprising:

• a shielded enclosure having an interior volume, the shielded enclosure configured to shield the interior volume from electromagnetic interference;
• a plurality of filters positioned along a periphery of the shielded enclosure and connected to electrical signal lines extending into the interior volume from external to the shielded enclosure, the filters configured to prevent high frequency, high power electromagnetic signals from entering the shielded enclosure, and wherein at least one of the electrical signal lines is connected to a power line signal;
• a harmonic analyzer positioned within the interior volume and electrically connected to the power line signal, the harmonic analyzer configured to output a total harmonic distortion on the power line signal;
• a threshold detector configured to compare the total harmonic distortion to a preset threshold signal, wherein the threshold detector is configured to output a switching signal if the preset threshold signal is exceeded;
• and
• a controller positioned within the interior volume and configured to receive the switching signal, the controller configured to drive one or more of a plurality of external switching components in response to the switching signal.

A method of self-testing operable within a system for detecting damaging or degrading events or signals at a transformer neutral, the method comprising:

• applying an alternating current signal at a transformer, the alternating current signal having a frequency different from that of the power system frequency;
• measuring a functionality and magnitude of a blocking characteristic of a direct current blocking (DC) component based on a known amplitude of the alternating current signal and a current measurement through the direct current blocking component;
• comparing the magnitude of the blocking characteristic of the direct current (DC) blocking component to an expected value to determine accurate operation of the direct current (DC) blocking component;
• applying a harmonic signal to a power line signal, the harmonic signal having an amplitude above the preset threshold defined by a threshold detector associated with a harmonic analyzer, the threshold defining a range of amplitudes;
• analyzing the harmonic signal at the harmonic analyzer to determine whether the harmonic analyzer detects the presence of the harmonic signal;
• applying a direct current (DC) voltage signal at the transformer neutral to simulate direct current flowing between the transformer neutral and a ground;
• and
• applying an electromagnetic detector (EM) signal, the EM signal having an amplitude above the preset threshold defined by a threshold detector, the threshold defining a range of amplitudes.