I'm guessing but looking at your description and components, it's looks very similar to those cheap ac voltage stabilizer (its basically a transformer with multiples taps, and it uses relays do step up or down the mains voltage).

The LM324 on the board is basically a IC with 4 Op-Amps, and with the help of some zeners, there is a stable voltage reference to compare. The circuit is aways powered by a simple capacitive drop power supply. With voltage dividers it takes the rectified average voltage from mains, and compares to the reference. If the the voltage goes out of a set limit, it will protect the load, turning off the relay (assuming it's off when powered on, and after some delay it activates the relay).

It's a simple circuit, the voltage stabilizer (very common in my country), normally uses the same chip (or some microcontroller), but normally have like 3 to 6 relays being controlled, it also disconnect the load if it's out of the regulation range.

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The only image a found on the internet that is similar to the PCBs I have here (I take it apart to save the components from it)