AVR Burden Resistor Corroded

[IIEE2]

Hi
I have some question regarding the AVR of our high speed genset, the Burden resistor of the AVR corroded.. before this happen we experience high current reading ... Can you help me on this matter on how this matter transpire????...or what is its caused and why?

 

[itsmoked]

The hotter something gets the faster chemical reactions move, doubling for every 10 degrees.

The power dumped into a resistor goes up by the square of the current. Doubling the current => four times the power => much hotter resistor => rapid oxidation/corrosion.

Could be getting too hot also destroyed an environmental protection coating.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[rcw retired EE]

The burden resistor may have been in the reactive compensation circuit or droop circuit. As the resistor starts failing and heating up, the feedback voltage to the regulator drops. The regulator senses a lower voltage so it boosts the excitation. That increases the generator voltage and var output so the resistor sees more current, heats up more and lowers the AVR sensing voltage. It can be a runaway condition. Hard to tell if the resistor went first or failed in response to another failure that boosted the generator output.

We had a VT fuse failure that sent the AVR to full output. The stiff utility system kept the voltage and var output in check, but the current went high but still below the relaying pickup. The feedback resistor finally failed. Since it created the most smoke, we initially thought it failed first.