Flux based utility disturbance detector

A method for detecting a voltage disturbance on an electrical line coupled to a utility, where the utility provides an electrical AC power signal on the line to an electrical system, said electrical system including a transformer, said method comprising:

• reading instantaneous voltage measurements of the power signal on the electrical line at a predetermined sample rate;
• calculating a flux value in the transformer at the sample rate for the power signal by adding the instantaneous voltage measurements at a current sample point and at a previous sample point;
• storing the calculated flux values at each sample point over a predetermined sample period where a newly calculated flux value replaces an oldest calculated flux value;
• calculating a flux error value for the power signal at the sample rate as a difference between the newly calculated flux value and the oldest calculated flux value;
• determining whether the flux error value of the power signal is greater than a first predetermined percentage;
• determining whether the flux error value of the power signal is less than a second predetermined percentage;
• and
• detecting the voltage disturbance if the flux error value is greater than the first predetermined percentage or less than the second predetermined percentage.

A method for detecting a voltage disturbance on an electrical line coupled to a utility, where the utility provides three-phase electrical AC power signals on the line to an electrical system, said electrical system including a transformer, said method comprising:

• reading instantaneous voltage measurements for each of the three-phase power signals on the electrical line at a predetermined sample rate of 4800 samples per second;
• calculating a flux value in the transformer at the sample rate for each of the three-phase power signals by adding the instantaneous voltage measurements at a current sample point and at a previous sample point, wherein calculating the flux value includes removing a DC flux offset;
• storing the calculated flux value at each sample point over a predetermined sample period of one AC cycle where a newly calculated flux value replaces an oldest calculated flux value;
• calculating an average flux value over the sample period using the stored flux values for each of the three-phase power signals, wherein removing the DC flux offset includes multiplying the average flux value by a proportional flux term defined by asymmetrical losses in a transformer core due to asymmetrical voltages on the core;
• calculating a flux error value for each of the three-phase signals at the sample rate as a difference between the newly calculated flux value and the oldest calculated flux value;
• determining whether the flux error value of any of the three-phase power signals is greater than a first predetermined percentage of 10%;
• determining whether the flux error value of any of the three-phase power signals is less than a second predetermined percentage of −10%;
• detecting the voltage disturbance if any of the flux error values is greater than the first predetermined percentage or less than the second predetermined percentage;
• and
• disconnecting the electrical system from the utility if the voltage disturbance is detected.