Method and system for real-time prediction of zero crossings of fault currents

A method for predicting zero crossings of a fault current in a power system comprising:

• sensing the fault current;
• estimating parameters of a model of the fault current;
• and
• using the estimated parameters to predict a zero crossing of the fault current by
• (a) predicting a predicted post-fault current zero crossing,
• (b) determining an actual post-fault current zero crossing,
• (c) determining a difference between the predicted and actual post fault current zero crossing, and
• (d) using the difference to predict an additional post-fault current zero crossing, the additional crossing occurring subsequent to the predicted crossing.

A method for predicting zero crossings of fault currents in a multi-phase power system comprising:

• sensing a fault current in each respective phase;
• estimating parameters of a model of each respective fault current, wherein estimating the parameters of each respective fault current includes, for each respective fault current,
• obtaining a direct current average value (DC(j-1)) of the current at a first sampling instant,
• obtaining a direct current average value (DC(j)) of the current at a second sampling instant,
• calculating the following equation to obtain a direct current offset decay time constant ({circumflex over (τ)}(j)):
• τ ^ ⁡ ( j ) = ( - T s ln ⁡ ( DC ⁡ ( j ) DC ⁡ ( j - 1 ) ) )
• wherein Ts represents a sampling frequency of the sensed fault current;
• and
• independently using the estimated parameters for each respective fault current to predict a zero crossing of the respective fault current.

A method for predicting zero crossings of fault currents in a multi-phase power system comprising:

• sensing a fault current in each respective phase;
• independently using the estimated parameters for each respective fault current to predict a zero crossing of the respective fault current, wherein independently using the estimated parameters for each respective fault current to predict the zero crossings of the respective fault current includes
• (a) selecting an initial time interval in which a zero crossing is present,
• (b) identifying a portion of the interval that includes the zero crossing,
• (c) changing the interval to comprise the identified portion,
• (d) determining whether the changed interval provides a desired resolution, and, if not, cycling through elements (b)-(d) until the changed interval provides the desired resolution.

A method for predicting zero crossings of fault currents in a multi-phase power system comprising:

• sensing a fault current in each respective phase;
• estimating parameters of a model of each respective fault current;
• and
• independently using the estimated parameters for each respective fault current to predict a zero crossing of the respective fault current wherein independently using the estimated parameters for each respective fault current to predict the zero crossings of the respective fault current includes
• predicting a predicted post-fault current zero crossing,
• determining an actual post-fault current zero crossing,
• determining a difference between the predicted and actual post-fault current zero crossing, the additional crossing occurring subsequent to the predicted crossing.

A system for predicting zero crossings of fault currents in a multi-phase power system comprising:

• means for determining a fault current in each respective phase;
• means for estimating parameters of a model of each respective fault current;
• and
• means for independently using the estimated parameters for each respective fault current to predict a zero crossing of the respective fault current, wherein the means for independently using the estimated parameters for each respective fault current to predict the zero crossings of the respective fault current includes
• (a) means for selecting an initial time interval in which a zero crossing is present,
• (b) means for identifying a portion of the interval that includes the zero crossing,
• (c) means for changing the interval to comprise the identified portion,
• (d) means for determining whether the changed interval provides a desired resolution, and, if not,
• (e) means for cycling through the functions performed by the means (b)-(d) until the changed interval provides the desired resolution.

A system for predicting zero crossings of fault currents in a multi-phase power system comprising:

• means for determining a fault current in each respective phase;
• means for estimating parameters of a model of each respective fault current;
• and
• means for independently using the estimated parameters for each respective fault current to predict a zero crossing of the respective fault current, wherein the means for independently using the estimated parameters for each respective fault current to predict the zero crossings of the respective fault current includes
• means for predicting a predicted post-fault current zero crossing,
• means for determining an actual post-fault current zero crossing,
• means for determining a difference between the predicted and actual post fault current zero crossing,
• means for using the difference to predict an additional post-fault current zero crossing, the additional crossing occurring subsequent to the predicted crossing.

A system for predicting zero crossings of fault currents in a multi-phase power system comprising:

• means for determining a fault current in each respective phase;
• means for estimating parameters of a model of each respective fault current;
• and
• means for independently using the estimated parameters for each respective fault current to predict a zero crossing of the respective fault current, wherein the controller is adapted to estimate the parameters of each respective fault current by, for each respective fault current,
• obtaining a direct current average value (DC(j-1)) of the current at a first sampling instant,
• obtaining a direct current average value (DC(j)) of the current at a second sampling instant,
• calculating the following equation to obtain a direct current offset decay time constant ({circumflex over (τ)}(j)):
• τ ^ ⁡ ( j ) = ( - T s ln ⁡ ( DC ⁡ ( j ) DC ⁡ ( j - 1 ) ) )
• wherein Ts represents a sampling frequency of the sensed fault current.

A system for predicting zero crossings of fault currents in a multi-phase power system comprising:

• means for determining a fault current in each respective phase;
• means for estimating parameters of a model of each respective fault current;
• and
• means for independently using the estimated parameters for each respective fault current to predict a zero crossing of the respective fault current, wherein the controller is adapted to independently use the estimated parameters for each respective fault current to predict the zero crossings of the respective fault current by
• (a) selecting an initial time interval in which a zero crossing is present,
• (b) identifying a portion of the interval that includes the zero crossing,
• (c) changing the interval to comprise the identified portion,
• (d) determining whether the changed interval provides a desired resolution, and, if not, cycling through elements (b)-(d) until the changed interval provides the desired resolution.

A system for predicting zero crossings of fault currents in a multi-phase power system comprising:

• means for determining a fault current in each respective phase;
• means for estimating parameters of a model of each respective fault current;
• and
• means for independently using the estimated parameters for each respective fault current to predict a zero crossing of the respective fault current, wherein the controller is adapted to independently use the estimated parameters for each respective fault current to predict the zero crossing of the respective fault current by
• predicting a predicted post-fault current zero crossing,
• determining an actual post-fault current zero crossing,
• determining a difference between the predicted and actual post-fault current zero crossing, and
• using the difference to predict an additional post-fault current zero crossing, the additional crossing occurring subsequent to the predicted crossing.