AC power line impedance monitoring method and system
AssigneeRockwell Automation Technologies, Inc.
InventorMichael Gasperi
Life of this patent
Estimating the term…
Abstract
A technique is disclosed for determining inductive and resistive components of power line impedance. A measurement circuit switches a burden or drain resistor between power line conductors to cause a droop or sag in a voltage waveform. The voltage waveform is sampled prior to inclusion of the resistor in the circuit, as well as after to identify the droop. The short circuit between the power lines is then removed by opening the circuit and a capacitor in the test circuitry causes a resonant ring due to the inductive component of the power line impedance. Based upon the period or frequency of the resonant ring, and upon the voltage measurements with and without the resistor in the circuit, the inductive and resistive components of power line impedance can be computed.
Claims34
A method for determining power line impedance comprising:
- measuring a first voltage of an ac waveform applied to an electrical line;
- draining current from the line and measuring a second voltage of the ac waveform during a droop in voltage resulting from the current drain;
- removing the current drain to cause a resonant ring in the voltage in the line;
- measuring a parameter of the resonant ring;
- and
- computing the line impedance based upon the measured first and second voltages and the measured parameter of the resonant ring.
A method for determining power line impedance comprising:
- measuring a first voltage of an ac waveform applied to an electrical line;
- closing a solid state switch to place a resistor between the line and a different electrical potential;
- measuring a second voltage of the ac waveform during a droop in voltage resulting from current drain through the resistor;
- opening the solid state switch to cause a resonant ring in the voltage in the line based on an inductive component of the line impedance;
- measuring a parameter of the resonant ring;
- and
- computing inductive and resistive components the line impedance based upon the measured first and second voltages and the measured parameter of the resonant ring.
A method for determining power line impedance comprising:
- sampling power line voltage with and without a burden resistor in short circuit with the power line;
- causing a resonant LC ring in the power line voltage and sampling power line voltage during the ring;
- identifying a parameter of the LC ring;
- and
- computing inductive and resistive components the line impedance based upon the measured voltages and the parameter of the LC ring.
A system for determining power line impedance comprising:
- a resistor configured to be coupled between power line conductors;
- a capacitor in series with the resistor;
- a switch for placing the resistor a short circuit between the power line conductors and for interrupting the short circuit to cause a resonant ring between the capacitor and an inductive component of the power line impedance;
- measurement circuitry for measuring voltages during a test sequence in which the switch is switched on and off;
- and
- processing circuitry for determining inductive and capacitive components of power line impedance based upon the measured voltages.
A system for determining power line impedance comprising:
- voltage measurement circuitry for measuring voltage valued in the power line;
- test circuitry including a solid state switch in series with a burden resistor and in parallel with a capacitor, the switch being switchable to place the resistor in a short circuit between the power line and a different potential and to cause a resonant ring between the capacitor and an inductive component of the power line impedance;
- drive circuitry for switching the solid state switch;
- and
- processing circuitry for determining inductive and resistive components of the power line impedance from voltage measurements made by the voltage measurement circuitry with and without the resistor in the short circuit and during the resonant ring.
A system for determining power line impedance comprising:
- means for measuring a first voltage of an ac waveform applied to an electrical line;
- means for draining current from the line and measuring a second voltage of the ac waveform during a droop in voltage resulting from the current drain;
- means for removing the current drain to cause a resonant ring in the voltage in the line;
- means for measuring a parameter of the resonant ring;
- and
- means for computing the line impedance based upon the measured first and second voltages and the measured parameter of the resonant ring.
Dependencies are inferred from the claim text.