Intelligent electronic device and method thereof
View Patent ↗An intelligent electronic device (IED) having a gain control unit adapted to selectively regulate operating ranges of output signals of a sensing circuit of the device is described. In one embodiment, the IED is a digital electric power and energy meter, which operating ranges for supply voltages and supply currents of electrical services may be adjusted to match pre-determined ranges for input signals of a data acquisition system or a data processing module of the meter.
1. An intelligent electronic device, comprising:
a metering module that measures at least one parameter of an AC electrical service; and
a processing module that processes the at least one parameter obtained using the metering module;
wherein the metering module samples supply voltages or supply currents of the AC electrical service at frequency-locked points to obtain frequency-locked samples, the frequency-locked points relating to zero-crossing points of the supply voltages or supply currents of the AC electrical service, the frequency-locked samples being obtained a predetermined number of times per cycle; and
wherein the metering module samples the supply voltages or supply currents of the AC electrical service at time-locked points to obtain time-locked samples, the time-locked points being independent of the frequency-locked points and corresponding to predetermined moments of time during a predetermined time interval.
2. The intelligent electronic device of claim 1 , wherein the processing module further comprises
a first buffer that stores the frequency-locked samples; and
a second buffer that stores the time-locked samples.
3. The intelligent electronic device of claim 2 , wherein the processing module synchronizes the frequency-locked samples stored in the first buffer with the time-locked samples stored in the second buffer.
4. The intelligent electronic device of claim 1 , wherein the processing module performs harmonic analysis on the frequency-locked samples.
5. The intelligent electronic device of claim 1 , wherein the processing module performs energy calculations on the frequency-locked samples.
6. The intelligent electronic device of claim 1 , wherein the processing module performs waveform analysis on the time-locked samples.
7. The intelligent electronic device of claim 1 , wherein the zero-crossing points are moments of time when a polarity of the supply voltages or the supply currents changes from a negative polarity to a positive polarity or when a polarity of the supply voltages or the supply currents changes from a positive polarity to a negative polarity.
8. The intelligent electronic device of claim 1 , further comprising a user interface unit that displays the at least one parameter, frequency-locked samples, time-locked samples, data processed by the processing module, or configuration settings of the intelligent electronic device.
9. The intelligent electronic device of claim 1 , further comprising a communication module that transmits, to a remote terminal, the at least one parameter, frequency-locked samples, time-locked samples, data processed by the processing module, or configuration settings of the intelligent electronic device.
10. The intelligent electronic device of claim 1 , wherein said intelligent electronic device is selected from the group consisting of a digital electrical power and energy meter, a Programmable Logic Controller (PLC), a Remote Terminal Unit, a protective relay, or a fault recorder.
11. The intelligent electronic device of claim 1 , wherein said intelligent electronic device is a digital electrical power and energy meter.
12. The intelligent electronic device of claim 1 , wherein the metering module comprises a voltage analog-to-digital converter and a current analog-to-digital converter, the voltage analog-to-digital converter and current analog-to-digital converter being synchronized with each other using the zero-crossing points.
13. The intelligent electronic device of claim 1 , wherein the processing module comprises at least one voltage analog-to-digital converter and at least one current analog-to-digital converter, the at least one voltage analog-to-digital converter and at least one current analog-to-digital converter being synchronized with each other using the zero-crossing points.
14. A method of using an intelligent electronic device to measure and process at least one parameter of an AC electrical service, the method comprising the steps of:
sampling supply voltages or supply currents of the AC electrical service at frequency-locked points using a metering module to obtain frequency-locked samples, the frequency-locked points relating to zero-crossing points of the supply voltages or supply currents of the AC electrical service, the frequency-locked samples being obtained a predetermined number of times per cycle; and
sampling the supply voltages or supply currents of the AC electrical service at time-locked points using the metering module to obtain time-locked samples, the time-locked points being independent of the frequency-locked points and corresponding to predetermined moments of time during a predetermined time interval.
15. The method of claim 14 , wherein the zero-crossing points are moments of time when a polarity of the supply voltages or the supply currents changes from a negative polarity to a positive polarity or when a polarity of the supply voltages or the supply currents changes from a positive polarity to a negative polarity.
16. The method of claim 14 , wherein the at least one parameter is a total harmonic distortion or harmonics thereof.
17. The method of claim 14 , wherein the at least one parameter is selected from the group consisting of a line voltage, a line current, a phase voltage, a phase current, a root mean square (RMS) value, energy, revenue, real power, reactive power, total power, and a power factor.
18. The method of claim 14 , wherein the at least one parameter is selected from the group consisting of a waveform of a line voltage, a waveform of a line current, a waveform of a phase voltage, and a waveform of a phase current.
19. The method of claim 14 , further comprising the step of synchronizing a voltage analog-to-digital converter of the metering and a current analog-to-digital converter of the metering module using the zero-crossing points.
20. The method of claim 14 , further comprising the step of processing the at least one parameter, frequency-locked samples, and time-locked samples using a processing module.
21. The method of claim 20 , further comprising the step of synchronizing at least one voltage analog-to-digital converter of the processing module and at least one current analog-to-digital converter of the processing module with each other using the zero-crossing points.