Method for validating voltage measurements in a digital-electricity transmission system

Abstract

Transmission-line voltage measurements in a digital-electricity power system are validated by acquiring a series of transmission-line voltage measurements during a sample period when a transmitter-disconnect device is in a non-conducting state. A numerical analysis is performed to determine a point in time at which AC components in the transmission line have diminished and at which the primary change in the transmission-line voltage measurement values is due to DC decay. A receiver acquires a series of receiver-voltage measurements during the same sample period; and a numerical analysis is performed on the receiver-voltage measurements to determine the point in time at which the AC components have diminished and where the primary change in the transmission-line voltage measurement values is due to DC decay. The transmitter-disconnect device is then placed in a non-conducting state based on an evaluation of those measurements.

Claims

1. In a digital-electricity power system comprising at least one transmitter, each transmitter monitoring and controlling voltage on respective transmission lines and interacting with one or more receivers connected to an opposite end of the respective transmission lines, a method for validating transmission-line voltage measurements, comprising: a) acquiring a series of transmission-line voltage measurements, measuring voltage in at least one of the transmission lines during a sample period when a transmitter-disconnect device is in a non-conducting state; b) performing numerical analysis on the transmission-line voltage measurements to determine a point in time at which AC components in the transmission line have diminished and at which the primary change in the transmission-line voltage measurement values is due to DC decay, and storing a first voltage measurement acquired at that point in time; c) using the receiver to acquire a series of receiver voltage measurements measuring voltage in the receiver, during the same sample period; d) performing numerical analysis on the receiver voltage measurements to determine the point in time at which the AC components have diminished and at which the primary change in the transmission-line voltage measurement values is due to DC decay and storing a second voltage measurement acquired at that point in time; e) performing a difference calculation, wherein the difference calculation determines a difference between the first stored voltage measurement and the second stored voltage measurement, and storing the difference; and f) placing the transmitter-disconnect device in a non-conducting state if the difference is greater than a predetermined maximum value, wherein the transmission-line voltage measurements cannot be validated.

2. The method of claim 1, wherein the transmitter acquires the series of transmission-line voltage measurements, performs the difference calculation, and takes action to place the transmitter-disconnect device in the non-conducting state, and wherein the transmitter or the receiver is used to perform the numerical analysis on the transmission-line voltage.

3. The method of claim 1, wherein the receiver performs the numerical analysis on the receiver voltage measurements, produces the transmission-line voltage measurement values, and communicates the transmission-line voltage measurement values to the transmitter.

4. The method of claim 1, wherein the receiver voltage measurements acquired by the receiver are communicated to the transmitter without performing the numerical analysis that determines when the AC components have diminished, and where the numerical analysis of the receiver voltage measurements is performed by the transmitter.

5. The method of claim 1, wherein, when the transmitter determines that the AC components of the transmission-line voltage measurements do not diminish within a predetermined time period, then the transmitter takes action to place the transmitter-disconnect device in a non-conducting state and registers a fault because the transmission-line voltage is considered unstable.

6. The method of claim 1, wherein the transmitter and receiver first determine a point in time when the AC components of their respective voltage measurements have diminished and then average a plurality of transmission-line voltage measurements after that point to produce one average voltage value for the transmitter and one average voltage value for the receiver, and wherein the transmitter uses the difference in the average values to determine if the transmission-line voltage measurements are valid.

7. The method of claim 1, wherein the transmitter is in electrical communication with a voltage source, the method further comprising the transmitter varying the voltage of the voltage source to perform voltage measurements over a wider range and testing whether voltage measurements by the receiver and voltage measurements by the transmitter continue to match when the primary change in the transmission-line voltage measurements is due to DC decay at different voltages.

8. The method of claim 1, wherein the receiver is supplied with the transmission-line voltage measurements, performs the difference calculations and communicates back to the transmitter if the transmission-line voltage measurements are invalid, and wherein the transmitter takes action to place the transmitter-disconnect device in a non-conducting state.

9. A digital-electricity power system, comprising: at least a pair of transmission lines; at least one transmitter in electrical communication with a transmission end of the transmission lines, wherein the transmitter is configured to transmit digital-electricity power over the transmission lines and is further configured to measure and control voltage on respective transmission lines; and at least one receiver in electrical communication with a receiving end of the transmission lines, wherein the transmitter is configured to interact with the receiver; a controller in the transmitter or in the receiver, wherein the controller includes a processor and a computer-readable medium in communication with the process and non-transitorily storing software code including instructions for: a) using the at least one transmitter to acquire a series of transmission-line voltage measurements, measuring voltage in at least one of the transmission lines, during a sample period when a transmitter-disconnect device is in a non-conducting state; b) using the receiver to acquire a series of receiver voltage measurements, measuring voltage in the receiver, during the same sample period; c) transferring the receiver voltage measurements to the transmitter; d) calculating when AC components of the transmission-line voltage measurements and AC components of the receiver voltage measurements have diminished to a point at which the primary change in the transmission-line voltage measurements is due to DC decay and storing a first voltage measurement acquired at that point; e) determining the voltage values at the transmitter and receiver at a point after the AC components have diminished to the point at which the primary change in the voltage measurements is due to DC decay in both the transmission-line and receiver voltage measurements; and f) placing the transmitter-disconnect device in a non-conducting state if the difference between the voltage value in the transmission lines and the voltage value in the receiver is greater than a predetermined maximum value, wherein the transmission-line voltage measurements cannot be validated.

10. The digital-electricity power system of claim 9, wherein the receiver is configured to be supplied with the transmitter voltage measurements, to perform the difference calculations, and to communicate back to the transmitter if the transmission-line voltage measurements are invalid, wherein the transmitter is configured to take action to place the transmitter-disconnect device in a non-conducting state.

11. The digital-electricity power system of claim 9, wherein the receiver is configured to first process voltage measurements acquired by the receiver to determine the point where the AC components have substantially diminished and to communicate back to the transmitter a value representative of the voltage at the receiver end of the transmission lines after the AC components have diminished.

12. The digital-electricity power system of claim 9, wherein the software code further includes instructions for the transmitter to take action to place the transmitter-disconnect device in a non-conducting state and to register a fault when the transmitter determines that the AC components of the transmission-line voltage measurements do not diminish within a predetermined time period because the transmission-line voltage is considered unstable.

13. The digital-electricity power system of claim 9, wherein the software code further includes instructions for the transmitter and receiver to first determine a point in time when the AC components of their respective voltage measurements have diminished, to then average a plurality of transmission-line voltage measurements after that point to produce one average voltage value for the transmitter and one average voltage value for the receiver, and to use the difference in the average values to determine if the transmission-line voltage measurements are valid.

14. The digital-electricity power system of claim 9, wherein the transmitter is in electrical communication with a voltage source, the software code further comprising instructions for the transmitter to vary the voltage of the voltage source to perform voltage measurements over a wider range and to test whether voltage measurements by the receiver and voltage measurements by the transmitter continue to match during the DC decay period at different voltages.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a block diagram of an exemplification of the safe power distribution system.

(2) FIG. 2 is an illustration of a packet-energy-transfer voltage waveform.

(3) FIG. 3 illustrates in-line power loss determination for a transmission line in the absence of electrical noise or line reflections.

(4) FIG. 4 illustrates an in-line power loss determination for a long transmission line with line reflections.

DETAILED DESCRIPTION

(5) The foregoing and other features and advantages of various aspects of the invention(s) will be apparent from the following, more-particular description of various concepts and specific embodiments within the broader bounds of the invention(s). Various aspects of the subject matter introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the subject matter is not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.

(6) Unless otherwise defined, used or characterized herein, terms that are used herein (including technical and scientific terms) are to be interpreted as having a meaning that is consistent with their accepted meaning in the context of the relevant art and are not to be interpreted in an idealized or overly formal sense unless expressly so defined herein.

(7) The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of exemplary embodiments. As used herein, singular forms, such as “a” and “an,” are intended to include the plural forms as well, unless the context indicates otherwise. Additionally, the terms, “includes,” “including,” “comprises” and “comprising,” specify the presence of the stated elements or steps but do not preclude the presence or addition of one or more other elements or steps.

(8) A representative digital-power system, as originally described in Eaves 2012, is shown in FIG. 1. The system includes a voltage source 1 and at least one load 2. The PET protocol is initiated by an operating switch 3 to periodically disconnect the source 1 from the power transmission lines 22 electrically joining the source 1 with the load 2. When the switch 3 is in an open (non-conducting) state, the lines are also isolated by isolation diode (D.sub.1) 4 from any stored energy that may reside at the load 2.

(9) Eaves 2012 offered several versions of alternative switches that can replace the isolation diode 4, and all versions can produce similar results when used in the presently described methods. Capacitor C.sub.3 5 is representative of an energy-storage element on the load side of the circuit.

(10) The transmission lines 22 have inherent line-to-line resistance R.sub.4 6 and capacitance C.sub.1 7. The PET system architecture, as described by Eaves 2012, adds additional line-to-line resistance R.sub.3 8 and capacitance C.sub.2 9. At the instant switch 3 is opened, capacitances C.sub.1 7 and C.sub.2 9 have stored charge that decays at a rate that is inversely proportional to the additive values of resistances R.sub.4 6 and R.sub.3 8. Capacitor C.sub.3 5 does not discharge through resistances R.sub.3 8 and R.sub.4 6 due to the reverse blocking action of isolation diode D.sub.1 4. The amount of charge contained in capacitors C.sub.1 7 and C.sub.2 9 is proportional to the voltage across them and can be measured at points 16 and 17 by a source controller 18 or load controller 19.

(11) As described in Eaves 2012, a change in the rate of decay of the energy stored in capacitances C.sub.1 7 and C.sub.2 9 can indicate that there is a cross-line fault on the transmission lines 22. The difference between normal operation and a fault, as presented by Eaves 2012, is illustrated in FIG. 2.

(12) Referring again to FIG. 1, the combination of switch S.sub.1 3; source controller 18; resistor R.sub.1 10; switch S.sub.2 11; resistor R.sub.2 12; switch S.sub.3 13; and resistor R.sub.3 8 can be referred to as a transmitter 20. The combination of switch S.sub.4 15; resistor R.sub.5 14; load controller 19; diode D.sub.1 4; capacitor C.sub.2 9; and capacitor C.sub.3 5 can be referred to as a receiver 21.

(13) A method to measure in-line resistance without a communications link, as specified in Eaves 2012, is depicted in FIG. 3, which shows an ideal case where there are no line reflections or external electrical noise. The transmitter 20 measures its terminal voltage and electrical current nearly simultaneously in a first sample 23 during the same energy-transfer period just before opening the source disconnect S.sub.1 3. The transmitter 20 opens disconnect switch S.sub.1 3 and immediately takes another voltage sample 25. The difference between the first and second voltage samples 23 and 25 is proportional to the line resistance. The voltage difference between the first and second voltage samples 23 and 25 is independent of the normal, slower decay in voltage that occurs for the remainder of the sample period because the second voltage sample 25 is taken before the voltage on the transmission lines 22 has had time to decay significantly. By multiplying the difference in voltage by the current measurement, a value of in-line power loss is obtained.

(14) FIG. 4 depicts the transmission-line voltage as seen by the transmitter 20 (solid line) and as seen by the receiver 21 (dashed line) in a longer transmission line and/or at higher electrical currents. In this case, line reflections increase the complexity of making the simple in-line power-loss calculation described for FIG. 3. At the point where the transmitter-disconnect switch S.sub.1 3 is opened 24, the line voltage is higher at the transmitter terminals 24 than it is at the receiver terminals 26 due to the voltage drop when current is passed through the resistance of the transmission line 22. As can be seen by the difference in the horizontal axis positions of points 24 and 26 in FIG. 3 (representing the voltage at the transmitter and receiver terminals, respectively), there is also a time delay, due to the inductive and capacitive elements of the line 22, from when the transmitter disconnect first causes a drop in voltage as seen at the transmitter terminals 24, and when the drop is first seen at the receiver terminals 26. Using numerical-processing techniques well known in the signal-processing industry, the transmitter processor and receiver processor can make a determination of when the AC components of the transmission-line voltage have diminished to an insignificant value, at point 28, and where the remaining change in voltage is a DC decay due to the cross-line resistance of the transmission lines 22 or a cross-line fault, both of which are forms of DC decay. Further refinements on separating DC decay from AC components were described in the Mlyniec Line Integrity Patent, but Mlyniec did not disclose the ability to validate receiver-side measurements. At point 30, the transmitter closes the disconnect switch S.sub.1 3 again, and the voltage of the transmission line 22 rises.

(15) It is in the area between points 28 and 30 that the voltage, as measured at the transmitter terminals 24, and the voltage, as measured by the receiver terminals 26, should match. Both the transmitter 20 and receiver 21 then calculate an average voltage value for the period between points 28 and 30. The receiver 21 transmits the average voltage value that it measured to the transmitter 20 using the communications link described in Eaves 2012 or using a communications data stream imposed on the transmission lines 22, as described in the Eaves Communication patent.

(16) In some cases, it would be useful for the transmitter 21 to vary the value of its voltage source for the purposes of performing voltage measurements over a wider range and, therefore, testing whether the voltage measurements by the receiver 21 and voltage measurements by the transmitter 20 continue to match during the DC decay period. This technique can uncover problems related to gain error in the analog or digital calibration of the voltage sensing components. Alternatively, via the transmitter 20 changing its source voltage according to a predetermined pattern, the technique can be used to verify that the transmitter 20 is communicating with the correct receiver 21, particularly when an external communication link is used, as the communication connection could be inadvertently connected between the wrong transmitter 20/receiver 21 pair.

(17) There are a number of numerical techniques well known to the signal-processing industry to extract the average voltage value between point 28 and point 30 of FIG. 3. These techniques can include simple averaging, digital filtering or interpolation methods, some of which are described in the Mlyniec Line Integrity Patent. Signal-processing tasks otherwise performed by the receiver 21 can be off-loaded to the transmitter 20 by transmitting “raw” voltage measurements from the receiver 21 to the transmitter 20.

(18) The systems and methods of this disclosure can be implemented in a computing-system environment. Examples of well-known computing system environments and components thereof that may be suitable for use with the systems and methods include, but are not limited to, personal computers, server computers, hand-held or laptop devices, tablet devices, smart phones, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, network personal computers (PCs), minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like. Typical computing system environments and their operations and components are described in many existing patents (e.g., U.S. Pat. No. 7,191,467, owned by Microsoft Corp.).

(19) The methods may be carried out via non-transitory computer-executable instructions, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, and so forth, that perform particular tasks or implement particular types of data. The methods may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.

(20) The processes and functions described herein can be non-transitorially stored in the form of software instructions in the computer. Components of the computer may include, but are not limited to, a computer processor, a computer storage medium serving as memory, and a system bus that couples various system components including the memory to the computer processor. The system bus can be of any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures.

(21) The computer typically includes one or more a variety of computer-readable media accessible by the processor and including both volatile and nonvolatile media and removable and non-removable media. By way of example, computer-readable media can comprise computer-storage media and communication media.

(22) The computer storage media can store the software and data in a non-transitory state and includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of software and data, such as computer-readable instructions, data structures, program modules or other data. Computer-storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed and executed by the processor.

(23) The memory includes computer-storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM) and random access memory (RAM). A basic input/output system (BIOS), containing the basic routines that help to transfer information between elements within the computer, such as during start-up, is typically stored in the ROM. The RAM typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by the processor.

(24) The computer may also include other removable/non-removable, volatile/nonvolatile computer-storage media, such as (a) a hard disk drive that reads from or writes to non-removable, nonvolatile magnetic media; (b) a magnetic disk drive that reads from or writes to a removable, nonvolatile magnetic disk; and (c) an optical disk drive that reads from or writes to a removable, nonvolatile optical disk such as a CD ROM or other optical medium. The computer-storage medium can be coupled with the system bus by a communication interface, wherein the interface can include, e.g., electrically conductive wires and/or fiber-optic pathways for transmitting digital or optical signals between components. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like.

(25) The drives and their associated computer-storage media provide storage of computer-readable instructions, data structures, program modules and other data for the computer. For example, a hard disk drive inside or external to the computer can store an operating system, application programs, and program data.

(26) Thus, the scope of the disclosed invention should be determined by the appended claims and their legal equivalents, rather than the examples given. In describing embodiments of the invention, specific terminology is used for the sake of clarity. For the purpose of description, specific terms are intended to at least include technical and functional equivalents that operate in a similar manner to accomplish a similar result. Additionally, in some instances where a particular embodiment of the invention includes a plurality of system elements or method steps, those elements or steps may be replaced with a single element or step; likewise, a single element or step may be replaced with a plurality of elements or steps that serve the same purpose. Moreover, while this invention has been shown and described with references to particular embodiments thereof, those skilled in the art will understand that various substitutions and alterations in form and details may be made therein without departing from the scope of the invention. Further still, other aspects, functions and advantages are also within the scope of the invention; and all embodiments of the invention need not necessarily achieve all of the advantages or possess all of the characteristics described above. Additionally, steps, elements and features discussed herein in connection with one embodiment can likewise be used in conjunction with other embodiments. Still further, the components, steps and features identified in the Background section are integral to this disclosure and can be used in conjunction with or substituted for components and steps described elsewhere in the disclosure within the scope of the invention. In method claims, where stages are recited in a particular order—with or without sequenced prefacing characters added for ease of reference—the stages are not to be interpreted as being temporally limited to the order in which they are recited unless otherwise specified or implied by the terms and phrasing.