Safe exposed conductor power distribution system

• US 8,781,637 B2
• Filed: 12/07/2012
• Issued: 07/15/2014
• Est. Priority Date: 10/27/2009
• Status: Active Grant

• Current Assignee: VoltServer, Inc.
• Original Assignee: VoltServer, Inc.
• Inventors: Eaves, Stephen S.
• Primary Examiner(s): DUNN, DARRIN D
• Application Number:
  US13/707,842
• Publication Number:
  US 20130103220A1
• Time in Patent Office: 585 Days
• Field of Search: 700/21, 700/22, 700/79, 700/177, 700/286, 700/292, 361/42, 361/59, 361/65, 361/83, 361/88, 361/93.1, 363/56.03, 363/56.04, 363/56.05
• US Class Current: 700/286
• CPC Class Codes: H02H 3/40 responsive to ratio of voltage and current
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities
• CPC Class Codes: H02H 7/261 involving signal transmission between at least two stations transmission of signals in general H02H1/0061
• CPC Class Codes: H02J 3/12 for adjusting voltage in ac networks by changing a characteristic of the network load

Abstract

A power distribution system (that can detect an unsafe fault condition where an individual or object has come in contact with the power conductors) regulates the transfer of energy from a source to a load. Periodically, the source controller opens an S1 disconnect switch, a and load controller opens an S2 disconnect switch. A capacitor represents the capacitance across the load terminals. If the capacitor discharges at a rate higher or lower than predetermined values after the S1 and S2 disconnect switches are opened, then a fault condition is registered, and the S1 and S2 switches will not be commanded to return to a closed position, thus isolating the fault from both the source and the load.

Claims

1. A power distribution system for regulating transfer of energy from a source on a source side and including source terminals to a load on a load side and including load terminals, the system comprising:

a) a source controller on the source side of the power distribution system responsive to a source sensor that provides feedback to the source controller that includes at least a signal indicative of a voltage across the source terminals;

b) a source disconnect device responsive to a control signal from the source controller for electrically connecting or disconnecting the source from the source terminals, wherein the source controller is configured to periodically interrupt the supply of power to the load by opening the source disconnect device, allowing at least the source terminal voltage to be measured during the-interrupted interval;

c) a load disconnect device for electrically decoupling the load from the load terminals; and

d) a logic device implemented in at least the source controller configured to open the source disconnect device and then to perform at least one source terminal voltage measurement when the disconnect device is opened, wherein the voltage measurement is representative of impedance between the source terminals and a corresponding discharge rate of capacitance between the source terminals and to determine whether a predetermined set of conditions that includes at least whether the voltage measurement falls outside of predetermined high and low limits, wherein a voltage measurement outside of the predetermined high and low limits indicates that there is a foreign object or individual making contact with the source or load terminals or a failure in the power distribution system, and to only close the source disconnect device if the voltage measurement falls within the predetermined high and low limits.

2. The power distribution system of claim 1, further comprising a load controller on the load side of the power distribution system responsive to a load sensor that provides feedback to the load controller that includes at least a signal indicative of the voltage across the load terminals.

3. The power distribution system of claim 2, further comprising a data communication link configured to exchange operating information between the source controller and the load controller, wherein the operating information includes at least a value indicative of the voltage across the load terminals that is acquired by the load controller.

4. The power distribution system of claim 3, wherein the data communication link comprises wireless communication circuits operating at carrier frequencies within an electromagnetic spectrum allowed by federal regulators.

5. The power distribution system of claim 3, wherein the data communication is accomplished by a modem in the source and load controllers that are operable to combine a communication signal with voltage waveforms present on the source or load terminals, and to later separate the communication signal from the voltage waveforms present on the source or load terminals, such that the source and load controllers can communicate with each other using only connections between the source and load terminals.

6. The power distribution system of claim 3, wherein the source and load controllers exchange a digital verification code that must match a predetermined value before energy transfer can be initiated.

7. The power distribution system of claim 2, wherein the source controller is configured to calculate the difference between the source terminal voltage acquired by the source controller and the load terminal voltage acquired by the load controller and to issue a command to open the source disconnect device if the difference does not fall between predetermined high and low values.

8. The power distribution system of claim 1, wherein the source disconnect device is responsive to a control signal from the source controller to vary the ratio of time that the source is connected to the source terminals in relationship to the time the source is disconnected from the source terminals so as to regulate the average energy transferred from the source to the load.

9. The power distribution system of claim 1, further comprising a current sensor that allows the source controller to acquire a signal indicative of the electrical current flowing from the source to the source terminals, and wherein the source controller is configured to open the source disconnect device to disconnect the source from the source terminals if the electrical current exceeds a predetermined maximum value.

10. The power distribution system of claim 9, wherein the source controller is configured to periodically multiply the source terminal voltage measurements with the source current measurements resulting in a calculated instantaneous power value and to integrate consecutive power values to derive a total energy value.

11. The power distribution system of claim 10, wherein the source controller is also configured to apply a financial charge to the user for energy extracted from the source.

12. The source disconnect device of claim 1, wherein the source disconnect device is configured to open the source disconnect device to substantially increase the impedance between the source and the source terminals to substantially diminish electric current from the source to the source terminals.

24. The power distribution system of claim 5, wherein the data communication is accomplished only when the source is disconnected from the source terminals, wherein the communication signals are not disrupted by electrical current flowing from the source terminals to the load terminals.

25. The power distribution system of claim 1, wherein the load disconnect device comprises a diode.

13. A method for implementing a power distribution system for the transfer of energy from a source to a load, where the power distribution system is configured to detect unsafe conditions that include electrically conducting foreign objects or individuals that have come in contact with exposed conductors in the power distribution system, the method comprising the steps of:

a) generating a responsive signal in a source controller to open a source disconnect device, resulting in interruption of an electrical connection between the source and source terminals;

b) following the opening of the source disconnect device, acquiring a first measurement of voltage across the source terminals using source terminal voltage sensors, and storing the first voltage measurement for access by the source controller;

c) after a predetermined time has expired, acquiring a second measurement of the voltage of the source terminals using the source terminal voltage sensor and storing the second voltage measurement for access by the source controller;

d) calculating a difference between the first stored voltage measurement and the second stored voltage measurement, wherein the difference represents a discharge rate of the capacitance across the source and load and terminals; and

e) generating signals from the source controller to close the source disconnect device if the difference between the first stored voltage measurement and the second stored voltage measurement falls within predetermined high and low limits, wherein a discharge rate outside of the predetermined high and low limits indicates that there is a conducting foreign object or individual making electrical contact with the source or load terminals, or a failure in the power distribution system hardware.

14. The method of claim 13, wherein the source controller communicates with the load controller using at least one of an optical, conductive and wireless communication link.

15. The method of claim 14, wherein the source controller acquires a digital verification code from the load controller via the communication link and acts cause the source disconnect to remain in an open state if the digital verification code does not match a previously stored code resident in memory of the source controller.

16. The method of claim 13, wherein the source controller acts to vary the conductive time period of the source disconnect device in relation to the non-conductive time period of the source disconnect device such that the average energy transferred from the source to the load can be regulated according to an algorithm being executed by the source controller.

17. The method of claim 13, further comprising:

f) executing code in the source controller to acquire a measurement of the electrical current flowing through the source terminals using a current sensor;

g) storing the electrical current value in the source controller memory; and

h) opening the source disconnect device to disconnect the source from the source terminals if the electrical current exceeds a predetermined maximum value.

18. The method of claim 13, further comprising executing an algorithm in the source controller to calculate the difference between the source terminal voltage acquired by the source controller using the source terminal voltage sensor and the load terminal voltage acquired by the source controller from the load controller, and acting to open the source disconnect device if the difference between the source terminal voltage and the load terminal voltage does not fall between predetermined high and low limits.

19. The method of claim 13, further comprising, at the source controller:

f) acquiring a measurement of the electrical current flowing through the source terminals using a current sensor;

g) acquiring a measurement of the source terminal voltage using a voltage sensor;

h) periodically multiplying the source terminal voltage measurements by the source current measurements to derive an instantaneous power value; and

i) integrating consecutive calculated power values with respect to time to derive a total energy value.

20. The method of claim 19, further comprising applying a financial charge to a user of the energy for energy extracted by the user from the source.

21. The method of claim 13, wherein the source controller acquires a first measurement of the source terminal voltage using a voltage sensor while the source disconnect means is closed then acquires a second measurement of the source terminal voltage immediately after the source disconnect is opened and computes the difference between the first and second voltage measurement, and where the source controller takes action to open the source disconnect if the voltage difference falls outside of predetermined high or low limits.

22. The method of claim 21, wherein the source controller also acquires a measurement of the electrical current flowing through the source terminals using the current sensor while the source disconnect is closed, and divides the voltage difference by the current measurement to derive a value for the resistance of the conductors between the source terminals and the load terminals, and where the source controller takes action to open the source disconnect if the resistance value falls outside of predetermined high and low limits.

23. The method of claim 13, further comprising connecting a first source circuitry output conductor to a center tap point on a secondary coil of a first isolation transformer and connecting a second source circuitry output conductor to a center tap point on a secondary coil of a second isolation transformer, and where a first load circuitry input conductor is connected to a center tap point on a primary coil of a third isolation transformer and a second load circuitry input conductor is connected to a center tap point of a primary coil on a fourth isolation transformer, such that the configuration substantially cancels any flux produced in the four transformers due to current flowing from the source circuitry to the load circuitry, and where the remaining unused terminals of the four transformers can be used to transmit and receive data that is electrically isolated and independent of electrical current flowing from the source circuitry to the load circuitry.

26. The method of claim 23, wherein the data is communicated using Ethernet technology.

27. The method of claim 23, wherein the data is communicated using Digital Subscriber Line technology.

28. The method of claim 13, further comprising having the source assume functions of the load and having the load assume functions of the source, resulting in a reversal of energy flow in the system.