Distributed monitoring and protection system for a distributed power network

• US 20030067725A1
• Filed: 10/01/2002
• Published: 04/10/2003
• Est. Priority Date: 02/12/1999
• Status: Active Grant

• Current Assignee: Bitronics, LLC
• Original Assignee: Areva T&D Incorporated (AES Corporation)
• Inventors: Butt, James Allen, Horvath, Vincent Victor
• Granted Patent: US 6,654,216 B2
• Time in Patent Office: Days
• US Class Current: 361/65
• 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 13/00002 characterised by monitoring
• CPC Class Codes: H02J 13/00017 using optical fiber
• CPC Class Codes: H02J 13/00028 involving the use of Internet protocols
• CPC Class Codes: H02J 13/00034 the elements or equipment being or involving an electric power substation
• CPC Class Codes: H02J 13/0004 involved in a protection system
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/20 using protection elements, arrangements or systems
• CPC Class Codes: Y04S 10/30 State monitoring, e.g. fault, temperature monitoring, insulator monitoring, corona discharge

Abstract

A distributed monitoring and protection system for a distributed power network. The system includes a plurality of high-speed measuring units (MUs), wherein each MU is coupled to a power line to measure values of electrical parameters of the power line. Electrical parameters, such as current, voltage, power and frequency are measured by the MUs. The MUs communicate with a control unit (CU) over a high-speed communications network. The CU includes a processor executing algorithms for evaluating the measured parameters to determine the status of the power network and the MUs. The processor also executes fault detection and isolation by comparing the measured values against predetermined threshold values. When a fault is detected by the CU, protective action, such as tripping of a circuit breaker, may be initiated by the CU directly or by transmitting the tripping command over the high speed data network to a local MU. The local MU may then trip the circuit breaker. The availability at the CU of concurrent measurements from the plurality of MUs enables improved coordination and sequencing of protective actions.

Claims

1. A distributed monitoring and protection system for a distributed power network comprising:

a plurality of lines for distributing electric power, the lines including protective devices,

at least one monitoring unit coupled to at least one line of the plurality of lines for measuring electrical parameters of the at least one line,

at least one control unit communicating over a data network with the at least one monitoring unit and receiving measured electrical parameters from the monitoring unit, the at least one control unit separated from the at least one monitoring unit, and

the at least one control unit including a processor for analyzing the measured electrical parameters and activating at least one of the protective devices when a fault in the power network is determined.

2. The monitoring and protection system of claim 1 wherein the measured electrical parameters include at least one of current, voltage, power, frequency, power factor, harmonic components of the current and harmonic components of the voltage in the at least one power line.

3. The monitoring and protection system of claim 1 wherein the processor analyzes the received measured electrical parameters and activates the at least one protective device in a duration that is less than a predetermined duration required to limit effect of the fault in the power network.

4. The monitoring and protection system of claim 3 wherein the predetermined duration is a function of the measured electrical parameters received from the at least one monitoring unit.

5. The monitoring and protection system of claim 4 wherein the predetermined duration is dynamically changed.

6. The monitoring and protection system of claim 1 wherein the measured electrical parameters are communicated to the control unit in one cycle duration or less of an AC cycle of the electric power.

7. The monitoring and protection system of claim 1 wherein the monitoring unit is coupled to the at least one power line by at least one current transformer (CT).

8. The monitoring and protection system of claim 1 wherein the control unit is coupled to at least one protective device and the at least one protective device includes at least one circuit breaker for opening a line when a fault in the power network is determined.

9. The monitoring and protection system of claim 8 wherein the coupling is by the data network.

10. The monitoring and protection system of claim 1 wherein the at least one monitoring unit includes a connection to the at least one protective device for activating the protective device when the fault in the power network is determined by the control unit and communicated to the monitoring unit.

11. The monitoring and protection system of claim 1 wherein the data network is a high-speed communications network transferring data at a rate of at least 1200 bits per second.

12. The monitoring and protection system of claim 1 wherein the data network is a high-speed communications network using Ethernet hardware.

13. The monitoring and protection system of claim 1 wherein the data network is a high-speed communications network using one of Modbus, DNP, UCA2.0 and Modbus Plus protocols.

14. The monitoring and protection system of claim 1 wherein the control unit includes a calculation of at least one value for at least one measured electrical parameter, and when the at least one value exceeds a threshold value, the control unit activates the at least one of the protective devices.

15. The monitoring and protection system of claim 1 wherein the control unit includes at least one Over Current (OC) setting and at least one Time Over Current (TOC) setting and one of the measured electrical parameters includes current varying in time, and

when a value calculated from the current exceeds one of the OC setting and the TOC setting, the control unit activates the at least one of the protective devices.

16. The monitoring and protection system of claim 1 wherein the measuring unit includes a clock for tagging a time of measurement of each of the measured electrical parameters.

17. The monitoring and protection system of claim 1 wherein the control unit includes a clock for determining a time of arrival of each of the measured electrical parameters.

18. A distributed monitoring and protection system for a distributed power network comprising:

a plurality of lines for distributing electric power, each line including a protective device for protecting the line,

a plurality of monitoring units, each monitoring unit coupled to a respective at least one of the lines for measuring electrical parameters of the respective at least one of the lines,

at least one control unit communicating over a high-speed data network with the plurality of monitoring units and receiving the measured electrical parameters from the plurality of monitoring units, and

the at least one control unit including a processor for analyzing the measured electrical parameters and activating at least one of the protective devices when a fault in the power network is determined.

19. The monitoring and protection system of claim 18 wherein the control unit includes a fault decision based on the measured electrical parameters received from more than one monitoring unit of the plurality of monitoring units.

20. The monitoring and protection system of claim 18 wherein the control unit provides a sequence of activation for each protective device.

21. In a distributed power network having a plurality of power lines and each power line including a circuit breaker, a method for tripping a circuit breaker in a respective power line comprising the steps of:

(a) measuring electrical parameters in each power line;

(b) transmitting the measured electrical parameters to a centralized control unit;

(c) analyzing the measured electrical parameters in the centralized control unit; and

(d) generating a tripping command to the circuit breaker based on results of step (c).

22. The method of claim 21 wherein step (b) includes transmitting the measured electrical parameters over a data network.

23. The method of claim 21 wherein step (a) includes measuring the electrical parameters by using a plurality of monitoring units, each monitoring unit measuring the electrical parameters of at least one power line;

and

step (d) includes transmitting the tripping command to one of the monitoring units and the one monitoring unit sending the tripping command to the circuit breaker.

24. The method of claim 21 wherein step (a) includes measuring a current value and step (c) includes calculating values from the measurement and analyzing the values with respect to threshold values, the threshold values being one of predetermined values and calculated values from a TOC curve.

25. The method of claim 21 further including:

(e) generating a second tripping command to a second circuit breaker; and

(f) determining a sequence for tripping the circuit breaker and the second circuit breaker.

26. The method of claim 21 wherein step (a) includes measuring the electrical parameters by using a plurality of monitoring units, each monitoring unit measuring the electrical parameters of at least one power line;

and

step (c) includes comparing the measured electrical parameters from one of the plurality of monitoring units with the measured electrical parameters from at least one other of the plurality of monitoring units, when the one monitoring unit and the at least one other monitoring unit are measuring electrical parameters from respective power lines connected at a node.

27. The method of claim 21 wherein step (c) includes analyzing the measured electrical parameters from at least two monitoring units, and step (d) includes generating the tripping command based on a combination of the measured parameters.

28. The method of claim 27 wherein the two monitoring units are measuring electrical parameters from two respective power lines connected at a node, and step (d) includes generating the tripping command when measured currents into and out of the node are substantially unequal.

29. The method of claim 26 further including determining health of the one monitoring unit based on the comparing step in step (c).

30. The method of claim 29 further including substituting another set of measured electrical parameters for a set of measured electrical parameters in the one monitoring unit when the one monitoring unit is determined to be nonfunctional, wherein the other set of measured electrical parameters are values calculated by the control unit.