Distributed monitoring and protection system for a distributed power network

• US 6,496,342 B1
• Filed: 12/09/1999
• Issued: 12/17/2002
• Est. Priority Date: 02/12/1999
• Status: Expired due to Term

• Current Assignee: Bitronics, LLC
• Original Assignee: Bitronics, Inc.
• Inventors: Butt, James Allen, Horvath, Vincent Victor
• Primary Examiner(s): Jackson, Stephen W.
• Application Number:
  US09/457,495
• Time in Patent Office: 1,104 Days
• Field of Search: 361/42, 361/47, 361/62-75, 361/93.1, 361/93.9, 361/94-97, 361/102, 307/38-42, 307/85, 307/86, 307/17, 307/19, 307/112, 307/113, 307/115, 307/116, 307/125, 307/126, 307/139, 307/141.4, 700/292, 700/295, 700/286
• 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, and at least two of the lines connected to different current nodes at different potentials,

an individual monitoring unit for measuring electrical parameters coupled to each of at least two of the lines, at least two of the monitoring units measuring electrical parameters from different current nodes at different potentials

at least one control unit communicating remotely over a high-speed data network with each monitoring unit,

the at least one control unit including a processor for (a) comparing in the control unit the measured electrical parameters of one respective monitoring unit with the measured electrical parameters of at least one other respective monitoring unit, and (b) producing in the control unit an activating signal based on the comparison of the measured electrical parameters of the one respective monitoring unit with the measured electrical parameters of the at least one other respective monitoring unit, and

the control unit coupled to at least one protective device of a respective line connected to a current node, wherein the control unit trips the protective device based on the activating signal.

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 two lines.

3. The monitoring and protection system of claim 1 wherein the processor both analyzes the received measured electrical parameters and activates the at least one protective device in a duration of time that is less than a predetermined duration of time 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 a 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 each monitoring unit is coupled to at least one power line by at least one current transformer (CT).

8. The monitoring and protection system of claim 1 wherein the coupling between the control unit and the protective device is by the data network.

9. 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 one megabit per second.

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

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. The monitoring and protection system of claim 1 wherein the control unit provides a sequence of activation for each protective device.

24. The system of claim 1 wherein each line in the plurality of lines includes three-phase lines.

25. The system of claim 1 wherein the control unit continuously receives the measured electrical parameters from each monitoring unit and the control unit is physically separated from each monitoring unit.

17. In a distributed power network having a plurality of power lines wherein at least two of the power lines are connected to different current nodes at different potentials and each power line includes a protective device, a method for activating a protective device comprising the steps of:

(a) measuring electrical parameters by respective monitoring units in at least two of the power lines connected to different current nodes at different potentials;

(b) transmitting at high speed the measured electrical parameters from the respective monitoring units to a remotely located control unit;

(c) comparing in the control unit the measured electrical parameters of one respective monitoring unit with the measured electrical parameters of at least one other respective monitoring unit;

(d) producing in the control unit an activating signal based on the comparison of the measured electrical parameters of the one respective monitoring unit with the measured electrical parameters of the at least one other respective monitoring unit; and

(e) tripping by the control unit a protective device of one of the at least two power lines based on the activating signal produced in step (d).

18. The method of claim 17 wherein step (b) includes transmitting the measured electrical parameters over a high speed data network at a data rate of at least one megabit per second.

19. The method of claim 17 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 (e) includes transmitting the activating signal to one of the monitoring units and the one monitoring unit sending an activation command to the protective device.

20. The method of claim 17 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.

21. The method of claim 17 further including:

(f) producing in the control unit a second activating signal to a second protection device; and

(g) determining a sequence for tripping the protective device and the second protective device.

22. The method of claim 17 wherein step (c) includes analyzing the measured electrical parameters from the at least two monitoring units, and step (d) includes producing the activating signal based on any combination of the measured parameters.

23. The method of claim 17 further including determining if the one monitoring unit is functioning and measuring electrical parameters based on the comparing step in step (c).

26. A distributed monitoring and protection system at one end of a power transmission line comprising:

a step down transformer for lowering a potential from the one end of the power transmission line to a feeder bus having multiple branches,

the multiple branches including protective devices,

an individual monitoring unit for measuring electrical parameters coupled to each of at least two branches connected to the feeder bus, each of the monitoring units measuring electrical parameters of a different branch,

at least one control unit communicating remotely over a high speed network with each monitoring unit,

the control unit including a processor for (a) comparing in the control unit the measured electrical parameters of one respective monitoring unit with the measured electrical parameters of at least one other respective monitoring unit, and (b) producing in the control unit an activating signal based on the comparison of the measured electrical parameters of the one respective monitoring unit with the measured electrical parameters of the at least one other respective monitoring unit, and

the control unit coupled to at least one protective device of a respective branch, wherein the control unit trips the protective device based on the activating signal.

27. The monitoring and protection system of claim 26 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 two branches.

28. The monitoring and protection system of claim 26 wherein the processor both analyzes the received measured electrical parameters and activates the at least one protective device in a duration of time that is less than a predetermined duration of time required to limit effect of the fault in the respective branch.

29. The monitoring and protection system of claim 28 wherein the predetermined duration is a function of the measured electrical parameters received from a monitoring unit.

30. The monitoring and protection system of claim 29 wherein the predetermined duration is dynamically changed.

31. The monitoring and protection system of claim 26 wherein the measured electrical parameters are communicated to the control unit in one cycle duration or less of an AC cycle of electric power.

32. The monitoring and protection system of claim 26 wherein each monitoring unit is coupled to at least one branch by at least one current transformer (CT).

33. The monitoring and protection system of claim 26 wherein the network is a high-speed communications network transferring data at a rate of at least one megabit per second.

34. The monitoring and protection system of claim 26 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.

35. The monitoring and protection system of claim 26 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.

36. The monitoring and protection system of claim 26 wherein the measuring unit includes a clock for tagging a time of measurement of each of the measured electrical parameters.

37. The monitoring and protection system of claim 26 wherein the control unit includes a clock for determining a time of arrival of each of the measured electrical parameters.

38. The monitoring and protection system of claim 26 wherein the control unit provides a sequence of activation for each protective device.

39. In a distributed power network including a step down transformer for lowering a potential from one end of a power transmission line to a feeder bus having multiple branches, and the multiple branches including protective devices, a method of activating a protective device comprising the steps of:

(a) measuring electrical parameters by respective monitoring units coupled to each of at least two of the branches of the feeder bus;

(b) transmitting at high speed the measured electrical parameters from the respective monitoring units to a remotely located control unit;

(c) comparing in the control unit the measured electrical parameters of one respective monitoring unit with the measured electrical parameters of at least one other respective monitoring unit;

(d) producing in the control unit an activating signal based on the comparison of the measured electrical parameters of the one respective monitoring unit with the measured electrical parameters of the at least one other respective monitoring unit; and

(e) tripping by the control unit a protective device of a respective branch based on the activating signal produced in step (d).

40. The method of claim 39 wherein step (b) includes transmitting the measured electrical parameters over a data network.

41. The method of claim 39 wherein step (a) includes measuring the electrical parameters by using a plurality of monitoring units, each monitoring unit measuring the electrical parameters of a respective branch;

and

step (e) includes transmitting the activating signal to one of the monitoring units and the one monitoring unit sending an activation command to the protective device.

42. The method of claim 39 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.

43. The method of claim 39 further including:

(f) producing in the control unit a second activating signal to a second protective device; and

(g) determining a sequence for tripping the protective device and the second protective device.