Point on wave switching using slow speed processing

• US 10,418,201 B2
• Filed: 02/14/2018
• Issued: 09/17/2019
• Est. Priority Date: 02/14/2018
• Status: Active Grant

• Current Assignee: Schweitzer Engineering Laboratories, Incorporated
• Original Assignee: Schweitzer Engineering Laboratories, Incorporated
• Inventors: Haes, Dennis
• Primary Examiner(s): Cao, Chun
• Application Number:
  US15/896,209
• Publication Number:
  US 20190252134A1
• Time in Patent Office: 580 Days
• Field of Search: 700298
• CPC Class Codes: G05B 19/0428 Safety, monitoring G05B19/0423 takes precedence
• CPC Class Codes: G05B 2219/21155 Over voltage protection
• CPC Class Codes: G05B 2219/24015 Monitoring
• CPC Class Codes: H01H 2009/566 with self learning, e.g. measured delay is used in later actuations
• CPC Class Codes: H01H 2011/0068 measuring the temperature of the switch or parts thereof
• CPC Class Codes: H01H 9/56 for ensuring operation of the switch at a predetermined point in the ac cycle
• CPC Class Codes: H01H 9/563 for multipolar switches, e.g. different timing for different phases, selecting phase with first zero-crossing
• CPC Class Codes: H02H 3/006 Calibration or setting of parameters
• CPC Class Codes: H02H 3/021 concerning the disconnection itself, e.g. at a particular instant, particularly at zero value of current, disconnection in a predetermined order disconnection at zero value in general H03K17/18
• CPC Class Codes: H02H 7/16 for capacitors for synchronous capacitors H02H7/06
• CPC Class Codes: H02H 9/001 limiting speed of change of electric quantities, e.g. soft switching on or off progressive control of electronic switches for eliminating interferences H03K17/16

Abstract

An intelligent electronic device (IED) may provide point on wave switching. The IED may receive a control operation request, and determine when to issue a control command to cause a switch to change positions. The actuation of the switch may occur at a target point on an alternating current. An IED may have a processor that is too slow to implement a switch when a desired point on an alternating current first occurs. Accordingly, some embodiments may compensate for the processing speed of an IED by determining a number of processor cycles needed (in advance) to issue a control command so that the resulting action results in the desired point on wave open or close.

Claims

1. An intelligent electronic device (IED) for point on wave (POW) switching, the IED comprising:

a communications interface to receive a control operation request;

a voltage sensor to detect a voltage phase angle and frequency; and

a processor in communication with the network interface and the voltage sensor, the processor to perform a series of operations when the network interface receives the control operation request, the operations comprising;

determine, via the voltage sensor, the present phase angle and frequency,

determine a number of processor cycles that allows issuing a control command to implement the control operation request,

determine an implementation period to execute the control command, the implementation period determined based on the number of processor cycles, and

begin to issue the control command when a target POW angle is the implementation period away from occurring based on the present phase angle and frequency.

2. The IED of claim 1, wherein the voltage sensor detects a present phase angle and frequency on each phase of a three-phase system, and

wherein the processor is further to determine an implementation period for each phase.

3. The IED of claim 2, wherein the processor is further to:

determine a series of target POW angles for each phase; and

determine a group of target POW angles with a shortest time between each phase using the series of target POW angles for each phase,

wherein the implementation period further comprises a delay based on the group of target POW angles.

4. The IED of claim 3, wherein the processor is further to compare the implementation period with a user defined implementation threshold, wherein if the delay causes the implementation period to exceed the user defined implementation threshold, the processor will determine a second group of target POW angles that is within the user defined implementation threshold.

5. The IED of claim 1, further comprising a switch,

wherein the processor further determines an operation time for the switch to complete the control command, and

wherein the implementation period includes the operation time.

6. The IED of claim 5, wherein the processor is further to adjust the operation time based on environmental conditions.

7. The IED of claim 6, wherein the environmental conditions comprise ambient temperature and time since last operation.

8. The IED of claim 5, wherein the processor is further to send an alarm signal if execution of the control command exceeds the operation time.

9. The IED of claim 5, wherein the operation time is based on execution time of previous control commands.

10. A method for point on wave (POW) switching, the method comprising:

determining an implementation interval, the implementation interval comprising processing cycles used by a processor to issue a control command;

measuring, via a voltage sensor, a present phase angle and a phase frequency;

determining a number of processing cycles between the present phase angle and a target phase angle at the phase frequency; and

issuing the control command beginning when a length of time to complete the number of processing cycles between the present phase angle and the target phase angle at the phase frequency is equal to the implementation interval.

11. The method of claim 10, further comprising determining an implementation delay, the implementation delay comprising a number of processing cycles between the present phase angle and the target phase angle reduced by the implementation interval, wherein the control command is issued after the implementation delay.

12. The method of claim 10, wherein determining a number of processing cycles between the present phase angle and a target phase angle is performed on each phase of a three-phase system.

13. The method of claim 12, further comprising determining a group of target phase angles based on how many processing cycles are between target phase angles corresponding to each phase.

14. The method of claim 13, wherein issuing the control command begins on each phase based on the group of target phase angles.

15. The method of claim 10, wherein the implementation interval further comprises an operation time for a switch to complete the control command.

16. A non-transitory computer readable medium storage medium including computer-readable instructions that, when executed by one or more processors, cause an intelligent electronic device (IED) to:

determine how many processing cycles are used by a processor to issue a control command;

measure, via a voltage sensor, a present phase angle and a frequency;

calculate how many cycles are between a present phase angle and a target phase angle at the frequency; and

execute the control command to cause a switch to change positions, wherein the processors begin to issue the control command prior to the target phase angle based on how many processing cycles are used by the processor to issue the control command.

17. The non-transitory computer readable medium storage medium of claim 16, wherein determining how many processing cycles are used by a processor to issue a control command is based on availability of processor resources.

18. The non-transitory computer readable medium storage medium of claim 16, wherein the instructions further cause the IED to calculate a delay caused by the switch and begin to issue the control command prior to the target phase angle based on how many processing cycles are used by the processor to issue the control command and the delay caused by the switch.

19. The non-transitory computer readable medium storage medium of claim 16, wherein the instructions further cause the IED to determine processing cycle delays between available target phase angles of each phase on a three-phase system within a predefined threshold.

20. The non-transitory computer readable medium storage medium of claim 16, wherein the control command is executed on each phase such that processing cycle delays between available target phase angles of each phase are minimized.