1. A method for detecting a fault in a power system comprising a first conductor electrically coupled to a second conductor through a transformer, the method comprising:
receiving a first phase-current measurement obtained from the first conductor;
receiving a second phase-current measurement obtained from the second conductor;
calculating a first negative sequence current of the first phase-current measurement;
calculating a second negative sequence current of the second phase-current measurement; and detecting a fault in the power system using an operating quantity and a scaled restraint quantity calculated from the first and the second negative sequence currents in a differential element when the operating quantity exceeds the scaled restraint quantity.
2. The method of claim 1, wherein the step of detecting a fault comprises comparing an absolute value of a sum of the first negative sequence current and the second negative sequence current to a scaled maximum of an absolute value of the first and the second negative sequence current.
3. The method of claim 1, wherein the step of detecting a fault comprises:
calculating an operating quantity comprising an absolute value of the sum of the first negative sequence current and the second negative sequence current;
calculating a restraint quantity comprising a maximum of an absolute value of the first negative sequence current and the second negative sequence current;
scaling the restraint quantity by a slope constant; and
detecting a fault if the operating quantity exceeds the scaled restraint quantity.
4. The method of claim 3, wherein a fault is detected only if the operating quantity exceeds a pickup current threshold.
5. The method of claim 3, wherein a fault is detected only if the operating quantity exceeds the scaled restraint quantity for a threshold number of phase-current measurements.
6. The method of claim 3, wherein a fault is detected only if the operating quantity exceeds the scaled restraint quantity for a threshold time period.
7. The method of claim 1, wherein a fault is detected only if an energization input is deasserted.
8. The method of claim 1, wherein a fault is detected only if an external fault input is deasserted.
9. The method of claim 1, wherein a fault is detected only if a current transformer open circuit is deasserted.
10. The method of claim 1, wherein the first phase-current measurement and the second phase-current measurement are time aligned.
11. The method of claim 1, wherein the first current measurement comprises a synchrophasor.
12. The method of claim 1, further comprising normalizing the first phase-current measurement and the second phase-current measurement before calculating the first negative sequence current or the negative sequence current.
13. The method of claim 1, further comprising:
normalizing the first phase-current measurement by a first normalization factor; and
normalizing the second phase-current measurement by a second normalization factor, wherein the first and the second normalization factors comprise a transformer rating, a voltage level of a conductor corresponding to the phase-current measurement, and a current ratio of a current transformer used to obtain the phase-current measurement.
14. The method of claim 1, wherein the step of detecting comprises detecting a turn-to-turn fault in a transformer.
15. An apparatus for detecting a fault in an electrical power system comprising a first node having a first voltage level electrically coupled to a transformer through a first conductor and a second node having a second voltage level electrically coupled to the transformer through a second conductor, the apparatus comprising:
a first current transformer configured to obtain a phase-current measurement on the first conductor; and
a second current transformer configured to obtain a phase-current measurement on the second conductor; and
a negative sequence differential element communicatively coupled to the first current transformer and the second current transformer, the negative sequence element configured to detect a fault between the first node and the second node using a first negative sequence current derived from a first phase-current measurement obtained from the first current transformer and a second negative sequence current derived from a second phase-current measurement obtained from the second current transformer.
16. The apparatus of claim 15, wherein the negative sequence element is configured to calculate an operating quantity comprising a sum of the first negative sequence current and the second negative sequence current, and a restraint quantity comprising a maximum of the first negative sequence current and the second negative sequence current, and wherein the negative sequence element is configured to detect a fault if the operating quantity exceeds the restraint scaled by a slope factor.
17. The apparatus of claim 16, wherein the negative sequence element is configured to detect a fault only if the operating quantity exceeds a pickup current threshold.
18. The apparatus of claim 16, wherein the negative sequence element is configured to detect a fault only if the operating quantity exceeds the scaled restraint quantity for a threshold number of phase-current measurements or a threshold time period.
19. The apparatus of claim 15, wherein the negative sequence element is configured to detect a fault only if an energization input, external fault input, and an open circuit current transformer input are deasserted.
20. The apparatus of claim 15, wherein the negative sequence element is configured to normalize the first phase-current measurement relative to the second phase-current measurement.
21. The apparatus of claim 15, wherein the negative sequence element is configured to normalize the first phase-current measurement using a first normalization factor and to normalize the second phase-current measurement using a second normalization factor, wherein the first normalization factor comprises a volt-ampere rating of the transformer, a voltage level of the first node, and a current ratio of the first current transformer, and wherein the second normalization factor comprises a volt-ampere rating of the transformer, a voltage level of the second node, and a current ratio of the second current transformer.
22. The apparatus of claim 15, wherein the negative sequence element is configured to time align the first phase-current measurement and the second phase-current measurement.
23. The apparatus of claim 15, wherein the second phase-current measurement comprises a synchrophasor.
24. A system for detecting a fault in an electrical power system comprising a first node at first voltage level electrically coupled to a transformer through a first conductor and a second node at a second voltage level electrically coupled to the transformer through a second conductor, the apparatus comprising:
a first intelligent electronic device (IED) to obtain a first phase-current measurement of a three-phase current on the second conductor;
a second IED to obtain a second phase-current measurement of a three-phase current on the second conductor;
a communication module communicatively coupled to the first IED and the second IED to receive the first phase current measurement and the second phase-current measurement therefrom, wherein the communication module comprises a time alignment module to time align the first phase-current measurement and the second phase-current measurement to a common time standard;
a negative sequence element communicatively coupled to the communication module to receive the time aligned first phase-current measurement and the time aligned second phase-current measurement,
wherein the negative sequence element is configured to detect a fault in the electrical power system between the first node and the second node by comparing an operating quantity to a scaled restraint quantity, wherein the operating quantity comprises an absolute value of a sum of a first negative sequence current derived from the first phase-current measurement and a second negative sequence current derived from the second phase-current measurement, wherein the restraint quantity comprises a maximum of an absolute value of the first negative sequence current and the second negative sequence current, and wherein the negative sequence element is configured to detect a fault if the operating quantity exceeds the restraint quantity as scaled by a slope factor.
25. A method for detecting a fault in a power system comprising a first conductor electrically coupled to a second conductor through a transformer, the method comprising:
receiving a first phase-current measurement obtained from the first conductor;
receiving a second phase-current measurement obtained from the second conductor;
normalizing the first phase-current measurement using a first normalization factor comprising a volt-ampere rating of the transformer, a current ratio of a first current transformer associated with the first phase-current measurement, and a voltage level of the first conductor;
normalizing the second phase-current measurement using a second normalization factor comprising a volt-ampere rating of the transformer, a current ratio of a first current transformer associated with the first phase-current measurement, and a voltage level of the first conductor;
calculating a first negative sequence current using the first normalized phase-current measurement;
calculating a second negative sequence current using the second normalized phase-current measurement;
calculating an operating quantity comprising an absolute value of a sum of the first negative sequence current and the second negative sequence current;
calculating a restraint quantity comprising a maximum value of an absolute value of the first negative sequence current and an absolute value of the second negative sequence current;
scaling the restraint quantity by a slope scale factor; and
detecting a fault in the power system if the operating quantity exceeds the scaled restraint quantity.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method, comprising playing out stored content from a computer-readable medium of a set-top appliance to a display device communicatively coupled thereto according to rules provided by an advertising module of the set-top appliance, the rules having been received from a remote server communicatively coupled to the set-top appliance via one or more computer networks and the stored content including one or more advertisements.
2. The method of claim 1, wherein the rules include commands for a processing unit of the set-top appliance which commands when executed by the processing unit cause the processing unit to disable one or more trick modes during playback of one or more of the advertisements.
3. The method of claim 2, wherein the commands are executed or not according to decisions of advertisers providing the one or more advertisements.
4. The method of claim 1, wherein different ones of the rules are applicable to the playing out of the stored content according to whether or not a viewer has paid a fee for viewing the stored content.
5. The method of claim 4, wherein the rules include commands for a processing unit of the set-top appliance which rules when executed by the processing unit cause the processing unit to disable one or more trick modes during playback of one or more of the advertisements.
6. The method of claim 1, wherein the rules are based on one or more of the following: viewer profile, viewer subscription agreement, advertising campaigns, time of day, day of week, and number of times the stored content has been viewed.
7. The method of claim 1, further comprising reporting playback of the one or more advertisements to advertisers associated therewith.
8. A method, comprising playing a series of multimedia files from a computer-readable medium of an appliance in a sequence determined by rules for playing advertisements and in response to a single selection operation of a viewer indicating a desire to view one of the series of multimedia files, the rules having been received from a remote server communicatively coupled to the appliance via one or more computer networks.
9. The method of claim 8, wherein the rules include commands for a processing unit of the appliance which commands when executed by the processing unit cause the processing unit to disable one or more trick modes during playback of one or more of the series of multimedia files.
10. The method of claim 8, wherein the multimedia files include content downloaded from one or more Internet hosts.
11. The method of claim 10, wherein the rules are configured to avoid playing of advertisements if a viewer has paid for downloading a selected one of the multimedia files.
12. The method of claim 10, wherein different ones of the rules are applicable to the playing out of the multimedia files according to whether or not a viewer has paid a fee for downloading some or all of the multimedia files.
13. The method of claim 10, wherein the rules include commands for a processing unit of the appliance which commands when executed by the processing unit cause the processing unit to disable one or more trick modes during playback of one or more of the series of multimedia files.
14. The method of claim 10, wherein the rules are based on one or more of the following: viewer profile, viewer subscription agreement, advertising campaigns, time of day, day of week, and number of times one or more of the multimedia files has been viewed.
15. An appliance, comprising a computer-readable medium having stored thereon one or more multimedia files and a computer processor coupled to the computer-readable medium and configured, under programmable control, to cause to be played out some or all of the multimedia files in a sequence determined by rules for playing advertisements and in response to a single selection operation of a viewer indicating a desire to view one of the series of multimedia files.
16. The appliance of claim 15, wherein the rules include commands for the computer processor which when executed by the computer processor cause the computer processor to disable one or more trick modes during playback of the one or more multimedia files.
17. The appliance of claim 15, wherein the rules are configured to avoid playing of advertisements if a viewer has paid for downloading one or more of the multimedia files.
18. The appliance of claim 15, the rules are based on one or more of the following: viewer profile, viewer subscription agreement, advertising campaigns, time of day, day of week, and number of times one or more of the multimedia files has been viewed.
19. The appliance of claim 15, wherein the rules are stored on a second computer-readable medium accessible by the computer processor.
20. The appliance of claim 19, wherein the rules are updated via communications with a remote server communicatively coupled to the appliance via one or more computer networks.
21. A user interface, comprising one or more Web forms configured to permit setting of trick mode controls associated with multimedia content to a program guide distributable to remote set-top appliances configured to permit downloading of the multimedia content from Internet hosts.
22. The user interface of claim 21, further configured to permit setting of advertising insertion settings associated with the multimedia content.
23. The user interface of claim 22, further including a provider portion and a reviewer portion, the provider portion configured to permit a provider of the multimedia content to enter a plurality of trick mode and advertisement insertion settings, and the reviewer portion configured to permit a human reader to review, accept, modify or reject the settings provided by the provider.