| Patent application number | Description | Published |
|---|
| 20090091867 | Transformer Through-Fault Current Monitor - A device is provided for monitoring through-fault current in an electric transformer on an electrical power system. The device generally includes a magnitude calculator for calculating the magnitude of current (e.g., a root means square value of current or magnitude of a fundamental of current) based on the current through the electric transformer. A through-fault energy calculator is further provided which is coupled to the magnitude calculator for calculating a through-fault energy value based on the magnitude of current or the calculated current through the transformer. An accumulator is coupled to the through-fault energy calculator for accumulating a plurality of through-fault energy values, and an alarm coupled to the accumulator for indicating that the accumulated through-fault energy values exceed a selected threshold. | 04-09-2009 |
| 20090231769 | Negative Sequence Differential Element - A negative sequence differential element may detect a fault in an electrical power system by computing a differential between negative sequence values derived from a first phase-current measurement and a second phase-current measurement. A transformer may be disposed between the first phase-current and second phase-current measurement location. The first phase-current measurement and the second phase-current measurement may be normalized and a negative sequence current may be calculated therefrom. The negative sequence currents may be used to calculate an operating quantity, which may be an absolute value of the sum of the first and second negative sequence currents, and a restraint quantity comprising a maximum of the first and second negative sequence currents. The restraint quantity may be scaled by a slope factor. A fault may be detected if the operating quantity exceeds the scaled restraint quantity and a pickup current threshold. | 09-17-2009 |
| 20100125373 | MINIMIZING CIRCULATING CURRENT USING TIME-ALIGNED DATA - A power system may comprise two or more transformers operating in parallel. A voltage differential may exist between the transformers, which may create a circulating current in the power system. The system voltage of the power system may be modified by performing a tap change operation on one or more of the transformers. The tap change operation may be configured to minimize the circulating current. The circulating current may be minimized by determining the bias between the transformers using an angular difference between the transformer currents. The angular difference may be calculated using time-aligned measurement data. A tap change operation configured to modify the system voltage, while minimizing circulating current, may be determined using the transformer bias. | 05-20-2010 |
| 20100264749 | DIFFERENTIAL ELEMENT WITH HARMONIC BLOCKING AND HARMONIC RESTRAINT OPERATING IN PARALLEL - An intelligent electronic device (IED) provides harmonic blocking and harmonic restraint differential protection operating in parallel. The IED includes a harmonically-blocked differential element supervised by one or more even harmonics of a raw operating current (a current comprising the fundamental operating current and the harmonics thereof). The IED also includes a parallel, harmonically-restrained differential element, which is restrained by harmonics of the raw operating current. Tripping signals output by the parallel harmonically-blocked differential element and the harmonically-restrained differential element may be selectively combined into a single tripping signal output. An additional harmonic blocking element may supervise both differential elements and/or the combined tripping signal. The additional harmonic blocking element may provide odd-harmonic blocking, such as harmonic blocking based on a fifth harmonic of the raw operating current. | 10-21-2010 |
| 20110035065 | ELECTRIC POWER SYSTEM AUTOMATION USING TIME COORDINATED INSTRUCTIONS - A system for controlling and automating an electric power delivery system by executing time coordinated instruction sets to achieve a desired result. A communication master may implement the execution of time coordinated instruction sets in a variety of circumstances. The communication may be embodied as an automation controller in communication with intelligent electronic devices (IEDs). The communication master may also be embodied as an IED that is configured to coordinate the actions of other IEDs. The time coordinated instruction sets may include steps for checking status of power system equipment before executing. The time coordinated instruction sets may include reactionary steps to execute if one of the steps fails. The time coordinated instruction sets may also be implemented based on a condition detected in the electric power delivery system, or may be implemented through high level systems, such as a SCADA system or a wide area control and situational awareness system. | 02-10-2011 |
| 20110035066 | ELECTRIC POWER SYSTEM AUTOMATION USING TIME COORDINATED INSTRUCTIONS - A system for controlling and automating an electric power delivery system by executing time coordinated instruction sets to achieve a desired result. A communication master may implement the execution of time coordinated instruction sets in a variety of circumstances. The communication may be embodied as an automation controller in communication with intelligent electronic devices (IEDs). The communication master may also be embodied as an IED that is configured to coordinate the actions of other IEDs. The time coordinated instruction sets may include steps for checking status of power system equipment before executing. The time coordinated instruction sets may include reactionary steps to execute if one of the steps fails. The time coordinated instruction sets may also be implemented based on a condition detected in the electric power delivery system, or may be implemented through high level systems, such as a SCADA system or a wide area control and situational awareness system. | 02-10-2011 |
| 20110035076 | ELECTRIC POWER SYSTEM AUTOMATION USING TIME COORDINATED INSTRUCTIONS - A system for controlling and automating an electric power delivery system by executing time coordinated instruction sets to achieve a desired result. A communication master may implement the execution of time coordinated instruction sets in a variety of circumstances. The communication may be embodied as an automation controller in communication with intelligent electronic devices (IEDs). The communication master may also be embodied as an IED that is configured to coordinate the actions of other IEDs. The time coordinated instruction sets may include steps for checking status of power system equipment before executing. The time coordinated instruction sets may include reactionary steps to execute if one of the steps fails. The time coordinated instruction sets may also be implemented based on a condition detected in the electric power delivery system, or may be implemented through high level systems, such as a SCADA system or a wide area control and situational awareness system. | 02-10-2011 |
| 20110063761 | Transformer Differential Protection - Transformer differential protection is provided by measuring a plurality of currents corresponding to a first set of windings and a second set of windings of a transformer, and compensating the currents based on their respective flows through either the first set of windings or the second set of windings. The compensated currents may be intentionally augmented to compensate for magnetizing inrush and/or stationary overexcitation conditions associated with the transformer. Augmentation based on stationary overexcitation, for example, may be based on either harmonic restraint or an addition of a V/Hz ratio to a restraining signal. A complex current ratio is calculated corresponding to the plurality of compensated currents. The complex current ratio may be based on a two-terminal equivalent power apparatus. Then, an alpha plane analysis is applied to the complex current ratio. Based on the alpha plane analysis, a power apparatus that includes the transformer is selectively tripped. | 03-17-2011 |
| 20110063766 | LINE CURRENT DIFFERENTIAL PROTECTION UPON LOSS OF AN EXTERNAL TIME REFERENCE - A line current differential protection system that uses an external time reference continues providing protection to a power apparatus upon the loss of the external time reference. An external time reference synchronization mode and a channel based synchronization mode may be selectively applied on a per channel basis such that only those channels in the system that are not guaranteed to stay symmetrical use external time reference synchronization. When the external time reference is lost, fallback strategies may be used such as disabling or de-sensitizing the line current differential protection function, switching from the external time reference synchronization mode to a channel based synchronization mode with appropriately selected protection settings, and/or marking the channel as unavailable to isolate the system from the consequences of synchronization errors over this channel and instead using a master-slave mode with other available channels to continue providing line protection with the current differential system. | 03-17-2011 |
| 20110063767 | CHARGING CURRENT COMPENSATION FOR LINE CURRENT DIFFERENTIAL PROTECTION - Current differential protection with charging current compensation is provided for a power apparatus, such as a power transmission line. Individual terminals dynamically determine their respective contributions, if any, to the charging current compensation value as availability of one or more voltage sources dynamically changes within the power apparatus. Respective terminals calculate local contributions to a charging current compensation value based on local voltage measurements. A loss of a voltage source is handled by adjusting multipliers for the remaining compensation points to reflect the total charging current. A local contribution is suppressed when the local voltage source is no longer available. After applying the local contributions, an alpha plane analysis may be used to determine when to trip the power apparatus. | 03-17-2011 |
