MXPA01001279A - Method and apparatus for deriving power system data from configurable source points - Google Patents

Abstract

A protective relay that derives and processes power system data from multiple user-configurable data source points. Data from multiple source points can be combined in the relay as a single source of data useful to perform a wide variety of monitoring and protection tasks. Multiple digital signal processing modules can be used to provide additional processing resources, including the ability to provide protection and revenue-class metering in a single device.

Description

METHOD AND APPARATUS FOR DERIVING DATA FROM THE ENERGY SYSTEM FROM POINTS CONNECTED TO THE SOURCE FIELD OF THE INVENTION The present invention relates to systems for distributing electrical energy. More particularly, the present invention relates to methods and systems for monitoring, protecting, and controlling a power distribution network.

BACKGROUND OF THE INVENTION It is important to monitor, provide protection, and control systems that distribute electrical power, and many techniques have been used to provide these functions. Referring now to Figure 1, a conventional group of protective functions applied to an energy transformer and to two circuit breakers configured in a circuit configuration and half system is shown. The protection scheme includes current transformers 14, 16, and 18, and voltage transformers 20. It should be noted that Figure 1 is a representation of a single line of a three-phase system. The scheme in Figure 1, therefore, provides the following available AC values (AC): three-phase currents (from each set of current transformers 14, 16, and 18), and three-phase voltage (from the voltage transformers twenty) . Figure 1 also includes indications of the desired protection and measurement, including the protection of the 50 BF breaker failure (instantaneous overcurrent) for the switches at points 24 and 26, the protection of the 87T transformer (current differential) through of the main transformer 22 (represented as 28), the transformer protection 50P (phase overcurrent snapshot) at point 30, and a watt measurement at point 32. Figure 2 shows a conventional relay application to achieve the desired protection and measurement goals of Figure 1. The relay application includes first and second relays 50BF protectors 34 and 36, which receive the inputs from the current transformers 14 and 16, respectively, and which provide the outputs to an adder element to 38. The 50BF protective relays provide the desired breaker failure protection. A transformer protection relay is also provided multiple functions 40, which receives the inputs from the external summing element 38, the current transformer 18, and a voltage source 20. The external summing element 38 produces a sum of the AC current values derived from the transformers 14 and 16 25 The differential relay of the transformer 40 receives data from __ jb_aJ _. ..-._. ^ ... * g ^ ft »Sk_. ~ ^. > - » .- ^^^ ~ ... voltage from the voltage transformer 20 by means of the voltage sensor 42, receives the summed current values from the external summing element 38 by means of the current sensor 44, and receives the current values from the current transformer 18 by means of the sensor Current 46. As shown in Figure 2, the differential relay of the transformer 40 provides the desired energy measurement by processing the voltage received in the voltage sensor 42, with the current values added from the external summing element 38 In addition, the transformer protection relay provides the instantaneous phase overcurrent protection of the desired phase, based on the summed current values from the external summing element 38, and provides the protection of the desired transformer differential based on both the values of the summed current from the external summing element 38 by means of the current sensor 44, com or from the current transformer 18 by means of the current sensor 46. The transformer protection relay 40 normally includes a single digital signal processor for performing the necessary calculations, and providing the protective control functions. It should be noted that, by summing the data of the energy system into an external summing element, the relay is unable to determine the individual components of the summed data values. U.S. Patent No. 5,224,011 discloses a multi-function protective relay system that implements a dual processing architecture, using a first digital signal processor (DSP) to execute the signal processing algorithms, and it uses a separate digital signal processor for the processing of the input / output data. A double-port random access memory (RAM) is used to allow separate DSPs to communicate with one another. The protective relay selectively trips and closes a circuit breaker in a generator or in a co-generator site, or in a site that connects them to an electrical service system. U.S. Patent No. 5,828,576 discloses an energy monitoring apparatus and method, with an object-oriented structure. Individual monitoring devices are used, each of which receives an electrical signal, and generates a digital signal representing the electrical signal. The objects within each device include modules and functional registers, which contain inputs, outputs, and establishment information for the modules. The function and configuration of each individual monitoring device can be changed. At least one module inside the device receives the digital signal as an input, and uses the signal to generate the measured parameters, and the additional modules can generate additional parameters from the measured parameters. Although it is usually desirable to perform the measurement in an energy distribution system, conventional protective relays do not adequately perform this function. The dynamic range requirement for protection at 0 to 20-50 times the rated current input (typically IA and 5A) results in a reduction in accuracy from the instrument transformer in the normal measurement range from 0 to 1.5- 2 times the nominal current input. The wide dynamic range also results in reduced accuracy and resolution for the subsystem of the measuring device (eg, microprocessor, analog-to-digital converter, and associated analog conditioning circuits). Although certain protective relay devices can provide a relatively accurate measurement through the current transformer inputs, in practice, these inputs are normally connected to the relay class current transformers, to ensure that the relay provides adequate protection . Current transformers of the relay class usually have an accuracy of about 5 to 10 percent.

From the above, it follows that it would be desirable to be able to derive data from the energy system from many points in a power distribution system in a single relay, and it would also be desirable if the points from which the energy system data can be derived , are configurable by a user. Furthermore, it would be desirable to be able to provide an income class measurement in a protective relay, to simplify the installation and integration of the system, and to provide the user of the protective relay with the ability to easily perform the income class measurement, in order to verify the accuracy of the service company's charges. Conventional protective relays do not adequately provide these capabilities.

SUMMARY OF THE INVENTION The present invention overcomes the deficiencies noted above, and achieves additional advantages, by providing, in an exemplary embodiment, a protective relay device with multiple digital signal processors that receive the configuration commands via an interface of the user. The configuration commands define the source points in a power distribution system, from which the electrical parameters can be derived. The derived data can be combined inside the relay, allowing a wide variety of measured parameters and protection capabilities within a single device. In addition, the use of multiple digital signal processors allows the protective relay to perform the measurement of the income class, in addition to the protection functions, by implementing a different dynamic range. In accordance with an example method of the present invention, data can be derived from a power distribution system by the steps of: configuring a protective relay, through a protective relay interface, to receive the system data from a plurality of source points; detect system parameters at source points; and perform the monitoring and control of the network in the protective relay, based on the detected system parameters. The data can be combined inside the protective relay to provide a variety of protective control options. In addition, the dynamic measurement range for a given source point can be modified, allowing the protective relay to measure the income class from a source, in addition to the protective functions from another source.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood more fully by reading the following detailed description in conjunction with the The accompanying drawings, in which the like reference indications refer to like elements, and in which: FIG. 1 is a diagram of a protection scheme of a convtecional energy system. Figure 2 is a diagram of an implementation to provide the desired protection for the scheme of Figure 1. Figure 3 is a diagram of a protection scheme of an energy system in accordance with an embodiment of the present invention. Figure 4 is a diagram showing the manner in which a relay according to the present invention can provide the protection scheme of Figure 3. Figure 5 is a diagram showing the example types of signal processing modules digital devices suitable for use with the present invention. Figure 6 is a conceptual diagram of an exemplary method for defining a configurable source point in accordance with an aspect of the present invention. Figure 7 is a conceptual diagram showing the definition of other aspects of a configurable source point.

DETAILED DESCRIPTION DENLAS PREFERRED MODALITIES In the application of protective relays to different elements (for example, transformers, lines, power supplies, generators, etcéteagggjll of a power system, it is often necessary to add several current signals from different power transformers. current, to obtain the net alternating current signal that follows inward from the element to be protected. In accordance with an aspect of the present invention, the sum of certain current signals can be defined by a user as a source. In this context, the source refers to a logical grouping of current and / or voltage signals, such that a source contains all the signals required to define the load or failure at a particular point of the power system. Accordingly, a source could contain one or more of the following types of signals: three-phase currents, single-phase ground current, three-phase voltages, and an auxiliary voltage. In accordance with one aspect of the present invention, all the signals forming a source can be provided to a single relay, which performs the appropriate grouping, proportion correction, addition, and other processing internally according to the establishments of configuration provided by a user. By using the internal combination and the processing of the source signal data, instead of the external sum, the individual signals are still available for the relay. The availability of individual signals allows the relay to perform additional calculations (such as calculating a restriction current), or to perform additional protective features that are based on individual currents. Referring now to Figure 3, there is shown a configuration for deriving power system data from the configurable source points in accordance with one embodiment of the present invention. The configuration, and the protection and measurement desired, is similar to the configuration shown in Figures 1 and 2; however, according to one aspect of the present invention, a user of the system defines a plurality of configurable source points. As described above, each configurable source point can be defined as a point in the energy system, from which it is desired to derive certain data from the energy system, such as current values, voltage values, energy data, values of frequency, harmonics, total harmonic distortion, or any other useful data to monitor or provide protective control in a power system. In the Example shown in Figure 3, the user-configurable source point 50 is based on the current transformer 14 and the voltage transformer 20, the user-configurable source point 52 is based on the current transformer 16 and the voltage transformer 20, the user-configurable source point 54 is based on the current transformers 14 and 16, as well as on the voltage transformer 20, and the user-configurable source point 56 is based on the current transformer 18. The way in which the user can define the source points configurable by the user will be explained in more detail below. Figure 4 shows an application of a protective relay, in accordance with an aspect of the present invention, to provide the desired protection and measurement in the configuration of Figure 3. In the relay 60, there is a voltage sensor 62 for receiving the voltage values from the voltage transformer 20, and 3 current sensors 64, 66, and 6_8 to receive the current values from the current transformers 14, 16, and 18, respectively. The relay 60 includes suitable processing circuits to perform an internal summation of the current data from the current transformers 14 and 16, to generate the data for the user-configurable source point 54, and these data are combined with the voltage values from the voltage transformer 20 to perform the desired energy measurement. The current data summed to the user-configurable source point 54, are also used to perform the protection 50P desired, and combined with the current data from the current transformer 68 (user-configurable source point 56), to perform the protection of the desired 87T transformer. The current data from the current transformers 14 and 16 (user configurable source points 50 and 52, respectively), are used by the processing resources of the relay 60, to provide the fault protection of the desired 50BF switch . It should be appreciated that the implementation of the invention shown in Figure 4 achieves numerous advantages over the conventional implementation of Figure 2. For example, in the implementation shown in Figure 4, a single device (relay 60) performs the protection of transformer and switch failure. In addition, the implementation of Figure 4 avoids the external summation of the current data, thus allowing the relay 60 to use the individual data values of the system, as well as their combinations. Still further, any point in the power system can be configured as a data source to be used in measurement and protection, as will now be described in more detail. In accordance with one embodiment of the present invention, the relay 60 includes at least two digital signal processing modules, each of which is typically limited to 8 inputs, due to limitations in packaging and processing resources. Each digital signal processor module includes a bank of channels, each bank consisting of four consecutive channels (for example, 1-4 or 5-8). In this mode, each bank is used to process data from current transformers, voltage transformers, or left empty. In accordance with one embodiment of the present invention, the multiple digital signal processing modules are connected by a dedicated communications bus from partner to partner, and each digital signal processor is further in communication with a central processing unit (CPU ) of the relay 60, which provides an interface for a user. In accordance with another embodiment of the present invention, the different relays are in communication with one another over a communications network, allowing * the benefits of the present invention to be applied to a protective relay network. Referring now to Figure 5, a conceptual presentation of different configurations of digital signal processing modules 70, 72, 74, 76, and 78 is shown. In module 70, channels 1-4 are assigned for data from the current transformer, and channels 5-8 are assigned for the dats of the voltage transformer. In the Example of Figure 4, channels 1-3 can be used for the three phases of the current transformer data from current 14 (user-configurable data source point 5), and the channel 4 can be used as a ground or auxiliary channel for the additional data of the current transformer. A similar channel usage scheme can be implemented for the four channels of the voltage transformer in the module 70, and for each channel bank of the digital signal processor in the other modules. The module 72 allocates all the channels as the channels of the current transformer, and the module 74 allocates all the channels as the voltage transformer channels, and the modules 76 and 78 have each only one bank of used modules, the module 76 which uses its four channels as the current transformer channels, and the module 78 which uses its four channels as the voltage transformer channels. In the example configurations of Figure 5, it can be accommodated virtually any possible hardware configuration, to achieve virtually any desired combination of configurable fonts by the user. For example, three digital signal processing modules can be used, one for each of the module 72, the module 70, and the module 78, for a three-coil transformer, or for a ¿& x. ^ k -HS 'two-coil transformer,. where one of the coils has a switch and a half configuration. It should be appreciated that many applications may require less than, or more than, three digital signal processing modules. The auxiliary channel can be used, for example to collect the data from a current transformer in a neutral-to-ground power transformer connection. This information can be used to provide protection for ground fault events. An auxiliary voltage input channel can be used to provide a voltage for use in a timing verification scheme. One way of defining the configurable sources by the user will be explained with reference to Figure 6. The current and voltage inputs can be programmed by selecting different positions through a user interface on the same end, or through a user interface of a computer in communication with the relay 60. This example, to each digital signal processing module containing the channels numbered 1-8, is assigned a slot indicator (e.g., "F"). Then the 8 channels are grouped into 4 sets, which are then defined as Fl, F4, F5, and F8. Set Fl consists of channels 1, 2, and 3. Set F4 consists of channel 4. Set F5 consists of channels 5, 6, and 7. Set F8 consists of channel 8. As shown in Figure 6, each set of channels (for example, Fl, F4, F5, F8) can have parameters (for example, primary and secondary current values, connection types, voltage values, proportions, etc.) assigned within different ranges . The parameters and ranges shown in Figure 6 are exemplary only. Referring now to Figure 7, a source can be configured by assigning a name (eg, source 1), an input of the phase current transformer (eg, Fl), an input of the current transformer of ground (for example, F4), an input of the phase voltage transformer (for example, F5), and an auxiliary input (for example, F8). It will be appreciated that it is also possible to define a source as the sum of any combination of the current transformers. Furthermore, it should be appreciated that different values may be selected or displayed by means of the relay or a communication network associated with the relay. For example, the calculated quantities associated with the actual current inputs with phase quantities can be displayed. In addition, the calculated quantities associated with each configured source, including all quantities related to the source (such as currents and phase voltages, neutral current, sequence quantities, power, energy, frequency, harmonic content) can also be displayed. The configurations required for different elements, such as phase time overcurrent elements, sub-frequency elements, synchronization check elements, transformer differential, etc., are considered within the experience of the technique, and therefore , they are not presented here. In accordance with a further aspect of the present invention, the inclusion of multiple digital signal processors in a single protective relay, can achieve additional significant advantages, including achieving the measurement of the income class in a protective relay. In particular, the relay 60 can be provided with dedicated inputs to be connected to the current transformers of the income class for the measurement, in addition to the inputs to be connected to the current transformers of the protection class, for the protection . Accordingly, a single protective relay can be used for all three-phase applications (feeder, line, transformer, motor, generator, etc.), and can provide accurate measurement and proper protection in a single device. Because the dynamic range of the voltage transformer is the same for measurement as for protection, a set of inputs can be used for both.

To provide the measurement of the income class in a protective relay, one of the multiple digital signal processing modules in the relay 60, may be provided with a set of three input submodules of the current transformer, with an adequate dynamic range for measurement (for example, from approximately 0 to 1.5-2 times the nominal input). The appropriate dynamic range can be implemented, for example, by using a higher load, or by using an appropriate interposed current transformer. The additional circuits remain substantially the same for the relay 60. The source points configurable by the user of the relay 60 can then be used to select the input of the reduced dynamic range for the measurement of the income class, and the widest range input standard for protection applications. In this way, the measurement of income class ^ and protection in a single device can be provided. Figure 8 shows an example of a modular implementation of the configuration of Figure 4. In Figure 8, a relay 60 includes a plurality of modules, including a power supply module 82, a central processing unit (CPU) 84. , digital signal processing (DSP) modules 86 and 88, digital input / output (I / O) modules 92, and a communications module 94. CPU 84 is the main processor for the relay, the signal processors 86 and 88 provide the appropriate signal processing to implement the protection scheme, the input / output modules 92 exchange inputs and outputs 5 related to the status and control information, and the communications module 94 supports communication using the formats of communications such as Ethernet, HDLC, and UART. In this example, each module is operatively connected to a data bus of high speed 96, which provides communication between the modules. In the implementation of Figure 8, the voltage transformer 20 (see Figure 4), and the current transformer 14, are associated with the digital signal processor module 86, the transformers of current 16 and 18 are associated with the digital signal processing module 88. The modular implementation of FIG. 8, accordingly, is suitable to support the protection scheme of FIG. 4 in a single relay. It should be further appreciated that, although the above exemplary embodiments have been described with respect to a circuit breaker and half transformer protection scheme, the present invention is not limited to this protection scheme. Actually, the benefits of this invention can be applied to achieve the protection of line, busbar protection, or other types of monitoring and control of the electric power system. To achieve certain types of protection, such as line protection, it may be desirable to synchronize the data of the power system, particularly from remote sources. This synchronization can be achieved using known techniques. One technique is described in Mills, "Internet Time Synchronization: The Network Time Protocol," IEEE Transactions on Communications, volume 39, No. 10, October 1991, pages 1482-93 (a so-called "ping-pong" technique that uses round trip timestamp messages to synchronize clocks that calculate communications delays). Another technique is described in U.S. Patent No. 5,809,045 to Adamiak et al. Entitled "Digital Current Differential System", which uses the information of currents measured from two or three transmission lines, and digital communication. The additional implementations of the present invention will now be described. Figure 9 shows a circuit breaker and half scheme that includes a three-coil transformer 23, which replaces the transformer 22 of Figures 1 to 4. In addition, the three-coil transformer 23 feeds two separate lines, one for the current transformer 18, and one for the current transformer 19. Otherwise, the Figure 9 is substantially similar to the schemes shown in Figures 1 to 4. Figure 10 shows a modular architectural solution for implementing the protection in the scheme of Figure 9 in a single relay. In the relay 60 of Figure 10, an additional digital signal processing module 90 has replaced one of the digital input / output modules 92 of Figure 8. In this implementation, the current transformer 19 is associated with the processor of additional digital signals 90, and the current data from the transformer 19 are used as an additional input to provide transformer protection for the three-coil transformer 23. Figure 11 shows an example implementation for providing busbar protection, in a section of six feeders of a busbar. In the implementation shown in Figure 11, a portion of a busbar 100 having six feeders 101-106 is shown. Each feeder is associated with a current transformer 107-112. The bus portion 100 is further shown having a voltage transformer 114. In the implementation shown in Figure 11, the current transformers 107-112 are configured as source points to provide current measurements to a relay 60. , the voltage transformer 114 is configured as a source point, and provides voltage measurements to the relay 60. These voltage and current measurements are used by the relay 60 to implement a protective control, including an overcurrent circuit breaker failure protection. instantaneous (50BF), a differential busbar protection (87B), and a sub-voltage protection (27G). Figure 12 shows a modular architecture solution for implementing the busbar protection scheme of Figure 11. In Figure 12, the relay 60 is configured substantially similar to that shown in Figure 10, but the relay of Figure 12 receives inputs from sources 114 and 107 in a first digital signal processing module, receives inputs from sources 108 and 109 in a second digital signal processing module, receives inputs from sources 110 and 111 in a third digital signal processing module, and receives input from source 112 in a fourth digital signal processing module. The relay 60 processes the information as shown, and performs the differential protection of the busbar 87B, based on the data used to provide the 50BF breaker failure protection for the current transformers 107-112. Figure 13 shows a modular distributed architecture solution for providing a busbar protection of 12 feeders according to one aspect of the present invention. In this implementation, the first and second relays 60 connected substantially as shown in Figure 12, and the first and second relays communicate over a communications link 130, which may be an Ethernet connection of 10 megabits per second (Mbps) between the communication modules of the relays 60. Of course, it will be appreciated that other suitable connections can be used. In addition, in the implementation of Figure 13, each of the relays 60 communicates with one of the remote relays 132 over the communication links 134, which may be an RS485 connection of 115 kilobits per second (Kbps), or another connection adequate It will be apparent from the above description, that the present invention allows a user to configure sources _ to be introduced to a relay or other intelligent electronic device (IED), and in this way, can provide very increased protection schemes. Once a source is configured, the measurement, protection, or relay control characteristics (normally encoded in hardware in the relay) can use a source as an input quantity. Therefore, any source that includes three-phase voltage and three-phase current will automatically be able to provide the energy measurement for that source. A protective element could have six time-overcurrent elements (TOCs) which can be used to protect six points in the power system, or three TOC elements can be assigned to protect two points of the power system, or two can be assigned TOC elements to protect three points in the energy system, or the TOC elements can be distributed in another suitable way. In addition, oscillography can also be configured to measure raw data or data derived from a given source. The present invention allows these and other advantages to be achieved. Although the foregoing description includes numerous details and specificities, it should be understood that these are provided for purposes of explanation only, and are not intended to limit the scope of the invention. Those of ordinary skill in the art will readily be able to make numerous modifications to the exemplary embodiments described above, without departing from the scope of the invention, as defined by the following claims and their legal equivalents.

Claims (22)

1. A method for deriving data in an energy distribution system, which comprises the steps of: configuring a protective relay, through a protective relay interface, to receive the system data from a plurality of source points; detect levels of system parameters at source points; and perform monitoring and control of the network in the protective relay based on the levels of system parameters detected.

The method of claim 1, wherein the protective relay includes a plurality of digital signal processors.

The method of claim 1, wherein the step of configuring includes the step of defining a source point and the parameters associated with the source point.

4. The method of claim 3, wherein one of the parameters associated with the source point is a dynamic range.

The method of claim 4, wherein the dynamic range is defined to provide measurement of the income class.

The method of claim 4, wherein the dynamic range is less than about 1.5 to 2.0 times the nominal input.

The method of claim 1, wherein each source point is defined based on one or more current transformers and voltage transformers associated with the power distribution system.

The method of claim 1, which further comprises the step of adding multiple levels of system parameters in the protective relay.

The method of claim 1, further comprising the step of communicating the system parameter levels to a remote protective relay device over a communications network.

10. A protective relay for monitoring a power distribution network, which comprises: an interface element connected to receive the configuration commands from a user, the configuration commands defining a plurality of source points in the distribution network of energy; a plurality of digital signal processing units inside the protective relay, the digital signal processing units being configured to receive the configuration commands from the user interface, and to execute the configuration commands to buffer the parameters of the network in the plurality of source points.

The protective relay of claim 10, wherein the plurality of digital signal processors combine the data of the power system from two or more of the 5 plurality of source points.

The protective relay of claim 10, wherein the protective relay performs protection for an element of the power system in the power distribution network, based on the parameters of the network monitored by the 10 units of digital signal processing.

The protective relay of claim 10, wherein the protective relay monitors the failure of the circuit breaker, based on the network parameters monitored by the digital signal processing units.

14. The protective relay of claim 10, wherein each digital signal processor includes a plurality of channel banks, with each bank of channels storing the processing data corresponding to the current transformers or voltage transformers in the power network. 0 distribution of energy.

The protective relay of claim 10, wherein the interface is provided through a central processing unit.

The protective relay of claim 10, wherein at least one of the plurality of signal processors The digital processor processes the data from one or more source points within a dynamic range, to perform the measurement of the income class.

The protective relay of claim 16, wherein the dynamic range is less than about 1.5 to 2.0 times the nominal input.

18. The protective relay of claim 10, wherein the plurality of digital signal processing units communicate with each other over a dedicated communications busbar.

19. The protective relay of claim 18, wherein each of the plurality of digital signal processing units communicates with a central processing unit.

The protective relay of claim 19, wherein the central processing unit communicates with a remote central processing unit of a remote protective relay over a communications network.

21. A method for processing energy system data into a protective relay associated with the power system, which comprises the steps of: receiving energy system data from multiple source points defined by the user in the power system; combine the data of the energy system from the multiple source points defined by the user in the protective relay; and provide protective control based on the combined energy system data.

22. A protective relay, comprising: at least one central processing unit, the central processing unit being connected to receive input from a user, and to provide a protective control output to an energy system; at least two digital signal processing units connected to the central processing unit by a data bus, each digital signal processing unit receiving the energy system data from multiple user-defined source points, and combining the data of the power system from the multiple source points defined by the user, wherein the at least one central processing unit provides a protective control output based on the data of the combined energy system. ^^ aa. ^^ ^ r ^ jfS & a a ^ - &