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PROTECTION SYSTEM FOR POWER
CROSS REFERENCE TO RELATED
This application is related to U.S. Patent Application No. 60/359,544 filed on Feb. 25, 2002 for "Integrated Protection, Monitoring, and Control" the contents of which are incorporated by reference herein. This application is also related 1° to U.S. Patent Application No. 60/438,159 filed on Jan. 6, 2003 for "Single Processor Concept for Protection and Control of Circuit Breakers in Low-Voltage Switchgear" the contents of which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
The present disclosure relates generally to power distribution systems. More particularly, the present disclosure relates to a protection system for power distribution systems. 20
Industrial power distribution systems commonly divide incoming power into a number of branch circuits. The branch circuits supply power to various equipment (i.e., loads) in the industrial facility. Circuit breakers are typically provided in each branch circuit to facilitate protecting equipment within the branch circuit. Circuit breakers are designed to open and close a circuit by non-automatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied 3Q within its rating. The circuit breakers commonly include supplementary protectors enclosed within the body of the circuit breaker. One common type of supplementary protector is known as an electronic trip unit. The circuit breaker and its supplementary protector have proven useful at man- 35 aging the protection of the loads on the circuit.
However, it can be desired to integrate the load management of the branch circuits to one another. Further, it can be desired to integrate the management of the loads on the branch circuits with the management of the power feeds 4Q feeding the branch circuits. Still further, it can be desired to provide for monitoring of the system.
In order to provide this integrated protection and monitoring, prior power distribution systems have required costly and difficult to implement solutions. Today, each of these 45 functions is performed by separate hardware often with separate sensors necessary to measure system parameters and auxiliary devices in power circuit interrupters to switch the power circuits. In such prior systems, hard wire connections between all of the electronic trip units in the system 50 was required in order to coordinate the load control decisions of each independent trip unit with the other trip units in the system. Further, hard wire connections were also required to provide information for the independent electronic trip units to the separate system performing feed 55 management decisions. The control decisions by the separate system performing feed management decisions is made more complex because the information from the various independent electronic trip unit is typically out of phase with one another. Additionally, another hardware device is 60 required to then provide the desired monitoring functionality.
Accordingly, there is a continuing need for power distribution systems having a fully integrated protection system. Moreover, there is continuing need for low cost, easy to 65 install, and easy to upgrade fully integrated protection system for power distribution systems.
SUMMARY OF THE INVENTION
In one exemplary embodiment, a protection system for a power distribution system is provided. The protection system includes a central computer, a plurality of data modules, and a data network. The data modules are each in communication with a different circuit breaker of the power distribution system. The data network communicates between the central computer and the plurality of data modules. The central computer sends an instruction to the plurality of data modules over the data network to aid in synchronization of sampling of a power condition at the plurality of data modules.
In another exemplary embodiment, a method of protecting a power distribution system is provided. The method includes sending a synchronization instruction to a plurality of data modules; sampling a power condition from the power distribution system in part based upon the synchronization instruction, each of the plurality of data modules being in communication with a different set of separable contacts in the power distribution system; transmitting a first message containing the power condition from each of the plurality of data modules to a central computer; determining a second message the central computer based upon the first message; and transmitting the second message to each of the plurality of data modules so that one or more of the plurality of data modules operates the different set of separable contacts in response to the second message.
In yet another exemplary embodiment, a power distribution system is provided. The power distribution system includes a processing unit, a first power bus, a first data module, a second data module, and a data network. The first power bus powers a first branch circuit through a first circuit breaker and a second branch circuit through a second circuit breaker. The first data module operates the first circuit breaker and samples a first parameter from the first branch circuit. Similarly, the second data operates the second circuit breaker and samples a second parameter from the second branch circuit. The data network links the first and second data modules to the processing unit. The processing unit performs all primary power distribution functions for the power distribution system based on the first and second parameters. The processing unit communicates a synchronization signal to the first and second data modules so that the first and second data modules sample the first and second parameters, respectively, within a predetermined time-window.
The above-described and other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic of a power distribution system having an exemplary embodiment of a integrated protection, monitoring, and control system;
FIG. 2 is a schematic of an exemplary embodiment of a data sample and transmission module of the integrated protection, monitoring, and control system of FIG. 1;
FIG. 3 illustrates an exemplary embodiment of a response time for the integrated protection, monitoring, and control system of FIG. 1; and
FIG. 4 is a schematic of a second power distribution system having an integrated protection, monitoring, and control system.
Referring now to the drawings and in particular to FIG. 1, an exemplary embodiment of a power distribution system generally referred to by reference numeral 10 is illustrated. 5 System 10 distributes power from at least one power bus 12 through a number or plurality of circuit breakers 14 to branch circuits 16.
Power bus 12 is illustrated by way of example as a three-phase power system having a first phase 18, a second 10 phase 20, and a third phase 22. Power bus 12 can also include a neutral phase (not shown). System 10 is illustrated for purposes of clarity distributing power from power bus 12 to four circuits 16 by four breakers 14. Of course, it is contemplated by the present disclosure for power bus 12 to 15 have any desired number of phases and/or for system 10 to have any desired number of circuit breakers 14.
Each circuit breaker 14 has a set of separable contacts 24 (illustrated schematically). Contacts 24 selectively place power bus 12 in communication with at least one load (also 20 illustrated schematically) on circuit 16. The load can include devices, such as, but not limited to, motors, welding machinery, computers, heaters, lighting, and/or other electrical equipment.
Power distribution system 10 is illustrated in FIG. 1 with 25 an exemplary embodiment of a centrally controlled and fully integrated protection, monitoring, and control system 26 (hereinafter "system"). System 26 is configured to control and monitor power distribution system 10 from a central control processing unit 28 (hereinafter "CCPU"). CCPU 28 30 communicates with a number or plurality of data sample and transmission modules 30 (hereinafter "module") over a data network 32. Network 32 communicates all of the information from all of the modules 30 substantially simultaneously to CCPU 28. 35
Thus, system 26 can include protection and control schemes that consider the value of electrical signals, such as current magnitude and phase, at one or all circuit breakers 14. Further, system 26 integrates the protection, control, and monitoring functions of the individual breakers 14 of power 40 distribution system 10 in a single, centralized control processor (e.g., CCPU 28). System 26 provides CCPU 28 with all of a synchronized set of information available through digital communication with modules 30 and circuit breakers 14 on network 32 and provides the CCPU with the ability to 45 operate these devices based on this complete set of data.
Specifically, CCPU 28 performs all primary power distribution functions for power distribution system 10. Namely, CCPU 28 performs all instantaneous overcurrent protection (10C), sort time overcurrent, longtime overcur- 50 rent, relay protection, and logic control as well as digital signal processing functions of system 26. Thus, system 26 enables settings to be changed and data to be logged in single, central location, i.e., CCPU 28. CCPU 28 is described herein by way of example as a central processing 55 unit. Of course, it is contemplated by the present disclosure for CCPU 28 to include any programmable circuit, such as, but not limited to, computers, processors, microcontrollers, microcomputers, programmable logic controllers, application specific integrated circuits, and other programmable 60 circuits.
As shown in FIG. 1, each module 30 is in communication with one of the circuit breakers 14. Each module 30 is also in communication with at least one sensor 34 sensing a condition of the power in each phase (e.g., first phase 18, 65 second phase 20, third phase 22, and neutral) of bus 12 and/or circuit 16. Sensors 34 can include current transform
ers (CTs), potential transformers (PTs), and any combination thereof. Sensors 34 monitor a condition of the incoming power in circuits 16 and provide a first signal 36 representative of the condition of the power to module 30. For example, sensors 34 can be current transformers that generate a secondary current proportional to the current in circuit 16 so that first signals 36 are the secondary current.
Module 30 sends and receives one or more second signals 38 to and/or from circuit breaker 14. Second signals 38 can be representative of one or more conditions of breaker 14, such as, but not limited to, a position of separable contacts 24, a spring charge switch status, and others. In addition, module 30 is configured to operate circuit breaker 14 by sending one or more third signals 40 to the breaker to open/close separable contacts 24 as desired. In a first embodiment, circuit breakers 14 cannot open separable contacts 24 unless instructed to do so by system 26.
System 26 utilizes data network 32 for data acquisition from modules 30 and data communication to the modules. Accordingly, network 32 is configured to provide a desired level of communication capacity and traffic management between CCPU 28 and modules 30. In an exemplary embodiment, network 32 can be configured to not enable communication between modules 30 (i.e., no module-tomodule communication).
In addition, system 26 can be configured to provide a consistent fault response time. As used herein, the fault response time of system 26 is defined as the time between when a fault condition occurs and the time module 30 issues an trip command to its associated breaker 14. In an exemplary embodiment, system 26 has a fault response time that is less than a single cycle of the 60 Hz (hertz) waveform. For example, system 26 can have a maximum fault response time of about three milliseconds.
The configuration and operational protocols of network 32 are configured to provide the aforementioned communication capacity and response time. For example, network 32 can be an Ethernet network having a star topology as illustrated in FIG. 1. In this embodiment, network 32 is a full duplex network having the collision-detection multipleaccess (CSMA/CD) protocols typically employed by Ethernet networks removed and/or disabled. Rather, network 32 is a switched Ethernet for managing collision domains.
In this configuration, network 32 provides a data transfer rate of at least about 100 Mbps (megabits per second). For example, the data transfer rate can be about 1 Gbps (gigabits per second). Additionally, communication between CCPU 28 and modules 30 across network 32 can be managed to optimize the use of network 32. For example, network 32 can be optimized by adjusting one or more of a message size, a message frequency, a message content, and/or a network speed.
Accordingly, network 32 provides for a response time that includes scheduled communications, a fixed message length, full-duplex operating mode, and a switch to prevent collisions so that all messages are moved to memory in CCPU 28 before the next set of messages is scheduled to arrive. Thus, system 26 can perform the desired control, monitoring, and protection functions in a central location and manner.
It should be recognized that data network 32 is described above by way of example only as an Ethernet network having a particular configuration, topography, and data transmission protocols. Of course, the present disclosure contemplates the use of any data transmission network that ensures the desired data capacity and consistent fault response time necessary to perform the desired range of functionality. The exemplary embodiment achieves sub