Electricity: electrical systems and devices – Safety and protection of systems and devices – Feeder protection in distribution networks
Reexamination Certificate
2002-08-05
2004-12-28
Leja, Ronald (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Feeder protection in distribution networks
Reexamination Certificate
active
06836395
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the predetermined settings used in a microprocessor-based protective relay for power systems, and more particularly concerns a protective relay system in which the protective relays themselves, i.e. the hardware, in the relay system are identical, with the settings in each relay depending on their particular location in the power system.
BACKGROUND OF THE INVENTION
Protective relays, including microprocessor-based protective relays, are used to detect faults in power systems and then to isolate the fault-affected portion of the power system. Typically, a plurality of such protective relays are positioned at various selected locations in the power system to provide comprehensive fault protection. In a small power system, for instance, six or seven protective relays may be used, while a somewhat larger system could include 20 protective relays or more. Very large systems can use as many as 500 relays.
In the smaller power systems, the relays used may be all the same (the identical hardware), with each relay having software setting information and operational firmware specifically adapted to the specific type of protection to be performed at each particular point in the power system. In addition to the particular protection functions carried out in accordance with the setting information, the number of electrical connections, i.e. connections with current transformers (CTs) and voltage (potential) transformers (PTs) will vary from location to location, as will the number of external interfaces. The specific location-based information is provided in the relay used at that location. The actual relay (hardware) will, as indicated above, often be the same from location to location (only one type of relay thus needs to be purchased), with the hardware capability being determined by the highest (most demanding) requirements location.
Historically, if a protective relay should fail within the system, a new relay, typically with default settings provided at the factory, is obtained, usually from an on-site or geographically close supply. The relay, however, must be programmed with the particular settings previously determined for the particular location of the relay to be replaced. This can be done either at the site itself or at the warehouse, manually with a dumb terminal or with a computer software package, or by other means.
However, this programming process for the replacement relay is prone to human error, because the correct settings for the particular relay which is being replaced must first be selected from a relatively large database, and then those settings must be manually entered into the relay.
SUMMARY OF THE INVENTION
Accordingly, the present invention is a protective relay system and corresponding method for use in a power system which has a plurality of protection locations for the protective relays, wherein the settings for the protection operation of the protective relays at each location are known, as well as the connection requirements between the protective relays and the power system for each location, wherein the relay system/method comprises: a plurality of protective relays for a power system, each relay having a memory for storing a plurality of groups of setting information, wherein the relay includes setting information for each of the protection locations in the power system; a key identifier member at each location in the power system at which a protective relay is to be located, providing information which identifies, directly or indirectly, the setting information used at each location; and an assembly in each relay for receiving the key member identifying information, wherein when power is supplied to a relay in the relay system, the relay gains knowledge of the particular setting information used at the location from the key member connected thereto, permitting the relay to obtain from memory the setting information for that location to operate in accordance therewith.
The invention also includes a protective relay system and corresponding method for use in a power system which has a plurality of protection locations for the protective relays, the protective relay system comprising: a plurality of protective relays for use in a power system, each protective relay having a memory for storage of a plurality of groups setting information, wherein the relay includes setting information for each of the protection locations in the power system; and a system computer which is linked uniquely to each location in the power system and includes identifying information which identifies, directly or indirectly, the setting information for each protective relay location, and for providing that information upon request from a protective relay at a given location, wherein the protective relay uses the setting information so identified to perform the protection functions required at that location.
REFERENCES:
patent: 5041737 (1991-08-01), Schweitzer et al.
patent: 5596263 (1997-01-01), Zavis et al.
patent: 6035263 (2000-03-01), Jeon
patent: 6239960 (2001-05-01), Martin
patent: 6496342 (2002-12-01), Horvath et al.
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Leja Ronald
Schweitzer Engineering Laboratories Inc.
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