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Relay Selection Guide (1)

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  RelaySelectionGuide     RelaySelectionGuide   GET-8048A MULTILIN   INTRODUCTION  PROTECTIVE ZONE PACKAGES Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Types of Distress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Detection Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Protection Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24Buses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Incoming Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31GE Relay Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36  PROTECTIVE ZONE PACKAGES  Table of Contents  INTRODUCTION     INTRODUCTION  INTRODUCTION                                                                                                                                                                                                                                                                                                                                                                                                                                                                                1  Figure 1 Zones include any circuit breakers associated with protected equipment  Zones of Protection Other zones could be defined tocomprise buses, generators, motors,cables, etc. Figure 2  shows one finalrequirement about these zones - theymust overlap. Because protection isapplied in association with these definedzones, it is absolutely essential that everyportion of the system must fall within azone in order to assure that there are noareas which are unprotected. Figure 2 Zones must overlap  ãAssociation with a significant component (in this case,a line).ãTerminates at and includes a circuit breaker (or otherinterrupter) which can respond to trip signals fromrelays associated with the zone.ãRepresents a minimum amount of system which mustbe de-energized to correct a problem anywhere in thezone. Primary and Backup Zones O ne of the most powerful conceptualtools available to the protection engineer isthe notion of “zones as shown in Figure 1 Rather than thinking of the powerdistribution system as unbounded,successful protection relies on visualizingthe system as a collection of discretezones which can be individually protectedusing equipment designed to detect theunique forms of abnormalitiesassociated with each component. I n spite of the best efforts of system designers andprotection specialists, and despite the fact that relays havea historical record of being among the most reliabilitycomponents of the power system, the unexpected willhappen. This has led to the practice of assuring that failureof a single relay can never result in loss of protection. Thisso-called “backup” can exist in any of several forms: Remote Backup  - in which the relays of one zone havethe ability to also detect problems in adjacent zones.  BASIC CONCEPTS BASIC CONCEPTS Remote backup protection is the most common practice inboth industrial and commercial applications, and usuallyinvolves time delays to assure selectivity. Local Backup  - in which each zone is equipped with acomplete set of redundant relays. Often the relays whichare designated as backup employ different measuringprinciples, and in more conservative schemes, may employtotally different signal sources, and even trip differentbreakers using different battery supplies.2

FEX800_P0330_M_EN

Jul 23, 2017
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