IEEE C37.2-1987 pdf free.IEEE Standard Electrical Power System Device Function Numbers.
IEEE C37.2 Prefixes and Suffixes. Lettersand numbers may be used as prefixes or suffixesto device function numbers to provide a morespecific definition of the function，as discussedbelow. They permit a manifold multiplication ofavailable function designations for the largenumber and variety of devices used in the manytypes of equipment covered by this standard.They may also serve to denote individual orspecific parts or auxiliary contacts of thesedevices or certain distinguishing features, characteristics, or conditions which describe the use ofthe device or its contacts in the equipment.
Prefixes and suffixes should, however, be usedonly when they accomplish a useful purpose. Forexample, when all of the devices in an equipmentare associated with only one kind of apparatus,such as a feeder or motor or generator, it is com-mon practice, in order to retain maximum simplicity in device function identification, not to addthe respective suffix letter F or M or G to any ofthe device function numbers.Defining Letter Sufmixes.In order toprevent any possible conflict or confusion,eachletter suffix should preferably have only onemeaning in an individual equipment.To accom-plish this, short distinctive abbreviations,such ascontained in ANSI Y1.1-1972[1]3, or any appro-priate combination of letters, may also be used asletter suffixes,where necessary. However，eachsuffix should not consist of more than three (andpreferably not more than two) letters, in order tokeep the complete function designation as shortand simple as possible. The meaning of each suffix should be designated on the drawings or in the publications withwhich they are used,similar to: TC-trip coil,V-voltage,X-auxiliary relay.
In cases where the same suffix (consisting ofone letter or a combination of letters) has different meanings in the same equipment, dependingupon the device function number with which it isused, then the complete device function numberwith its suffix letter or letters and its correspond-ing function definition should be listed in thelegend in each case, as follows: 63V-vacuum relay,7OR-raising relay for device 7o，9ov-voltageregulator.
Suggested Prefixes. A similar series of num-bers, prefixed by the letters RE (for “remote”) maybe used for the interposing relays performingfunctions that are controlled directly from thesupervisory system. Typical examples of suchfunctions are RE1，RE5, and RE94.IEEE C37.2 pdf download.