The widely used United Sates standard ANSI/IEEE C37.2 'Electrical Power System Device Function Numbers, Acronyms, and Contact Designations' deals with protective device function numbering and acronyms.. Multifunction relays have combinations of device numbers. A 27/59 device, for example, is a combination under/over voltage relay. Letters.. The ANSI standard device numbers ( As per ANSI/IEEE standard C37.2) are used in the design of an electrical power system. These devices protect the electrical network in the case of a fault in the system. The list of ANSI device numbers with their acronyms is as given below.
In the design of electrical power systems, the ANSI Standard Device Numbers (ANSI /IEEE Standard C37.2) denote what features a protective device supports (such as a relay or circuit breaker). These types of devices protect electrical systems and components from damage when an unwanted event occurs, such as an electrical fault... ANSI/IEEE codes dictate how and when to apply devices for certain circuits or situations. Some devices fall under multiple designations and may receive dual code numbers (for example 50/51 relay). Some code designations are expressly written on circuit diagrams to identify how a device is being used.