Application - ABB 615 series Technical Manual

1MAC059074-MB A
4.1.1.7
615 series ANSI
Technical Manual
The Type of reset curve setting does not apply to 50P-3 or when the DT
operation is selected. The reset is purely defined by the Reset delay time
setting.

Application

51P, 50P, 50P-3 is used in several applications in the power system. The applications
include but are not limited to:
• Selective overcurrent and short-circuit protection of feeders in distribution and
subtransmission systems
• Backup overcurrent and short-circuit protection of power transformers and
generators
• Overcurrent and short-circuit protection of various devices connected to the power
system, for example shunt capacitor banks, shunt reactors and motors
• General backup protection
51P, 50P, 50P-3 is used for single-phase, two-phase and three-phase non-directional
overcurrent and short-circuit protection. Typically, overcurrent protection is used for
clearing two and three-phase short circuits. Therefore, the user can choose how many
phases, at minimum, must have currents above the pickup level for the function to trip.
When the number of pickup-phase settings is set to "1 out of 3", the operation of 51P, 50P,
50P-3 is enabled with the presence of high current in one-phase.
When the setting is "2 out of 3" or "3 out of 3", single-phase faults are not
detected. The setting "3 out of 3" requires the fault to be present in all three
phases.
Many applications require several steps using different current pickup levels and time
delays. 51P/50P consists of three protection stages:
• Low 51P
• High 50P
• Instantaneous 50P-3
51P is used for overcurrent protection. The function contains several types of time-delay
characteristics. 50P and 50P-3 are used for fast clearance of very high overcurrent
situations.
Section 4
Protection functions
217