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ABB Distribution Protection Unit 1500R/2000R
Application Note AN-24
Two-Phase, 50P Tripping
Introduction
The 2 Phase-50P Trip in the DPU1500R/2000R is used to increase sensitivity and improve clearing time for three-
phase, phase-to-phase, and two-phase-to-ground faults on the main section of radial distribution lines. The 2 Phase-
50P Trip is not sensitive to single-phase-to-ground faults. When the 2 Phase-50P Trip is enabled in the settings table,
the 50P-1, 50P-2, and 50P-3 functions will trip only when 2 or 3 phases exceed these trip for phase-to-ground faults
when the residual current exceeds the instantaneous 50N-1, 50N-2, or 50N-3 pickup settings.
On distribution lines, the phase and ground instantaneous overcurrent elements are often set very high in order to
coordinate with large downstream fuses. When using the DPU1500R/2000R in these applications, the 50N-1 function
can be set to coordinate with the large downstream fuses. By enabling the 2 Phase-50P Trip, the 50P-1 function can
be set below the 50N-1 pickup setting to increase sensitivity and improve clearing time for three-phase, phase-to-
phase, and two-phase-to-ground faults on the main section of the radial feeder.
For example, a 100A downstream fuse may require the upstream 50N-1 pickup setting to be 4000A or more. By
enabling the 2 Phase-50P Trip, the 50P-1 function can be set at 2000A. For three-phase, phase-to-phase, and two-
phase-to-ground faults greater than 2000A, a 50P-1 instantaneous trip will occur. No 50P-1 trip occurs for single-
phase-to-ground faults when the fault current is between 2000 and 4000A. For single--phase-to-ground faults where
the current is greater than 4000A, a 50N-1 instantaneous trip will occur.
On manual closing of the circuit, consideration may need to be given to cold load inrush. In the DPU1500R/2000R,
the 50P-1, 50P-2, 50N-1, and 50N-2 functions can be delayed from 0 to 200 seconds by the cold load pickup time
(CLPT) setting.
Applications Notes
website:www.abb.com/papd
13-17
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