
To ensure that the 50P element picks up for the calculated fault current, select some current
value below the calculated 620 ampere value for the 50P setting. This setting accounts for arc
resistance and errors in fault study calculations. In this example, the value selected for the
50P setting is 370 A (approximately 60% of the minimum fault current).
- Setting Limit Check
The primary limit check allows for 50P settings of 0.25 - 50,000 A. The secondary check
allows for a secondary amp setting of 0.5 - 40 A.
Calculations:
CTR = 200:1
The 50P setting of 370 A for this example lies within the relay setting limits.
- Relay Word Bits and Other Settings Affected
50P bit in the Relay Word and all phase distance elements: Relay Word bits Z1P, Z2PT, Z3,
Z3T, and LOP. REJO bit when REJOE = P.
High-Set Phase Overcurrent Element Setting
The 50H element is intended for use as a high set non-directional phase overcurrent detector
in the switch-onto-fault logic. If a line breaker is closed into a close-in three-phase bolted
fault where line-side potential transformers are used, polarizing voltage for the three-phase
distance elements is never established. In this situation, the distance elements do not operate.
The 50H element is provided to help prevent a failure to trip the line breaker in this instance.
The 50H element measures current magnitude in each phase with no dependence on polarizing
voltages. This element is non-directional and should be used only in the switch-onto-fault
logic mask (MTO) when the line breaker is closed to test the line on a radial basis. If fault
duty in front of the line terminal is much greater than behind it, the 50H element can also be
used in the unconditional trip logic mask (MTU) to provide rapid clearance of close-in faults.
Typical 50H settings are 50% - 70% of three-phase fault duty at the local bus.
The three-phase fault duty for a fault at Bus B is 2180 A. To assure rapid clearance of this
fault, a 50H setting of 1500 A is selected for this example.
Date Code 920508
Applications
SEL-221F, -1 Instruction Manual
5-19
Содержание SEL-221F
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Страница 170: ...Figure 6 2 Horizontal Front and Rear Panel Drawings Date Code 920508 Installation 6 7 SEL 221F 1 Instruction Manual ...
Страница 174: ...Figure 6 8 Dc External Connection Diagram Typical Date Code 920508 Installation SEL 221F 1 Instruction Manual 6 11 ...
Страница 228: ...APPENDICES TABLE OF CONTENTS Parts Placement Diagram Date Code 920508 Table of Contents SEL 221F 1 Instruction Manual i ...
Страница 229: ...SEL 200 Series Relay Main Board Troubleshooting Test Points and Jumper Locations ...