Overview
The “Underfrequency load shedding” function detects underfrequencies in the electrical power systems, switches off the medium-voltage busbar or feeders that consume active power to stabilize the frequency, and maintains operations for the medium-voltage busbar or feeders that generate active power.
For more detailed information on “Underfrequency load shedding” function, refer to SIPROTEC 5 devices, V8.30 & higher manuals.
To see other supported functions, click here.
Structure/Embedding of the Function
Setting Parameters
Setting parameters for Underfrequency load shedding Function
| Addr. | Parameter | C | Setting Options | Default Setting |
| General | ||||
| _:18121:101 | General:Minimum voltage | 0.300 p.u. to 0.900 p.u. | 0.700 p.u. | |
| _:18121:103 | General:Power criterion | no yes |
yes | |
| _:18121:104 | General:Min. current (power crit.) | 0.020 p.u. to 0.200 p.u. | 0.050 p.u. | |
| _:18121:115 | General:Positive power direction | inv. to CT neu.pnt sett. acc. to CT neu.pnt sett. |
inv. to CT neu.pnt sett. | |
| _:18121:106 | General:Phi (power crite- rion) | -30° to 30° | -5° | |
| _:18121:107 | General:df/dt-rising blk. criterion | no yes |
no | |
| _:18121:108 | General:df/dt-rising blk. threshold | 0.1 Hz/s to 20.0 Hz/s | 1.0 Hz/s | |
| _:18121:109 | General:df/dt-falling blk. criterion | no yes |
no | |
| _:18121:110 | General:df/dt-falling blk. threshold | 0.1 Hz/s to 20.0 Hz/s | 3.0 Hz/s | |
| _:18121:111 | General:df/dt measuring window | 2 periods to 5 periods | 5 periods | |
| _:18121:112 | General:df/dt dropout differential | 0.02 Hz/s to 0.99 Hz/s | 0.10 Hz/s | |
| _:18121:113 | General:f< stabilization counter | 1 to 20 | 6 | |
| Stage 1 | ||||
| _:18151:1 | Stage 1:Mode | off on test |
off | |
| _:18151:2 | Stage 1:Operate & flt.rec. blocked | no yes |
no | |
| _:18151:3 | Stage 1:Threshold | 40.00 Hz to 70.00 Hz | 49.00 Hz | |
| _:18151:5 | Stage 1:Dropout differ- ential | 20 mHz to 2000 mHz | 20 mHz | |
| _:18151:6 | Stage 1:Operate delay | 0.00 s to 60.00 s | 0.10 s | |
Logic Diagrams & highlights
Logic Diagram of the General Functionality
Power-Criterion Checking at Phi (power criterion) ≤ 0
Power-Criterion Checking at Phi (power criterion) > 0
Application Scenarios
Logic Diagram of the Underfrequency Load Shedding Stage
