Slow Load Shed Logic - ABB RELION 630 Series Technical Manual

Section 7
Power management functions
7.4.4.8
226
can be activated either at minute 2 of the maximum demand scenario
1 or at minute 3 of the maximum demand scenario 2.
This module inhibits MAX_DMD_ALM output in any of the following conditions.
• The input INHIBIT_TRG is TRUE.
• The input SLS_DISABLE is TRUE.
• The load-shedding blocking status (from the Block logic module) is TRUE.
If the Demand based load shed module is disabled, MAX_DMD_ALM is FALSE, and
the AVG_DEMAND and PERIODIC_KWH outputs are zero.
This module provides the MAX_DMD_ALM to Slow load shed logic module and Binary
to integer module.

Slow load shed logic

This module calculates the available power, active power, slow load-shedding start,
slow load-shedding trigger and slow load trigger inhibition signals. The Slow load
shed logic module also calculates the overload amount during the overloading of the
power source.
If the load-shedding blocking status is TRUE due to bad IED quality in the circuit
breaker open position and the Bypass block setting is "Quality bad CB open", the
outputs AVA_POWER and ACTIVE_POWER are zero, else the outputs are the same as
the available power and active power calculated in the Power monitoring module.
The slow load shed start and slow load-shedding trigger signals are activated based on
various conditions, provided active power of the power source is positive. If the active
power value is negative, the slow load-shed start and slow load-shedding trigger
signals remain inactive.
The slow load-shedding start is activated if any of the following conditions satisfy.
• The OC_STR output is TRUE.
• The MAX_DMD_ALM output is TRUE.
• The external slow load-shedding trigger changes from FALSE to TRUE.
The slow load-shedding trigger is activated if any of the following conditions satisfy.
• The OC_OPR output is TRUE.
• The MAX_DMD_ALM output is TRUE.
• The external slow load-shedding trigger changes from FALSE to TRUE.
The slow load-shedding trigger is provided by the SLOWLS_OPR output.
1MRS757256 F
PML630/Compact Load-Shedding Solution
Technical Manual