Demand Based Load Shed - ABB RELION 630 Series Technical Manual

Section 7
Power management functions
7.4.4.7
224
This module inhibits the OC_STR and OC_OPR outputs and slow load-shedding
trigger due to external input 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 Over current based load shed module is disabled, the outputs OC_OPR and
OC_STR are FALSE, the Slow load shed trigger module due to external input
EXT_OC_SLST is inactive and the outputs OC_TIME and ELAPSE_TIME are zero.
The Over current based load shed module provides the OC_STR (overcurrent start)
signal to the Slow load shed logic module. It also provides the OC_OPR (overcurrent
operate), external slow load-shedding trigger signal to the Slow load shed logic
module and the Binary to integer module.

Demand based load shed

This module calculates the linear average demand based on an active power (from the
Power monitoring module) of the power source over a set interval time. Based on the
comparison of the linear average demand and set maximum demand value of source,
demand-based slow load-shedding action is initiated.
The Slow load shed mode setting enables or disables the Demand based load shed
module. If the Slow load shed mode setting is "Max Dmd Trg" or "OC, Max Dmd, Ext
Trg", the Demand based load shed is enabled, else it is disabled
Based on the measured powers (power received from source IED), the Demand based
load shed module internally calculates the linear average of the demand over the
Demand interval setting. The Demand interval setting can be set to "1 Minute", "5
Minute", "10 Minute", "15 Minute", "30 Minute", "60 Minute" or "180 Minute". A
new demand value is obtained every one minute, indicating the actual demand over
the time interval preceding the update time. Based on the sliding average and final
output value, the demand values are updated at the end of the time interval. For
monitoring, the demand value output is AVG_DEMAND in kilowatt and the energy
demand output is PERIODIC_KWH in kilowatt hour.
For example, the demand value based on the setting interval "180 Minute" is displayed
in the output for the first time after 180 minutes and the value is calculated from the
interval t0 – t180. The next value is displayed at the t180+1 and it is based on the
average between t0+1 – t180+1.
If the linear average of the demand on the power source exceeds the Maximum demand
setting limit, the MAX_DMD_ALM output (maximum demand operate) is TRUE. The
RESET_DEMAND input resets the Demand based load-shedding module. If the
RESET_DEMAND input is TRUE, the MAX_DMD_ALM output is TRUE and both the
AVG_DEMAND and PERIODIC_KWH outputs are reset to zero.
1MRS757256 F
PML630/Compact Load-Shedding Solution
Technical Manual