Sel SEL-787 - Figure 4.47 Demand Current Logic Outputs

4.63
Date Code 20150130 Instruction Manual SEL-787 Relay
Protection and Logic Functions
Demand Metering
The demand current level settings are applied to demand current meter outputs
as shown in Figure 4.47. For example, when residual ground demand current
IGD goes above corresponding demand pickup GNDEMP, Relay Word bit
GNDEM asserts to logical 1. Use these demand current logic outputs
(PHDEM, GNDEM, and 3I2DEM) to alarm for high loading or unbalance
conditions.
Figure 4.47 Demand Current Logic Outputs
The demand values are updated approximately once a second. The relay stores
peak demand values to nonvolatile storage every six hours (it overwrites the
previous stored value if it is exceeded). Should the relay lose control power, it
will restore the peak demand values saved by the relay.
Demand metering peak recording is momentarily suspended when
SELOGIC
control equation setting FAULT is asserted (= logical 1).
The differences between thermal and rolling demand metering are explained
in the following discussion.
PHDEM
Relay
Word
Bits
Demand Current
Pickup Settings
(A Secondary)
IBD
IAD
IAWn
ICD
Analog
Quantities
Demand
Currents
Instantaneous
Currents
Serial Port
Command
Demand Function
Maximum
Current
Logic
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
Reset
Demand
PHDEMP
IGD
Reset
Demand
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
GNDEM
GNDEMP
IGWn
(residual)
Demand Function
3I2D
Reset
Demand
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
3I2DEM
3I2DEMP
3I2Wn
MET RD
Demand Function