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7.9
Date Code 20171006
Instruction Manual
SEL-400 Series Relays
Metering
Demand Metering
NOTE:
Changing EDEM or DMTC
resets the demand meter values to
zero. This also applies to changing the
active settings group where either
setting EDEM or DMTC is different in
the new active settings group.
(Changing demand current pickup
settings PDEMP, GDEMP, and QDEMP
will not affect the demand meters.)
shows how the relay applies the demand current pickup settings over
time. When residual ground demand current IG(DEM) exceeds the correspond-
ing demand pickup setting GDEMP, Relay Word bit GDEM asserts to logical 1.
Use these demand current logic outputs (PDEM, GDEM, and QDEM) for control
or alarm for high loading or unbalance conditions.
View or Reset Demand Metering Information
The relay shows demand metering quantities and time-stamped peak demand
quantities when you use a communications port or QuickSet to view these quanti-
ties. In addition, you can read the demand and peak demand quantities on the
relay front-panel LCD screen.
To reset the demand metering values use the
MET RD
command from a commu-
nications terminal, or use the
RESET
button in the QuickSet
HMI > Meter and
Control > Demand/Peak
window, or answer
Y
and press
ENT
at the
Demand Sub-
menu
reset demand prompt on the front-panel LCD screen. The relay begins the
demand meter sampling period from the time of the demand meter reset.
To reset the peak demand metering values, enter the
MET RP
command from a
communications terminal, or use the
RESET
button in the QuickSet
HMI > Meter
and Control > Demand/Peak
window, or answer
Y
and press
ENT
at the
Demand
Submenu
reset peak demand prompt on the front-panel LCD screen. You can also
reset demand metering with Global settings RST_DEM and RST_PDM (for
demand and peak demand) when EDRSTC (Data Reset Control) is Y.
Figure 7.5
Demand Current Logic Outputs
setting EDEM change,
or setting DMTC change
Demand Function
Thermal (EDEM := THM)
or
Rolling (EDEM := ROL)
Demand Function
Thermal (EDEM := THM)
or
Rolling (EDEM := ROL)
Demand Function
Thermal (EDEM := THM)
or
Rolling (EDEM := ROL)
IA
IG
(Residual)
3I2
3I2(DEM)
(Residual)
Command
MET RD,
_
+
_
+
max.
phase
demand
current
Demand
Currents
Relay
Word Bits
Demand Currents
Pickup Settings
IA(DEM)
IB(DEM)
IC(DEM)
IG(DEM)
PDEMP
GDEMP
_
+
QDEMP
Reset Demand
Reset Demand
Reset Demand
PDEM
GDEM
QDEM
Instantaneous
Currents
Summary of Contents for SEL-421-4
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