Schweitzer Engineering Laboratories SEL-311C - Demand Meter Settings; Table 8.4 Demand Meter Settings and Settings Range; Figure 8.13 Demand Current Logic Outputs

8.24
SEL-311C Relay Instruction Manual Date Code 20060320
Breaker Monitor and Metering Functions
Demand Metering
Rolling demand meter response at “Time = 15 minutes” = 3.0/3 = 1.0 per unit
Demand Meter
Settings
The demand current pickup settings in Ta ble 8.4 are applied to demand current
meter outputs as shown in Figure 8.13. For example, when residual ground
demand current I
G(DEM)
goes above corresponding demand pickup GDEMP,
Relay Word bit GDEM asserts to logical 1. Use these demand current logic
outputs (PDEM, GDEM, and QDEM) to alarm for high loading or unbalance
conditions. Use in other schemes such as the following example.
Figure 8.13 Demand Current Logic Outputs
Five-Minute Totals Corresponding Five-Minute Interval
1.0 per unit 0 to 5 minutes
1.0 per unit 5 to 10 minutes
1.0 per unit 10 to 15 minutes
3.0 per unit
Table 8.4 Demand Meter Settings and Settings Range
Setting Definition Range
EDEM Demand meter type THM = thermal
ROL = rolling
DMTC Demand meter time constant 5, 10, 15, 30, or 60 minutes
PDEMP Phase demand current pickup OFF
GDEMP Residual ground demand current pickup 0.10–3.20 A {1 A nominal}
0.50–16.0 A {5 A nominal}
QDEMP Negative-sequence demand current pickup in 0.01 A steps
NOTE: Changing setting EDEM or
DMTC resets the demand meter values
to zero. This also applies to changing
the active setting group, and setting
EDEM or DMTC is different in the new
active setting group. Demand current
pickup settings PDEMP, GDEMP, and
QDEMP can be changed without
affecting the demand meters.
The examples in this section discuss
demand current, but MW and MVAR
demand values are also available, as
stated at the beginning of this
subsection.
PDEM
Relay
Word
Bits
Demand Current
Pickup Settings
(A Secondary)
I
B(DEM)
I
A(DEM)
I
A
I
C(DEM)
Demand
Currents
Instantaneous
Currents
Serial Port
Command
Demand Function
Maximum
Phase
Demand
Current
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
Reset
Demand
PDEMP
I
G(DEM)
Reset
Demand
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
GDEM
GDEMP
I
G
(residual)
Demand Function
3I
2(DEM)
Reset
Demand
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
QDEM
QDEMP
3I
2
MET RD
Demand Function