Schweitzer Engineering SEL-351P, Quick Start Manual

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Date Code 990430 Breaker/Recloser Monitor, Battery System Monitor, 8-21
Metering, and Load Profile Functions
SEL-351P Manual Técnico
Demand Metering
The SEL-351P factory default settings enable the control to provide Thermal Demand Metering.
The SEL-351P offers the choice between two types of demand metering, set with the Access
Level 2 enable setting:
EDEM = THM (Thermal Demand Meter)
or
EDEM = ROL (Rolling Demand Meter)
The demand metering settings in Table SECTION 8: .5 are available via the Access Level 2 SET
command (see Table 9.1 in
Section 9: Setting the SEL-351P Recloser Control and also Settings
Sheet 10 of 23 at the end of Section 9 . Also refer to MET D – Demand Metering in MET
Command (Metering Data) , in Section 10: Serial Port Communications and Commands ).
With either Thermal Demand, or Rolling Average Demand enabled, the SEL-351P provides
demand and peak demand metering for the following values:
Currents I
A,B,C,N
Input currents (A primary)
I
G
Residual ground current (A primary; IG =3I0 = IA + IB + IC)
3I
2
Negative-sequence current (A primary)
Power MW
A,B,C,3P
Single- and three-phase megawatts
MVAR
A,B,C,3P
Single- and three-phase megavars
Depending on enable setting EDEM, these demand and peak demand values are thermal demand
or rolling demand values. The differences between thermal and rolling demand metering are
explained in the following discussion.
Comparison of Thermal and Rolling Demand Meters
The example in Figure SECTION 8: .9 shows the response of thermal and rolling demand meters
to a step current input. The current input is at a magnitude of zero and then suddenly goes to an
instantaneous level of 1.0 per unit (a “step”).