Schweitzer Engineering Laboratories SEL-787 - Demand Metering; Figure 4.40 Loss-Of-Potential (LOP) Logic

4.63
Date Code 20081022 Instruction Manual SEL-787 Relay
Protection and Logic Functions
Demand Metering
Figure 4.40 Loss-of-Potential (LOP) Logic
Demand Metering
The SEL-787 provides demand and peak demand metering, selectable
between thermal and rolling demand types, for the following values:
Either Winding 1 or Winding 2 currents:
➤ IA, IB, IC, phase currents (A primary)
➤ IG Residual ground current
(A primary; IG = 3I0 = IA + IB + IC)
➤ 3I2 Negative-sequence current (A primary)
Table 4.23 shows the demand metering settings. Also refer to Section 5:
Metering and Monitoring and Section 7: Communications for other related
information for the demand meter.
60
S
R
Q
Q
0
0
60
1
0
LOP
| V1 | > 5 V
Δ| V1 | > 20%
Δ ∠ I1 > 10˚
| I1 |> 0.1 • INOM
Δ ∠ I2 > 10˚
| I2 | > 0.1 • INOM
Δ ∠ I0 > 10˚
| I0 | > 0.1 • INOM
| V2 | < 5 V
| V0 | < 5 V
| V1 | >
0.75 • VNOM*1000
√3*PTR
(RESET has priority)
Note: INOM is 1 A or 5 A depending on the part number and VIWDG.
INOM is the phase secondary input rating. VNOM and VIWDG are relay settings.
Timer PU and DO times
are in cycles.
Relay
Word
Bit