Sel SEL-787 - Figure 4.3 Differential Element (87-1) Quantities

4.8
SEL-787 Relay Instruction Manual Date Code 20150130
Protection and Logic Functions
Basic Protection
Figure 4.3 Differential Element (87-1) Quantities
Figure 4.4 shows how the differential element quantities are used to generate
the unrestrained 87Un (87U1, 87U2, 87U3) and restrained 87Rn/87HRn
(87R1, 87R2, 87R3, 87HR1, 87HR2, 87HR3) elements.
Unrestrained elements (87U1, 87U2, and 87U3) compare the IOP quantity to
a setting value (U87P), typically about 10 times TAP, and trip if this level is
exceeded. Elements 87U1, 87U2, and 87U3 are combined to form element
87U, as shown in the lower left corner of Figure 4.4. Harmonic blocking or
restraint is not performed on the unrestrained elements. Use these elements to
protect your transformer bushings and end windings while maintaining
security for inrush and through-fault conditions. Operating current elements
87On (87O1, 87O2, 87O3) are not available as Relay Word bits.
IOP1
E87
I1W1C1
I1W2C1
Σ
ABSOLUTE
I1W1C2
I1W2C2
I1W1C4
I1W2C4
IRT1
I1H24
I1H2
I1H4
Σ
h
ABSOLUTE
ABSOLUTE
100/PCT2
100/PCT4
E87
Σ
ABSOLUTE
ABSOLUTE
E87
Σ
I1F2
I1F4
Σ
I1W1C5
I1W2C5
100/PCT5
E87
Σ
ABSOLUTE
I1F5
I1H5