Sel SEL-787 - Figure 4.2 Winding 1 Compensated Currents

4.7
Date Code 20150130 Instruction Manual SEL-787 Relay
Protection and Logic Functions
Basic Protection
similar names. The I1 compensated currents are used with differential element
87-1, I2 with element 87-2, and I3 with element 87-3.
Figure 4.2 Winding 1 Compensated Currents
NOTE:
The SEL-787 restraint
quantity IRTn calculation differs from
the SEL-587 and SEL-387 by a factor
of 2.
Figure 4.3 illustrated how the IOP1 (operate), IRT1 (restraint), I1H24
(harmonic restraint), I1H2 (second harmonic), I1H4 (fourth harmonic), and
I1H5 (fifth harmonic) quantities are calculated for the 87-1 element. IOP1 is
generated by summing the winding currents in a phasor addition. IRT1 is
generated by summing the magnitudes of the winding currents in a simple
scalar addition. The 87-2 and 87-3 quantities are calculated in a similar
manner.
For each restraint element (87R-1, 87R-2, 87R-3), the quantities are summed
as phasors and the magnitude becomes the Operate quantity (IOPn). For a
through-current condition, IOPn should calculate to about 1 + (–1) = 0, at
rated load. Calculation of the restraint quantity (IRTn) occurs through a
summation of all current magnitudes. For a through-current condition, this
will calculate to about (| 1 | + | –1 |) = 2, at rated load.
I1W1C1
I2W1C1
I3W1C1
I1W1C2
I2W1C2
I3W1C2
I1W1C4
I2W1C4
I3W1C4
IAW1
IBW1
ICW1
Data
Acquisition
Fundamental
Frequency
Filter
TAP1
Scaling
Connection
Compensation
(CTC1)
Second-
Harmonic
Filter
TAP1
Scaling
Connection
Compensation
(CTC1)
Fourth-
Harmonic
Filter
TAP1
Scaling
Connection
Compensation
(CTC1)
I1W1C5
I2W1C5
I3W1C5
Fifth-
Harmonic
Filter
TAP1
Scaling
Connection
Compensation
(CTC1)