3.4
SEL-387-0, -5, -6 Relay
Instruction Manual
Date Code 20170601
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
Differential Element
Figure 3.4
Differential Element (87-1) Quantities (All But SEL-387-0)
shows how the differential element quantities are used to generate
the unrestrained 87U
n
(87U1, 87U2, 87U3) and restrained 87R
n
(87R1, 87R2,
87R3) elements. These elements are combined to form differential element
targets (87-1, 87-2, 87-3).
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 right corner of
. 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
87O
n
(87O1, 87O2, 87O3) are provided for testing purposes.
Restrained elements (87R1, 87R2, and 87R3) determine whether the IOP
quantity is greater than the restraint quantity using the differential
characteristic shown in
. Set HRSTR =Y (harmonic restraint, all but
SEL-387-0) to modify this characteristic as a function of the second- and
fourth-harmonic content in the input currents.
In element 87R
n
, for example, the IOP
n
and IRT
n
quantities determine
whether the relay trips. The logic enclosed within the dotted line of
implements the
characteristic. The differential element calculates a
threshold as a function of IRT
n
. IOP
n
must exceed this threshold to produce
IOP1
E87W1
I1W1C1
I1W3C1
I1W2C1
I1W4C1
E87W2
E87W3
E87W4
Σ
|
Σ
I1WnC1 |
E87W1
I1W1C2
I1W3C2
I1W2C2
I1W4C2
E87W2
E87W3
E87W4
E87W1
I1W1C4
I1W3C4
I1W2C4
I1W4C4
E87W2
E87W3
E87W4
n=1, 2, 3, 4
IRT1
IHRT1
I1HB2
I1HB4
Σ
Σ
Σ
Σ
h
|
Σ
I1WnC2 |
|
Σ
I1WnC4 |
| I1W4C1 |
| I1W3C1 |
| I1W2C1 |
| I1W1C1 |
100/PCT2
÷
2
100/PCT4
Содержание SEL-387-0
Страница 6: ...This page intentionally left blank ...
Страница 12: ...This page intentionally left blank ...
Страница 50: ...This page intentionally left blank ...
Страница 200: ...This page intentionally left blank ...
Страница 248: ...This page intentionally left blank ...
Страница 380: ...This page intentionally left blank ...
Страница 422: ...This page intentionally left blank ...
Страница 440: ...This page intentionally left blank ...
Страница 458: ...This page intentionally left blank ...
Страница 516: ...This page intentionally left blank ...
Страница 540: ...This page intentionally left blank ...