ABB REL 356 Current Differential Protection
4-8
Measuring Elements and Operational Logic
AG
BG
CG
AB
BC
CA
ABG
BCG
CAG
|
∆
I
A
| > 1.5 * |
∆
I
B
|
X
X
X
|
∆
I
A
| > 1.5 * |
∆
I
C
|
X
X
X
|
∆
I
B
| > 1.5 * |
∆
I
A
|
X
X
X
|
∆
I
B
| > 1.5 * |
∆
I
C
|
X
X
X
|
∆
I
C
| > 1.5 * |
∆
I
A
|
X
X
X
|
∆
I
C
| > 1.5 * |
∆
I
B
|
X
X
X
none = ABC
Figure 4-7. Phase Selector
The fault type is identified by any two comparisons being true as shown in Figure 4-7. If no single phase to ground, two
phase or two phase to ground fault is identified, the fault is determined to be three phase.
Differential Protection Disable
An opto-isolated input has been provided in the relaying system to disable Local and Remote differential protection when
the input is energized by a dc voltage. This input has not effect on the optional distance backup system except where
the setting BKUP is set to CTDD, then it will enable the distance protection. See backup distance protection below.
Optional Backup Functions
Distance Protection
The distance units in the REL 356 system are only operative when the communication channel is unsound, with excep-
tion of the out of step trip logic that is always active, if OST is set to WAYI or WAYO.
The backup distance relaying system includes two zones of a conventional non-pilot distance protection.
Line measurements techniques applies to each zone include:
·
Single phase to ground fault detection
·
Three phase fault detection
·
Phase to phase fault detection
·
Phase to phase to ground fault detection
Zone 2 and Zone 3 Distance Relaying
The optional backup system consists of two zones of distance protection for both phase and ground faults. Each zone
consists of four distance units that are able to detect all fault types. The impedance units are three phase to ground units
(AG, BG and CG) and a phase to phase unit.
The phase to ground units detect all single phase to ground faults (SLGF), three phase faults and some phase to phase
to ground faults within its operating characteristic. The ZGF and ZFG (forward and reverse) settings apply to ground
faults and the ZP (forward phase reach) settings apply to three phase faults.
The phase to phase unit detects all phase to phase faults and some phase to phase to ground faults. Since this unit is
inherently directional only the forward reach, ZP, is used.
All phase to phase to ground faults are detected by the phase to ground units and/or the phase to phase units.
Summary of Contents for REL 356
Page 23: ...ABB REL 356 Current Differential Protection 1 10 Product Overview and Specifications ...
Page 83: ...ABB REL 356 Current Differential Protection 3 36 Settings and Application ...
Page 127: ...ABB REL 356 Current Differential Protection 5 28 Testing ...
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