ABB Relion 670 series, Technical Reference Manual

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The output signal is 1 for single phase-to-ground fault, 2 for phase-to-phase fault and 3
for three-phase fault. At this point the filter does not know if ground was involved or not.
Typically there are induced harmonics in the non-faulted lines that will affect the
result. This method allows for a significant tolerance in the evaluation of FaultType
over its entire range.
When a single phase-to-ground fault has been detected, the logic determines the largest
quantity, and asserts that phase. If phase-to-phase fault is detected, the two largest
phase quantities will be detected and asserted as outputs.
The faults detected by the delta based phase selector are coordinated in a separate
block. Different phases of faults may be detected at slightly different times due to
differences in the angles of incidence of fault on the wave shape. Therefore the output
is forced to wait a certain time by means of a timer. If the timer expires, and a fault is
detected in one phase only, the fault is deemed as phase-to-ground. This way a
premature single phase-to-ground fault detection is not released for a phase-to-phase
fault. If, however, ground current is detected before the timer expires, the phase-to-
ground fault is released sooner.
If another phase picks up during the time delay, the wait time is reduced by a certain
amount. Each detection of either ground-to-phase or additional phases further reduce
the initial time delay and allow the delta phase selector output to be faster. There is no
time delay, if for example, all three phases are faulty.
The delta function is released if the input DELTAREL is activated at the same time as
input DELTABLK is not activated. Activating the DELTABLK input will block the
delta function. The release signal has an internal pulse timer of 100 ms. When the
DELTAREL signal has disappeared the delta logic is reset. In order not to get too
abrupt change, the reset is decayed in pre-defined steps.
Symmetrical component based phase selector
The symmetrical component phase selector uses preprocessed calculated sequence
voltages and currents as inputs. It also uses sampled values of the phase currents. All
the symmetrical quantities mentioned further in this section are with reference to phase
A.
The function is made up of four main parts:
A Detection of the presence of ground fault
B A phase-to-phase logic block based on V
2
/V
1
angle relationship
C A phase-to-ground component based on patent US5390067 where the angle relationships
between V
2
/I
0
and V
2
/V
1
is evaluated to determine ground fault or phase- to-phase to ground fault
D Logic for detection of three-phase fault
1MRK505222-UUS C
Section 6
Impedance protection
291
Technical reference manual