filter produces significant non-zero output. The filter output is processed by the delta
function. The algorithm uses an adaptive relationship between phases to determine if a
fault has occurred, and determines the faulty phases.
The current and voltage delta based phase selector gives a real output signal if the
following criterion is fulfilled (only phase A shown):
Max(ΔVA,ΔVB,ΔVC)>DeltaVMinOp
Max(ΔIA,ΔIB,ΔIC)>DeltaIMinOp
where:
ΔVA, ΔVB and ΔVC are the voltage change between sample t and sample t-1
DeltaVMinOp
and
DeltaIMinOp
are the minimum harmonic level settings for the voltage and current
filters to decide that a fault has occurred. A slow evolving fault may not
produce sufficient harmonics to detect the fault; however, in such a
case speed is no longer the issue and the sequence components
phase selector will operate.
The delta voltages ΔVA(B,C) and delta current ΔIA(B,C) are the voltage and current
between sample t and sample t-1.
The delta phase selector employs adaptive techniques to determine the fault type. The
logic determines the fault type by summing up all phase values and dividing by the
largest value. Both voltages and currents are filtered out and evaluated. The condition
for fault type classification for the voltages and currents can be expressed as:
( , , )
( , , )
VA VB VC
FaultType
Max IA IB IC
å D D D
=
D D D
EQUATION1808-ANSI V1 EN
(Equation 52)
( , , )
( , , )
IA IB IC
FaultType
Max IA IB IC
å D D D
=
D D D
EQUATION1809-ANSI V1 EN (Equation 53)
The value of FaultType for different shunt faults are as follows:
Under ideal conditions: (Patent pending)
Single phase-to-ground; FaultType=1
Phase-to-phase fault FaultType=2
Three-phase fault; FaultType=3
Section 6 1MRK505222-UUS C
Impedance protection
290
Technical reference manual
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