ABB Relion 670 Series Technical Reference Manual page 296

Line differential protection ansi

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Impedance protection

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

ΔVA, ΔVB and ΔVC

DeltaVMinOp and DeltaIMinOp

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:

EQUATION1808-ANSI V1 EN

EQUATION1809-ANSI V1 EN

The value of FaultType for different shunt faults are as follows:

Under ideal conditions: (Patent pending)

Single phase-to-ground;

Phase-to-phase fault

Three-phase fault;

are the voltage change between sample t and sample t-1

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.

1MRK505222-UUS C

(Equation 52)

(Equation 53)

Technical reference manual

Relion red670