Manta MTS-3000 Series, Руководство по эксплуатации и справочник, Страница: 84 / 156

ADVANCED OPERATION - Section 5
5-12 MTS-3000 SERIES OPERATION AND REFERENCE MANUAL
0$17$ # 7(67 # 6<67(06
CU M004 01A
Consider an A-phase to ground fault. The voltage seen by the relay is:
VA = I
1
Z
1
+ I
2
Z
2
+ I
0
Z
0
Ι
f we make assumptions that the fault impedance is zero, and that the faulted line isn’t mutually coupled to
another 3
Φ
line, and that there are no other sources of zero sequence current between the relaying location
and the fault, the Z1 from the relay to the fault is:
Z
1
= VA
IA + K I
0
where I
0
= IA + IB + IC (residual current)
K = Z
0
- Z
1
(zero sequence compensation factor)
3 Z
1
(In this equation for K, Z
1
and Z
0
are the positive and zero
sequence impedances respectively of the entire line)
For relay testing, we generally set current in the unfaulted phases to zero, and assume that Z
1
and Z
0
for the
line are at the same angle. If we make these assumptions, the formula for Z
1
generalized for any phase
reduces to:
Z
1
= V (positive sequence impedance seen by the relay)
I(1 + K)
Phase to phase faults (
φφφφ
-
φφφφ
) Z = V / I
This mode displays the positive sequence impedance (Z
1
) for phase to phase faults.
Z = V / I
Where: V =
φ
-
φ
voltage
I =
φ
-
φ
current
Three Phase faults (3
φφφφ
) Z = V / I
This mode displays the positive sequence impedance (Z
1
) for three phase faults.
Z = V / I
Where: V =
φ
-N voltage
I =
φ
-N current