8.3.2
Application
Sub-transmission networks are being extended and often become more and more
complex, consisting of a high number of multi-circuit and/or multi terminal lines of
very different lengths. These changes in the network will normally impose more
stringent demands on the fault clearing equipment in order to maintain an unchanged
or increased security level of the power system.
The high speed distance protection function (ZMFCPDIS) in the IED is designed to
provide sub-cycle, down to half-cycle operate time for basic faults. At the same time,
it is specifically designed for extra care during difficult conditions in high voltage
transmission networks, like faults on long heavily loaded lines and faults generating
heavily distorted signals. These faults are handled with outmost security and
dependability, although sometimes with reduced operating speed.
8.3.2.1
System earthing
The type of system earthing plays an important role when designing the protection
system. Some hints with respect to distance protection are highlighted below.
Solidly earthed networks
In solidly earthed systems, the transformer neutrals are connected directly to earth
without any impedance between the transformer neutral and earth.
IEC05000215 V2 EN
Figure 95:
Solidly earthed network
The earth-fault current is as high or even higher than the short-circuit current. The
series impedances determine the magnitude of the fault current. The shunt admittance
has very limited influence on the earth-fault current. The shunt admittance may,
however, have some marginal influence on the earth-fault current in networks with
long transmission lines.
The earth-fault current at single phase-to-earth in phase L1 can be calculated as
equation
L1
L1
0
1
2
0
f
1
N
f
3 U
U
3I
Z
Z
Z
3Z
Z
Z
Z
×
=
=
+
+
+
+
+
EQUATION1267 V3 EN
(Equation 81)
Section 8
1MRK 502 071-UEN -
Impedance protection
214
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
Содержание Relion REG670
Страница 1: ...RELION 670 SERIES Generator protection REG670 Version 2 2 IEC Application manual...
Страница 2: ......
Страница 108: ...102...
Страница 132: ...126...
Страница 324: ...318...
Страница 442: ...436...
Страница 476: ...470...
Страница 628: ...622...
Страница 718: ...712...
Страница 728: ...722...
Страница 768: ...762...
Страница 778: ...772...
Страница 779: ...773...