![ABB RELION RET670 Скачать руководство пользователя страница 329](http://html.mh-extra.com/html/abb/relion-ret670/relion-ret670_applications-manual_4714329.webp)
Effectively grounded networks
GUID-5F4CCC18-2BAC-4140-B56C-B9002CD36318 v1
A network is defined as effectively grounded if the ground-fault factor f
e
is less than
1.4. The ground-fault factor is defined according to equation
max
e
pn
V
f
V
=
ANSIEQUATION1268 V1 EN-US
(Equation 201)
Where:
V
max
is the highest fundamental frequency voltage on one of the healthy phases at single
phase-to-ground fault.
V
pn
is the phase-to-ground fundamental frequency voltage before fault.
Another definition for effectively grounded network is when the following
relationships between the symmetrical components of the network source impedances
are valid, see equation
0
1
X
3 X
< ×
EQUATION2122 V1 EN-US
(Equation 202)
0
1
R
R
£
EQUATION2123 V1 EN-US
(Equation 203)
Where
R
0
is the resistive zero sequence source impedance
X
0
is the reactive zero sequence source impedance
R
1
is the resistive positive sequence source impedance
X
1
is the reactive positive sequence source impedance
The magnitude of the ground-fault current in effectively grounded networks is high
enough for impedance measuring element to detect ground-fault. However, in the same
way as for solid grounded networks, distance protection has limited possibilities to
detect high resistance faults and should therefore always be complemented with other
protection function(s) that can carry out the fault clearance in this case.
High impedance grounded networks
GUID-099F53F9-7CD8-4D96-811D-7B55EF249FFF v1
In high impedance networks, the neutral of the system transformers are connected to
the ground through high impedance, mostly a reactance in parallel with a high resistor.
1MRK 504 163-UUS A
Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI
323
Application manual
Содержание RELION RET670
Страница 1: ...RELION 670 SERIES Transformer protection RET670 Version 2 2 ANSI Application manual ...
Страница 2: ......
Страница 48: ...42 ...
Страница 64: ...58 ...
Страница 74: ...68 ...
Страница 104: ...98 ...
Страница 194: ...188 ...
Страница 518: ...512 ...
Страница 618: ...612 ...
Страница 648: ...642 ...
Страница 666: ...660 ...
Страница 672: ...666 ...
Страница 682: ...676 ...
Страница 844: ...838 ...
Страница 868: ...862 ...
Страница 956: ...950 ...
Страница 964: ...958 ...
Страница 1004: ...998 ...
Страница 1014: ...1008 ...
Страница 1015: ...1009 ...