ABB Relion 670 series, Руководство по применению, Страница: 434 / 760

1
0
step3 step2
02
3I
I .2 I
3I
³ × ×
EQUATION1204 V4 EN-US
(Equation 489)
where:
I
step2
is the chosen current setting for step 2 on the faulted line.
Step 4
M15282-177 v4
This step normally has non-directional function and a relatively long time delay. The task for
step 4 is to detect and initiate trip for earth faults with large fault resistance, for example tree
faults. Step 4 shall also detect series faults where one or two poles, of a breaker or other
switching device, are open while the other poles are closed.
Both high resistance earth faults and series faults give zero-sequence current flow in the
network. Such currents give disturbances on telecommunication systems and current to earth.
It is important to clear such faults both concerning personal security as well as risk of fire.
The current setting for step 4 is often set down to about 100 A (primary 3I
0
). In many
applications definite time delay in the range 1.2 - 2.0 s is used. In other applications a current
dependent inverse time characteristic is used. This enables a higher degree of selectivity also
for sensitive earth-fault current protection.
8.5 Four step directional negative phase sequence
overcurrent protection NS4PTOC
GUID-E8CF8AA2-AF54-4FD1-A379-3E55DCA2FA3A v1
8.5.1 Identification
GUID-E1720ADA-7F80-4F2C-82A1-EF2C9EF6A4B4 v1
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Four step negative sequence
overcurrent protection
NS4PTOC
I2
4
4
alt
IEC10000053 V1 EN-US
46I2
8.5.2 Application
GUID-343023F8-AFE3-41C2-8440-1779DD7F5621 v2
Four step negative sequence overcurrent protection NS4PTOC is used in several applications
in the power system. Some applications are:
• Earth-fault and phase-phase short circuit protection of feeders in effectively earthed
distribution and subtransmission systems. Normally these feeders have radial structure.
• Back-up earth-fault and phase-phase short circuit protection of transmission lines.
• Sensitive earth-fault protection of transmission lines. NS4PTOC can have better
sensitivity to detect resistive phase-to-earth-faults compared to distance protection.
• Back-up earth-fault and phase-phase short circuit protection of power transformers.
• Earth-fault and phase-phase short circuit protection of different kinds of equipment
connected to the power system such as shunt capacitor banks, shunt reactors and others.
Section 8 1MRK 505 343-UEN B
Current protection
428
Application manual