Alstom MiCOM P846, Technical Manual

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P846/EN OP/D Operation
(OP) 5-14
MiCOM P846
OP
ges and have fixed setting:
•
Pickup level 30V (Vn 100/120V) or 120V (380/440V)
10V (Vn 100/120V) or 40V (Vn 380/440V)
•
VA>, VB>, VC> level detectors are operating on phase volta
•
Drop off level
•
V2> level detector operates on negative sequence voltage. It has a fixed setting of
10V/40V depending on VT ratio (100/120 or 380/440)
D
D
D
IA>
IB>
IC>
1
DDB All P oles De a d (35 9 )
1
IA>
IB>
IC>
1
LD VB>
LD VC>
LD VA>
&
&
S E T: VTS I 2 >
&
&
&
2 40ms
1
DDB Any P ole De a d (358)
LD
LD
LD
1
S
R
Q
&
S E T: VTS Reset Mode M a nu a l
S E T: VTS Reset Mode Auto
S
R
Q
1
&
t
0
S E T: VTS Time Del a y
DDB VTS Slow Block (77 2 )
1
S E T VTS 1 >
&
DDB VTS F a st Block (77 1 )
1
S
R
Q
1
2 0ms
0
&
S
R
Q
&
&
Indic a tion VT
F a il Al a rm
&
I N TSIG Acceler a te Ind
I N TSIG Any Volt a ge
Dependent Function
DDB MCB/VTS (40 2 )
V 2 >
S E T: VTS St a tus Blocking
P1111ENe
N ote: I N TSIG Acceler a te Ind = Sign a l from a f a st tripping volt a ge dependent funtion
Figure 10: VTS Logic
The VTS > Inhibit or VTS 2> Inhibit elements are used to override a VTS block in event of a
trigger the VTS logic. Once the VTS block has
ndesirable for subsequent system faults to
phase voltages above the phase level detector settings mentioned previously. A VTS
2.4
ainly because
rs. However, these pieces of
equipment are prone to degradation of their capacitive dividers and unbalances between the
three phase voltages may occur during the normal operation of the line.
Ι Ι
fault occurring on the system which could
been established, however, then it would be u
override the block. The VTS block will therefore be latched after a user settable time delay
‘VTS Time Delay’.
Once the signal has latched then two methods of resetting are available. The first is
manually via the front panel interface (or remote communications) provided the VTS
condition has been removed and secondly, when in ‘Auto’ mode, by the restoration of the 3
indication will be given after the VTS Time Delay has expired. In the case where the VTS is
set to indicate only the relay may potentially maloperate, depending on which protection
elements are enabled. In this case the VTS indication will be given prior to the VTS time
delay expiring if a trip signal is given.
CVT asymmetry detection
Capacitive voltage transformers are frequently used on EHV and UHV lines m
of their lower cost compared with magnetic potential transforme