ABB Relion 670 Series Applications Manual page 270

Section 10
Unbalance protection
L1
L2
L3
C
C
C
C
IEC19000310 V1 EN-US
Figure 127: Protection scheme for ungrounded double WYE capacitor bank
Figure 127
WYE capacitor bank. In this configuration, the two neutrals (N1 and N2) of the WYE capacitor
banks are connected together and the neutral to system ground voltage is measured. Similarly,
this type of connection can be used for an ungrounded single WYE SCB configuration.
The neutral voltage measuring device can be selected with lowest voltage ratio attainable,
while still being able to withstand the transient and continuous over-voltage conditions to
obtain the maximum unbalance detection sensitivity.
10.4.3 Setting guidelines
Setting procedure on the IED
The parameters for the SCUVPTOV are set using the local HMI or through the dedicated
software tool such as Protection and Control Manager (PCM600).
Common base IED value for primary voltage (
settings function GBASVAL.
GlobalBaseSel : This is used to select the global base value (UBase) for the voltage from the
GBSVAL function.
Operation : Set the neutral unbalance voltage protection to On / Off .
BlockTrip : This is used to control the activation of the trip outputs, so that the function can be
used for alarming only, or for both alarming and tripping.
• If the
any condition.
• If the
delay from the START signal as per the selected
UMin> : The minimum start level setting should be set as % of UBase. Typical value of setting is
75% of UBase. This setting gives the lower limit of permitted busbar voltage.
264
C C
C
C
C C C C
C C C
C
C C
C
C
N2
N1
V
N
shows the neutral voltage unbalance protection scheme for an ungrounded double
BlockTrip is set to Trip disabled , then the TRIP signal will be blocked irrespective of
BlockTrip is set to Trip enabled , then the TRIP signal will be activated after a time
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C
V V V
L1 L2 L3
C
C
C
UBase ) is set in the global base values for the
CurveType .
1MRK 511 401-UEN Rev. K
Pre processing SCB Neutr al V oltage
Functio n B lock Unbala nce Function
SMAI
SCUVPTOV
GRP1Lx G1AI3P U3P
SMAI
U3NEUT
G2AI3P
GRP2N
IED
Where x = 1 , 2, an d 3
IEC19000310-1-en.vsdx
GUID-969DCA0A-9BE4-4FB4-A3E2-0D2ED4AC5C39 v1
Bay control REC670
Application manual