ABB Relion 670 Series Applications Manual page 241

1MRK 511 401-UEN Rev. K
For both single WYE and H-bridge configurations, the unbalance currents are proportional to
the respective phase currents. Hence, each phase current is considered as a reference to
measure its respective unbalance current. The following table shows the typical CT selection:
Table 33:
Location
Phase current measurement
Unbalance current measurement
10.2.3 Setting guidelines
Setting procedure on the IED
The parameters for the current unbalance protection function SCUCPTOC are set through the
local HMI or Protection and Control Manager (PCM600).
Common base IED values for the primary current (IBase1) and unbalance current (IBase2) are
set in the global base values for the settings function GBASVAL.
GlobalBaseSel1 : This is used to select the global base value (IBase1) for the phase current from
the GBSVAL function.
GlobalBaseSel2 : This is used to select the base value (IBase2) for the unbalance current from
the GBSVAL function.
Operation : Set the current unbalance protection to On/Off .
SCBConf : This parameter setting can be set to either 1 unbalance curr or 3 unbalance curr .
• If this parameter setting is set to
connected to the function.
• If this parameter setting is set to
connected to the function.
BlockTrip : This setting is used to control the activation of the trip outputs. During energization
or de-energization of SCB or while commissioning the function, this setting can be used to
block the TRLy and TRIP signals. After successful energization or commissioning, the setting
shall be brought back to normal.
• If this setting is set to
are enabled.
• If this setting is set to
are disabled.
IMin : This setting is used to set the minimum reference current to release the function for
operation in % of IBase1. The typical value is 10%.
IUnbalWrn> : This setting is used to set the warning level in % of IBase2. This setting can be
used to set the warning level above the natural errors so that it operates reliably on the failure
of one or two elements. The typical value is 10%.
tDefWrn : This setting is used to set the definite delay for warning signal in seconds. The
typical value is 5 seconds.
IUnbalAlm> : This setting is used to set the alarm level in % of IBase2. This setting can be used
to set the alarm level of 50%-75% of the trip level, that is, 15% to 22.5% of IBase2 if the trip
level is set to 30%.
tDefAlm : This setting is used to set the definite delay for alarm signal in seconds. The typical
value is 5 seconds.
Bay control REC670
Application manual
Typical CT selection
Trip enabled , then trip outputs TRLy (where y = 1, 2, and 3) and TRIP
Trip disabled , then trip outputs TRLy (where y = 1, 2, and 3) and TRIP
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Type of CT
Normal
Normal or differential
1 unbalance curr , then one unbalance current is
3 unbalance curr , then three unbalance currents are
Unbalance protection
CT ratio Global base value
1000/1 A IBase1
75/1 A IBase2
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Section 10
235