ABB Relion 670 Series Applications Manual page 242

Section 10
Unbalance protection
IUnbal> : This setting is used to set the trip level in % of IBase2. This setting can be used to set
the trip level at which the healthy unit voltage is at the verge of exceeding 110% of its nominal
voltage. The typical value is 30%.
CurveType : This setting can be set to either Definite time or Programmable .
• If this setting is set to
operation.
• If this setting is set to
programmable curve.
tDefTrip : This setting is used to set the definite delay for trip signal in seconds. The unbalance
protection function trip should have enough time delay to avoid false operations due to inrush,
system ground faults, switching of nearby equipment, and asymmetrical pole operation of the
energizing switch. For most applications, the typical value is 0.1 second.
The below settings are taken with reference to the programmable curve, refer
manual for more information.
tMin : Set the minimum time parameter for the programmable curve in seconds.
k : Set the time multiplier for the programmable curve.
tACrv : Set the programmable curve parameter A.
tBCrv : Set the programmable curve parameter B.
tCCrv : Set the programmable curve parameter C.
tPCrv : Set the programmable curve parameter P.
tReset : Set the reset time delay for all the warning, alarm, and trip outputs in seconds.
10.2.4 Setting examples
Example 1
Consider a 13.8 kV and 7.31 MVAr ungrounded external fused double WYE connected filter that
is protected by the current unbalance protection function.
Table 34: Parameters of the ungrounded capacitor bank
Parameters of SCB
Connection type of SCB
Rated filter voltage
Filter rated MVAr
System frequency
Number of parallel group capacitor units per
section (P
Number of series capacitor units per section (S
Number of parallel group capacitor elements in a
unit (P
e
Table continues on next page
236
Definite time , then the definite delay is considered for the trip
Programmable , then delay for the trip operation is based on the
The timers related to trip outputs (TRLy and TRIP) start only if the setting
BlockTrip is set to Trip enabled .
)
u
)
© Copyright 2017 Hitachi Power Grids. All rights reserved
Value
Externally fused ungrounded double WYE
13.8 kV
7.31 MVAr
60 Hz
3
) 1
u
4
1MRK 511 401-UEN Rev. K
Technical
GUID-4EDB79B2-258E-47AF-99D6-DD47628119F9 v1
Bay control REC670
Application manual