CHAPTER 5: SETTINGS GROUPED ELEMENTS
B90 LOW IMPEDANCE BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 5-175
5
The instantaneous overcurrent element is used primarily for supervising main protection trip commands on a per-breaker
basis (that is, differential, breaker failure, and end fault protection). It responds to a single-phase current. If the intention is
to allow three-phase tripping if any phase current is above the threshold, the appropriate FlexLogic operands are passed
between the IEDs using the B90 fiber optic communications (Direct I/Os).
Instantaneous Overcurrent supervision can also be used to prevent tripping feeders with low currents or for definite time
backup protection.
The pickup setting is specified in per unit values. The nominal current as entered under
SYSTEM SETUP AC INPUTS
CURRENT BANK XY CT XY SECONDARY
is 1 p.u. The element can be effectively enabled only when B90 FUNCTION is set to
"Protection". One instantaneous overcurrent element is available per each CT input of the relay.
Figure 5-91: Instantaneous overcurrent logic
5.6.6.4 Time overcurrent (ANSI 51)
SETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) CURRENT ELEMENTS TIME OVERCURRENT 1(24)
IOC1 PICKUP DELAY:
0.000 s
Range: 0.000 to 65.535 s in steps of 0.001
IOC1 RESET DELAY:
0.000 s
Range: 0.000 to 65.535 s in steps of 0.001
IOC1 BLOCK:
Off
Range: FlexLogic operand
IOC1 TARGET:
Self-Reset
Range: Self-Reset, Latched, Disabled
IOC1 EVENTS:
Disabled
Range: Disabled, Enabled
TIME
OVERCURRENT 1
TOC1 FUNCTION:
Disabled
Range: Disabled, Enabled
TOC1 CT:
F1
Range: Available current channels
TOC1 PICKUP:
1.200 pu
Range: 0.020 to 30.000 pu in steps of 0.001
TOC1 CURVE:
IEEE Mod Inv
Range: see OVERCURRENT CURVE TYPES table
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