Supply of ABB new original bus adapter FPBA-01

Description

The base for the percent differential setpoints is the S2 SYSTEM SETUP  WINDING 1 

WINDING 1 PHASE CT PRIMARY setpoint value. The percent differential setpoints are

explained below.

PERCENT DIFFERENTIAL PICKUP: Enter the minimum differential current required for

operation. This setting is chosen based on the amount of differential current that

might be seen under normal operating conditions.

PERCENT DIFFERENTIAL SLOPE 1: Enter the slope 1 percentage (of differential current

to restraint current) for the dual-slope percent differential element. The slope 1 setting

is applicable for restraint currents of zero to the kneepoint, and defines the ratio of

differential to restraint current above which the element will operate. This slope is set

to ensure sensitivity to internal faults at normal operating current levels. The criteria

for setting this slope are:

To allow for mismatch when operating at the limit of the transformer’s onload

tap-changer range.

– To accommodate for CT errors.

PERCENT DIFFERENTIAL KNEEPOINT: Enter the kneepoint for the dual-slope percent

differential element. This is the transition point between slopes 1 and 2, in terms of

restraint current, in units of relay nominal current. Set the kneepoint just above the

maximum operating current level of the transformer between the maximum forced

cooled rated current and the maximum emergency overload current level.

PERCENT DIFFERENTIAL SLOPE 2: Enter the slope 2 percentage (of differential current

to restraint current) for the dual-slope percent differential element. This setting is

applicable for restraint currents above the kneepoint and is set to ensure stability

under heavy through fault conditions which could lead to high differential currents as

a result of CT saturation.

Note

Since

, the differential current is not always greater than 100%

of the restraint current. Because of this enhancement, the PERCENT DIFFERENTIAL SLOPE 2

setting may cause slow operation (in rare cases no operation) in the following situations:

PERCENT DIFFERENTIAL SLOPE 2 is set above 100%.

2. The source is connected to one winding only.

Therefore, the PERCENT DIFFERENTIAL SLOPE 2 value cannot be greater than 100%. To

increase dependability, the Slope 2 settings should be less than 98%

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