Toshiba GR200 Series Instruction Manual page 409

Line differential protection ied

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FL calculation with data at a local-terminal only

When considering the FL calculation with data at a local-terminal only, user should note the

time of this calculation is longer than the time of FL calculation with data at a local-terminal

and remote-terminals

obtained by measuring the change in current before and after the fault occurrence. The

reference current is used to remove the influence of load voltage and arc voltage.

Note: In the

that are longer than three-cycles as fault continuing time—is required.

Conversely, minimum two-cycles as fault continuing time are required in the

calculation with data at a local-terminal and remote-terminals

If a phase-to-phase fault occurs,

with data of the reference current (Iβ"), which is obtained by measuring the change in current

before and after the fault occurrence.

If an earth fault occurs,

reference current (Iα"), which is similarly obtained by measuring the change in the current

before and after the fault.

In order to maintain the measurement accuracy, the compensation factors for impedance

imbalance are considered in the calculation when the variation of the impedance in each phase

Calculation principle for phase-to-phase fault

Equations for the calculation in the case of phase-b-to-phase-c fault

We suppose the occurrence of a phase-b-to-phase-c fault. The fault distance (χ) is calculated

with the following Equations (2.32-13) to (2.32-16). Equation (2.32-16) is a general expression

when lines are treated as having lumped constants; and this expression is sufficient for lines

within 100km.

. This FL calculation requires data of the reference current, which is

FL calculation with data at a local-terminal only

Calculation principle for phase-to-phase fault

Calculation principle for earth fault

6F2S1914 (0.49)

, more calculation time—

is used with another

GRL200 (Soft 033 & 037)

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