Toshiba GR200 Series Instruction Manual page 403

Line differential protection ied

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Calculation Principle

Calculation on two-terminal application

Figure 2.32-1 shows two IEDs exist at the end of the line GH. Voltages due to the fault are

calculated by Equation (2.32-1) and Equation (2.32-2).

Voltage at IED G

I G : Current at IED G

Voltage at IED H

Current at IED H

χ: Distance ratio of GF to GH

V f : Voltage at fault point

Impedance on line GH

Substituting Equation (2.32-1) for Equation (2.32-2) gives,

The distance ratio (χ) is also calculated with the differential current (Id) because the net

currents at the IED G and the IED H are equal to the differential current (Id= I G +I H ):

Note: User should set the Z GH into Line1_Element. For further information, see section

2.32.5(ii). For setting methods, see section 2.32.6(iii).

Calculation on three-terminal application

The principle mentioned above is also applicable for the operation of three terminals, as shown

in Figure 2.32-2. Note that one of three calculations (Calc. 1 to 3) determines the fault location.

Figure 2.32-1 IED G and IED H on line GH

− ( 1 − χ ) ∙ Z

6F2S1914 (0.49)

GRL200 (Soft 033 & 037)

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