Toshiba GR200 Series Instruction Manual page 405

Line differential protection ied

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Note: User should set the values of each section impedances into each Line_Element.

For the consideration of the section and their Line_Element, see section 2.32.5(i)

and section 2.32.6(iii).

For instance, the IED G makes calculation in the following sequences:

➢ At the outset, the IED G makes calculation of the equation (2.32-5) assuming that the fault

arises on line GJ.

➢ If the calculation result is not identical to the input data from a line, then the IED G makes

calculation with Equation (2.32-6) assuming that the fault arises on line JH.

➢ Then, the IED G makes calculation with Equation (2.32-7), when both Equation (2.32-5)

and Equation (2.32-6) do not hold true for the input data from a line, and finally the IED

G decides that the fault arises on line JS, as shown in Figure 2.32-2.

Equations by symmetrical components

In practice, the FL calculation is carried out in symmetrical components; hence, Equations

(2.32-4) to (2.32-7) are converted to symmetrical equations in the FL.

For example, in Figure 2.32-1, the distance ratio (χ) can be expressed in symmetrical

components when we substitute symmetrical components† for Equation (2.32-4).

I1H, I2H and I0H:

I1d, I2d and I0d:

Z11, Z12 and Z10‡

†Note: When we can assume that the respective mutual-impedances are equal (Z ab =Z bc ,

Z bc =Z ca , and Z ca =Z ab ), symmetrical components (Z 11 , Z 12 and Z 10 ) are obtained

from the following Equations (2.32-10) to (2.32-12):

Positive-sequence voltage at IED G

Positive-sequence voltage at IED H

Current (IH) at IED H represented by positive-sequence,

negative-sequence, and zero-sequence

Differential current (Id) represented by positive-sequence,

negative-sequence, and zero-sequence

Line impedance (ZGH) represented by positive-sequence,

negative-sequence, and zero-sequence

6F2S1914 (0.49)

GRL200 (Soft 033 & 037)

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