GE D90 Plus Instruction Manual page 206

Line distance protection system

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GROUPED PROTECTION ELEMENTS

Transformer Current Connection

Range: None, Dy1, Dy3, Dy5, Dy7, Dy9, Dy11, Yd1, Yd3, Yd5, Yd7, Yd9, Yd11

Default: None

This setting specifies the location of the current source with respect to the involved

power transformer in the direction of the zone. In section (a) of the following figure, zone

1 is looking through a transformer from the delta into the wye winding. Therefore, the

Transformer Current Connection

at the same side as the read point. Therefore, the zone 4

is set to "None."

Figure 174: Applications of the transformer voltage and current connection settings

Range: 0.02 to 500.00 ohms in steps of 0.01

Default: 1.70 ohms

This setting specifies the zone reach for the forward and reverse applications. In the

non-directional applications, this setting defines the forward reach of the zone. The

reverse reach impedance in non-directional applications is set independently. The reach

impedance is entered in secondary ohms. The reach impedance angle is entered as the

Zone 1 is characterized by transient overreach of less than 5% under source impedance

ratios of up to 30. When setting an under-reaching zone 1 for direct tripping and under-

reaching pilot schemes (DUTT, PUTT), also consider other factors as per rules of distance

relaying. In non-directional applications, this 5% transient accuracy applies to the

forward reach only.

is set to "Dy11." In section (b), the CTs are located

LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL

CHAPTER 7: PROTECTION

Transformer Current