GE D90 Plus - Page 206

196 D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
GROUPED PROTECTION ELEMENTS CHAPTER 7: PROTECTION
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
zone 1
Transformer Current Connection is set to “Dy11.” In section (b), the CTs are located
at the same side as the read point. Therefore, the zone 4
Transformer Current
Connection
is set to “None.”
Figure 174: Applications of the transformer voltage and current connection settings
Reach
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
RCA setting.
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.
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