Woodward HighPROtec MCDLV4, Manual, Page: 599 / 1275

Protective Elements
About application type 1:
The rated transformer current “In” is to be used here as the reference current “Ib” of the line differential protection.
In general there should be the same type of phase current transformers at both ends, so that the following holds:
Ib = CT
A prim
= CT
B prim
If in special cases current transformers with different primary rated currents are used then the reference current “Ib”
has to be set on both sides. Usually the one with the higher value is selected.
For each of the two devices it must be selected via parameter [Field settings / General / Ib Reference] whether the
“local” CT or the “remote” CT shall take the reference current “Ib” as a reference.
Example:
If the primary rated current of the CT at substation B with current transformer CT
B
(1000:1) is higher than the
primary rated current of the CT at substation A with current transformer CT
A
(800:1) the reference current Ib shall
be defined from CT
B
as 1000 A.
The following settings have to be done for the protective device at substation A:
[Field settings / General / Ib Reference
= CT Remote ]
[Field settings / CT Local / CT pri = 800 A]
[Field settings / CT Remote / CT pri = 1000 A]
The following settings have to be done for the protective device at substation B:
[Field settings / General / Ib Reference
= StW Lokal ]
[Field settings / CT Local / CT pri = 1000 A]
[Field settings / CT Remote / CT pri = 800 A]
The equation on the following pages have indices “W1” and “W2”, which usually represent the two winding sides of
the transformer. These equations, however, are also true of application type 1 (i. e. without transformer) if one
inserts a “virtual transformer” within the line, with vector group Yy0 and a ficticious voltage transformation ratio
W1:W2 = 1:1.
599 MCDLV4 DOK-HB-MCDLV4-2E