7PG21 Solkor Rf Settings
©2012 Siemens Protection Devices Limited
Chapter 4 Page 3 of 4
1 Differential Protection settings
1.1 Protection Sensitivity
Protection sensitivity is fixed, based on secondary current rating, with the only settable variable being the use of
the N/N1 tap. Different sensitivity is applicable to different phases and fault types.
The following settings are shown as a percentage of rated current and are directly applicable to the local relay of
a connected pair when subjected to current injection at the local end only.
Relays in R mode will typically have sensitivity similar to the settings quoted below as Nominal for the Rf mode.
If the local relay is injected in isolation i.e. with pilots disconnected, the operate level will be approximately 50% of
the quoted value.
If Pilot Supervision is fitted, the settings will be increased by 20-50%.
In Rf mode the remote end relay will operate at a similar level to the local relay, typically -10% of quoted
setting.
In R mode the remote end will typically operate at 2.5 times the local end setting.
Fault settings (% In)
Solkor Rf without isolating transformers
Solkor Rf with isolating transformers
Nominal Typical Nominal
Typical
Type of
fault
N1 tap
N tap
N1 tap
N tap
N1 tap
N tap
N1 tap
N tap
R-E
16 22 18 25 22 31 25
35
Y-E
18
27.5 21 32 26 39 30
44
B-E
22 37 25 42 31 52 35
59
R-Y 110
125
155
177
Y-B 110
125
155
177
B-R 55
62
77.5
88.5
3 P
63
72
89
101
1.2 Pilot Resistance
The padding resistance is set by adding series resistance to that of the pilots to achieve a standard value. The
total loop resistance required depend on the R or Rf mode selected and the tap position of the isolation
transformers if they are used, see Applications Guide in this manual.
The link is fitted in the ‘OUT’ position to short out the resistor.
