Siemens 7PG21 Solkor Rf Technical Manual page 38

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 within +-10% of quoted
setting.
In R mode the remote end will typically operate at 2.5 times the local end setting.
Solkor Rf without isolating transformers
Type of
fault
Nominal
N1 tap N tap
R-E 16 22
Y-E 18 27.5
B-E 22 37
R-Y 110
Y-B 110
B-R 55
3 P 63
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.
©2012 Siemens Protection Devices Limited
Fault settings (% In)
Typical
N1 tap N tap N1 tap
18 25 22
21 32 26
25 42 31
125
125
62
72
7PG21 Solkor Rf Settings
Solkor Rf with isolating transformers
Nominal
N tap N1 tap
31 25
39 30
52 35
155
155
77.5
89
Chapter 4 Page 3 of 4
Typical
N tap
35
44
59
177
177
88.5
101