7PG21 Solkor Rf Description of Operation
2 Description
The Solkor Rf protection system (excluding current transformers) is shown below. The alternative basic Solkor R
protection circuit is also shown
.
Figure 1 Solkor Rf schematic
Figure 2 Solkor R schematic
Conversion of the Solkor Rf to Solkor R is arranged by wire links, internal to the relay.
The relay contains an 8-way internal terminal block. 4 wires marked 1-4 must be moved from 4 terminals marked
‘Solkor Rf’ to 4 adjacent terminals marked ‘Solkor R’. Additionally a wire link must be fitted, externally to the relay
on the rear terminal block to use the relay in Solkor R mode.
In addition to the basic components there are at each end, three non-linear resistors, a tapped ‘pg’ resistor and
three diodes. The non-linear resistors are used to limit the voltage appearing across the pilots and the operating
element. The purpose of the ‘padding’ resistors at each end is to bring the total pilot loop resistance up to a
standard value. The protection is therefore always working under constant conditions and its performance is to a
large extent of the resistance of the pilot cable’ The ‘padding’ resistors comprise five series connected sections,
each section having a short circuiting link. The values of the resistance on the sections are 35 ohms, 65 ohms,
130 ohms, 260 ohms and 500ohms.
For Solkor R the value chosen should be as near as possible to ½(1000-R
p
) ohms, where R
p
is the pilot
resistance. The 500 ohm resistor should therefore be fitted for the Solkor R and the link will always be fitted for
this mode.
For Solkor Rf without isolating transformers the value chosen should be as near as possible to ½(2000-R
p
) ohms.
©2011 Siemens Protection Devices Limited
Chapter 1 Page 4 of 13
