
17
Date Code 20200326
SEL Application Guide 2020-04
C
ONCLUSION
This application guide discusses the settings and configuration requirements to connect two dis-
similar relays for POTT and DCB schemes. SEL does not recommend connecting dissimilar relays
for pilot protection, but if it is necessary, be aware of the capabilities of both relays. Consider the
following important factors:
➤
That the directional and protective element sensitivities at both line terminals match.
Use the same protective elements at each line terminal whenever possible, and set the
reverse-reaching elements at a greater sensitivity than the remote overreaching
elements.
➤
That the directional elements and pickup settings at each line terminal have sufficient
operating quantities to detect both internal and external faults.
➤
If you cannot follow the previous considerations, consider disabling the echo keying
logic at the least-sensitive terminal. Doing this avoids a misoperation when the least-
sensitive terminal does not pick up a reverse-looking element for an out-of-section fault
while the remote relay does.