ABB Relion 670 Series Applications Manual page 105

1MRK 505 370-UUS Rev. K
• Normally closed auxiliary contact
• "b" contact (that is, 52b)
• "open"
Typically both contacts are used to provide position indication and supervision for busbar protection.
Minimum contact requirements
The minimum requirement for the busbar replica is the record of the disconnector position by using just
one auxiliary contact, either "normally open" or "normally closed" type. However recording a pair of
auxiliary contacts, representing the "open" and "close" position, offer additional features which can
improve the reliability of the bus replica including supervision possibilities.
Auxiliary contact evaluation logic
Two logic schemes can be found.
• Scheme1_RADSS "If not OPEN then CLOSED"
As the name of the scheme suggests, only when the auxiliary contacts signal clean open position
("normally open auxiliary (NO) contact input" = inactive and "normally closed auxiliary (NC) contact input"
= active), the disconnector is taken to be open. For all other signal combinations the disconnector is
considered to be closed. This scheme does not pose any special requirements to the auxiliary contact
timing. Only the disconnector NC contact must open before the disconnector main contact is within
arcing distance. The time during which the POSOPEN and POSCLOSE signal inputs disagree (that is,
both binary inputs are active or both are inactive) is monitored by the isolator supervision function. The
maximum time allowed before an alarm is given can be set according to the disconnector timing.
• Scheme2_INX "Closed or open if clear indication available otherwise last position saved"
As the name of the scheme suggests, only when the auxiliary contacts signal clean "open" or clean
"closed" position, disconnector is considered to be open respectively closed. However this poses the
stringent requirements on the auxiliary contacts that the PSCLOSED signal must become active a certain
time (>150 ms) before current starts flowing for example, through arcing. Otherwise this current will not
be taken into account in the busbar protection and this can result in a maloperation. Therefore, good
timing of two auxiliary contacts is definitely required.
The time during which the POSOPEN and POSCLOSED signals disagree (that is, both binary inputs are
active or both are inactive) is monitored by the isolator supervision function for both of the above two
schemes. The maximum time allowed before an alarm is given can be set according to the disconnector
timing.
Table 13
Busbar protection REB670
Application manual
and the following two figures summarize the properties of these two schemes.
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Section 6
Differential protection
SEMOD127523-18 v2
SEMOD127523-21 v3
SEMOD127523-24 v3
SEMOD127523-27 v4
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