sepam 20 user manual - Schneider Electric

4
Control and monitoring
functions
4/16
Self-tests and fail-safe position
Presentation
The reliability of a device is the property that allows its users to have well-placed
confidence in the service it delivers.
For a Sepam protection relay, operational reliability consists of ensuring the safety
and availability of the installation. This means avoiding the following 2 situations:
b Nuisance tripping of the protection
Continuity of the electrical power supply is as vital for a manufacturer as it is for an
electricity distribution company. Nuisance tripping caused by the protection can
result in considerable financial losses. This situation affects the availability of the
installation.
b Failure of the protection to trip
The consequences of a fault that is not eliminated can be catastrophic. For safety of
operation, the protection relay must detect faults in the power supply as quickly as
possible, using discrimination. This situation affects the safety of the installation.
Self-tests and monitoring functions
On initialization and cyclically during operation, Sepam runs a series of self-tests.
These self-tests are designed to detect any failure in its internal and external circuits
so as to ensure Sepam's reliability. These failures are classified into 2 categories,
major failures and minor failures:
b A major failure reaches the hardware resources used by the protection functions
(program memory and analog input for example).
This type of failure risks resulting in failure to trip on a fault or nuisance tripping. In
this case, Sepam must go into the fail-safe position as quickly as possible.
b A minor failure affects Sepam's peripheral functions (display, communication).
This type of failure does not prevent Sepam from protecting the installation and
providing continuity of service. Sepam then operates in downgraded mode.
The classification of failures into 2 categories improves both safety and availability of
the installation.
The possibility of a Sepam major failure must be taken into account when selecting
the trip command type to maximize availability or safety of the installation (see
“Selecting the trip command and examples of use” page 4/19).
In addition to the self-tests, the user can activate the trip circuit and closing circuit
supervision function to improve the installation monitoring.
This function sends an alarm message to the Sepam display unit and a data item is
automatically available to the communication to alert the user.
PCRED301005EN - 06/2008