ABB CI547 3BNP004429R1 Communication board with slave
forwards or reverse measurement. The char acteristic angle is set to ±90°(U0 · I0 · sin ) in ungrounded systems and to
0° or 180° (U0 · I0 · cos ) for systems with
Petersen coils. The neutral current is always
used for measurement in the case of systems
with Petersen coils, but in ungrounded sys tems its use is determined by the value of the
capacitive current and measurement is per formed by a measuring CT to achieve the
required sensitivity. To perform this function
the BU03 with 3I, 1MT and 5U is required.
Definite time over- and undercurrent pro tection
This function is used as Main 2 or as back-up
function respectively for line, transformer or
bus-tie bays. This function can be activated in
the phase- and/or the neutral current circuit.
Inverse time overcurrent protection
The operating time of the inverse time over current function reduces as the fault current
increases and it can therefore achieve shorter
operating times for fault locations closer to the
source. Four different characteristics accord ing to British Standard 142 designated normal
inverse, very inverse, extremely inverse and
long time inverse but with an extended setting
range are provided. The function can be con figured for single phase measurement or a
combined three-phase measurement with
detection of the highest phase current.
Inverse time earth fault overcurrent protec tion
The inverse time earth fault overcurrent func tion monitors the neutral current of the sys tem. Four different characteristics according
to British Standard 142 designated normal
inverse, very inverse, extremely inverse and
long time inverse but with an extended setting
range are provided.
Directional overcurrent definite / inverse
time protection
The directional overcurrent definite time func tion is available either with inverse time or def inite time overcurrent characteristic. This
function comprises a voltage memory for
faults close to the relay location. The function
response after the memory time has elapsed
can be selected (trip or block).
Definite time over- and undervoltage pro tection
This function works with a definite time delay
with either single or three-phase measure ment.

Self-supervision
All the system functions are continuously
monitored to ensure the maximum reliability
and availability of the protection. In the event
of a failure, incorrect response or inconsistency, the corresponding action is taken to
establish a safe status, an alarm is given and
an event is registered for subsequent diagnostic analysis.
Important items of hardware (e.g. auxiliary
supplies, A/D converters and main and program memories) are subjected to various
tests when the system is switched on and also
during operation. A watchdog continuously
monitors the integrity of the software functions
and the exchange of data via the process bus
is also continuously supervised.
The processing of tripping commands is one
of the most important functions from the reliability and dependability point of view. Accordingly, every output channel comprises two
redundant commands, which have to be
enabled at regular intervals by a watchdog. If
the watchdog condition is not satisfied, the
channels are blocked.
Extension of the system
The system functions are determined by software, configured using the software configuration tool.
The system can be completely engineered in
advance to correspond to the final state of the
station. The software modules for new bays or
features can be activated using the HMI500
when the primary plant is installed or the features are needed.
Additional system functions, e.g. breaker failure, end fault protection or bay level
back-up / Main 2 functions can be easily activated at any time without extra hardware.