ABB Distributed busbar protection REB500

and are available as standard also in the

REB500 functionality.

Directional sensitive earth fault protection

for grounded systems

A sensitive directional ground fault function

based on the measurement of neutral current

and voltage is provided for the detection of

high-resistance ground faults in solidly or lowresistance

grounded systems. The scheme

operates either in a permissive or blocking

mode and can be used in conjunction with an

inverse time earth fault overcurrent function.

In both cases the neutral current and voltage

can be derived either externally or internally.

This function works either with the same communication

channel as the distance protection

scheme or with an independent channel.

Directional sensitive earth fault protection

for ungrounded or compensated systems

The sensitive earth fault protection function for

ungrounded systems and compensated systems

with Petersen coils can be set for either

forwards or reverse measurement. The characteristic

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 systems

its use is determined by the value of the

capacitive current and measurement is performed

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 protection

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 overcurrent

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 according

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 configured

for single phase measurement or a

combined three-phase measurement with

detection of the highest phase current.

Inverse time earth fault overcurrent protection

The inverse time earth fault overcurrent function

monitors the neutral current of the system.

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 function

is available either with inverse time or definite

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 protection

This function works with a definite time delay

with either single or three-phase measurement.