ABBDistributed busbar protection REB500 including line and transformer protection Product Guide

voltage input channel. Several stages of the 

rate-of-change frequency protection are often 

Distributed busbar protection REB500

including line and transformer protection

Page 15 

needed. This can be achieved by configuring 

the rate-of-change frequency function several 

times.

Definite time overfluxing protection

This function is primarily intended to protect 

the iron cores of transformers against excessive flux. The function works with a definite 

time delay. The magnetic flux is not measured 

directly. Instead the voltage/frequency-ratio, 

which is proportional to the flux is monitored.

Inverse time overfluxing protection

This function is primarily intended to protect 

the iron cores of transformer against excessive flux. The function works with an inverse 

time delay. The inverse curve ca be set by a 

table of 10 values and the times t-min and tmax. The magnetic flux is not measured directly. Instead the voltage/frequency-ratio, 

which is proportional to the flux is monitored.

Power function

This function provides single, or three phase 

measurement of the real or apparent power. 

The function can be configured for monitoring 

reverse, active or reactive power (power 

direction setting). Phase angle errors of the 

CT/VT inputs can be compensated by setting. 

The operating mode can be configured either 

to underpower or to overpower protection.

Logics and delay/integrator

These functions allow the user the engineering of some easily programmable logical functions 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.

Distributed busbar protection REB500

including line and transformer protection

Additional functionalities (cont’d)

Three-phase current plausibility

This function is used for checking the sum and 

the phase sequence of the three-phase currents.