Measuring Modes - ABB 615 series Technical Manual

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Supervision functions

The time characteristic is according to DT. When the alarm timer reaches the value set by

Alarm delay time, the ALARM output is activated. If the fault disappears before the module

generates an alarm signal, the reset timer is activated. If the reset timer reaches the value

set by Reset delay time, the alarm timer resets. The activation of the BLOCK signal resets

the Timer and deactivates the ALARM output.

Lockout logic

MCS-A, MCS-B, MCS-C is provided with the possibility to activate a lockout for the

ALARM output depending on the Alarm output mode setting. In the "Lockout" mode, the

ALARM must be reset manually from the LHMI Clear menu after checking the CT

secondary circuit. In the "Non-latched" mode, the ALARM output functions normally, that

is, it resets as soon as the fault is cleared.

Measuring modes

The function operates on two alternative measurement modes, DFT and Peak-to-Peak.

The measurement mode is selected using the Measurement mode setting.

MCS-A, MCS-B, MCS-C is a dedicated phase-segregated supervision function to be used

along with the high-impedance differential protection for detecting the broken CT

secondary wires. The operation principle of MCS-A, MCS-B, MCS-C is similar to the

high-impedance differential protection function 87A, 87B, 87C. However, the current

setting of MCS-A, MCS-B, MCS-C is set to be much more sensitive than 87A, 87B, 87C

and it trips with a higher time delay. A typical example of the MCS-A, MCS-B, MCS-C

Pickup value setting is 0.1 pu with an Alarm delay time of 3 s or more.

As the current setting of MCS-A, MCS-B, MCS-C is more sensitive than the actual

differential stage, it can pick up internally under the through-fault conditions; however, a

sufficient time delay prevents false alarm. If the bus wire is broken, differential current

arises depending on the load of the feeder with the broken bus wire.

1MAC059074-MB A

615 series ANSI

Technical Manual

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