Calculated Measurements - ABB 615 series Technical Manual

1MAC059074-MB A
11.7
615 series ANSI
Technical Manual
Peak-to-peak with peak backup
The peak-to-peak with peak backup measurement principle is selected with the
Measurement mode setting using the value "P-to-P+backup". It is similar to the peak-to-
peak mode, with the exception that it has been enhanced with the peak backup. In the peak-
to-peak with peak backup mode, the function starts with two conditions: the peak-to-peak
value is above the set pickup current or the peak value is above two times the set Pickup
value. The peak backup is enabled only when the function is used in the DT mode in high
and instantaneous stages for faster operation.
Wide peak-to-peak
The wide peak-to-peak measurement mode is available only in the three-phase
overcurrent protection function 51P in REG615 standard configurations C and D. The
wide peak-to-peak measurement principle is available in products where it is necessary
for overcurrent protection to operate already starting from as low frequency as 2 Hz during
the generator start-up or shutdown phase. The wide peak-to-peak measurement principle
is selected with the Measurement mode setting "Wide P-to-P".
The measurement mode calculates the average from the positive and negative peak values
over the 500 ms wide measurement window, independently of the Frequency adaptivity
setting value. Retardation and reset times are longer due to the length of the measurement
window. The frequency of the fault current affects the operate time. The damping of the
harmonics is quite low and practically determined by the characteristics of the anti-
aliasing filter of the protection relay current inputs.
When using measurement mode "Wide P-to-P", the protection relay
accepts only Trip delay time setting value 800 ms or longer and Operating
curve type 5="ANSI Def. Time" or 15="IEC Def. Time".
Operation accuracy in the frequency range 2...85 Hz is ±1.5% or ±0.003 × I
accuracy in definite time mode is ±1.0% of the set value or ±60 ms when I
Pickup value and the fault current frequency is 10...85 Hz.

Calculated measurements

Calculated residual current and voltage
The residual current is calculated from the phase currents according to equation:
Io ( I I I )
= − + +
A B C
GUID-B9280304-8AC0-40A5-8140-2F00C1F36A9E V1 EN
General function block features
Section 11
. Operate time
n
= 2 × set
Fault
(Equation 184)
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