ABB REO 517, Applications Manual

Page: 141 / 440

131
100 Hz protection (HHZ)
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The 100 Hz protection, HHZ, is intended for 16 2/3 Hz, single-phase systems and is ap-
plicable in systems supplied from static frequency converters.
The HHZ protection detects if a 100 Hz component exists in the line current and trips
the circuit-breaker if the component exceeds the set operating level. The function en-
sures that no 100 Hz component is distributed in the network from the converters and
are suitably used on the track feeder network where the signal system works in the fre-
quency range 90 -110 Hz.
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The current measuring element in one of the built-in digital signal processors continu-
ously measures the phase current. The current signal is conditioned by a filter to reduce
the sampling frequency to 500 Hz. The input signal is additionally filtered by a number
of second order bandpass filter, rectified and smoothed. The signal is compared with the
set operate value I100>.
A non-intentional time delay (approximately 0.5 s) is inevitable due to response time of
the measuring element. The activation of the output signal HHZ-TRIP is delayed by a
timer t.
The 100 Hz function is blocked if the input signal HHZ-BLOCK is activated.
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