HT instruments PQA824 - Manual (Page 135)

PQA400 - PQA823 - PQA824
EN - 134
10.6. VOLTAGE FAST TRANSIENTS (SPIKES) (ONLY PQA824)
The meter considers all the phenomena associated to the phase voltage as voltage spikes
which have the following properties:
 Fast slope variations of voltage waveforms.
 Exceeding a limit threshold fixed by user before starting a recording.
The maximum number of recorded events in a half period (10ms @ 50Hz, 8.3ms @ 60Hz)
is 4. The maximum number of recorded events by meter during a recording is 20000.
To better understand the features of this analysis refer to the following picture where a
typical voltage spike at 50Hz frequency is shown:
Fig. 211: Typical voltage spikes at 50Hz frequency
The meter continuously checks the input voltage signals performing 2 simultaneous
routines with different sampling rates. In particular:
 SLOW:
The signals of input voltage are sampled with a 256 samples/period
rate (20ms @ 50Hz, 16.7ms @ 60Hz).
 FAST:
The signals of input voltage are sampled at 200kHz frequency.
As soon as an event occurs, the meter automatically checks whether one of the following
conditions are respected:
 dV/dt > 100V/5s  type of event FAST.
 dV/dt > 100V/78s  type of event SLOW @ 50Hz.
 dV/dt > 100V/65s  type of event SLOW @ 60Hz.