PM8000 harmonic alarm configuration with ION Setup for frequency variations at +- 1.75 Hz of 50Hz where the required pickup time is <300ms.

[Ian_Gichuru]

Hello,

I have 2 PM8240 at incomer level, One monitoring Generator backup and one monitoring mains unit.

The customer wants the meter to report any Frequency variations at +- 1.75 Hz of 50Hz.

This is then required to raise an alarm on the meter itself and then a subsequent software alarm can be raised on the PME at site.

The required pickup time is <300ms on the meter (less than 300ms).

Any idea on how to do this?

Best regards, Ian.

[Charles_Murison]

Hello Ian,

To might be able to do this with 2 setpoint modules. I do not have a meter where I can change frequency so I cannot test this.

1 setpoint would be configured for greater than evaluation , one for less than, with the corresponding high and low limits. The sustain On and Off can be configured to give the desired timeframe. Would need to link frequency to the High Speed power meter module. See ION Reference for more details.

The relative setpoint module is not able to have the sustain ON be set to fractions of a second.

Regards,

Charles

[DanL · Accepted solution]

For 50Hz systems, the PM8000 provides gapless harmonic measurements of150 cycles (3s nominal window).
All harmonics readings are the RMS of a 15Hz band over the 150 cycle window (synchronized to the 10minute boundary as specified by IEC61000-4-30). Shorter update intervals for harmonics are not available.

You can use a 1s arithmetic module to monitor 1s frequency to conditionally enable a HarmonicEvaluation (aka HEV) module (or Setpoint, or SignalLimit, etc) that monitors the 3s harmonic readings

[Ian_Gichuru]

Thank you @DanL  and @Charles_Murison . 

A quick clarification, is it possible to set this to a  pickup time of 300 millisecond or less?

Regards,

Ian.

[DanL]

no, not really.
as I said, the meter only provides results every 150 cycles (nominally every 3 seconds), so configuring a "pickup time" shorter than 3 seconds would not make sense

[Ian_Gichuru]

Thank you @DanL