Why I get netagive value from power meter (powerlogic pm500) for the reactive and Active Power?

[ucf ElHD]

i read data every minute, and some time i get negative values, can any one explain me, i'm not an electrical engineer (i'm IT developer) so please be nice with technical terms.

 

[Lucien Nunes]

Reactive power is not actual energy flow. merely a mathematical way of analysing how current that is out-of-phase with the voltage flows around the system. According to whether your connected equipment presents a net inductive or capacitive load (e.g. whether mainly motors or electronic power supplies are in use) so the reactive power can swing from positive to negative. An ideal situation is to minimise reactive power flow, but whether it is positive or negative is not very critical.

Negative active power indicates that energy is flowing from your equipment to the power network, i.e. that you are generating. That can happen briefly in various situations, e.g. if a hoist motor is being driven by its payload. If your loads can't regenerate, you must be consuming power and the monitor is possibly connected with either its current or voltage sensing reversed.