Landis+Gyr ZMQ202 User Manual page 17

Single phase energy
calculation
Active energy
Reactive energy
H 71 0200 0215 f en - ZMQ202 / ZFQ202 - User Manual
Description of Unit
These values are now available as calibrated raw data. They are stored in
the output buffer of the signal processor from where they are transferred
to the microprocessor by an SPI interface.
The calculation of the energy per phase is a two-step procedure:
1. The instantaneous, single-phase values of power are produced by
multiplying the instantaneous, single phase values of voltage U and
current I.
2. The single-phase values of power are then integrated over the
integration period.
The active power is the product of the voltage multiplied by the current
component parallel to the voltage I
I
Q
ϕ
I
P
The instantaneous value of active power P is then integrated over the
integration period of 0.2 seconds to form a digital value of active energy.
For the instantaneous value of reactive power Q the instantaneous values
of voltage U and current I must be rotated by +45° and -45° respectively
prior to the multiplication.
The reactive power is the product of the voltage multiplied by the current
component vertical to the voltage I
I
Q
ϕ
I
P
The instantaneous value of reactive power Q is then integrated over the
integration period of 0.2 seconds to form a digital value of reactive energy.
.
P
I
Calculation per phase of
. .
P = U I cos ϕ
.
P = U I
P
U
.
Q
I
Calculation per phase of
. .
Q = U I sin ϕ
.
Q = U I
Q
U
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