Electricity is generated by generating stations and transmitted to load centers from where it is distributed to end consumers. These load centers are controlled by distribution utilities, and there is an inter-change of energy between different utilities connected to the grid.
Consumers connected to the distribution utilities, though consuming active energy may or may not consume reactive energy. There may be consumers whose loads are predominantly inductive and other consumers whose loads are predominantly capacitive. There may be bulk consumers who have their own generators who operate their generators in synchronism with the grid, drawing active energy from the system or even exporting active energy into the system.
The exchange of electricity is complex in such situations, and four quadrant energy measurements are needed to accurately measure the active and reactive energy under different export/import conditions for both active & reactive energy.
Energy measurement under such situations will depend on applicable tariff structures, and hence to cater for different tariff structures in the environment of import/export of active/reactive energy special data logging/measuring features are required in meters. In this regards there are three forms of measurements to deal with (in metering) and these are active energy, reactive energy & apparent energy. The definitions and inter-relations are explained for import/export are explained below.
Quadrant I
Quadrant I is defined as an area where both powers flow positively. Both are delivered to the consumer load. In many cases the CLOU terminology is forward. The power factor is lagging; we have inductive influence.
IEC literature uses the term import.In this quadrant we have import of active power and import of reactive power.
Active energy is considered as “import”, reactive energy is also considered as “import”. This is called reactive (inductive) while active import. The power factor of this type of load is a lagging power factor.
Quadrant II
In quadrant II, reactive power is positive and active power flows negatively. In many cases the CLOU terminology is reversed. The IEC literature uses the term export.
Active energy is considered as “import”, but reactive energy is considered as “export”. This is called reactive (capacitive) while active import The power factor of this type of load is a leading power factor.
Quadrant III
In quadrant III, reactive and active power flow negatively (both powers are received from the customer). This is also an export condition.
Active energy is considered as “export”, reactive energy is also considered as “export”. This is called reactive (inductive) while active export because this is a mirror image of inductive import (of quadrant 1). The power factor of this type of load is a lagging power factor.
Quadrant IV
In quadrant IV, reactive power flows negatively, and active power flows positively. This is an import condition.
Active energy is considered as “export”, but reactive energy is considered as “import”. This is called reactive (capacitive) while active export because this is a mirror image of reactive import (capacitive) (of quadrant 2). The power factor of this type of load is a leading power factor.
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