Standards are usually very dry texts that are difficult to read. Today we are looking at point 5.5 Reactive power behavior in VDE AR-N-4110.
It contains the technical rules for the connection of customer installations to the medium-voltage grid and their operation. Many grid operators have adopted these user rules as their “Technical Connection Conditions” (TAB) and may have adapted them with their own additions.
Let’s now take a closer look at the area of reactive power behavior. Among the changes compared to the previous version, we noticed three points in particular:
- Capacitive reactive power consumption is generally not permitted
- The displacement factor cos φ has increased from 0.9 to 0.95
- If a connection user cannot comply with the required values, it must install a sufficiently dimensioned system to compensate for the reactive power
What does this mean in practice? There are now building connections, for example in office buildings, that draw capacitive reactive power from the grid – which is no longer permitted. The solution is inductive reactive current compensation with inductors or electronic compensation. You are welcome to contact one of our nationwide sales engineers for planning.
The grid operator may insist that the cos φ of 0.95 must be achieved. Incidentally, this is independent of whether the energy supplier calculates the reactive energy.
The cos φ must be regulated at the transfer point (meter). This means that it would have to be measured at the medium voltage. KBR has come up with a smart solution to prevent the installation of a separate and expensive measuring field: The required reactive power of the transformer at no-load and full load can be programmed in the multicompD6 controller. It now not only takes this into account on the low voltage, but also the inductive reactive power of the transformer depending on the load. This means that no medium-voltage measurement needs to be set up for the control system – quite clever.
What also stands out in the standard is the fact that the reactive power is to be recorded as a function of the active power in 15-minute average values. In practice, this is currently neither regulated nor billed in this way. The cos φ average value over a month is recorded and calculated.
Another point to be observed in the standard is the control of reactive power in systems in which energy is drawn exclusively. Power factor correction must be controlled via the cos φ. In the case of individual compensation, this must be switched on or off with the load devices. A capacitor that is connected to the mains independently of a load is not permitted.
Incidentally, electrical planners use this standard as a basis for designing the power factor correction system.