Medium Voltage DC configuration and Control

The end result of carrying electricity is the distribution to the consumers from transmission systems. With the transmission lines, the distribution substations are connected and the voltage is decreased to medium voltage via the transmission systems.

In this article, the main focus is on DC medium voltage stage ranging between 2KV and 35 KV.

DC systems: why there is a need for expansion.

Because of the following uses, the DC transmission has been widely grown:

1) Total investment costs are reduced

2) Good voltage stability

3) Power supply with high quality is available

4) Better voltage stability

5) At various frequencies for connecting the grids, it has a capacity.

DC configuration and Medium Voltage

There is a Normally Open Point (NOP) in the Medium voltage distribution rings which is split into two feeders. For reducing the faulty effects by restricting the number of consumers affected is the main goal of Normally open point.

Harmonics

Reason

On MV systems Harmonics are increased due to power factor correction application. They are produced by commercial and residential customers with nonlinear and electronic loads in the Ac drives, induction furnaces, and arc furnaces.

For limiting the harmonics to acceptable limits is not that easy and when there is a condition called resonance by conventional harmonic filters overload and the power faction correction inside customer facilities leading to resonance conditions on the main system.

Solution

For the purpose of power factor correction, the capacitor banks are used on the distribution system and with respect to transmission system voltage support. There is a use of substation capacitor bank with respect to harmonic filter than decrease the size of further compensation for harmonic level control and also offering the power factor correction and voltage support.

Voltage Stabilization

Reason

With MV and LV the PV plants are connected in the same part of grid leading to high voltage variance and the extra renewable energy sources leading to a voltage increase of 5 % UN with respect to LV grid.

Solution

For controlling the voltage rapidly the use of variable controlled HV/MV transformer is recommended. The increased or decreased test voltage is realized in the same time of loaded LV and MV grid for removing under voltage or over voltages in LV distribution grid as it is very much possible for setting variables on the output of HV/MV transformer and the voltage will be in the acceptable range.

The faults are easily detected with the help of automation and note the overall system and thus if there is any change that is to be noticed in the system as you can enhance the performance with the help of:

1) At bus of low voltage, the capacitor is connected.

2) Closed loop is made

3) Overexcited generators are used for injecting reactive power into system

4) Transmission line chosen has reduced losses

5) Controls the voltage.

Institute of Electrical training is always available for you to make your career in this field.