Power supply for thermal power plants
For reliable operation of protection, monitoring and control in thermal power plants quality uninterrupted DC voltage is necessary. It can only be provided by power supply system which is appropriately, precisely designed, professionally manufactured, competently tested and professionally implemented in the plant. For the production of such power supply systems KONČAR uses only the highest quality components of renowned manufacturers (battery, special circuit breakers for DC distribution panels etc.). The numerous positive references from different thermal power plants confirm the soundness of the approach and practices.
The right choice for such facilities is redundant parallel connection of two completely independent power supplies. Thereby independent double supply of each load or a small group of loads is provided. Redundancy of cables themselves is often applied. High reliability is based on the requirement that the failure of one system does not in any way affect the operation of other system, which continues to supply all loads without interruption.
For the smallest plants, with a small number of end loads, DC voltage distribution bord is designed with selectivity in two levels. In most other plants DC voltage distribution bord is designed with selectivity in three levels. There are very large plants with several hundred meters long cables by which the equipment is connected to the power supply. In their case the selectivity in three levels is unsatisfactory solution so DC voltage distribution bord is designed with selectivity in four levels.
It is necessary to carefully design DC voltage distribution bords in order for the selectivity to be ensured in all border situations. This is especially true for the most complex systems with DC distribution bords where it is necessary to achieve selectivity in four levels. Such configurations represent a real design challenge as only a very few circuit breakers are eligible for such applications, and the distribution bord itself inevitably has increased price.
Isolation quality control and detection of earth-fault is a standard part of the power supply system. In major facilities a special system for monitoring and locating earth fault is applied which allows the determination of the outgoing feeder where earth-fault occurred even after its expiry.
In such cases it is necessary to examine the actual state of power supply and implement appropriate reconstruction. Often it is necessary to redo the design and reconstruct a complete power supply system. It is a very delicate task, which requires a high skill and experience. KONČAR successfully reconstructed many substations, but because of the scope and complexity of the activities, the most important references are impeccable reconstruction of the largest hydro power plants and thermal power plants in Croatia.