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NOHÁČOVÁ, L., ŽÁK, F., KROPÁČEK, V.
CAPACITIVE EARTH-FAULT CURRENT IN DISTRIBUTION NETWORKS OPERATED WITH THE ISOLATED NEUTRAL POINT
KOMUNALNA ENERGETIKA / POWER ENGINERING, 29
This paper deals with the method of solution of capacitive earth-fault current in distribution. The value of phase earth capacity in the network can be determined using the voltage ratio in the network and the capacity value of the connected capacitor. The new indirect method of measurement and calculation of phase-earth capacity in networks with isolated neutral point is based on creation of short-term phase capacity asymmetry in the network. When expanded, the method can be also used for leakage current estimation. Furthermore, this method can be applied to periodic controls of the earth capacitive current value. For the evaluation of the phase earth capacity, a single-purpose automatic can be used and thus the whole process of measurement and evaluation is conducted with a defined period (at a given hour, day, month…) or on operator’s command.
KOUBA, D., NOHÁČOVÁ, L.
TWO SIMULTANEOUS FAULTS IN MIDDLE VOLTAGE DISTRIBUTION NETWORK
KOMUNALNA ENERGETIKA / POWER ENGINERING, 14
This paper deals with the method of solution of two simultaneous faults in the middle voltage distribution network, specifically two-port network theory. The main focus of this thesis is on the earth faults, in the resonant earthed neutral system of the middle voltage network and hence simultaneous single-phase earth faults are described in detail. Theoretical formulations are used to solve examples and results are commented.
KŘÍŽ, J., PISTORA, M., NOHÁČOVÁ, L., VELEBA, J.
POSSIBILITIES OF BLACK-START WITH USING RENEWABLE SOURCES ENERGY
KOMUNALNA ENERGETIKA / POWER ENGINERING, 16
The risk of a large loss of power supply (blackout) cannot be entirely excluded. Therefore the power grid has to be prepared for power restoration. One possibility of power supply restoration after blackout is a black-start of one energy source and starting up self-consumption of a larger power station.
Due to rapid increase in renewable energy sources installed power, many new large-enough power plants have been built in recent years. These power plants would be sufficient to power-up self-consumption of a larger power plant.
This paper evaluates the possibility of starting self-consumption of coal power plant Ledvice using wind farm Kryštofovy Hamry.
VELEBA, J., NOHÁČOVÁ, L., KŘÍŽ, J.
ELECTRIC POWER SYSTEM OPERATION – STEADY–STATE VOLTAGE STABILITY
KOMUNALNA ENERGETIKA / POWER ENGINERING, 10
There are many software possibilities capable to solve demanding power engineering problems. Continuation load flow analysis is shown along with Author's developed computational software in Matlab environment for full-scale voltage stability analysis of larger power systems. Steady-state system stability is defined as the capability of the network to withstand a small disturbance (fault occurrence, small change of parameters, topology modification) without leaving its stable equilibrium point.
For comparison, alternative approach is further introduced for voltage stability solution using the non-commercial optimization tool. This paper deals with steady-state voltage stability problem as one of the main topics of interest in today's power system operation and control worldwide.
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