Abstract
The main reasons for installation of power quality meters in distribution transformer substations are power quality monitoring and global evolution of electrical network towards the ‘smart grid’. In case that all measurements from the meters are properly synchronised and centralised, new possibilities of control or evaluation of the network are enabled. This contribution proposes the possibility for an earth fault localisation with the aid of synchronised data recorded on the low-voltage side of the medium voltage/low voltage transformers in compensated neutral distribution networks which are equipped with auxiliary resistor for short-time increasing of the active part of the fault current. The described method uses voltage sags evoked by connecting of the auxiliary resistor for locating the faulty section. The proposed method is tested with the help of numerical model which presents a part of the distribution network.
Highlights
The resonant earthed network is the most common type of Czech distribution networks, which its purpose is to compensate network capacitive current during an earth fault (EF) and to limit the EF current level
Fault current increasing by the connection of auxiliary resistor during an EF (SB is switched on) evokes voltage sag on the low voltage (LV) side of DTs ΔUS which can be expressed by the following equation
Simulation tool known as PSCAD Professional was used to model a part of 22 kV compensated distribution network that consists of six 22/0,4 kV distribution transformer stations (DTSs) equipped with voltage monitors on its LV side
Summary
The resonant earthed network is the most common type of Czech distribution networks, which its purpose is to compensate network capacitive current during an earth fault (EF) and to limit the EF current level. The drawback of mentioned methods is calculation of an EF position based on currents and voltages measured only in one point of the network in supply substation, which is mostly far away from the real fault location its sensitivity is lower than for measurement point close to the fault. This could lead to significant errors in the determination of the fault location what complicates quick fault location. Each of the known methods for EF location, especially in compensated network has its advantages and disadvantages and perhaps there is no universal method, which would allow EF location with sufficient accuracy and reliability for locating all types of EFs keeping reasonable costs for operation and implementation of a location system
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