Case studies

Grid modelling for wind farm harmonic voltages evaluation

A prospective wind farm consisting of 21 turbines with 2 MW double-fed induction generators is planned to be connected to a 110 kV substation in distribution system.

In this case study, different network configurations are modelled.

The influence of the accuracy of grid modelling on grid harmonic impedance characteristic at a particular point is analysed, and a comparison of the results is done for the different network configurations.

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Power Quality in a Customers Supplying Low-Voltage Line

This case study is an assessment of electric power quality in a low voltage supply network in rural environment, based on measurements.

The subject of measurements was a low voltage line in which large disturbances occurred in the supply voltage, being the cause of customers' complaints. A modernisation of the installation was done; additional insulated cable was added and then the MV/LV transformer was replaced with a new one of larger rated power.

The conclusion from the final measurements is to consider other mitigation solutions.

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Voltage fluctuations in a low voltage network

This case study presents the control of quality parameters of electric power supplied from a low-voltage network to household consumers and public utility buildings.

The measures aimed at the power quality improvement, taken by the electric power supplier, are presented.

A comparison is done before and after replacement of a transformer to assess whether or not the choice was right.

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Power Quality Control In An Industrial Estate

This case study presents a methodology for improving power quality in an important industrial estate. A project was initiated to reduce the number of interruptions and enhance power quality in the estate and focused on reducing weak points in the power distribution system by inspecting distribution lines in both customer and utility areas. Once weaknesses were identified, corrective action would be taken and preventative measures taken to prevent re-occurance in order to provide high power availability to customers.

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Circuit Breaker Tripping in Semiconductor Plant Caused by Voltage Dips

A semiconductor plant experienced a problem where the LV side main circuit breaker was tripped by voltage dips. As a result, power to all connected loads was interrupted and manufacturing processes were halted. The main cause of this problem was the unsuitable design of the under-voltage protection system. When a voltage dip occurred it was misinterpreted as an under-voltage event by the protection system, which erroneously tripped the circuit breaker.

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