| Summary: | The technological advancements in the substation automation give rise to many new challenges for the engineers. The IEC 61850 standard de nes the most advanced techniques towards the digital substation development. It describes the communication mappings for the substation automation of both conventional and digital substations. The most important challenge is to replace old successful and reliable protection relays with the newly born microprocessor based relays called intelligent electronic devices (IEDs). The IEC 61850 standard gives the novel ideas in its sub-clauses IEC 60044-8 and IEC 61850-9-2 about digital communication and sampled values transmission over an Ethernet link called process bus. As this thesis is the Part-A and it is mainly based on the development of the conventional instrument transformers, analog to digital data converter and a multi-bus power system. The scope of this study contains the development of current and voltage transformer models in SIMULINK which gives the ideal behaviour of the conventional instrument transformers for voltage and current measurements.The methodology of this study is to model the Sigma-Delta analog to digital converter in the SIMULINK and then simulated results are veri ed according to the standard. The 4KHz output (Voltage/Current) signal is obtained in the digital form with 16-bit resolution. The SNR (Signal to Noise Ratio) and ENOB (Eective Number of Bits) of the data converter is veri ed both theoretically and practically. In the next phase the multi-bus power system is modelled in the SIMULINK using SimPowerSystems Library to make the nal tests on the developed product. Finally the developed models of Project Part-A have been integrated with the transmission model developed in the Project Part-B, collectively known as Merging Unit. The functionality of this complete developed product is to get 3-phase analog signals of currents and voltages from the instrument transformers, perform signal processing on these signals and then transmit them on the Ethernet port in the form of SV (Sampled Value) stream according to the IEC 61850-9-2 standard. The developed Merging Unit is then connected to the dierent nodes of the power system to test the performance and reliability of the Merging Unit. The over current and dierential protection functions are tested on the ABB's RET 670 IED (Protection Relay for Transformer). In both test cases three phase short circuit fault is applied to the power system to check the behaviour of the Merging Unit during normal and abnormal conditions. It detects all the values correctly during pre-fault condition, fault condition and post-fault condition.
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