Abstract:
Protection system of Extra High Voltage (EHV) network in Pakistan is
constantly being upgraded and new microprocessor based numerical protection relays
called Intelligent Electronic Devices (IEDs) are replacing old electromechanical
protection relays. Retrofitting of Numerical relays is need of the hour and currently an
ongoing process throughout power system of Pakistan. But lack of proper testing
techniques and understanding is resulting in under performance of protection system.
The Intelligent Electronic Devices (IEDs) offer variety of functions and features and
are supplied by different reputed manufacturers (Siemens Germany, Alstom France,
General Electric USA, SEL USA, ABB Switzerland). Thorough understanding of
settings, testing and performance difference is of utmost importance for smooth
operation of power system.
Differential and Distance relays are two of the most significant and abundantly
installed protection relays in EHV network of Pakistan which provide primary
protection to electrical equipment (Generators, Bus Bars, Transformers, Shunt
Reactors and Transmission Lines). Due to their key importance and complexity,
numerical differential relay (for protection of Transformer) and distance relay (for
protection of Transmission Line) are discussed in detail with special focus on their
testing and comparative analysis of relays supplied by two reputed manufacturers
(Alstom and Siemens). The differential and distance relays to be installed at Extra
High Voltage Grid Stations in Pakistan are used for testing and comparative analysis
under real – time settings and situations. Universal Relay Testing Set (Secondary
Injection) will be used for testing purposes. We will be using The Micom P642
(Make: ALSTOM) differential relay for detailed testing and The 7UT512 (Make:
Siemens) differential relays for comparative analysis of similar slope characteristics
and The Micom P443 (Make: ALSTOM) distance relay for detailed testing and The
7SA51 (Make: Siemens) distance relay for comparative analysis of similar distance
features
