Power System Protection – Past, Present Future

Reliability and stability of power systems are among the most critical and controversial issues confronted by system operators, planning engineers, and protection engineers. In fact, due to the advent of smart grids and the need for sensitive and reliable control of power system parameters, power grids are becoming more complicated and therefore, different switching scenarios and control schemes would emerge in daily system loadings which should be handled by suitable switching schemes based upon related planning and protection studies.

Undoubtedly, power utilities and industrial plants would prefer to own and run a very reliable and stable interconnected network, where the customers, feeders, and essential and critical loads receive sufficient electric power at their requested demand at very low outage rates, where the variations of frequency and voltage are kept at minimum levels and within the permissible variation ranges. This, however, cannot be achieved unless the electric network is equipped with modern protection devices commanded through intelligent protection schemes set up by advanced control logic configurations.

So, what do we mean by modern power system protection? For years, one of the most difficult tasks in achieving power system reliability and stability has been (and still is) to achieve good coordination between different protection devices all across the network. In other words, if the protective devices are well coordinated within overlapped protection zones, then any possible fault will be cleared and isolated in the shortest possible time before it spreads to the healthy parts of the system. However, nowadays, due to the complexity of power systems and their interconnection at different voltage levels, protection coordination is becoming more difficult.

In fact, the need for having advanced power systems these days has dictated the need for the establishment of smart grids at different levels, which are protected and controlled by modern protection systems and complicated control logic schemes, where all the protection and control equipment and devices – known as IED’s – can communicate via standard protocols at very high data transfer rates by means of data switches, Ethernet networks, data buses, intertripping schemes, etc.

Currently, the trend of technology is towards upgrading the old communication systems and also developing newly established data centres and SCADA master stations which are well tuned and coordinated by means of satellite clock pulses, and wide coverage of data transfer over large areas of land. This can be facilitated by hiring advanced technologies to provide better visibility for point-to-point and point-to-multiple points connections. Hence, the new generation of relays using digital technology are equipped with advanced control and communication devices and serial ports using high speed fibre optic cables to ensure signal immunity to noise and high speed transfer of protection and control signals. This is the knowledge that is in very high demand now and it will be the gateway to future breakthroughs in protecting and controlling advanced power systems.

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