Cluster Based Protection Coordination using a New Voltage Current Time Inverse Relay

coordinated operation of protective relays generally remains intact only for a particular fault level and network configuration. Penetration of distributed energy resources (DER) in a power network changes the systems fault level depending upon their size, location and number. This results in loss of coordinated operation of the protection relays. Weak fault infeed from especially photovoltaic (PV) based DER results in sluggish operating time of over current relays and poor protection coordination. In this article, a voltage-current based time inverse relay model is proposed to enhance the operating time of the relays for protection coordination in weak fault systems. This relay model is also utilized for a cluster based protection coordination for power network penetrated with varying location, size and penetration level of DER. It is observed that for a small power network, it may be feasible to obtain a universal relay settings for coordinated operation of relays for varying infeed from DER. But for a big power network, it become difficult to obtain a universal relay setting for coordinated operation of relays for multiple network configurations. The cluster based protection coordination scheme may be a reliable solution for maintaining the protection coordination of relays for varying location, size and variable infeed from DER. The performance of the proposed relay model & coordination schemes is compared with standard time inverse relays and other published relay models based protection coordination. It is found that the proposed coordination scheme gives superior results in terms of quality of protection coordination.