IJSRD - International Journal for Scientific Research & Development| Vol. 5, Issue 10, 2017 | ISSN (online): 2321-0613 All rights reserved by www.ijsrd.com 780 A New Fast Detection Module for Short-Circuit Current Detection in PV Grid System Krishnakant Kasar 1 Prof. P.C.Tapre 2 1 PG Scholar 2 Assistant Professor 1,2 Department of Electrical Engineering 1,2 Savitribai Phule Pune University, S.N.D.C.O.E. & RC, Nashik, India Abstract— In electric power systems, integration of more Distributed Generators (DGs) in the network increase the short circuit level due to the short circuit current contribution of the DGs during faults. As compared to the synchronous and induction machine based generators, the inverter based generators, such as Photovoltaic (PV) solar systems, contributes lower fault current to the network due to the characteristics of PV panels and inverter operation. Although, each PV solar farm may contribute short currents as above, the total amount of fault current contribution may become unacceptably large for a feeder which has several PV systems connected. It is apprehended that short circuit current contributions from multiple solar systems in the distribution feeders may add up to levels that could be damaging to the circuit breakers. As a first step, adequate modeling of PV solar plants for predicting their short circuit contributions during network faults is essential. So far, the above fast faults detection techniques have been used for protection of network and DGs; and for unsymmetrical fault detection in fault current limiters (FCL). However these techniques have not been used to prevent any short circuit current contribution in excess of the rated or utility- acceptable current output of PV solar inverters. In this paper, a new fast detection module for short-circuit current detection has been discussed based on the rate of rise of current together with the current magnitude in a PV solar system based DG. There can be two control operations, as per the applicable grid code in that region, one of which is the disconnection of the PV inverter before the current exceeds the rated output current of the inverter. The second one discusses about transforming the PV inverter into a dynamic reactive power compensator STATCOM and provides grid support functions. A new concept of utilizing PV solar farms as STATCOM (PV-STATCOM) both during nighttime and daytime for different grid support functions was introduced in this paper. Key words: Photovoltaic (PV) Systems, Distributed Generator (DG), Inverter, Short Circuit Current, Protection, STATCOM, PV-STATCOM I. INTRODUCTION The interconnection of more Distributed Generators (DGs) in the network increases the short circuit level due to the short circuit current contribution of the DGs during faults. Compared to the synchronous and induction machine based generators the inverter based generators, such as Photovoltaic (PV) solar systems, contribute lower fault current to the network due to the characteristics of PV panels and inverter operation. Fig. 1: Transient Behavior of Short Circuit Current The short circuit current contribution from a PV system inverter is typically in the range of 1.2 times rated current for the large size inverter (1MW), 1.5 times (500 kW) for medium size inverter and between 2 - 3 times for smaller inverters. Although, each PV solar farm may contribute short currents as above, the total amount of fault current contribution may become unacceptably large for a feeder which has several PV systems connected. It is apprehended that short circuit current contributions from multiple solar systems in the distribution feeders may add up to levels that could be damaging to the circuit breakers. Hence circuit breakers will need to be upgraded and substations will need to be modified at significant cost to the utility. II. LITERATURE SURVEY Adequate modeling of PV solar plants for predicting their short circuit contributions during network faults is essential. The traditional relay technologies mainly use overvoltage, under voltage and over current signals to detect the faults, and subsequently operate protective breakers. Continuous Wavelet Transform (CWT) has been used to process voltage and current transients for calculating the change in supply impedance. The occurrence of a grid fault can be identified within half a supply cycle and decision can be made if the fault requires a distributed generation unit to be disconnected [1]. A four-stage fault protection scheme against short- circuit fault for inverter based DGs is proposed in. The inverter is initially controlled as a voltage source, which changes to the current controlled mode upon detection of the fault, thereby limiting the inverter output current. A lab validated pilot protection system based on time- synchronized measurements of instantaneous currents is proposed in, that is capable of tripping the fault in less than half a cycle [2]. A concept of rate of change of current has been proposed as a minimum fault-current change limit to prevent