Frankfurt (Germany), 6-9 June 2011 Analysis of Protection Malfunctioning in Meshed Distribution Grids Evita PARABIRSING Dr. Edward COSTER Dr. Marjan POPOV Stedin- The Netherlands Stedin – The Netherlands TU Delft – The Netherlands Paper 0374

Frankfurt (Germany), 6-9 June 2011  Introduction  Analysis of Short Circuits and Protection Relay Detection in a 25.6 kV Meshed Grid Section  Possible Solution Strategy  Conclusions Evita N. Parabirsing – The Netherlands – RIF Session 3 – Paper 0374 Presentation Overview

Frankfurt (Germany), 6-9 June 2011 Introduction  Problem definition: Short Circuit If = If_1 + If_2 If If_1 If_2 Directional Relay (DIR) mal-operation occurs in networks with similar construction

Frankfurt (Germany), 6-9 June 2011 Analysis of Short Circuits and Protection Relay Detection in a 25.6 kV Meshed Grid Section  25.6 kV Meshed grid section IOC= overcurrent relay DIR= directional relay

Frankfurt (Germany), 6-9 June 2011  Analysis of short circuits and circulating fault currents 0%100% Short Circuit k If Cable length = 1.97 km

Frankfurt (Germany), 6-9 June %100% 18 kA 3,2 kA 14,5 kA 30% If – If_2b If_2b I> 840 A “Dead Zone”

Frankfurt (Germany), 6-9 June 2011  For all types of short circuits there are certain ‘dead zones’ available in the network, caused by low fault currents which are detected by the directional relay (DIR) System FaultDead ZoneCable Length Three Phase Faults 0% < k < 8%~ 160 m of 1,97 km Double Phase Faults 0% < k < 9%~180 m of 1,97 km Single Phase to Ground Faults 0% < k < 15%~300 m of 1,97 km Double Phase to Ground Faults 0% < k < 8%~ 160 m of 1,97 km

Frankfurt (Germany), 6-9 June 2011  Overview of ‘dead zones’ in the studied network

Frankfurt (Germany), 6-9 June 2011 Possible solution strategy  Is there a possibility that faults within the ‘dead zone’ could be detected by the I>>, Ie>> settings of the IOC relays ? Step 1: Detected fault currents for faults within ‘dead zone’ System FaultWithin Dead Zone If (IOC) Three Phase Faults0% < k < 10%15.6 kA < If(IOC) < 16 kA

Frankfurt (Germany), 6-9 June 2011 Step 2: Detected fault currents for faults outside the protected area System FaultOutside Dead Zone If (IOC) Three Phase Faults0% < k < 10%11.4 kA

Frankfurt (Germany), 6-9 June 2011 Proposed I>>, Ie>> and t>>, te>> settings of the IOC relays: System FaultInside Dead ZoneOutside Dead Zone Three Phase Faults 15.6 kA < If(IOC) < 16 kAIf(IOC)= 11.4 kA I>> Ie>>t>>, te>> 11.4 kA > ) < 15.6 kA0.99 kA >) < 1.36 kA0.3 seconds

Frankfurt (Germany), 6-9 June 2011 conclusions  Analysis and Simulation results show that there exist ‘dead zones’ within the protected zones of the studied network  ‘Dead zones’ will always be available in network sections with single point of supply. The ‘dead zones’ are caused by the low magnitude of the fault current through the Directional relay  By activating and adjusting the I>>, Ie>> and t>>, te>> settings of the overcurrent protection relays in this study case, selective switching can be achieved for short circuits within ‘dead zones’

Frankfurt (Germany), 6-9 June 2011 Thank You Paper 0374: Analysis of Protection Malfunctioning in Meshed Distribution Grids Evita PARABIRSING Dr. Edward COSTER Dr. Marjan POPOV Stedin- The Netherlands Stedin – The Netherlands TU Delft – The Netherlands