Frankfurt (Germany), 6-9 June 2011

Analysis of Protection Malfunctioning in Meshed Distribution Grids

Evita PARABIRSING Stedin- The Netherlands Dr. Edward COSTER Stedin – The Netherlands TU Delft – The Netherlands [email protected] [email protected]

Dr. Marjan POPOV [email protected]

Paper 0374

Frankfurt (Germany), 6-9 June 2011

Presentation Overview

 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

Frankfurt (Germany), 6-9 June 2011 

Introduction

Problem definition:

Short Circuit If_1 If = If_1 + If_2 If 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% kZ1 If Short Circuit 100% (1-k)Z1 k Cable length = 1.97 km

Frankfurt (Germany), 6-9 June 2011

0% 100% 30% If – If_2b If_2b

2 x 10 4 1.8

1.6

1.4

1.2

1 0.8

0.6

0.4

0.2

I> 840 A “Dead Zone” 0 0 0.1

14,5 kA 18 kA 3,2 kA

0.2

0.3

0.4

0.5

0.6

Fault Location (0%

0.8

If If 2 b (If - If 2 b) 0.9

1

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 Fault

Three Phase Faults Double Phase Faults Single Phase to Ground Faults Double Phase to Ground Faults

Dead Zone

0% < k < 8% 0% < k < 9% 0% < k < 15% 0% < k < 8%

Cable Length

~ 160 m of 1,97 km ~180 m of 1,97 km ~300 m of 1,97 km ~ 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 Fault

Three Phase Faults

Within Dead Zone

0% < k < 10%

If (IOC)

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 Fault

Three Phase Faults

Outside Dead Zone

0% < k < 10%

If (IOC)

11.4 kA

Frankfurt (Germany), 6-9 June 2011

Proposed I>>, Ie>> and t>>, te>> settings of the IOC relays: System Fault

Three Phase Faults

Inside Dead Zone

15.6 kA < If(IOC) < 16 kA

Outside Dead Zone

If(IOC)= 11.4 kA

I>>

11.4 kA < ( I>> ) < 15.6 kA

Ie>>

0.99 kA < (Ie>>) < 1.36 kA

t>>, te>>

0.3 seconds

Z1 IOC DIR V Z net Z2 Z3 IOC I>> 14 kA t>> 0.3 sec Ie>> 1.2 kA te>> 0.3 sec I> 840A t> 2 sec Ie 120A te 2 sec IOC Z4 Z5 DIR DIR Load I> 840A t> 0.5 sec Ie 120A te 0.5 sec

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 Stedin- The Netherlands Dr. Edward COSTER Dr. Marjan POPOV Stedin – The Netherlands TU Delft – The Netherlands [email protected] [email protected]

[email protected]