Frankfurt (Germany), 6-9 June 2011
Analysis of Protection Malfunctioning in
Meshed Distribution Grids
Evita PARABIRSING
Stedin- The Netherlands
evita.parabirsing@stedin.net
Dr. Edward COSTER
Stedin – The Netherlands
edward.coster@stedin.net
Paper 0374
Dr. Marjan POPOV
TU Delft – The Netherlands
m.popov@tudelft.nl
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
If
Short Circuit
0%
100%
kZ1
(1-k)Z1
k
Cable length = 1.97 km
Frankfurt (Germany), 6-9 June 2011
0%
100%
30%
If_2b
If – If_2b
4
2
x 10
18 kA
Three phase short circuit current,I
f
1.8
I> 840 A
1.6
14,5
kA
1.4
1.2
1
0.8
0.6
If
If2b
3,2 kA
0.4
0.2
“Dead Zone”
0
(If - If2b)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Fault Location (0%<k<100%)
0.8
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
Dead Zone
Cable Length
0% < k < 8%
~ 160 m of 1,97 km
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
Three Phase Faults
Double Phase Faults
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
Within Dead Zone
If(IOC)
Three Phase Faults
0% < 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 Fault
Outside Dead Zone
If(IOC)
Three Phase Faults
0% < k < 10%
11.4 kA
Frankfurt (Germany), 6-9 June 2011
Proposed I>>, Ie>> and t>>, te>> settings of the IOC relays:
System Fault
Inside Dead Zone
Outside Dead Zone
Three Phase Faults
15.6 kA < If(IOC) < 16 kA
If(IOC)=11.4 kA
I>>
Ie>>
t>>, te>>
11.4 kA < ( I>> ) < 15.6 kA
0.99 kA < (Ie>>) < 1.36 kA
0.3 seconds
IOC
V
Z net
DIR
Z2
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
Z1
Z3
DIR
Z4
IOC
Load
DIR
Z5
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
evita.parabirsing@stedin.net
Dr. Edward COSTER
Stedin – The Netherlands
edward.coster@stedin.net
Dr. Marjan POPOV
TU Delft – The Netherlands
m.popov@tudelft.nl