Analysis of Protection Malfunctioning in Meshed Distribution Grids

Frankfurt (Germany), 6-9 June 2011

Analysis of Protection Malfunctioning in Meshed Distribution Grids

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

Paper 0374


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


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


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


Analysis of short circuits and circulating fault currents

0% 100%

Short Circuit

k

If

kZ1 (1-k)Z1

Cable length = 1.97

km


0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2x 10

4

Fault Location (0%<k<100%)

Thre

e p

hase s

hort

circuit c

urr

ent,

If

IfIf2b

(If - If2b)

0% 100%

18 kA

3,2 kA

14,5 kA

30%

If – If_2b If_2b

I> 840 A

“Dead Zone”


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

Three Phase Faults0% < k < 8% ~ 160 m of 1,97 km

Double Phase Faults0% < 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


Overview of ‘dead zones’ in the studied network


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


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


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

V Z net

Load

IOC

IOC

IOC

DIR

DIR

DIR

Z1

Z2

Z3

Z4

Z5

I>> 14 kAt>> 0.3 secIe>> 1.2 kAte>> 0.3 secI> 840At> 2 secIe 120Ate 2 sec

I> 840At> 0.5 secIe 120Ate 0.5 sec


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’


Thank You

Paper 0374: Analysis of Protection Malfunctioning in Meshed Distribution Grids

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

Analysis of Protection Malfunctioning in Meshed Distribution Grids

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