Post on 21-Jul-2018
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Lifeng YangABB Inc.
Lake Mary, FL
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
What issues faced with cable fault localization?▪ Conventional fault location technique such as distance based approach might not work due to the
unique characteristic of cable fault current.▪ Not visually accessible (buried underground or in conduit) .
Aim of this paper▪ Introduce the cable fault detection technique.▪ Present faulty cable branch localization system.
Water
Zs xZl (1-x)Zl
Zld
CB
Relay
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
What is cable fault?▪ Short duration▪ Self clearing▪ Relatively high magnitude
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Field recorded data:
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Approaches published to deal with cable fault current:• Travelling wave• Transient signal analysis• Wavelets analysis• Neuro net• Short window DFT• Etc.
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Cable Fault Detection Function:• Short window DFT based (as result from the DOE
research project)• Separate Phase and ground • Pickups can be fixed setting or adapt to load• Able to detect as short as a quarter cycle pulse• Intend to identify early stage of faulty cable to avoid
unplanned power outage• Field proved technology• Wont indicate fault location
Cable Fault Detection
Inputs:Ph & Gnd currentsBreaker position
Outputs:CFD indicationCFD counts
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
M1 M2
TIE1
DG Load
Source 1 Source 2
Motor
MT1
Motor
MT2
Load Load Load
F1F2
F3F4
F5
N.O.
Typical Simple MV Cable Network Configuration
▪ A fault occurs downstream F3, multiple relays upstream could also seethe fault▪ Need not only to detect the fault but
identify the faulty branch
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Local tier
neighborhood tier
Fault Branch Localization strategy:
▪ Divide and conquer from bottom up
▪ Three tiers system: Local, Neighborhood and Central
▪ Local decision reports to neighborhood, and neighborhood reports to central
Laptop
Ethernet Switch
IEC 61850 8-1 Laptop
Ethernet Switch
IEC 61850 8-1
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Neighborhood Tiers
Central Tier
Load Load
F1 F2 F3 F4
Ethernet Switch
Laptop
PCM600
Relay
Non-
Conventional
VT/CT
B1
Load Load
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Local Tier
▪ Radial ▪ Close to load▪ Lowest in the hierarchy ▪ Master processing unit on top branch▪ GOOSE communication
GOOSE
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Local Tier Implementation:
▪ Five inputs on left are the cable fault indications from the relays (four feeders and one branch)
▪ Five outputs on top are the faulty branch indications.
▪ Output on right indicates whether the fault is within this local tier .
B1 FI
F1 FI
F2 FI
F3 FI
F4 FI
B1_F F1_F F2_F F3_F F4_F
B1_FT
M1 M2
TIE1
DG
Source 1 Source 2
Motor
MT1
Motor
MT2
N.O.
B1 B2DG
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Neighborhood Tier
▪ May not a simple STAR formation dependent on tie breaker position.
▪ Contain some local tiers.▪ Mid level in the hierarchy ▪ Master processing unit can be any of
main branches and tie breaker. For redundancy, can be implemented on both main branches.
▪ GOOSE communication
Local TierLocal Tier
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Neighborhood Tier Implementation:
▪ Inputs on left are the cable fault indications from the relays (local tiers, DG, Motor loads, Mains and tie breaker)
▪ Outputs on top are the faulty branch indications for each breaker involved.
▪ …
B1_FT
MT1_FT
B2_FT
MT2_FT
DG_FT
B1_F MT1_F DG_F B2_F MT2_F
M1 FI
T1 Close
M2 FI
M1_F M2_F
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Neighborhood Tier Implementation:
▪ Fault indication within this neighborhood tier .
B1_FT
MT1_FT
B2_FT
MT2_FT
DG_FT
B1_F MT1_F DG_F B2_F MT2_F
M1 FPI
T1 Close
M2 FPI
M1_F M2_F
NH1_F
Fault Location System for Radial MV Underground Distribution Cable Networks
71st Texas A&M University Relay Conference
Conclusions:
▪ Faulty cable branch can be identified with a hierarchy fault location system.▪ Local and neighborhood tiers can be implemented on the existing relay that has
user configurable logic gates.▪ Logic needed is relatively simple and easy to implement.▪ Logic can be easily scaled up or down according to the network topology.▪ No extra cost.▪ Faulty cable branch can be immediately identified once a cable fault is detected
in the tiers.▪ No need to manually determine the faulty branch, save time and money.▪ Early faulty cable branch identification to avoid unplanned power outage,
reducing down time and increasing power distribution network reliability.▪ The fault location system presented here can be used for generic fault
localization.