evolving transmission line faults while single phase … · evolving transmission line faults while...
TRANSCRIPT
Evolving Transmission Line Faults While Single
Phase OpenWestern Protective Relaying Conference 2014
Charles HenvilleHenville Consulting Inc, and
Tony JiaoBC Hydro
Evolving faults are rare… And even more rare under single phase
open conditions…but they do happen!What are the problems associated with
them during single phase open (SPO)? Two recent cases in BC Hydro are
presented And protection performance is analyzed
Single phase open
Directional relays have some difficulties during SPO
is like an LLG fault
BC Hydro transmission (part)
12 August 201314:28 hours lightning strike
Followed by another strike 90 ms after first strike.
AG Fault followed by correct single phase trip in 3 cycles
BG Fault followed by correct (but slow) 3 phase trip in 24 cycles
Line manually reclosed OK
REV Terminal
Zoom
Zoomed AreaFault plasma ionizes air Second fault
on B Phase
Arc from second fault is close to the ionized air from first
REV Terminal
REV Zone 1 Quad sees initial fault
SPO Blocks all quads
MG2 No Op.51S1T Trips 3P and Key 3P DTT
Check relay response to faults
ACK Trips from A PH DTT Received
ACK Terminal
Modeled Response
REV Zone 1 Quadoperates
ACK All distance elements restrain
11
5L72
SYA Series Capacitor Station
12
Shield wire
13
February 4th, 2014 - 6:48amSC controller issued auto isolation command (OCT supervision logic mis-operation)
With 5BP2 not electrically closed,5D3 and 5D4 tried to interrupt 600A load current. Arcs start across open contacts
5CB2 and 5BP2 closed automatically by isolation sequence. But 5BP2 did not close electrically
14Snow on 5BP2 contact
Arcs rise due to heat
Source More Arcs 'n Sparks! http://205.243.100.155/frames/longarc.htmWith permission from Bert Hickman, http://www.capturedlightning.com
16
Seymour Arm Series Capacitor Station
A phase arcing to shield wire
5L72 tripped 3-phase at both ends in 3 cycles.
5L72 tripped A-phase at both ends in 3 cycles.
16 cycles later, C phase arcing to shield wire
5L72 reclosed 3-phases successfully 80 cycles later, and initiated arcing on 5BP2, arcing melted snow between MOD main contacts and eventually 5BP2 fully contacted. 5BP2 RFI ball and corona ring damaged.
17
Burn mark on 5D3
18
5BP2 Corona Ball gone!
19
5BP2 Corona Ring burned!
5L72 current before SC bypass, 800A 5L72 current after SC bypass, 600A
SYA 5CB2 closed, SC2 bypassed
21MCA Terminal
87LQ/87LG detected A-G fault in less than 1 cycle
87LC detected C-G fault in less than 1 cycle
A phase trippedAll 3 phases tripped
SYA 5D3 A-Phase arcing to shield wire
16 cycles after a phase open, SYA 5D3 C-Phase arcing to shield wire
NIC Terminal
87LQ/87LG detected A-G fault in less than 1 cycle 87LC detected C-G fault in less than 1 cycle
A phase tripped All 3 phases tripped
A – G fault 16 cycles after a phase open, C – G fault
ConclusionsPOTT Line Differential
PN Speed(Normal)
1 cycle 1 cycle
PN for GND FLT (during SPO)
Ground mho & 51NT
Blocked PN:67G2, 67Q2 and
All Quads
87LA, 87LB, 87LC
87LG and 87LQBlocked PN:
NonePN Speed
(SLG during SPO)
1 cycle to 1 second
1 cycle
Simulating the event in Fault Study model
Series of events Prefault load flow SLG on A phase A phase open at both ends LLG on A and B phases (A ph. Still open) No fault
Create a bus for line side VTs Create a relay test file in Comtrade format Repeat until satisfied
Some differences between real and simulated events
Conclusions Some quadrilateral and directional protection
may be degraded during open phase condition Phase and ground mho elements on unfaulted
phases will still clear low impedance faults (at both ends)
Ground time overcurrent is useful during open phase period.
Line current differential protection is more robust during single pole open conditions
P&C Planning 27
Questions?