application experience with line current differential relays on three terminal lines
DESCRIPTION
Application Experience With Line Current Differential Relays on Three Terminal LinesTRANSCRIPT
Application Experience with Line Current Differential Relays on Three Terminal Series Compensated Lines
Tom Roseberg Aaron Martin Ilija Jankovic Roger Hedding BPA BPA ABB Inc. ABB Inc.
Outline of Presentation• Series compensated line challenges• Distance relay Protection• Line current differential protection• Bonneville Power Administration line protection replacement• BPA Testing• BPA Results• Conclusions
Series compensated line challenges• Capacitive nature of the fault• Metal Oxide Varistor operation• Spark Gap operation• Voltage inversion• Current Reversal
Series Capacitor installation
𝑃=¿¿¿Sin Θ
Apparent impedance of line
Distance Relay challenges• Three terminal lines
• Under-reach effect for internal faults due to current infeed at the T point• Over-reach effect for external fault due to outfeed at one terminal
• Series compensated lines• MOV Operation• Voltage inversion• Current reversal• Subharmonic oscillations
MOV operating characteristics
Series compensated line impedance diagram
Voltage Inversion
Current inversion
Subharmonic Oscillations
Line current differential scheme
Line current differential advantages• Not subject to
• Voltage Inversions• Power Swings• CCVT transients• Overreaching
• Simple Kirchoff’s law : If Ilocal – Iremote > 0, then internal fault• However, it is communication dependent !
Current differential operating characteristic
Line charging current
Multi terminal line
BPA Service Territory
BPA 500kV operation• Use series compensated lines with MOV to limit voltage across
capacitor to 2.0 – 2.5 per unit.• Bypass breaker closes when accumulated energy or MOV current
exceeds preset threshold• Bypass breaker remains closed during single pole trip and reclose
operation ( 1.4 – 1.7 seconds)• Series capacitors on unfaulted phases remain in service leading to
short term load current unbalance which relays must allow.
BPA reliability criteria at 500kV• Two redundant sets of relays• Two redundant communications systems• 1 cycle operation for close in, high magnitude faults
• Additional cycle for communication aided tripping
Relays being replaced• 2 redundant sets of static travelling wave relays• Each operating in parallel with static distance relay• Logic for single pole operation done with e/m auxiliary relays with
static timers• Schemes
• Single pole communication independent Zone 1• Communication independent mode wave detectors• Permissive zone 2• Permissive travelling wave detectors
Schemes• Single pole communication independent:
• Zone 1 distance• wave detectors
• Permissive Communications aided:• zone 2• travelling wave detectors
• Back up time delayed protection• Distance• Directional overcurrent
• Travelling wave units no longer available• Replacement all in one microprocessor unit• BPA replacing analog microwave with digital communications channel• Line current differential now viable
BPA Protection Challenge• New relays had to combine fully functional single pole line distance
relay for series compensated line with a fully functional single pole line current differential relay.
• Since not practical to upgrade communications equipment with relay replacement, new relays at some locations had to operate with older communications equipment till upgraded.
• When the digital communications is available, the relays are connected for relay to relay communications and line current differential function is turned on.
Operation of new BPA protection system• Primary single pole trip
• Line current differential relay• Communications independent Zone 1• Permissive Zone 2
• Back up three pole tripping• Time delayed ground and phase distance element• Directional ground overcurrent
Back up three pole tripping uses• Multi phase faults• Evolving faults• Failure to reclose• Reclose into fault• For a fault that occurs after successful reclose but before reset time• External events such as breaker failure• Reclosing is blocked for all back up trips
Testing• Fault data from EMTP studies used to test settings, programming, and
performance of the protection system• EMTP fault files are created to explore relay operations for difficult
system conditions• Heavily loaded systems with maximum series compensation• Longer lines• Terminals that have weak sources• Three terminal lines• Lines that share the same corridor with heavy mutual coupling
• All fault types studied
Modeled protected lineGrizzly 525kV
To Bake Oven
10.3%
Captain Jack 525kV
Summer Lake
10.3% 20.7% 19% 15.5%
Malin 525kV
34.5%
Ponderosa #1230kV
20.7%
30.4% 18.6% 15.2% 35.8%
19%
Ponderosa #2 230kV
15.5%
7 miles
To OLinda
To RoundMoutain
Klamath
To Buckley
To Round Butte
Sand Springs Series Caps
Fort Rock Series Caps
Sycan Series Caps
-30.8% -20.5% -30.8%
-58.9% -39%
-30% -20% -30%
Faults chosen• Faults were simulated on the line side of the series capacitors at both ends of the
line. For these cases the series capacitors will bypass during the fault operation. • Faults were simulated on the line near each terminal, but far enough out on the line
such that the series capacitors are fully in service. • High resistive line to ground faults similar to one that occurred on the BPA in 2006
was also included for testing. • The faults were rotated between phases to provide a more thorough test of the
internal logic in the relays. • The faults were run with an average line load of 1000 megawatts and also with an
emergency line load of 2100 to 2300 megawatts. • The ground faults were run with varying values of ground resistance up to 100 ohms.
Grizzly 525kV
To Bake Oven
10.3%
Captain Jack 525kV
Summer Lake
10.3% 20.7% 19% 15.5%
Malin 525kV
34.5%
Ponderosa #1230kV
20.7%
30.4% 18.6% 15.2% 35.8%
19%
Ponderosa #2 230kV
15.5%
7 miles
To OLinda
To RoundMoutain
Klamath
To Buckley
To Round Butte
Sand Springs Series Caps
Fort Rock Series Caps
Sycan Series Caps
-30.8% -20.5% -30.8%
-58.9% -39%
-30% -20% -30%
Fault I1 A – Ground 9.4 miles from Grizzly
I1X
Test I1• Single line to ground fault near one terminal• 1000 MW load• 1 set of series capacitors in service• Under heavy load line is nearly 100% compensated, this limits the ability to set zone 1.• For most faults zone 1 will not operate• Distance relay will operate by permissive tripping logic• Line differential will operate normally• During reclose dead time line will have to loaded phases on one open phase creating
3IO on this line and adjacent lines• A four reactor scheme is used at terminal 1 to extinguish the secondary arc
Grizzly
Differential trip time = 20ms
Permissive trip time = 37 ms
Breaker trip output = 20ms
Summer Lake
Differential trip time = 17 ms
Permissive trip time = 37 ms
Breaker trip output = 17ms
Ponderosa
Differential trip time = 17.5 ms
Permissive trip time = 37 ms
Breaker trip output = 17.5 ms
I1 results
Grizzly Trip Test I1
Grizzly Trip and Reclose Test I1
April 22, 2023
I 16 BC-G Fault near Summer Lake
| Slide 33
Grizzly 525kV
To Bake Oven
10.3%
Captain Jack 525kV
Summer Lake
10.3% 20.7% 19% 15.5%
Malin 525kV
34.5%
Ponderosa #1230kV
20.7%
30.4% 18.6% 15.2% 35.8%
19%
Ponderosa #2 230kV
15.5%
7 miles
To OLinda
To RoundMoutain
Klamath
To Buckley
To Round Butte
Sand Springs Series Caps
Fort Rock Series Caps
Sycan Series Caps
-30.8% -20.5% -30.8%
-58.9% -39%
-30% -20% -30%
I16 X
B phase to C phase to ground fault Zone 1 will not operate for most faults Distance will operate by permissive trip logic Line differential will operate normally Since this is multi phase fault all terminals will
trip 3 pole and block reclosing Back up three pole trip will be sent to all
terminals
Test I16
Grizzly
Differential trip time = 23ms
Permissive trip time = 50ms
Breaker trip output = 23ms
Summer Lake
Differential trip time = 19ms
Permissive trip time = 48ms
Breaker trip output = 19ms
Ponderosa
Differential trip time = 19ms
Permissive trip time = 39ms
Breaker trip output = 19ms
Test I16 Results
Grizzly Trip Test I16
April 22, 2023 | Slide 37
I28 North of Sand Spring B phase to ground , 100 Ohm fault resistance
Grizzly 525kV
To Bake Oven
10.3%
Captain Jack 525kV
Summer Lake
10.3% 20.7% 19% 15.5%
Malin 525kV
34.5%
Ponderosa #1230kV
20.7%
30.4% 18.6% 15.2% 35.8%
19%
Ponderosa #2 230kV
15.5%
7 miles
To OLinda
To RoundMoutain
Klamath
To Buckley
To Round Butte
Sand Springs Series Caps
Fort Rock Series Caps
Sycan Series Caps
-30.8% -20.5% -30.8%
-58.9% -39%
-30% -20% -30%
I28 X
Phase B to ground fault with 100 Ohm ground resistance Heavily loaded line – 2300MW All series compensation in service Zone 2 settings limited by load and sub harmonic
oscillations As fault resistance increases Zone 2 elements have
difficulty detecting the fault. If more than one Zone 2 elements fail to detect the fault,
then the distance elements will not trip Time delayed directional ground overcurrent element
provides back up to distance elements
Test I 28
Grizzly
Differential trip time = 26ms
Permissive bit transmit = 37ms (no permissive trip)
Breaker trip output = 26ms
Summer Lake
Differential trip time = 26ms
Permissive trip time = NA (no permissive trip)
Breaker trip output = 26ms
Ponderosa
Differential trip time = 26ms
Permissive trip time = NA
(no permissive trip)
Breaker trip output = 26ms
Test I28 results
Grizzly trip Test I28
April 22, 2023
External Fault E13 on Ponderosa 500kV TX1 A -G
| Slide 41
Grizzly 525kV
To Bake Oven
10.3%
Captain Jack 525kV
Summer Lake
10.3% 20.7% 19% 15.5%
Malin 525kV
34.5%
Ponderosa #1230kV
20.7%
30.4% 18.6% 15.2% 35.8%
19%
Ponderosa #2 230kV
15.5%
7 miles
To OLinda
To RoundMoutain
Klamath
To Buckley
To Round Butte
Sand Springs Series Caps
Fort Rock Series Caps
Sycan Series Caps
-30.8% -20.5% -30.8%
-58.9% -39%
-30% -20% -30%
E13
Phase A to ground fault at Ponderosa on the bus side of the line breaker
Zone 2 at both terminals will operate and transmit the permissive signal to Ponderosa.
At Ponderosa, zone 3 will pick up and block permissive tripping at all terminals.
Test check coordination between remote zone 2 and local zone 3 relays.
Differential will not operate because this is an external fault
External fault E13 on Ponderosa 500kV
Grizzly
Differential trip time = did not op
Permissive bit transmit = 42ms
Breaker trip output = did not op
Summer Lake
Differential trip time = did not op
Zone 3 pick up time = 14ms
Breaker trip output = did not op
Ponderosa
Differential trip time = did not op
Permissive bit transmit = 17ms
Breaker trip output = did not op
External fault E13 results
Ponderosa Test E13
©April 22, 2023
Distance elements are used along with line current differential elements for this protection
The line current differential complements the distance function
Line current differential has no setting or operational issues when a series compensated line is either adjacent to or in the zone of protection
Line current differential has the same operating quantities at each terminal, so the tripping time is the same for each terminal.
Conclusions
| Slide 45
April 22, 2023
EMTP results have shown the line current differential relays are stable at the more sensitive settings and give proper single pole operation for ground faults with higher values of fault resistance.
Ground faults that used to be cleared by time delayed back up three pole tripping are now properly cleared single pole with reclosing.
The addition of the line current differential element significantly improved the overall performance of the new protective relay system.
Conclusions
| Slide 46
April 22, 2023 | Slide 47
Questions ?