PETROEL ÉCT RICA DE LOS LLANOS (PEL) BENEFIT S
EXCELLENT PERFORMANCE OF THE SEL-T400L RELAYS
FROM
THE
On August 1, 2019, a pair of SEL-T400L Time-Domain Line Protection relays
detected a C-phase-to-ground fault while monitoring the 153.2 km (95.2 mi) 230 kV
PEL transmission line from Jagüey to Quifa. This line is part of the 260 km (161.6
mi) 230 kV PEL transmission corridor from Chivor to Rubiales in Northeast
Colombia, shown in Figure 1. The fault was induced by lightning that caused an
insulator flashover.
Figure 1 – Map showing the location and route of the PEL transmission corridor from Chivor to
Rubiales.
An SEL-421 Protection, Automation, and Control System primary line protection
relay at each terminal detected the flashover fault event. Both relays tripped the Cphase circuit breaker pole via the Zone 1 ground distance (Z1G) element and then
successfully reclosed. The Jagüey SEL-421 relay tripped (Z1G asserted) in 23 ms,
and the circuit breaker opened 18.5 ms later (total of 41.5 ms), as shown in Figure
2. The line was reclosed in 1.36 s and 1.49 s from the Quifa and Jagüey terminals,
respectively.
Figure 2 – Jagüey SEL-421 event report data showing C-phase trip.
The SEL-T400L relays monitoring the line at each terminal recorded the flashover
fault event. Figure 3 shows the 1 MHz high-resolution currents and voltages captured
by the SEL-T400L.
Figure 3 – Jagüey SEL-T400L oscillograph data showing C-phase fault and trip.
Figure 4 shows the traveling waves (TWs) captured by the SEL-T400L relays at
Jagüey (black) and Quifa (blue). We observe that the first TW arrived at Jagüey
terminal 105.548 µs before the first TW arrived at Quifa terminal. The TWs recorded
at the two terminals are in phase, as we expect for an internal (on the line) event or
fault.
Figure 4 – Jagüey SEL-T400L oscillograph data showing C-phase local (black) and remote (blue)
TWs.
The SEL-T400L relays used the DE-TWFL method to calculate the distance to the
fault as 60.995 km from Jagüey and 92.175 km from Quifa.
Based on the SEL-T400L fault location, the PEL patrol crew started inspecting the
line at transmission tower 320, located 61.025 km from Jagüey. They then inspected
tower 321, located at 61.501 km, and noticed the damaged C-phase insulator shown
in Figure 5. The SEL-T400L-reported location is 506 m (1,660 ft) beyond the patrol
crew-reported fault location, which is just over one tower span! Figure 6 shows the
new insulator.
Figure 5 – Damaged C-phase insulator as found.
Figure 6 – Replaced C-phase insulator.
To evaluate the SEL-T400L line protection, which uses incremental-quantity and TW
elements, the event report data in Figure 7 shows the voltage and current signals
sampled at 1 MHz by the SEL-T400L at the Jagüey terminal. The figure also shows
the performance of the TW directional (TW32) element, incremental-quantity
directional (TD32) element, TW differential (TW87) element, POTT scheme, and
incremental-quantity distance (TD21) element, which operated in 69 µs, 1.37 ms,
1.47 ms, 2.17 ms, and 7.67 ms, respectively.
Figure 7 – Jagüey SEL-T400L oscillograph data showing TW32F, TD32F, TW87, PTRXC, and
TD21G assertions.
Table 1 compares the SEL-T400L and SEL-421 relay operating times without and
with the 18.5 ms circuit breaker time.
Relay
SEL-T400L
SEL-421
Trip Element
TW87 (ms)
POTT (ms)
TD21G (ms)
Z1G (ms)
Relay
Operating
Time
1.47
2.17
7.67
23.00
Relay +
Breaker
Operating
Time
19.97
20.67
26.17
41.50
Table 1 – SEL-T400L and SEL-421 operating times.
As this event report confirms, the SEL-T400L can reduce repair time, improve
system stability, and reduce arcing time, leading to an increased likelihood of a
successful reclose. Reducing the tripping time improves power quality and reduces
the impact of service interruptions.
SEL recommended to PEL that they reconfigure the protection schemes so that the
SEL-T400L relays are enabled to trip the circuit breakers for faster tripping and
reduced fault duration.
Please continue to send user experiences and events related to this technology, or
requests for more-detailed information, to TD_Support@selinc.com.
For more details about these specific projects, contact Product Engineer Greg
Smelich.
About PEL
Petroeléctrica de Los Llanos Ltd. is the owner of the transmission corridor that
supplies more economical and reliable electricity service to the Rubiales and Quifa
fields in the Colombian eastern plains, where it is used for crude oil extraction,
treatment, and transportation operations. The presence of PEL in the area has
brought oil sector customers of adjacent fields together.
The 260 km (161.6 mi) corridor crosses the departments Boyacá, Casanare, and
Meta, from the Chivor substation in the mountains to the Rubiales substation in the
eastern plains, via double-circuit transmission towers. The current electric power
demand is approximately 140 MW. In route along the corridor are the Jagüey (85
km), Quifa (240 km), and Rubiales (260 km) substations. PEL’s project plans include
a future Corocora substation located approximately 185 km from Chivor in the
department of Meta.
The 230 kV transmission lines between the Chivor and Quifa substations have SEL421 relays as the main (primary) and secondary transmission line protection with
single-pole tripping and reclosing.
PEL’s customers need the highest electric power service reliability possible for their
supply connection to the National Transmission System (NTS) via the PEL
transmission network. The high isoceraunic (thunderstorm) activity during the rainy
season along the 260 km corridor can result in lightning discharge currents as high
as 200 kA, which increases the risk of service interruptions due to insulator surface
flashovers and failures. To facilitate the accurate location of faults, which impedancebased fault location cannot provide, PEL has installed two SEL-T400L relays on the
line section from Jagüey to Quifa.