A large utility in Europe requested the commissioning and
diagnostic testing of a hybrid transmission cable system (3 cables land and
subsea) over 40 km in length rated at 220 kV-230 kV phase to phase terminated
between a transmission substation to a remote Gas Insulated Substation (GIS) mounted
on an offshore platform.
Testing requirement
- Perform
commissioning testing in compliance with IEC 62067 standards at 1.7Uo for 60
minutes at testing frequency (20-300Hz).
- Perform
Partial Discharge Diagnostic testing on the cable accessories including joints
for the onshore cable section and terminations both onshore and offshore.
Equipment required
Based
on the overall capacitance and other parameters of the hybrid transmission
cable system, Kinectrics engineers determined the following equipment was
required to achieve the requested testing:
- Six
(6) Resonance test systems (RTS) rated (260 kV / 83 A) connected in a parallel
configuration. Each with 22MVA reactor fed by 220 KVA exciter transformer
- An
additional 220 KVA exciter transformer for a total of seven (7) feeding units
- Synchronized
diesel generators rated at 4.2 MVA to power up the RTS network
- Capacitive
Sheath Partial Discharge Sensors to be installed near the direct buried joints
on the land cable sections
- High
Frequency Current Transforms (HFCT) partial discharge sensors to be installed
at the cable terminations on both ends
Equipment set-up
- Kinectrics
manufactured and supplied the required capacitive sheath sensors to the client
on time to be permanently installed by the cable manufacturer and installer.
- The
Six (6) Resonance Test System network with the additional exciting transformer
was assembled by Kinectrics engineers and technicians at the remote
transmission substation.
- Kinectrics
engineers and technicians installed the daisy-chained partial discharge
monitoring devices on each of the land cable section joints connected via the
preinstalled multimode optical fiber cables.
- Kinectrics
engineers and technicians installed High Frequency Current Transformers
(HFCT’s) on the terminations both onshore and the remote platform 40km
offshore.
- Kinectrics
engineers and technicians installed seven (7) 600kVA synchronized diesel
generators to power up the network of RTS systems.
Successful Testing
Kinectrics
successfully completed commissioning the AC Hi-Pot test with partial discharge
diagnosis on a 220 kV hybrid cable system (Land and Subsea) terminated at a GIS
on a platform approximately 40 km offshore.
Using
six (6) Resonant Test Systems rated at 260 kV/83 A each connected in a parallel
configuration and an additional control feeding unit powered by 4.5 MVA of
diesel generators, we were able to successfully apply 227 kV phase to ground
equivalent to 1.7Uo of test voltage on each of the 3 cables for 60 minutes in
compliance with IEC 62067 Standards.
During the commissioning testing, Kinectrics used our
synchronized daisy-chained partial discharge monitoring system, configured via
the multimode optical fiber cables, to monitor and record PD activity on the
land cable section accessories. In addition, at the remote platform
termination on the GIS approximately 40 km offshore, Kinectrics used a
real-time Partial Discharge monitoring system to record and diagnose PD
activity on each of the 3 cables using local 4G LTE network.
Results
The combined AC Hi-Pot at 1.7Uo with Partial Discharge
diagnosis testing provided our test engineers with accurate test results in
compliance with the IEC 62067 standards, and in turn, our client with a higher
confidence level regarding the overall health and the installation quality of
the cable system.
Kinectrics
was able to achieve the required test voltage at 1.7Uo and maintain it for 60
minutes as required by the client and the industry standards. During the
commissioning testing, we monitored and recorded the partial discharge activity
on all the land cable section joints and terminations onshore at the substation
end, and at the platform GIS 40km offshore. The cable
system passed the required testing and was reported fit for service.