NAME : Nadia Helena Gama Ribeiro de Louredo
COUNTRY : Brazil
REGISTRATION NUMBER : 1797
GROUP REF. : B1
PREF. SUBJECT : 2
QUESTION N° : 4
Question PS2.Q4: New diagnostic technologies allow better use to be made of existing systems.Is an ideal
« wish list » ,what are the parameters and phenomena that utilities ,end users , or TSOs ,may want to monitor ?
A) Monitoring technologies are always welcome allowing the system reliability.
There are three main monitoring systems :
1.
The first one is responsible for underground system thermal performance , regarding the power cables
ampacity, due to the changes in thermal environment which are difficult to control without a monitoring
system.This is the most important and object of interest for all underground transmission systems.
2.
The second one refers specifically to power cables whose insulation contains oil (laminated and
impregnated paper insulation). In Brazilian underground transmission systems almost all installations
has oil filled impregnated paper insulation power cables.
3.
The third one has a condition -based maintenance for the integrity of power cable systems , since most
defects causes partial discharges under AC stress. Despite the importance related to the installation of a
PD monitoring system, we realized that the Utilities, or the Brazilian transmission system owners ,
don’t have a real perception of the ' added value ' to this system yet.
B) Monitoring system regarding thermal environment control ( ampacity , temperature) :
Actually the Brazilian National System Operator is keeping under review the procedures and requirements for
transmission system . In fact , it was included the basic requirements to underground systems in EHV.
One of the several basic requirements refers to real time thermal rating and temperature monitoring systems and
the « wish list » below was proposed :
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•
•
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Real time temperature
Real time ampacity
Real time temporary power capacity
The monitoring system must at least furnish: maximum temporary current for a pre-determined duration
, duration of a temporary pre-determined current, and maximum current in steady state condition for the
actual environmental conditions.
C) Monitoring system regarding the events in OF power cables (leakage):
The basic « wish list » it is :
• Real time control of the oil pressure
• Ability to accurately indicate any oil leak points
D) PD monitoring systems
There are still fairly aware of the real value of this system due to inconsistencies generated perhaps by the results
interpretation (PD levels) which indicate in fact if such defects may or not results in failure on power cables and
/or system components.
E) Brazilian experience with monitoring sytems:
It’s interesting to mention some Brazilian examples of installations regarding their monitoring systems:
1.
UG Transmission line - 230 kV - 362 MVA/circuit , 12.0 km long , 1 circuit - special grounding
system : crossbonding (Energization:2011).
•
This UG transmission line has a DTS monitoring system .
1
2.
UG Transmission line - 88/138 kV(operating in 88 kV) - 300 MVA/circuit , 4.6 km long , 2 circuits special grounding system : crossbonding (Energization :2010)
•
3.
UG transmission line - 88/138 kV ( operating in 88 kV) - 110 MVA/circuit , 6.0 km long (
approximatelly 5.4 km in duct banks ,and 0.6 km in tunnel- end line portion at the vicinity of
substation entrance) 2 circuits - special grounding system : crossbonding ( Energization :1985)
•
4.
This UG transmission line it was prepared to receive in the future a DTS monitoring system ( the
power cable has attached optical fibers sensor cables).
The portion installed in tunnel has a monitoring system that should « turn-on » a ventilation
system whenever the temperature inside the tunnel reachs certain temperature level (« taps »),
allowing , for example, the presence of maintenance team. For a specific temperature, the
ventilation system should never be « turn-on » since it could indicates the possibility of fire. Even
the temperature « taps » are linked to ventilators air speed.
UG transmission line - 345 kV - 1500 MVA, 8.5 km long - 3 circuits - special grounding system :
crossbonding ( Energization : 1980).
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In 2004 it was installed a monitoring system to control the following parameters/phenomena : oil
pressure in each hydraulic section , current in the metallic sheaths, voltage and current in the
conductor, power cable and environment temperature, joint boxes access and joint boxes control
of flood.