Power lines: The main challenges in terms of monitoring and inspection in Chile
Although they have different specific objectives, power line monitoring and inspection aim to improve the availability of these vital elements of our electrical infrastructure. In general, monitoring is related to the real-time operation of the system while line inspection is a maintenance task (preventive or corrective).
Power lines are a fundamental part of transporting energy to points of consumption. For this reason, optimal availability and operational continuity are required, carrying out line monitoring and inspection activities for this purpose: the former have to do with the technical supervision of electrical parameters, while the latter, with environmental or climatological aspects.
“Both practices are tremendously relevant to ensure low levels of failures attributable to distribution and/or transmission companies and, therefore, to achieve high standards of supply quality with low rates of customer disconnections (quantity and time) due to power failures. because of the company”, explains Luis Gutiérrez, Director of the Civil Engineering in Energy Program at the Adolfo Ibáñez University.
Leonardo Hinojosa, Professor of the Electricity, Electronics and Telecommunications Area INACAP Concepción Talcahuano, adds that the monitoring of a transmission line ensures reliability and is reflected in the quality of service in all the elements of the Electric Power System: generation plants, substations, consumption centers and, therefore, end users.
“On the other hand, the lines are exposed to aggressive environments, where preventive maintenance is necessary. In this case, the insulators must be washed periodically and those that are broken must be replaced; damaged sections of conductor must be repaired or replaced. The foregoing is a non-negligible cost, so it must be considered when projecting the line”, he adds. And although the inspections of the lines in Chile are carried out without problems (normally visually), the problem that exists in our country, according to Fernando Torres, Academician of the Faculty of Engineering of the University of Talca, is that practically no monitoring is done on the lines, except for some quite particular technologies that are appearing today, such as DTR (Dynamic Thermal Rating) systems.
“In other countries, monitoring is used a little more extensively and in those cases the line temperature is recorded. Mechanical stress and deflection are also being measured. This last parameter is important, because technical regulations regularly establish a minimum distance that the lowest point of a conductor must have with respect to the ground and that depends on the voltage level of that particular transmission line”, he maintains.
What should be monitored?
In a transmission line, the maximum or minimum flows of active and reactive power must be monitored at all times; voltage regulation and thermal capacity of the line that are transmitted to the receiving end.
In addition, as Jasson Ulloa, Professor at the Duoc UC Puente Alto School of Engineering, indicates, one of the fundamental elements that must be supervised is the state of the electrical protections, since these are the ones in charge of ensuring their correct operation. “In the event of a fault, these act and disconnect part of the load; therefore, if the status of the electrical protections is remotely monitored, it is possible to know exactly where the fault is located and reduce search times by the team”, he explains.
Gutiérrez adds that an essential variable to monitor for operational purposes is the level of use of the lines. “This last aspect is key in the National Electric System, prone to congestion given our longitudinal geography and where, for example, large levels of solar energy discharge have been seen in the North of the country due to restrictions on transmission to the central zone.”
In relation to environmental aspects, Torres points out that normally what has to be considered, especially when a line is being built, are a series of factors such as air quality, archeology and cultural heritage, protected areas, geomorphology, availability of water resources, in addition to flora and fauna.
“Naturally, the line is always going to have a visual impact, so you have to try to minimize it,” he says. “Weather conditions can affect the transport capacity of the line, so it is important that the communication systems that allow the recording and sending of information in real time to the National Electrical Coordinator (CEN) do not have factors that generate erroneous information” adds Hinojosa.
One of the main monitoring system existing system today is the DTR which, based on the measurement of wind speed and direction, ambient temperature and solar radiation, can determine the maximum allowable ampacity for the line. “It makes it possible to determine this variable in a rather dynamic and not static way as is currently done by the CEN”, Torres points out.
Today there are quite a few devices that have an Internet connection, allowing their status to be verified in real time and their history to be known through a database of their actions and, accordingly, to monitor their useful life.
It should be noted, adds Ulloa, that the use of drones to check high-voltage distribution networks has taken a major role, especially in areas of dense vegetation. “It is a fast, economical and safe mechanism, allowing the use of thermographic cameras to detect hot spots in the network, corroded or damaged systems and warn of the presence of birds and other animals that may cause damage to electrical structures.”
Hinojosa points out that Smart Grid device technologies are currently being used, which are installed directly on the conductor of the transmission lines, and are connected to the cloud through a georeferenced system to collect and transmit data on the status of the transmission cabless. “These devices are capable of monitoring variables such as temperature and vibration of the conductor, key information for optimal maintenance planning and that gives greater quality and robustness to the supply of the transmission system.”
He also mentions OTLM technology, a modern active control system that allows monitoring of a transmission line ranging from 60 to 1000 KV.
According to Gutiérrez, the most interesting technologies for monitoring are probably presented in the area of HV cables, to which fiber optics are being incorporated, which is used to monitor temperature and partial discharges in the insulation, also including intermediate sleeves (junctions and derivations ) and terminals.
Regulations and recommendations
The National Energy Commission is in charge of analyzing the technical norms or standards that must be taken into consideration by companies that produce, generate, transport and distribute electricity, in order to have a quality service.
Although companies in Chile normally have their own protocols to be able to carry out the maintenance of their transmission lines, the 2020 Technical Standard for Security and Quality of Service defines the minimum requirements for the design of transmission facilities, as well as for information systems and communication.
“In Chile, the main regulation in force is the supply quality law that obliges companies to reduce the interruption time of the lines to set standards, at the same time, to compensate customers when service interruptions are generated” explains Ulloa. “In turn, the correct monitoring of the parameters of the line allows taking actions for its regulation and that it is within the parameters established in the technical standards of supply quality (CNE, May 2005)”, he adds.
The academic adds that it is necessary to be aware of the regulations that regulate these issues, since, in the event of system failures, the company must act in a timely manner and restore supply in a minimum amount of time. “At the same time, as clients, we can facilitate their work by indicating if we observe abnormalities in the network.”
Torres recommends paying attention to high voltage and direct current (HVDC) transmission systems, since they have lines that are lighter and, normally, the physical space used by the structures is smaller. “So, they have several technical and environmental advantages over their alternating current counterparts.”
Hinojosa indicates that it is necessary to take a look at the “Fringe Studies”, which have audiovisual information and an orientation guide. “In short, this is a document that addresses everything from conflicts to monitoring and evaluation of transmission lines.”
Finally, Gutiérrez expresses that the development of scalable technology should also be promoted and that it can be incorporated by different companies in the same field, practices that aim to improve the quality of service in our networks.