Checking the pulse of transmission lines

An industry analysis on the importance of testing and checking the health of power transmission network

The power transmission network plays a vital role in the functioning of power sector and any failure in the transmission network has the potential to disrupt power evacuation and hamper power supply to end-consumers. Hence, timely testing of transmission lines is of high importance for maintaining reliable power supply. Here, experts from the industry talk about the importance of testing and checking transmission lines and network.

Testing & checking defects of transmission lines
For overhead lines, fault identification is simpler and online tests are used for testing purposes. Although power cables offer many benefits, the time and costs involved in addressing disruptions or faults in underground cable systems are substantial.

Parag Yelegaonkar, Manager – Business Development, Testo India Pvt Ltd, says, “Any malfunction or interruption in power transmission and distribution is often preceded by thermal warming. Overhead power lines in high-voltage systems, switch yards, and transmission lines must be regularly checked for routine maintenance for thermal anomaly detection purposes.”

Typically, these locations are difficult to access. Anomalies like hotspots are not visible easily. For such locations and all other locations, testing and checking can be done by thermal inspection as a predictive maintenance tool. Yelegaonkar suggests using a thermal imager through which thermal anomalies can be tested with non-contact method and from a safe distance, without endangering the user or without needing to shut down the entire power transmission network.

Describing the online fault location system, Nilay Ray, AGM (Product Specialist Group), SCOPE T&M Pvt Ltd, says that it is based on travelling waves, which are voltage and current surges propagating along the power line, arising from power system disturbances such as fault, switching operations, and lightning. “The travelling wave fault locator determines the distance to fault by measuring the time for the surge to travel from the fault to the substation bus,” he adds.

He says that the travelling wave fault locator system can accurately locate faults in transmission and distribution power lines. Distance measurement errors are less than 50 m independent of line length, and are free from various factors, which can affect fault location accuracy of traditional impedance measurement methods.

Commenting on distance relays, JayantDeo, Engineer (Product Specialist Group), SCOPE T&M Pvt Ltdsays, “The fault location of distance relays works on theimpedance method. It calculates the impedance from the relay to the fault point to determine the distance to the fault.

There are a lot of factors affecting its accuracy, for example, CT and VT errors, fault resistance, the impedance of the return path (zero sequence impedance), line configuration etc. Therefore, its accuracy is less as compared to TWFL. It is only suitable for uncompensated AC lines; therefore, its applications are limited. Distance relay has zone protection up to 80 per cent of the line. The return path of the distance relay is not homogenous, so inaccuracies occur.

Unlike the impedance measurement method, which is limited to locating short-circuit faults in AC power lines, the travelling wave technique can be used to measure the distance to fault in all kinds of power lines.

T&M instruments for smart power network
Consistent testing and measurement in power plants is very critical throughout its life cycle. Yelegaonkar says that during the installation phase, the T&M equipment are very much required and used in setting up benchmark parameters for various process tags.

“One can derive the optimum efficiency of each power plant equipment and rWecord the measured parameter values by using T&M equipment for future use and all kinds of troubleshooting jobs” he says. About the enhancement of life of any power plant, a small lapse in preventive and predictive maintenance can lead to highly unsafe conditions and, thus, results in loss of huge revenue and system breakdown, which can be easily corrected with the advanced T&M equipment.

“As a matter of fact, the latest trends and technologies that we are witnessing are turning out to be so beneficial. Smart solutions and automated processes are all over,” says Yelegaonkar. “Considering our latest and most advanced solutions for instance, our electrical Instruments are very distinct and unique in their features. They are excellent instruments to inspect the electrical components and circuit failure threats.”

Overhead power lines and transmission lines must be regularly checked for routine maintenance for thermal anomaly detection purposes
Parag Yelegaonkar, Manager – Business Development, Testo India Pvt Ltd

Travelling wave fault locator system can accurately locate faults in transmission and distribution power lines
Nilay Ray, AGM (Product Specialist Group), SCOPE T&M Pvt Ltd