Transmission lines are one of the most important power system
components, responsible for delivering energy from generating
plants to consumers. Those lines may present a high failure rate
since, in most cases, they cover large distances and are exposed
to different climate conditions.
The distance protection method is one of the most used techniques
for preventing damages that can be inflicted to transmission
lines. The conventional distance protection is based on
impedance measurement elements that estimate the line impedance
from the relay to the fault point using voltage and current
phasor quantities. The ANN-based algorithms have been developed
as an alternative to conventional methods, since they present very
promising results with regard to precision and operating time.
Refs. [1–7] present ANN-based algorithms that act as classifiers,
indicating whether the fault is located inside or outside the protection
zones. Refs. [8–10] present ANN-based algorithms that act as
function approximators which point out, directly or not, the fault
distance.The algorithms presented in [4,6,10] are based on the phasor
quantities of voltage and current fundamental components, obtained
via DFT. Those components are used as inputs for their
ANN. The other algorithms but [9] are based on voltage and/or current
samples. Those samples are used as inputs for their ANN.
The ANN-based transmission line protection methods described
in [1–10,16] surely present limitations once they are trained to correctly respond only to a particular transmission line. Therefore,
considering such methods, it shall be necessary to re-create a
new simulation environment set containing hundreds or thousands
of fault cases for each change made at the transmission line
characteristics. Besides that, it shall be also demanded to repeat
the whole ANN training process, resuming the major drawback
presented by those algorithms.
It is proposed then the development and implementation of a
new ANN-based algorithm, suitable for protecting any transmission
line, regardless of its characteristics (such as tower geometry,
type of conductors, length and voltage level). This new ANN-based
algorithm does not need any topology adaptation or ANN parameters
adjustment when applied to different transmission lines [17–
19]. It was developed to exceed the existing limitations of previously
developed ANN-based algorithms, allowing it to be implemented
in commercial relays.
This ANN-based algorithm operates as a function approximator,
estimating the line impedance from the relay to the fault point.
Similarly to conventional distance protection relays, this algorithm
is also based on six impedance measurement elements, which estimate
the line impedance, based on current and voltage samples
provided by CTs and VTs, respectively.