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modes such as damage or overload of 6-35 kV power transmission lines occur, their elimination
time is long and therefore many adverse events are observed;
In contrast to rural power supply, urban and large industrial enterprises are relatively
convenient to operate due to the short length of supply lines for shops and other departments from
several substations (proximity and mainly the use of cable lines). Reduces
the time to identify the
location of the injury and repair it).
However, the operation of agricultural overhead transmission lines is a bit more complicated.
For example, if a single-phase ground fault (6-35 kV networks) occurs in a feeder, a small
operational team will be required to inspect each line according to the schedule. In general,
accidents on 6-35 kV transmission lines can be divided into two groups: natural-climatic [6] and
accidents caused by exploitation [6, 2].
According to today's
statistics, single-phase ground faults on 6-35 kV transmission lines,
which account for 75% of the total damage, are a dangerous problem [4].
Rapid detection of single-phase grounding and thus taking measures to ensure long-term
disconnection of electricity consumers is a topical issue today.
In general, it is not possible to detect single-phase ground faults in 6-35 kV neutral insulated
or compensated overhead lines in a timely manner and to locate the fault using conventional relay
protection and automation devices [7]. Due to the fact that the connection group of 6-10 kV
overhead lines is connected by Δ/Δ method, the method of determining the short-circuit location
of single-phase grounding
used in high-voltage lines, as well as the use of installed devices is
inefficient.
Therefore, it is advisable to inspect the entire line using portable electrical devices [8] to
determine the point of damage. Remote location of damage on overhead transmission lines is
usually done when the line is off. Such detection methods are divided into the following groups:
- impulsively,
- wavy
- nodal [8].
There are a number of limitations to all methods. For example, the pulse method is applied to
only one dead line, the wave method is used for cable lines and tested under high voltage, the node
method is tested on both sides of a single dead line [9]. New methods for determining the location
of a single-phase grounding device are currently being actively used in overhead lines [7] that are
sensed by the electromagnetic field around the line [10], but the detection of a single-phase
grounding is still relevant. To reduce the time of emergency response, the method of remote single-
phase ground detection is widely used today. The operative inspectors
receives a single-phase
ground signal, performs measurements to determine the location of the connection, and performs
search operations. The following work is performed to determine the location of a single-phase
ground connection on an overhead transmission line:
In this case, the mode of remote location of damage on overhead transmission lines involves
the implementation of the following sequences [4, 8]:
1)
records data on single-phase grounding (unselective signaling);
2) identify the damaged line;
3)
Identify the damaged section of the line (
distance)
4) Determines the point of injury (topographic or OMP along the way).
5) The non-selective signaling device records the single-phase ground connection generated
in the line:
a) This reduces the insulation resistance; The phase voltage between the damaged line and
the ground decreases;
b) A zero sequence voltage is occured [7, 8];
c) The detection uses the sequence of deleting lines;
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Pic.2. Zero-Sequence Ground Fault No Trip Test Example Test Procedure
d) When the faulty line is disconnected, the zero-sequence voltage is lost (or the ground phase
voltage is restored).
The use of selective signaling devices for maintenance and repair of existing 6-35 kV
distribution lines is yielding good results. In particular, the selective
signaling devices used in
developed countries can be divided into the following groups:
1.
100 Hz high harmonics were used,
2.
to a loaded current with a frequency of 25 Hz,
3.
to the emergency components of the symmetry of current and voltage,
4.
Signaling devices based on the use of current and time feedback characteristics .
