Tips for ACSR cable fault location

The occurrence of ACSR Cable 336.4 MCM  faults is accompanied by the laying and use of cables. The location of cable faults varies with cable laying methods, and the difficulty in locating is gradually increasing. Among them, the positioning and searching of bridges, tunnels, and trenches are relatively simple, while the direct-buried method is the most difficult to locate. When the nature of the fault is simple, a dedicated cable fault location device can be used to locate the fault within tens of minutes. When the fault is special, it often takes 4-5 days or even longer to locate the fault.
When using the echo method to locate cable faults, sometimes through the transfer of faulty phases and wiring methods, complex faults are often transformed into simple faults, and the fault location can be quickly determined to gain time for on-site line repairs. This is important for power supply departments. Significant.

Low-voltage power cables are generally multi-core cables. After a fault occurs in continuous use after laying, they generally show two-core and multi-core phase-to-phase or relative-to-ground short-circuit faults. Sometimes when it is detected that the fault waveform collected by a certain core is not ideal, consider switching the wiring to other faulty cores for fault waveform detection. Unexpected effects will often occur, and the collected and detected waveforms will become More typical and regular, so you can quickly determine the specific location of the cable fault point.
In the long-term on-site measurement process of cable customers, it is found that after the failure of small cross-section copper core direct-buried power cables (35mm2 and below) and aluminum core cables, there may be short-circuit and disconnection faults at the same time. During on-site detection, according to the nature of the failure of each faulty core The difference between the short-circuit fault and the disconnection fault measurement will often get twice the result with half the effort.

For low-voltage cable and  direct-buried power cables with extruded armored inner lining, most of the faults are caused by external mechanical damage. When the insulated core fails, the inner lining may have been damaged. When encountering a special cable insulation fault, it is difficult to use a professional cable fault meter to collect waveforms. Consider using the acoustic measurement method to directly apply high-voltage pulses between the steel strip and the copper shielding layer of the cable, which will often quickly fix the point.
During the on-site measurement process, we also found that when the low-voltage cable fault point is determined by the acoustic measurement method, when the high-voltage wire and the ground wire are connected between the bad phase and the metal shield or armor, the insulation resistance of the two shows a low-resistance metallic connection. State, the sound is very small, the probe cannot be used to listen to the fixed point, and the effect is not ideal. Through the actual listening side many times, it was found that the distance between the discharge ball gaps was appropriately increased, and the high voltage and grounding wires were reconnected between the two phases where the fault occurred. Often the discharge sound will become louder, and the fault point will be quickly determined. .

Overhead lines need “nine checks”

The inspection of overheadcable is one of the basic contents of the operation and maintenance of overhead lines. Defects can be found in time through inspections so that preventive measures can be taken to ensure the safe operation of the line. Usually, line inspectors should do “nine inspections” when inspecting overhead lines.
Check the pole tower. Check whether the tower is collapsed, tilted, deformed, decayed, damaged, whether the foundation is cracked, and whether the iron components are bent, loose, skewed or rusted. Check whether the wire length of the iron bolts or iron screw caps of the tower is insufficient, the screws are loose, the binding wires are broken and loose. Check whether there are bird nests and other objects on the tower.
Second, check the crossarm and fittings. Check whether the cross arm and fittings are displaced, whether they are firmly fixed, whether the weld seam is cracked, whether the nut is missing, etc.
Three check the situation along the line. Check whether flammable, explosive or strongly corrosive substances are piled on the ground along the line, whether there are illegal structures near the line, whether there are buildings and other facilities that may harm the line during thunderstorms or strong winds; check the poles and towers Whether to erect other power lines, communication lines, broadcast lines, and install broadcast speakers, etc.; check whether the lines are connected to electrical equipment without authorization.

Four check the route. Check the wires and lightning protection wires for broken strands, back flowers, corrosion, damage from external forces, etc.; check whether the distance between the wires, the ground and adjacent buildings or adjacent trees, sag, etc. meet the requirements, and whether the sag of the three-phase wire is unbalanced Phenomenon: Check whether the wire connector is in good condition, whether there are signs of overheating, severe oxidation, and corrosion.
Five check insulators. Check the insulator for cracks, dirt, burns and flashover marks; check the deflection of the insulator string and the damage to the iron parts of the insulator.
Six check lightning protection devices. Check whether the size of the protection gap is qualified and whether the auxiliary gap is intact. Check whether the external gap of the tubular arrester changes and whether the grounding wire is intact. Check whether the porcelain sleeve of the valve-type arrester is cracked, dirty, burned, or flashover marks, and the sealing is good. Check whether the down conductor of the arrester is intact, whether the grounding body is exposed by water washing, and whether the connection between the grounding down conductor and the grounding body is firm.

Seven check pull lines. Check the power cable for rust, slack, broken strands and uneven force on each strand. Whether there is any decay or damage to the cable pile and protection pile Whether the cable anchors are loose, lack of soil and sinking of soil irrigation. Whether the wire rod, wedge-shaped wire clamp, UT-shaped wire clamp, and wire-holding hoop are corroded, whether the nut of the UT-shaped wire clamp is missing, and whether the stop device of the turnbuckle is in good condition. Whether the pull cord is pulled into the wood pole at the binding place.
Switch equipment on eight check poles. Check whether the switchgear is installed firmly, whether there is any deformation, damage or discharge traces, whether the operating mechanism is intact, and whether the distance between the leads and the ground meets the regulations.
Nine check crossing points. Check whether there are new crossing points, whether the crossing distance meets safety requirements, and whether the original crossing points endanger the safe operation of the line. Whether the protective measures are perfect.

Main Types of Overhead Cable & Wire

Overhead power lines mainly refer to overhead electrical wires, erected on the ground, and are transmission lines that use insulators to fix transmission wires on poles standing upright on the ground to transmit electrical energy.

What type of wire is used for overhead?
The wires used in low-voltage overhead lines are divided into bare wires and insulated wires. According to the structure of the conductor, it can be divided into single-strand conductor, multi-strand conductor and hollow conductor; its common types are AAC/AAAC/ACSR/ACAR.
The bare wire is the main body of the overhead line and is responsible for transmitting electrical energy. Since the wires are erected on the poles, they must often bear the effects of self-weight, wind, rain, ice, snow, harmful gas erosion, and air temperature changes. Therefore, the wire is required not only to have good electrical conductivity, but also to have sufficient mechanical strength and good corrosion resistance.

(1). All Aluminum Conductor (AAC): This bare concentric-lay stranded conductor is constructed with a straight round central wire surrounded by one or more layers of helically layed wires. These wires are of aluminum 1350 and can be provided in different classes of stranding and tempers.

(2). All Aluminum Alloy Conductor (AAAC): This bare concentric-lay-stranded conductor, made from round aluminum alloy 6201 -T81 wires, is constructed with a central core surrounded by one or more layers of helically laid wires.
It was designed to attend the needs of an economic conductor for the applications on aerial circuit that require a larger mechanical resistance than the one of an All Aluminum Conductor (AAC), and a better corrosion resistance than the one produced by the aluminum conductor steel reinforced(ACSR). The conductors of Aluminum Alloy 6201-T81 are harder and have a better resistance to the abrasion than the conductors of aluminum 1350.

(3).Aluminum Conductor Steel Reinforced Conductor (ACSR) : This bare concentric-lay-stranded conductor is made from round aluminum 1350-H19 (extra hard) wires and round zinc-coated or aluminum-coated steel core wire(s) to be used as overhead electrical conductors.Used as bare overhead transmission cable and as primary and secondary distribution cable. ACSR offers optimal strength for line design. Variable steel core stranding enables desired strengthto be achieved without sacrificing ampacity.

(4).Aluminum Conductor Alloy Reinforced Conductor (ACAR)This bare concentric-lay-stranded conductor is made from round aluminum 1350-H19 (extra hard) wires and round aluminum alloy 6201-T81 core wires for use as overhead electrical conductors.It presents a higher mechanical resistance.

Overhead insulated cable is an overhead wire equipped with an insulating layer and a protective sheath. It is a special cable manufactured by a production process similar to that of a cross-linked cable. It is a new transmission method between overhead wires and underground cables.

Aerial bundled cables (also aerial bundled conductors or simply ABC) are overhead power lines using several insulated phase conductors bundled tightly together, usually with a bare neutral conductor. The conductor can be all aluminum, aluminum alloy or aluminum with a steel core, used for overhead power distribution as an alternative to bare conductor.


ABC cable used for low voltage overhead line transfer, structured by stranded aluminum conductor or aluminum conductor with steel core , both single core and multi-cores ,insulated by UV resistant XLPE.

Overhead ABC Cable Advantage:
ABC cable provide better level of safety and reliability ,lower power losses, easier to install ,less maintenance and operative cost.

  1. High reliability of power supply
    The use of overhead cables can greatly reduce various short-circuit faults (especially the common flashover faults of overhead bare wires). Compared with overhead bare wires, the failure rate is 4-6 times lower.
  2. Good power supply safety
    The use of overhead cables greatly reduces personal injury and death accidents due to electric shock.
  3. Convenient installation and maintenance
    Overhead cables can be erected on any kind of poles and towers, or along walls. Under special circumstances, they can also run through the bushes and be directly fixed on tree poles with hardware. It can be erected on a single circuit or multiple circuits on the same pole without requiring a wide “electrical corridor”.
  4. Reasonable economy
    Although the use of overhead cables is more expensive than the use of overhead bare wires, it is cheaper than ordinary underground cables. Therefore, although the one-time investment is slightly higher for the use of overhead cables, the operating cost will be significantly lower than that of overhead bare conductors based on other factors.

Laying method of overhead ABC cable 
A single conventional laying method. This erection method is to use the current conventional cement poles, iron accessories and ceramic insulator accessories with bare conductors, and erect according to the bare conductor erection method, which is more suitable for the area where the old line is reconstructed and the corridor is sufficient.
A special insulating bracket is used to suspend the wires for single laying. This method can increase the number of circuits erected, save the line corridors, and reduce the cost of the line unit.

How to Ensure Outdoor Cable Performance ?

Many users and installations are faced with the problem of cheap and efficient data transmission between buildings in the park environment. The choice of routing, transmission distance and application environment will all affect the choice of cable medium. Incorrect or inappropriate choice will result in a shortened period of wiring investment, and reinstallation will also cause the network system to stop running.
If it is an outdoor application, the fiber optic system is usually the choice for campus network connection. The real cost of optical fiber lies in the termination of optical fiber cabling system and optoelectronic equipment. When users only need to transmit 10Mbps or 100Mbps within a distance of 50 meters between buildings, optical fibers are generally not used.

Buying conventional Category 5 copper cables underground or laying overhead may cause transmission failure of a certain network along the wiring line. Therefore, choosing the existing outdoor direct-buried enhanced type cable will bring a cheap link. Before deciding to choose these outdoor LAN cables, you should fully understand their design.

Anti-moisture protection nets have been used in communication cables for many years. These aluminum polymer materials have overlapping seals as protection to reduce the penetration path of water vapor to prevent water from entering. However, an unprotected dry cable will need to suffer as long as six months to a year of liquefaction due to infiltration, and a dry cable with a moisture-proof protective net will be completely protected. The cable designed in this way is approximately similar to a foil-screened LAN cable, and it is easy to connect and use.

Therefore, the wiring system designer must consider the application environment, which includes the following environment and parameters that affect the cable:
1. Whether the cable is placed under the eaves; as long as the cable is not directly exposed to sunlight or ultra-high temperature, the standard LAN cable can be used. It is recommended to use pipes:
2. External walls; avoid direct sunlight on the walls and man-made damage;
3. In the pipe (plastic or metal); if in the pipe, pay attention to the damage of the plastic pipe and the heat conduction of the metal pipe;
4. For suspended applications/overhead cables, the sag and pressure of the cable should be considered. Which bundling method you intend to use. Whether the cable is directly irradiated by sunlight; laying directly in the underground cable trench, this environment is the smallest control range. The installation of the cable trench should be checked regularly for dryness or humidity;
5. Underground pipeline. In order to facilitate future upgrades, cable replacement, and isolation from surface pressure and the surrounding environment, laying pipes is a better method. But don’t expect that the pipe will always remain dry, which will affect the choice of cable types.

Factors affecting cable performance include:
1. Ultraviolet (UV)-Do not use cables without UV protection in direct sunlight. You should choose cables with black polyethylene or PVC sheaths, such as Brand-Rex’s 4 pairs of reinforced type 5 MegaOutdoor outdoor cable, with metal mesh moisture-proof protective layer and black polyethylene sheath, is suitable for most inter-building connections, whether it is overhead laying, ground installation or pipeline construction, it can be used:

2. Heat-the temperature of the cable in the metal pipe or trunking is very high. Many polymer materials will reduce the service life at this temperature. Black polyethylene or PVC sheathed power cable should be selected;

3. Water-Water is the real killer of LAN cables. The moisture in the twisted-pair cable of the local area network will increase the capacitance of the cable, thereby reducing the impedance and causing near-end crosstalk problems. If it is extremely effective to prevent moisture and water vapor, a protective layer of metal shielding net is required;

4. Mechanical damage (repair costs)-the repair of optical cables is very expensive, and at least two terminations are required at each discontinuity;


Grounding-if the shielding layer of the cable needs to be grounded, the corresponding standards must be followed;

The total length of the route (not only between the buildings)-Use outdoor-grade LAN twisted-pair cables between the buildings, and the total length should be limited to 90 meters.
For a network of 100Mbps or 1000Mbps, the laying distance cannot exceed this limit. If the laying distance is between 100 meters and 300 meters, optical cable should be selected.
The following simple experiments can be used to self-test whether the wiring investment is safe: use a 20-meter enhanced category 5 UTP cable to terminate at both ends; carefully remove the cable sheath at the midpoint of the cable to expose a small section of copper cable (1 cm ); Test the cable according to AN/NZSD standard; soak the cut part of the cable in water for 1-2 minutes, and then retest.