What Are Cable Lugs?

The cable connector is also called the cable head. After the cable is laid, in order to make it a continuous line, the segments must be connected as a whole. These connection points are called cable joints. The cable joints in the middle of a cable line are called intermediate joints, and the cable joints at both ends of the line are called terminal heads. The cable connector is used to lock and fix the incoming and outgoing wires, and it is waterproof, dustproof and shockproof.

According to the installation site, it can be divided into indoor and outdoor.

According to the production and installation materials, it can be divided into heat shrinkable (the most commonly used), dry pack, epoxy cast and cold shrink.

According to the core material, it can be divided into copper core power cable head and aluminum core power cable head.

According to the joint material, it is divided into plastic cable joint and metal cable joint. Metal cable connectors are further divided into porous metal cable waterproof connectors, anti-bend metal cable connectors, double-locked metal cable waterproof connectors, plastic hose cable connectors, metal hose cable connectors, and so on.

Its main function is to make the line unobstructed, keep the cable sealed, and ensure the insulation level at the cable joint, so that it runs safely and reliably. If the seal is not good, not only will oil leakage cause the oil-soaked paper to dry up, but moisture will also penetrate the inside of the cable, causing its insulation performance to decline.

Causes of connector heating

Some electrical installation builders often pay no attention to the installation when laying the wires

1. Connection of the conductor The connection of the conductor requires low resistance and sufficient mechanical strength, and no sharp corners can appear at the connection. The connection of medium and low voltage cable conductors is usually crimping. Pay attention to crimping:

(1) Select a conductor connecting tube with appropriate conductivity and mechanical strength;

(2) The fit clearance between the inner diameter of the crimp tube and the outer diameter of the connected core is 0.8 to 1.4 mm;

(3) The resistance value of the joint after crimping should not be greater than 1.2 times of the conductor of equal section, and the tensile strength of the copper conductor joint is not less than 60N / mm2;

(4) Before crimping, the outer surface of the conductor and the inner surface of the connecting pipe are coated with conductive glue, and the oxide film is destroyed with a wire brush;

(5) Sharpened corners, burrs, etc. on the connecting pipe and the core conductor should be smoothed with a file or sandpaper.

2. Internal semiconductor shielding treatment.

Where the cable body has an inner shield layer, the inner shield layer of the connector of the crimping pipe conductor must be restored when the joint is made, and a part of the inner semiconductor shield of the cable must be left in order to allow the inner shield of the connector on the connection pipe to communicate with each other. Ensure the continuity of the inner semiconductor, so that the field strength at the joint takeover is evenly distributed.

3. Treatment of external semiconductor shielding.

The outer semiconductor shield is a semi-conductive material that acts as a uniform electric field on the outside of the insulation of cables and cable joints. Like the inner semiconductor shield, it plays a very important role in cables and joints. The outer semiconductor port must be neat and uniform, and smooth transition with insulation is required, and the semiconductor tape at the cable connector is overlapped with the semiconductor shield of the cable body.

4. Treatment of cable reaction force cone.

During the construction, the shape and size of the reaction force cone are accurate and the potential distribution is the same on the entire cone surface. When making the cross-linked cable reaction cone, a special cutting tool is generally used, or it can be heated slightly with a fire, and performed with a fast knife. After cutting and basic molding, use 2mm thick glass to scrape, and finally use sandpaper to grind from thick to fine until smooth.

5. Metal shielding and grounding treatment.

The role of metal shields in cables and joints is mainly used to conduct cable fault short-circuit currents, and shield electromagnetic fields from electromagnetic interference to nearby communication equipment. Under operating conditions, metal shields are at zero potential under good grounding conditions. When a cable fails, It has the ability to conduct short-circuit current in a very short time. The ground wire should be reliably welded, the metal shield and armor tape on the cable body at both ends should be firmly welded, and the grounding of the terminal should be reliable.

6. Sealing and mechanical protection of joints.

The sealing and mechanical protection of the joint are the guarantee to ensure the safe and reliable operation of the joint. Moisture and moisture shall be prevented from entering the cable joints. In addition, joint protection grooves or cement protection boxes shall be installed at the joints. ^[2]

1. Temperature sensing cable. Place the temperature sensing cable in parallel with the cable. When the temperature of the cable exceeds a fixed temperature value, the sensing cable is short-circuited and an alarm signal is sent to the control system. The disadvantages of ordinary temperature-sensing cables are: destructive alarms, fixed alarm temperatures, incomplete fault signals, inadequate system installation and maintenance work, and easy equipment damage; analog line-type temperature-sensing cables can only use a certain segment as an alarm unit Therefore, it cannot accurately locate the alarm signal generated by a certain point.

2. Thermistor temperature measurement. The thermistor can be used to measure the temperature of the cable, but they are all analog outputs, which require signal amplification and A / D conversion to be received. Each thermistor requires independent wiring, the wiring is complicated and the thermistor is easy. Damage, large amount of maintenance, the sensor does not have self-check function, need to be checked often.

3. Infrared sensor type temperature measurement. Infrared sensing is to use all objects whose temperature is higher than absolute zero to continuously emit infrared radiation energy to the surrounding space. The size of the object's infrared radiation energy and its distribution according to wavelength are very closely related to its surface temperature. Therefore, by measuring the infrared energy of an object, it can accurately determine its surface temperature. Infrared sensing is non-contact measurement, so it has good security. The disadvantage is that it is affected by the object's emissivity, environment and aerosol during temperature measurement, and it has poor anti-interference ability.

4. Thermocouple type temperature measurement. The thermocouple needs to use a dedicated compensation cable for transmission signals, and the transmission distance should not be too long, which is not suitable for the actual situation of a wide distribution of cable heads; the thermistors are usually platinum resistors, which generally require three-wire transmission and balanced bridge output. The transmission distance should not be too long, and the ability to resist interference is poor.

5. Integrated circuit temperature measurement. There are many types of integrated circuit type temperature measuring elements.Among them, the current output type element has a large internal resistance and is suitable for long-distance transmission.It is usually small in size and can be sealed at the measurement point with anti-corrosion, moisture-proof and high-temperature-resistant thermal silica gel The external wiring is led by two wires to transmit data, but it is greatly affected by electromagnetic at the measured point.

6. Optical fiber distributed temperature monitoring. Optical fiber distributed temperature measurement system is a relatively advanced system. The temperature is measured by the back Raman scattering temperature effect generated by the laser pulse transmitted in the optical fiber. The latest fiber-optic distributed temperature monitoring system can allow fiber-optic loop lengths of up to 12 km and measurement accuracy of ± 1 ° C. The advantage of using an optical fiber distributed temperature monitoring system is that it can accurately locate the hotspots along the cable, can display and record the temperature change curve trajectory, and can show the location of hotspots on the line. This system requires the location of the hot spots to be determined when installed, but relies on pre-manufactured monitoring equipment and optical / thermal data processing, which not only increases additional equipment investment, but also requires new equipment to face maintenance issues. ^[3]