Importance of Using Tested Accessories for AB Cable Power Distribution Lines
Aerial Bundled Cable (ABC) is an innovative concept for Over Head (OH) power distribution. When compared to the conventional bare conductor OH distribution system, ABC provides higher safety and reliability, lower power losses, stability in voltage regulation and ultimate system economy by reducing installation, maintenance, and operation cost.
The construction and mechanical properties of the AB Cable system originate from the HD 626 standard. The AB Cable itself is available in several constructions including the Insulated Messenger system, the Self-Supporting System (2 core or 4 core), and the uninsulated messenger system. The commonality amongst all these systems is that the current-carrying high strength aluminum alloy phase conductors are insulated with PE or XLPE material and then twisted around the messenger cable (insulated messenger and uninsulated messenger systems) or twisted amongst themselves (self-supporting system). You can read more about the cable construction of AB Cables in our article here: Components of an LV AB Cable Distribution Line
As mentioned in our article on the ‘Lifespan of ABC Lines in Moist / Wet Environments’, the most influential factor in aging ABC cables is the use of non-standard cable connectors, accessories and clamps because they allow water ingress which slowly damages the cable.
Thus, as with any power distribution system, if the goal is to minimise downtime of the line and extend its lifetime, then the accessories that are used along with a LV AB Cable system should be tested according to the relevant testing standards. The following article goes into detail on the testing standards and their requirements for the various accessories and components used along with a LV AB Cable Power Distribution system.
Testing of AB Cable Accessories
The testing of Accessories to Low Voltage AB Cable systems can be broken down into 3 major testing buckets:
- Mechanical Testing
- Electrical Testing
- Environmental Testing
The major products that are used as accessories to Low Voltage AB Cable systems are as follows:
Suspension Clamps are used along with a bracket or other supporting hardware to suspend and grip, without damaging, a LV AB Cable system. As shown in the images below, they can also be used in conjunction with insulation piercing connectors to provide service connections by tapping the mainline.
Anchoring Clamps are used along with a bracket or other supporting hardware to strain the messenger or cable to terminate the line or to provide an angle of up to 90 degrees for the LV AB Cable system without damaging the cable's insulation.
Service Clamps are used along with a bracket or other supporting hardware to strain the insulated service conductor of a LV AB Cable system to provide turn angles, anchor service lines on walls, or support tap-offs for the service lines without damaging the cable's insulation.
Insulation Piercing Connectors (IPC’s)
Insulation Piercing Connectors are used on all AB cable systems (messenger wire & supporting system) to take a tap connection. This tap can be used to continue the line, distribute the line, used in street lighting or in-service connections to households. The design allows the connection to be completely sealed against any water ingress, thus acting as a waterproof connector
Midspan Joints or Insulated Bimetallic Lugs
- Pre-insulated midspan joints are used for the insulated AB cables phase or neutral to join two cables.
- Pre-insulated Bimetallic lugs are used for insulated AB cables phase or neutral to terminate the cables.
Low Voltage Distribution Boxes
A distribution box is a key component of an electrical supply system. From a single, common enclosure, it helps to divide an electrical power main feed into multiple subsidiary outgoing connections that can be used to provide electrical connections to individual homes, buildings, or other requirements.
In general, these products are tested per the following testing standards:
|Suspension Clamps||NFC 33 - 040 / BS EN 50483|
|Anchoring Clamps||NFC 33 - 041 / BS EN 50483|
|Service Clamps||NFC 33 - 042|
|Insulation Piercing Connectors||NFC 33 - 020 / BS EN 50483|
|Midspan Joints & Pre-insulated Bimetallic Lugs||NFC 33 - 021|
The clamps and connectors mentioned above undergo load tests, slip tests & endurance tests to ensure that the device can withstand the load conditions of the AB Cable in real-world scenarios without slippage. The midspan joints and pre-insulated bimetallic lugs are put through their mechanical tests after the crimping of the products.
The insulation piercing connectors also have to make their connection without causing damage to the conductor. Thus, the tap and main conductor are put through a tensile strength test after the application of the IPC to ensure that cable strands have not been cut through the application of the product which would weaken the conductor.
The clamps and connectors are put through a 6 kV test to ensure that none of the components of the product become electrified during the test. The reason for this test is to ensure the safety of the power line worker or any other person who may accidentally touch the product while the line is live.
As mentioned earlier in the article, the most influential factor in aging ABC cables is the use of non-standard cable connectors, accessories, and clamps because they allow water ingress which slowly damages the cable. Since the primary function of the Insulation Piercing Connector is to pierce through the XLPE insulation covering the aluminium conductor to form an electrical connection, water ingress on an AB Cable is most likely at the location of the IPC if non-standard products are used. Axis IPC’s are tested to a 6kV underwater test to ensure a waterproof connection without any electrical leakage.
Since these products are used on outdoor overhead power distribution systems, the clamps must undergo corrosion & climatic aging to ensure that the clamps can withstand the harsh conditions that exist outdoors such as direct sunlight, rain, etc.
Low voltage distribution boxes for AB Cable Systems are a complex product that requires testing as per many different standards including IS 14772, IS 8623, UL 746C & IEC:60695-2.
The distribution boxes are put through several mechanical testing including impact tests, IP tests, glow wire tests and flammability tests. The purpose of the impact tests is to ensure that the product is not brittle and can endure some physical damage in the outdoor environment. IP testing ensures safety from water and dust ingress. The glow wire and flammability test are both conducted to make sure that, in case of a fire, the box is able to self-extinguish a fire and not propagate the fire.
Axis Low Voltage Distribution Boxes are also put through electrical tests where they are tested for surges from 2 kV to 4 kV. The purpose of the test is to ensure that there is no leakage current and therefore no chance of a human suffering an electrical shock in case they touch the product. This test also showcases that the box would be intact without any failure in case of an electrical surge.
As with all the other products in the system, these distribution boxes are used outdoors and are thus tested to check for the effect of UV rays on the product.
At Axis, we conduct an intensive system of testing for all our products as per the appropriate international testing standards during design, validation, and final production. We are confident of our products and offer them to our customers with the assurance that our products will not fail on the line. It is paramount that contractors use tested products along with their AB Cable systems. To learn more about Axis’s range of tested AB Cable Accessories, please read our catalogue here or contact us through this form.
Along with using the correct products, it is also important that the products are installed correctly. To watch how to correctly install our range of AB Cable Accessories, please watch our series of videos here.
You can read more on the factors that impact the ‘Lifespan of ABC Lines in Moist / Wet Environments’. You can also learn more about the ‘Components of an LV AB Cable Distribution Line’.