Amazing High Voltage Power Line and Health Risk

⚡ Are High Voltage Power Lines a Risk to Human Health?

Background: The Debate Over EMF Exposure

Concerns about electromagnetic fields (EMFs) and their impact on human health first gained attention in 1979. Since then, scientific debate has continued without a clear consensus.

• 👨‍🔬 One group argues that prolonged exposure to residential power lines may increase the risk of cancer in children and young adults.

• 🧪 Another insists that ambient EMF levels are too weak to pose serious health threats.

Despite extensive studies, definitive evidence remains elusive. Nonetheless, numerous articles suggest that high-voltage transmission lines may contribute to health issues ranging from headaches and skin disorders to cancer.

How Does Superconductor Work?

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What is a superconductor? 

We want to know how superconductors work and what a superconductor material is. The material that achieves the superconductivity property is known as a superconductor. Now, the question is, what is the superconductivity property? How can a material achieve the superconductivity property?

This phenomenon was first discovered in 1911 by Heike Kamerlingh Onnes, and it has since led to various technological advancements and applications.

Commissioning and Test Procedure of Power Cable and Equipment

Testing methods for power cable insulation depend basically on the type and material of cable insulation. Cross-linked Polyethylene (XLPE) is now spreading widely for power cable insulation at the rated voltage of 66 to 500 kV worldwide.

Quick and easy understanding of commissioning tests for transmission lines and major equipment. Here specially focused on the underground power transmission line, underground cable megger testing, cable fault location and main causes of cable fault, and some manufacturing faults. You also find some megger test procedures for transformer or circuit breakers, or common methods for insulation tests and megger tests.   

To see the slide view, click the link below,

Electrical Power Cable Short Circuit Current Capacity

How Calculate Cable Short Circuit Current from Short Circuit Current from Table?

You may find the short circuit current for a particular type of cable for a specified period of time from your cable manufacturer’s provided catalogue. For example the below table is showing different sizes from 16 square mili-meter to 2500 square mili-meter of cable in first left column and time duration from 0.1 second to 5 second in next 10 columns.

Cable Basic Parameters Resistance, Inductance and Capacitance

Cable Basic Parameters Resistance, Inductance, and Capacitance

What Happen If Cables Placed In Magnetic Metal Conduit

What Happens If Cables Placed In Magnetic Metal Conduits 

Do we know what happens if cables are in a magnetic metal conduit? Yes, at least we know that in any circumstances, the individual phase of an AC (alternating current) circuit is in a separate magnetic metal conduit. 

Manufacture Of Electric Power Cables and Chronological Development

Underground Power Cable Installation

This Video Clip shows how to install underground power cables. 

This is not used in modern equipment and technology.

You could see the initial technology for the oilfield underground power cable and its installation and erection procedure. 

Why is Powder Used inside Cables?

Fig-Different Types of Cables

The Reason Why Various Powder Used Inside Electrical Cables

You may notice some white powders are used in electrical current-carrying power cables. Obviously, some questions arise in your mind about why they are used.

 So let's discuss why is white powder used inside electrical power cables. Hope this article will give questions' answer.

Various powders are used inside power cables for various reasons according to the requirement.

Partial Discharge in HV & EHV Power Lines

A video clip for Brug cable PD Measure

Partial Discharge in High and Extra High Voltage Lines

Partial Discharge (PD) is very important for Underground Power Cables. If you work with Power Cable, you must know why and where Partial Discharge is present. It will help to take action at the right place at the right time. 

Why Need Power Cable Test After Installation

Power Cable Test After Installation

HV/EHV power cable testing in the field after installation is a common requirement for cable users. Meanwhile, MV-normal voltage, HV-high voltage, and EHV-extra high voltage power cables are carefully tested by the manufacturer before consignment with AC-alternating or DC-direct voltage. 

ARMOUR EARTHING ASSEMBLING FOR SINGLE CORE CABLE

Armour Earthing Assembly for Wire Armour Single Core Cable

33kV Cable Earthing System

Cable armour earthing is important for medium voltage (MV), high voltage (HV) and extra high voltage (EHV) system. 

Our discussion on this article is limited only single core plastic or paper cable wired armour earthing procedure for medium voltage (MV) system or 7.2 kV to 36 kV ranges.

The crystal clear step-by-step assembly figure shown the complete procedure of earthing system for wired armour cable.

If you follow the shown 9 step carefully, we hope you will be able to assemble the cable armour earthing successfully.

9 Step to Earth Cable Armour  

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1. First of all remove the over-sheath according to the dimension given the appropriate manufacturer Installation Instruction, Remove the armour according to dimension as per shown in the drawing. Clean the end of the over-sheath for a length of 250 mm.
2. Then slide the outer sleeve over the cable, and disassemble the clamping rings. Slide one clamping ring lug-downwards over the cable as shown in the figure 2.
3. Following the figure no-3 spread the armour wires as shown in the drawing and screw the other clamping ring loosely to the lugged clamping ring.
4. Install the termination in accordance with the Installation Instruction of termination manufacturer. Pass the end of the earth lead down through the clamping rings and connect it to one lug of the clamping ring. Tighten the clamping rings, refer to figure no-4.
5. With a small overlap and slight tension wrap two layers of sealant tape round the overs-heath for a length of 50 mm, just below the armour wire ends. Wrap two layers of sealant tape round the earth conductor so that it will be just below the armour wire ends. Attach the earth conductor to the other lug of the clamping ring as figure-5.
6. As shown in figure-6, bend the armour wires back and bind the ends to the over-sheath with a wire binder or plastic tape. noted that all sharp wire ends must be covered with plastic tape.
7. With a slight tension and small overlap wrap two layers of sealant tape over the lower end of the termination for a length of 50 mm.
8. Position the top end of the outer sleeve level with the top of the sealant tape. Shrink it into place starting at the center. Shrink the lower end first and work towards the upper end.
9. Yes, you have done; installation of earthing assembly for armour is completed.

This is the basic instruction for cable armour earthing, to do it physically you must follow the manufacturer installation instruction and necessary safety code. If it is helpful, then share with others to help them. 

Thermosetting and Thermoplastic: Cable Insulation

Thermosetting and Thermoplastic:  Cable Insulation

PVC-insulated cables are not going to be called pvc cables anymore they are thermoplastic insulated cables and rubber cables are thermosetting! The use of the terms thermoplastic and thermosetting is the solution to the problem of an ever increasing number and variety of materials and blends available for the manufacture of cables. 

Underground Power Cable Site Test after Installation

Fig- Cable High Voltage Testing Kit

Site Test or Pre-commissioning Test Just after Underground Power Cable Installation

Many cable failures are the result of poor installation practices; so, all new installations should be thoroughly tested before they are put into service. Since the cable itself will have been tested at the factory, on-site testing of newly installed cables focuses on identifying localized problems that have occurred during installation. 

Site test after installation of the underground power cable is required to confirm that the line is installed correctly and there is no damage during laying.

POWER CABLE TERMINATION AND SEALING

Power Cables Termination and Sealing End Requirements

The servicer should terminate and connect up the power cables in accordance with diagrams or details approved by the employer Engineer. 

Considering the following requirements, power cable along with others controlling and communication cable sealing end should be terminate in an adequate manner.

Underground Power Cable Termination Coupling With Over Head Line

High Voltage test for Power Cable

High Voltage Test Guide for Power Cables

A complete high-voltage test guide for power cables is essential for both cable users and contractors to get a clear idea about cable pre-commissioning and commissioning. 

PARTIAL DISCHARGE TESTING OF POWER CABLE

Partial Discharge (PD) in Electrical Power Cable:

Why PD?

No matter way where you are an engineer or a technician for electrical power cable, you need a piece of pretty good knowledge about Partial Discharge or shortly PD to understand your cable life or the possibility of unwanted cable faults. You may gather knowledge about PD by watching video clips on YouTube or reading a blog or article about PD.

Introduction of Partial Discharge (PD):  

Partial discharge (PD) is one of the most important factors for a power cable system. The partial discharge measurement methods of assessing the quality of the insulation of power cable systems, especially for extruded insulation materials.

Where Partial Discharge Occur:

We can think of partial discharge for cable systems from two major points of view:

01. Partial Discharge within the whole cable

02. Partial Discharge in an individual              location

Partial Discharge Measurement:

 

Normally major factory test carried out on the insulation of the whole drum of extruded cable is the partial discharge test. This is usually done at power frequency, but can also be carried out at very low frequency and at some voltage significantly higher than normal working voltage to ground. PD test is a very sensitive method to find out very minor failures such as little void or skip of insulation layer during manufacturing time.

But this factory test is not sufficient for the end users of the cable systems, during cable shipping, cable installation, cable jointing, and termination; cable insulation may damage or crack. Minor damage or crack is not possible to find out during commissioning or energizing time. After a little longer time this defect increased slowly and finally cracked. By statistics from the cable systems, most of the cable faults occur in cable jointing and termination point.

For Better Results:

So it is better to observe the magnitude and phase of the partial discharge signals and how they vary with increasing and then decreasing test voltage, results will disclose information on the type and position of the defects and their probable effect on cable life.

Finally in conclusion we can say, if the cable system can be tested in the field to show that its partial discharge level is comparable with that obtained in the factory tests on the cable and accessories, it is the most convincing evidence that the cable system is in excellent condition.

Recycling of Underground Power Transmission Line

What happened to Underground Power Cable Line after it finished Lifetime:

What will happen to the underground power transmission line at end of service life, the cable can be recovered for recycling or left in place forever.

In a conventional overhead power transmission line, every part of the material including the conductor is easy to recollect and recycle.

Direct buried cable is not so easy to recollect from 1.5-meter deep earth. Still, lots of oil-filled cables which already buried, and we can’t just leave them in place after the end of their service life, they are containing some hazardous materials, leaking oil to the vicinity for a long time!

The good news is that modern special graded XLPE cables replace older oil-filled cable technology, polyethylene which has cross-linked molecules to allow extremely high temperatures without melting.

Typically each circuit line has 3 conductors and the amount of copper up to 25 tons per kilometer for a larger core. This hues amount of copper can recycle into the same graded copper which can recover plant costs and keep a positive footprint for carbon-di-oxide emissions.

During planning and designing a new underground power transmission line project, it should consider the recycling of cables. Route line selection and laying procedure should be well-matched to cable recycling in the future. 

Cable Parameters: Insulation Resistance,Charging Current, Dielectric Losses

Cable Parameters: Insulation Resistance, Charging Current, Dielectric Losses

Before we formulated cable basic parameters resistance, inductance, and capacitance, now we will try to 3 more parameters like Insulation Resistance, Charging Current and Dielectric Losses.

Cable Insulation Resistance:

Using the following formula you can calculate insulation resistance in mega-ohm per kilometer of cable, to do this you consider the insulation material, diameter of cable including a semiconductor layer, and the diameter of the insulated core.

R =K In (D/d )  MΩ/km

Where

R = Insulation resistance in MΩ/km;

K = Constant depends on the insulation material;

d = Diameter of the conductor in mm including the semiconducting layer;

D = Diameter in mm of the insulated core;

MΩ- mega ohm, km- kilo meter, mm- mili meter.

Cable Charging Current:

The charging current is the capacitive current that flows when AC voltage is applied to the cables as a result of the capacitance between the conductor and earth, and for a multi-core cable in which cores are not screened, between conductors. The value can be calculated from the following equation.

IC = Uo ωC 10^-6   A/km

Where

IC = Charging current in Ampear/km;

Uo =Voltage in volt between phase and earth;

ω= 2 π f (π=22/7, f= frequency in hertz) Hz;

C= Capacitance in micro-farad per kilo-meter to neutral;

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Cable Dielectric Losses:

To calculate the dielectric losses of an AC cable are proportional to the Capacitance, the frequency, the phase voltage and the power factor. The value in watt per kilo-meter per phase can be calculated from the following equation.

WD = 2 π f C Uo² tanδ 10^-6   watt/km/phase

Where 

WD = Dielectric losses in watt/km/phase;

f = Frequency in hertz;

C = Capacitance in micro-farad per kilo-meter to neutral;

Uo = Voltage in volt between phase and earth;

tanδ=Dielectric power factor.

High Voltage DC Test is Killer for XLPE Insulated Power Cable

Fig- Formation of Electric Tree on XLPE Cable Insulation

High Voltage DC Test is Killer for XLPE Insulated Power Cable

The high-voltage DC (Direct Current) test carry out actually confirm the cable is capable to take the pressure. AC (Alternating Current) test instate of DC test can do if anyone interested. The problem is AC high voltage arrangement at the site is not physible to do. 

In operating conditions cables will operate the AC system, so AC high voltage test is no problem for it, rather AC is better than DC. Repeating the DC high voltage test may internal injure the cable that may cause cable failure in the future.

Why High Voltage DC Test is Danger for XLPE Insulated Power Cable?

The high voltage DC test is alternately referred to as the Hi-Po test. The high voltage DC (Direct Current)  testing method is performed for a long time on cable insulation systems, especially for field tests which are broadly known as SAT (Site Acceptance Test) for users and contractors. 

But recent research has shown that DC testing is the cause of certain types of defects and that it can make worse the deteriorated condition of some aged cables insulated with extruded dielectrics and affected with electrical-tree and water-tree. That’s why our article question “Is High Voltage DC Test Killer for XLPE Insulated Cable”.

LVDC or Low voltage DC testing is covering voltages up to 5 kV and HVDC high voltage dc testing covers voltage levels above 5 kV.

Type of DC Hi-Po Test:

DC Withstand Test: DC withstand test is a Hi-Po test where the voltage at a prescribed level is applied for a prescribed duration. The cable system will be considered acceptable if no breakdown occurs.

Leakage Current Tests: 

The leakage current test is a Hi-Po test with the function of time where the total apparent leakage output current is recorded to a prescribed voltage level. Not the absolute value, but the variations of leakage current with time is recorded which presents the diagnostic information of the cable system.

Voltage Test: 

The voltage test is also known as Leakage Current Tip-up Test where voltage is increased in small steps while the steady-state leakage current is recorded until the maximum test voltage is reached.  The relationship graph between current and voltage denotes whether the insulation system is defective or not.

Weak Points of DC Hi-Po test for Power Cable:

• This test is blind to certain types of defects, such as clean voids and cuts. 
• May not replicate the stress distribution existing with power frequency ac voltage. The stress distribution is sensitive to temperature and temperature distribution.
• May cause undesirable space charge accumulation, especially at accessory cable insulation interfaces.
• May adversely affect the future performance of water-tree-affected extruded dielectric cables.

Though the DC Hi-Po test is simple and easy recently experts are thinking DC high voltage test keeps some signs that bring bad effects for cable at age. Consequently, we can say the above-mentioned disadvantages of the DC Hi-Po test turn themselves into a killer for XLPE insulated power cable.

Underground Cable Installation Key Activity

Underground Cable Installation Key Activities that should be Followed at Site

Installation of Underground Cables:

Before installation of underground cables in a nice and perfect way it is necessary to consider some points carefully like the excavation of cable trenches, cable laying, cable joint bay and jointing, termination at both ends and back-filling the cable trenches and reinstate the roads, then testing and commissioning for final energizing the cable line.

To ensure the best quality work must engage the qualified personnel who have sufficient knowledge and experience in the construction of underground cable for each part of the work. For dedicated project work, it is important to keep in mind taking appropriate approval from the employer or concern authority before the execution or installation of the cable.

Cable Drum Handling Procedure:

Cable drums shall be unloaded handle and in an approved manner on the hard and well-drained surface so that they must not sink. 

In no case shall the drum store flat i.e. with flange horizontal rolling of drums shall be avoided. For unreeling of cables, the drum shall be mounted on suitable jacks or on wheels. 

All possible care shall be taken during unreeling and laying to avoid dusting twists, kinks or sharp bends.

Cable Bending Radius:

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Cable bending radius is not the same for all sizes and types of cable. 

So keep in mind to follow the bending radii for cables as per the manufacture’s recommendations. 

The cable trench, especially in bending points, should prepare carefully to comply with the manufacturer's instructions and it should be strictly adhered to and a necessary conducting medium shall be provided over the cable outer sheath for checking the healthiness of the outer sheath applied.

Cable Trenches and Cable Joint Bay:

Cable trenches may be constructed for directly buried cables or concrete ready-made trench inside the compound as per employer requirement. 

For cable trench, some key points like road crossing, rail-line crossing, existing power line, communication line or other utilities line crossing should be considered as per international or local standard.  

For direct buried cable trench depth may vary site to site, normally an average depth of 1.5 meters from finished ground level for a typical 132kV underground cable. 

Important for cable trench is sieved sand bedding, riddled soil cover, concrete protective covers backfilling and compacting, route marker and joint marker.

Location of cable joint bay should consider the less traffic, road crossing, water storage, easy access etc.

Cable Laying Formation:

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Cable laying formation may various types, very commonly used formation types are trefoil and flat formation.

 Cable Earthing and Bonding:

Earthling of cable metallic sheath with the cross bonding system and the sheath/screen bonding to the earth through disconnecting type link boxes at straight through joints and both end of cable terminations to avoid any induced voltage is also very important for underground cable system

Finally considerable for the system of cable jointing and termination work should be carryout by experienced joiners who shall have adequate skill and experience in jointing and termination for specified types and voltage grade of cable.