UNDERGROUND CABLE'S EMF

ACTIVITY ON 23//4/10

STUDY OF POWER FREQUENCY MAGNETIC FIELD FROM UNDERGROUND CABLES

This study conducted by :
(1) EMF Research Group, College of Engineering, UNITEN
(2) Tashia Marie Anthony

- this project purpose is actually to evaluate magnetic field from underground cables.

- Magnetic field from underground cables generally affected by a number of variables including :
i) magnitude of phase current
ii) distance of cables from ground
iii) phase configuration
iv) lateral distance from underground cables

Magnetic Field measurement
- this test was done on existing underground cable system in Putrajaya at the following locations :
--> PPU PJ13 (Alam Warisan)
--> PPU CJ16
--> PMU Cyberjaya North

* PPU PJ13 & PPU CJ16 cable laid in cable ducts. PMU CBJN were direct buried cables

Measuring Equipment

- Simulation Software
--> EMCALC 2000 (UNITEN)
--> CymCAP (TNBR)

- Site measuring equipment
--> EMDEX II meter
--> Linear Data Acquisition (LINDA) wheel

EMDEX II meter

LINDA Wheel

Cable Route

Magnetid field measurement

* EMDEX II records data at a fixed rate, walking slowly with the LINDA wheel will produce more detailed measurements over a short distance, while walking quickly will produce more generalized measurement over longer distance.

* the measurement should be perpendicular to the cable route. (roll the LINDA wheel perpendicularly to the cable route.)

MONDAY BUZZ

ACTIVITY ON 19/4/10

Every Monday morning all TNBRians must attend a morning talk... it is not a very formal talk...its just like a warming up to start a new week....nothing much to say in this entry but just want to share informative info with u guys..

First : Email Tracking in Microsoft Outlook (from ICT Slot by En. Shah)

- if we implement email tracking in our Outlook, we can know wether the receipient had recieved/read our email yet or not

- how to set the tracking ??
1) make sure open the microsoft outlook
2) go to TOOLS --> Tracking --> Recieve/Read (tick both)
* if try x jadi, it maybe i missed out somthing..so you can try and error lah.. =D

- after done with the set up, once you send an email you will recieve two receipts which are recieve reciept and read reciept. this two reciepts will tell you (the sender) that the reciepient had already recieved and read the email.

" NO DIG POLICY "

ACTIVITY ON 14/4/10


DUCTBANK @ PUTRAJAYA

TNBD Putrajaya has a unique underground cable installation which is using ductbank and manhole system. This is because the relevant authority had imposed a ' no dig policy ' in Putrajaya area. For the cable installed in ductbank and manhole, the maximum current carrying capacity or ampacity is the main concern. It is crucial for the planner or engineer to know the ampacity of each cable in order to avoid overloading. Overloading the cable will cause the cables to operate at temperature greater than 90 degree celcius which is the maximum operating temperature of XLPE cable. this should be avoided since it will cause premature failures and decreases the insulation strength.

In the project the pipe used in the ductbank was High Density polyethylene (HDPE). In early 2009, due to 400km ductbank collapse, UNITEN had give recommendation to use Polyvinylchloride (PVC) pipe instead using HDPE pipe. this recommendation given by UNITEN was solely based on civil and mechanical reasons. If different material of pipe are used, it might effect the ampacity since the ampacity is a function of the heat generated in a cable (I^2R) and the amount of heat conducted away from the cable. This heat conduction is very dependent to the thernal resistivity of the material used. It should be noted that the thermal resistivity of PVC is higher than HDPE.

samples of cable installation in ductbank:

Few of cable laying terms used by TNB has different meaning in the IEC 60287 and CymCAP software. The cable lying terms used in the IEC 60287 and CymCAP are :

Direct Buried : The cable are buried directly in its original or native soils

Ducts : The cables are inside the PVC, PE, GI or other pipes, which are buried directly in its original or native soils.

Ductbanks : Ductbank consists of series of ducts (e.g PE pipes) which is surrounded with concrete. The cables are inserted through the ducts from one end to another end.

Trough : Long shallow rectangular-shaped excavation, where the walls, bottom and cover are made of concrete. The trough can be filled with a thermally good material or left unfilled (air filled)

R&D Project
Prepared by : Zairul Aida (Researcher@TNBR)

INVESTIGATION OF THE GROWTH OF WATER TREES IN XLPE CABLES

ACTIVITY ON 14/4/10

If u guys still remember, my last entry about CBM i mentioned about water tree right?? so, this entry i will discuss more details about the process to investigate the water tree.

water tree is a phenomena happened inside undeground cable which cannot be see with our naked eye. there for we used the microscop to check the existence of water tree.

Procedures :

1st : this is a pure cable from underground. this cable was taken after diagnostic team do the cable maintenances at certain area

2nd : chopped cable



3rd : take off the jacket

4th : slicer machine

5th : the white cable is the insulation material (in this case they used XLPE insulation). the amputation process cannot be handle by using the normal cutter because its dangerous the person who do it. (silap haribulan tepotong jari)

6th : this is what the slicer machine did. (now u know how difficult to do it manually right?)

7th : slicing of the sampe cable to thin slices

8th : this is the overall sliced cable

9th : dyeing process.

this process is just to colour the plain cable in order to enhance the visibility of these water trees. btw, the cables are soak in the Fluid Methlene Blue

10th : this is water bath. need to boil the water until the temperature reach 60 degree celcius

11th : put the immersing cable into the water bath and cook it for about 4 hours

after 4 hours, take out the cable and dry it. then, use the microscope to see the water trees existence. thare 2 types of water tree : bow-tie tree and bush tree (u can refer to the CBM entry)

Experiment prepared by : En. Jamal & En. Saiedin (thanks to both of them for inviting me to join them doing the experiment )

SHEATH

ACTIVITY ON 13/4/10


The sheath - to provide continuous earthing connections and return path for fault current.

In TNBD system, they applied concentric copper wires and cooper tape as sheaths for the cables. (single core and ABC cables)

Where was sheath located??

Internal cable compartment

cable cross section area

Cable sheath bonding arrangement :


- single point bonding
- both end bodings



Arrangement 1 : Single Point Bonding

- metallic sheath of 3 single core cables are connected and grounded at one point-usually at the cables' end.

- since it is only grounded at one end >> current flow in the conductor produced magnetic flux in the metallic sheath and hence, induces a voltage in the sheath.

- in conductor >> as the current increase, voltage will increase as well (V proportional to I)

- voltage increases as the distance from the ground bond increase

- induced voltage in the sheath = standing voltage


* figure below illustrates the phenomena of induced voltage

Arrangement 2 : Both Ends Bonding

- metallic sheath of the 3 single core cables are connected and grounded at both cable ends.

- the magnetic flux induces a current to flow in the sheath of the completed circuit.

- sheath current inversely proportional to the resistance of the sheath. V=0

- induced current in the sheath = circulating current


* figure below illustrate the phenomena of induced current

what happen if standing voltage in the metallic sheath is high ??

- it's unsafe and causes degradation of the jacket and insullation material

what happen if circulating current in the metallic sheath is high ??

- temperature rise by the contributed heat energy and overheating of the cables.



to overcome thus two problems, it is a must to know the value of it's induced volatge and current of different bonding arrangements. so that, the further action will fits the needss of particular installation without seriously affecting the ampacity of the cable.

*ampacity = current carrying capacity

the CymcCAP software was used to calculate the cables induced voltage for single point bonding and induced current for both ends bonding with respect to cable loading as well as at maximum ampacity on the IEC 602887.




** R&D Project : Sheath Induced Voltage and Current of Different Bonding Arrangements with Respect to Cable Loading for MV Single Core Cables and Aerial Bundle Cables
Prepared by : Tashia Marie (Reseacher@TNBR)

CONDITION BASE MAINTENANCE (CBM)

ACTIVITY ON 12/4/10

Purpose of CBM are :

> to monitor health of cable before any failure occur

> as a precaution before cable get damage

There are two types of Advance Testing :
(1) Dielectric Spectroscopy

(2) Partial Discharge

Abbreviation
* PILC - Paper Insulated Lead Cable

XLPE - Crosslinked Polyethylene

TYPE 1 - Dielectric Spectroscopy

DS testing is acttualy to check the moisture of insulation.

- the result taken will be compare with the references table provided (*only PILC had the references table, XLPE has no limit)

- if the data didn't match with the table, further action are required base on the recommendation

- if the moisture is high , its easy for water tree to happen

- DS usually used for PILC cable. However it also can be apply to XLPE cable but it needs extra High Voltage set in order to check the XLPE moisture.

TYPE 2 : Partial Discharge

Types :

- on-line PD testing

- on-PD monitoring

- off-line PD testing

PD Theory :

- Electric discharges which do not bridge electrode are called partial discharge. between the electrodes a sound dielectric is present in the form of solid, liquid or gaseous insulator.

- PD belongs to a far greater group of gas discharges. In all these discharges gas molecule are ionized by impact of electrons.

- Classification : corona discharge, surface discharge, and internal discharge.

PD Diagnostic (in general)

Advantages :

- Non-destructive test

- Technology which can defect and locate high impedances defects such as void, cuts, elctrical trees and tracking (symptoms for Water Tree)

- On-line application possible

- Effective at locating defects in mixed dielectric systems

Limitations :

- limited to cables with a continuous neutral shield

- requires a trained analyst to interpret measurements

- cannot detect or locate conduction type defects

- loses accuracy in branched network applications

two ways to handle PD testing :

(1) VLF - Very low frequency

(2) OWTS - Oscillating Wave Testing System (default by TNBR)


i will share with u guys bout the PD Mapping (site measurement) later

UG Vs OH CABLES

ACTIVITY ON 8/4/10

discussion with Mr. MOH (external mentor for Cable Unit @ TNBR)

what is UG Vs OH ???

UG is abbreviation of UNDERGROUND Cable
OH is abbreviation of OVERHEAD Cable
both cables are used to distribute electric to consumer or we also can call it as conductor.

Underground Cable

do you know what type of conductor widely used in Malaysia??

- most area in Malaysia use Underground Cable as the conductor


there are Pro n Cons between UG and OH

UG Vs OH

Advantages of UG Cables

- Environmental

- Minimal Visual Impact

- Low EMF

- No corona discharge, RI and TVI

- No bush fire problem

- Minimal lightning problems

- High level of personnel and public safety

- Good working condition

Disadvantages of Ug Cables

- Cost, must consider life time costs not just initial
- Cost differential decreasing with time
- Cost losses (30-60% less than OH), maintenance and repaire
- Undergrounding 25% of the existing EHV and HV lines in Italy and UK will increase the price of electricity by 3-5%
- Undergrounding all of the lines in Italy would increase the cost of electricity by 16%

Biggest contributor supply interuption is Underground Cable Failure


Problems :

- Susceptible for water to enter the cable
- There are a lots of vibration
- Need to dig for further maintenances


At Putrajaya, the underground cables installed was different from other place. they used an advances technology to lay the underground cable. the technology came from Japan which known as Duct Bank. actually at Putrajaya any digging activity are not allowed at all. that is why they used Duct Bank.


Duct Bank : many PVC pipe buried underground was with and without cables inside it. if they need to do the cable maintenances or change the cables they just need to duct the cable from one end until another end. no digging required.. pictures below shows the Duct Bank







Duct Bank



Problems with Duct Bank :

- all the cables (11kV, 30kV,..etc) gathered in one place..since all the cables generate heat, therefore the temperature inside Duct Bank will increase. when the temperature high, resistance will high and I^2R losses will increase..when the area inside is too hot, the cables tend to melt and cause damage to the cable. to implement this technology pic should make sure the insulation material can withstand with the heat produced and use superconductor to carry infinite current with low temperature.

* weather in Malaysia is absaloutely different with Japan... temperature factor are not really considered before implement the system.

TORQUE TEST

ACTIVITY ON 7/4/10

before i explain more, below was a short conversation with Mr. SZASKB

Mr. SZASKB : what is torque??

FN : torque is a force

Mr. SZASKB : what force??

FN : a force laa

Mr. SZASKB : yeah true..but what kind of force??

FN : ermm..don't know

Mr. SZASKB : torque is a twisting force (he explained with the demo as well)


by the way torque test is actually another test for IPC inspection...this process is the earliest procedure in the test....this test is a simple test...joint two cable and connect them with IPC in the middle. the IPC will lock with a pair of bolt and nut on top of it..special device used to apply the twisting force..


what the foreman in the picture below did is he plug in the device to the nut and turn it clockwise until the head broken from it socket..then, by looking at the meter we can know how much force has been applied...

En. Saeidin (TNBR Foreman) doing the torque test

picture above is what have been done in the lab...below is the implemented procedure at the top of electrical pole

*ehsan by mohd hafizul hamzah

how to now how much torque should be applied??

- every IPC has it's own torque specification, if the head break before the specification torque, means the IPC not suitable to the cable.

CR Measurement

- the procedure is just the same like heat cycle test. two cables are connected at both end.
- switch ON the device, the reading will display in analog...the low the resistance..the better the CR... the range of resistance usually between mili ohm - micro ohm

CR wires connection completed

CR Measurement Device

Notification 1

i dont know what happened...there's a gap between my previous post..please scroll down for the next entries...TQ

HEAT CYCLE TEST

ACTIVITY ON 6/4/10


We are not given any specific task yet..therefore i took this opportunity to ask the technician about the on going project. one of it is HEAT CYCLE TEST....

what is HEAT CYCLE TEST ??

its actually part of a test should be done in IPC (Insulation Piercing Connector) inspection...since IPC used in Malaysia don't have the standard, therefore TNBR did a research about it. the reason of it because there is a case where IPC melt and dropped on consumer's house and they claimed compensate to TNB. furtheremore, it also dangerous to the resident....

how the test look like??

Heat Cycle Test (HCT)

where can we find it in our daily life ??

it's located at the top of electrical pole

another purpose of this test are :

> to determine the contact resistance characteristic (CR)

> to check the endurance of conductor (cables)

How to conduct the test??

1) 1st of all, for sure need to setup the equipment

2) connect an IPC for every each extension (there are 5 cables overall)
3) current flow in a loop supplied by Current Transformer (two big black boxes in HCT figure)

4) connect a multimeter to the loop

since we are dealing with current, they will be heat produced

5) to monitor the temperature, they used data logger

> every 30 minutes technician will take the reading.

> we need 1 hour to complete 1 cycle, during 1 hour there will undergoes two process,

current inject and current remove. this also know as aging process.

Data Logger

actually, this is a long project since it has to complete 200 cycles

1 CR - 25 Cycles

1 Cycle - 1 Hour

1 Cable - 200 Cycles

1 Cable - 8 days

*if after 200 cycles there is no failure occure at IPC or cables, its mean the IPC suit with the cable...end of this test, only one cable left..

6) CR measurement

> Big Clamp for current measurement

> Small Clamp for voltage measurement

the design of the clamp comes with two sizes because as we know that the flow of current will

produce heat, so that it needs big size to avoid the clamp from melt. since the increasing of voltage won't gives any effect, small size is sufficient.

CR Measurement Device

as told by the technician, only current flow in the loop and zero voltage. how current will flow without voltage????

* u as engineer, u should know how to explain... ^_^

lets have a short review....

we know that current cannot flow without voltage right?? it already stated in Ohm's Law " no current without voltage V=IR ". so that, it is impossible to happen right??

now, lets engineer (wanna be) explain to you... =D

actually like this, as i mentioned before current was supplied by Current Transformer...what do you remember about transformer?? (think deep..said my boss)

this case happened because of two factors :

(1) Transformer Effects

(2) Energy

Transfromer Effecs

- depends on number of turns

- consist of two conduction modes : step up & step down

- two windings : primary & secondary winding

- Principles of Induction Faraday Law applied

- Any system in the world cannot violet the law of Physics

- only AC supply allowed to operate the Transformer

*we focused on 3 bolted point

Energy

- general info : energy cannot be create and destroy

- the energy is supplied by the CT

- main power and primary winding also provide the energy

- energy will convert to very high current with low voltage

- we know that, P = VI cos (phi)

P = constant, if I increase, V decrease (when current high, voltage yeild is very small) * usually engineer will neglect the small value

in simple explainasion, put a pinch of salt into a gallon of water won't change it taste right?? same goes to the system, if want to produce high current, we low the voltage.

* apply the right law at the right place

my workplace

* forgot to upload this picture yesterday... ^_^

sample of cables that available in Malaysia

HVCD Lab environment

* i'll be here for the next 3 month ^_^

HIGH VOLTAGE CABLE DIAGNOSTIC TEAM

* pic : file from my Boss *

1st Day at Workplace

salam wbt... ^_^

today was my first day intern at TNB Research...im not alone here, i was accompanied by Sham Izzaidi and Hadi Gan...I and Hadi were placed at same department which is Distribution while Sham at Transmission department...by the way, my mentor is Dr. Ir. Ahmad Basri bin Abd Ghani

* my 1st day tentative

8.00 - arrived at TNBR

8.15 - TNBR Morning Talk (every Monday)

9.30 - waiting for Mr.Amirul at HR Department

10.00 - enrolment

11.00 - meeting with Dr. Basri

12.00 - visit Diagnostic Cable Lab

1.00 - lunch

3.00 - short briefing by Mr. Saeidin (foreman)

5.00 - meeting with Dr. Basri again

6.15 - sign off

everyone at Distribution department was very friendly and kind to us.... especially our bos, he taught us about EMF all over again...(i can't remember it very well =D ) ... what impressed me, within 2 hours (more less) he told us so many things...if im not misteken, i manage to jotted almost 10 pages of what he said...before we dismiss he hand over to me and hadi, each a file of TNB Distribution Division Maintenance Manual : Underground Cable System and i also has been assigned by Dr. Basri to follow a team supervise by Ms Tashia Marrie...my team will perform new project as told by Dr.Basri... he just told me that the project will have experiments and also site visit...to do the experiments, we dont have the manual but we will come out the procedure later...furthermore, the design, setup, current withstand and etc will decide by our team... (this is what my boss told me)

* i guess thats all for today...i have to study the file that my boss gave to me... will be update again later..cya