Week 1 (Day 4)

- Attend the meeting which held every morning at 8am by team pencawang
- Follow team pencawang to site to do some maintainence job at substation

- There are 4 types of substation:
a) Indoor substation
b) Outdoor substation
c) Pole mounted substation (H-pole)
d) Package or Compact substation


- Reached the indoor substation , P/E Damai Taha (Pencawang Elektrik)(11kV)
- Then, we start the maintainence job.

- The technician replacing the old EFI with the new EFI.

- Encik Mohd Shafiee explained to me about the transformer, Switch gear, LVDB and Earth Fault Indicator.


- There are 4 main compartments of a substation.

1) Transformer

Function 

- changes an electrical voltage or current from one level to another

- Ex : Step-up transformer or Step-down transformer

2) Switch Gear (VEI)

 Function of switchgear

a) Received the 11kV and feed to transformer.

b) Isolate supply when it is needed

There are few types of switchgear:

a) Vacuum circuit breaker (VCB)

b) Ring main unit (RMU)

1) Oil insulated

2) Gas insulated

3) LVDB (Low Voltage Distribution Board) or Feeder Piller
(cable size 1600mmp or 800mmp to connect from transformer to LVDB )

             

Function

 -a device that used to divide the output or supplies the low voltage to consumers.

4) EFI (Earth Fault Indicator)

Function
- detects earth faults & short circuit faults






















***** EXPLAINED MORE DOWN *****





- Then, we went to second destination , P/E SG KETAPA.

- We proceed the maintainence job (cleaning the nearby tree branch and weeds).

- Another type of Switch gear (INDKOM) in P/E SG Ketapa.

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Vacuum Circuit Breaker (VCB) Switchgear

VCB is also called vacuum insulated switchgear. In TNB, types of VCB used are TAMCO, EPE and AICHI. VCB will trip if any fault occurred. VCB is used in important substation and in a row substation. 30 V dc supply from battery bank is used to operate the relay system of VCB. Normally VCB is used in Main Intake Substation (PMU).

The advantages of vacuum circuit breakers are:

a) Long life with minimum maintenance.

b) Compact, completely closed and sealed construction and can be used any orientation.

c) Extremely short and consistent arcing and total break times.

d) No fire risk and noise.

e) Suitable for very fast auto re-close as very little mechanical energy is required to operate them because of the much smaller contact separation.

Battery charger is used to supply the VCB.The vacuum will cover the circuit from blow.

There are relay in VCB. When trip occur,current produced was large,so the relay use a ratio to minimize the current.If the relay did not minimize the value of the current,it may cause damage to the relay and switch box.

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FEEDER PILLER

· There are two types of feeder pillar – 1600 amp and 800 amp

· Feeder pillar is designed with cover to protect the bask bar 

· There are components in feeder pillar (which is the same with LV Board) such as link, outgoing fuse, current transformer, thermal demand indicator meter (TDI), instrument supply 6A, cut-out & neutral link 60A and phase barrier

· The 1600 amp one have 8 outgoing cable whereas the 800 amp have 4 outgoing cable

· Outgoing fuse is used connect the bask bar to low voltage cable.

· The 1600 amp feeder pillar is not suitable to use with 500mm cable because the load will not be enough to support it

· There are 3 fuses in each outgoing bar.

· Fuse factor is 1.5. If the blow point of the fuse is written 160A, then the exact load the will make the fuse blow is 160A × 1.5 which is equal to240A.

· There are several test that must been made before PPVR is operated. It is of course to make sure that PPVR is safe for the staff to work with it.

· The PPVR test is divided into two which is a) before installation and b) after installation.

· Before installation test : Phase-to-Phase test and Phase-to-Neutral test need to be done, and the insulator resistance must be ≥ 1MΩ

· After installation test: There are three test need to be check for which are voltage test, ujian turutan fasa, and feedback test.

· Voltage test is operated to make sure the voltage out from the PPVR is standard with the safety of TNB

· Feedback test is drive to make sure there are no feedback voltage from the consumer (houses and factories) that were using genset.

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EFI ( Earth Fault Indicator)

Indicator Unit

Earth Fault Element

Contoller Unit

-Earth Fault Indicator are used in conjunction with RMU (Ring Main Unit) and VCB (Vacuum Circuit Breaker) units to provide a means of indicating the passage of earth fault current along a radial or open-ring cable system.
-It detects earth faults & short circuit faults on underground cables.
- The operating points for earth fault and short circuit are adjusted with a threshold level electronic. 
-When the current exceeds the pre-adjusted threshold level, a signal is sent to the reading instrument for  evaluation. 
-The respective indicator (RED high intensity LED) is activated and starts flashing.
-The led will be placed outside the substation so that it is easier for the technician to see which substation has tripped.

 * TRIP LEVEL

- Settable in range 40A to 120A with four selections; 40A, 60A, 80A and 120A

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