(15/4/2010-26/4/2010)

1)A fault is defined as any defects, weakness, inconsistency or non-homogeneity that affects the performance of a cable

2)CAUSES OF CABLE FAULT

There are many reasons why fault occurs. The more common faults are due to the following:

1. Damaged accidentally by external mechanical means.
2. Damage caused as a result of mishandling the cable during initial laying.
3. Poor workmanship in cable jointing.
4. Manufacturer's defects
5. Natural causes due to aging of cable, and
6. Damage caused by movement of soil & erosion.

3)TYPES OF CABLE FAULT

In general fault can be divided into series & shunt types.

1.Series (Open Circuit) Fault

- A fault involving the failure of continuity in either the conductors or cable sheath.

2.Shunt (Short Circuit) Fault

- A fault involving the failure of insulation in the conductor(s).

(5/4/2010-14/4/2010) substation

In the electrical distribution network, a sub-station has many components such as circuit breaker, transformer, and switches, fuses which must be housed properly to ensure continuous and reliable service. According to construction of sub-station, several factors need to be taken for the construction such as location and load demand

There have 4 types of sub-stations in electrical distributions network

Indoor substation

Outdoor substation

Pole-mounted substation (H-pole)

Compact substation

Components in substation

Switchgears – not available in H-pole.

Ring Main Unit – located in PPU only.

Transformers

Protections

Protection Relays and Vacuum Circuit breaker (VCB) – located in PPU only.

Transformer Fuses

Isolating Switch – Located in H-Pole only

Pin Insulator – Located in H-Pole only

Low Voltage Fuses – Located in H-Pole only

Lightning Arresters – Located in H-Pole only

Earthling

Underground Cables

PILC

XLPE

Distribution Boards

Low Voltage Distribution board (LVDB)

Feeder Pillar

Substation work

I. Visual Inspection

Done once per 3 months

Done by seeing, hearing, smelling and feeling the substation and its equipment to see if there is anything wrong with the particular substation

If there were any defect, report to Authorized Person (AP) for corrective maintenance.

II. Routine Maintenance

Done once every 6 months

Take substation data, load reading

Work including cleaning and repairing inside and outside substation such as cut grass, throw rubbish, repairing broken gate and take LV current

Data reading at LVDB.

III. Preventive Maintenance

Done once every 18 months

Full maintenance from top to bottom, involving all of the equipment inside and outside the substation

Done by either the Substation Team or an outside contractor

Among the list of things to do include servicing the LV distribution board (LVDB), servicing the switchgears and servicing the transformers