Fuse Unit

Fuse unit is used to control distribution feeders. Normally fuses are provided on all the three phases. This gives over current protection and short circuit protection. These fuses are commonly used in distribution transformers to protect the lines.

Above is a typical fuse unit mounted near a transformer. This provides protection and control of the lines. Technicians can remove the fuse to a particular line and carry out the maintenance works. Also this provides a protection for over current supply and short circuit current. Fuses will blow off during over current and short circuit current.

Fuses are made of porcelain and the conducting parts are copper. Graded alloy wires are used for re-wire able fuse links. Sometimes HRC fuses are used to link between terminals. Technicians use a hand gloves while handling these fuses. It is very convenient to test the supply by using line tester.

How to identify Earth Fault Location in large electrical systems

Earth faults are common fault condition in an electrical system. This will get noticed suddenly on a raining day. Once earth fault is detected it is Electrical Engineers headache to find the cause of earth fault. It can be a faulty device or a loose wire or wet terminal block. It is very important to locate the position of the earth fault and the reason for it.

In my experience a live line checking is easy. It is easy to go from the higher end. Go to the main distribution board and switch off all loads on by one. When you switch off one load the earth fault indication will vanish. (If it is not vanishing after switching off all individual feeders then the cause can be inside the panel or there can be multiple faults. To locate multiple faults you have to switch off all feeders and switch on loads one by one).

Once you have identified one feeder go down with that feeder. If it is a sub distribution board repeat the exercise and find out the affected feeder. If it is a motor starter check the starter without motor and later the motor. Once you have pin pointed the location it is easy to find the reason for the fault. For complicated systems you have to isolate individual systems and locate the location. Make groups of three or four items and remove supply to that line.

Remember it is important for any system to clear off earth faults before a second fault occur. So be fast in tracing the fault.

LT SWITCHBOARD–Low Tension Power Control Centre

LT SWITCHBOARD–Low Tension Power Control Centre is used to control power flow at low voltage level (415 Volt) three phase 3/4 wire systems. There are power distribution boards, Power Generation Control Boards, Feeder Control Boards and Motor Control Panels come under this category. I short these are system/panels which are used for 415 V (phase to phase) , for electrical distribution and motor control, in any type of industries. The boards are fabricated and comply with IEC 60439-1 as well as with derived national standards NF EN 60 439-1, VDE 0660 Part 5, DIN 41-488, BS 5486, NBN C63 439 and CEI Italy 542 concerning the construction of type-tested assemblies (TTA). Types of LT SWITCH BOARD – Low Tension Power Control Centre are:

PCC-Power Control Centre
PDB-Power Distribution
MPDB-Main Power Distribution Board

MCC-Motor Control
ACDB-Alternating Current Distribution Board

DCDB-Direct Current Distribution Board