control devices.ppt

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PROTECTION / CONTROL PROTECTION / CONTROL DEVICESDEVICES



• Refer To IEE Regulation every electrical installation must be protected/controlled by protection devices.

• Protection Devices functions is to protect burn down,damages,short circuit and others to the electrical installation.

• Protection Devices are normally inside the DB or SSB.



Types of Protection Devices

• MAIN FUSE / SWITCH• ELCB• RCCB• MCB• FUSE• EMERGENCY STOP BUTTON



MAIN SWITCH (SWITCH FUSE) & FUSE

63A Double Pole L & N 63A Single Pole L & N



Symbol ( Main Switch )

63A Double Pole L & N 63A Single Pole L & N



Symbol ( Fuse )



FunctionsMain switch (switch fuse)

A unit that contains the isolator with a fuse that can be pulled out.It's almost like a fuse switch, but has the following differences: -

i. The fuse are used is without the tag and do not need to screw and nut (fuse cartridges) compare than using the switch fuse HRC type .

ii. Proportional /Rating Current is below 63A . iii. When is off condition ,It is not separate from the bus bar.

It is used for the single phase (SP and SPN) and 3-phase (TP and TPN)A fuse will be protect over current occurred.



ELCB ( EARTH LEAKAGE CIRCUIT BREAKER )



RCCB( Residual Case Circuit Breaker )



Symbol ELCB/RCCB



FunctionEarth Leakage Circuit Breaker (ELCB)

Its function as a protection to the earth leakage current and the separator circuit.There are two types ELCB commonly are used :

i. Voltage Operating ELCB.ii. Current operating ELCB.

i. Voltage Operating ELCB.

According to IEE Regulations, if the leakage to ground current are not be protected by control devices such as in Regulation D 22, then this type ELCB can be used when the multiple value of impedance and ground current operation (tripping current) exceeds 40 or the other purposes when the controlled ability increase of 40 V or when the earth loop exceeds the of the value.

ELCB 0.5 A, the maximum impedance of the earth rings allowed is 240V/0.5A 40V/0.5A or equivalent or to 80 ohms.

In practice, the value of earth loop impedance normally less than 500 ohms is easily found in all places, But the rare value of earth resistance value is more than 100,000 ohm/cm3.

The resistance of earth electrode for less than 500 ohms usually have 8 feet long and 2 "inches in diameter. This means that by planting six or seven rods either electrode is connected or separate are enough to get the value of the earth electrode resistance for less than 100 ohms.

However, to get the value of earth loop impedance of 4 ohms it is impossible because a fuse of 30 A are used as a controller, especially in terms of leakage current in economical factor .



FunctionThis is because Earthing Cost is very high compared with the installation cost. Therefore, then ELCB used as a controller leakage current to ground while the fuse as the over current controller when the main switch rated less than 60A.

If the rating fuse in main switch is 100A then it will be used as dense grounding (earthing solid) and oil circuit breaker or air (Oil Circuit Breaker - OCB or Air Circuit Breaker - ACB) as an earth leakage circuit breaker which can act with the operating current.

Effect of parallel flow to ground (earth parallel paths).

This problem occured when there is leakage current to ground, partly by other conductors without passing through the ELCB earth electrode completely to disactived (trip off).

This problem does not occured in the ELCB current operating.

For example, leakage occurs at the water heater (water heater) in which the leak occurred, and then totap water and the earth. Since water usually has a relatively low resistance of the earth, then only a lot of leakage current can increase the pipe voltage to 40V to enable voltage-operated ELCB disactived to cut the circuit.



One thing to concern is the earth tap or the earth electrode of this type should avoid this ELCB near metals or semiconductors that could cause a flow parallel to the Earth's leaking like a water pipe .

This is to ensure that planting outside of the pipe an earth intended resistance .

When leakage occured, ELCB coil disactivated and will not even occurs a large leakage current potential and the electrode.

The best way to protect this problem is used ELCB current operating type but the cost is quite expensive.



ii. Current Operating ELCB

In a complete circuit, current flows in the various branches of the same live line are same the current flowing in the neutral line when there is no current leaked to the ground.

When there is a leakage current to earth or any earth circuit ,so the current flowing in the live and neutral lines are not balanced. This unbalanced are causes flux electromagnet force are unbalanced in the magnetic core.

So, the problem of current flow to the earth and the effectiveness of the grounding line can be solved when it’s disactivate because it’s causes by total of current but not total of voltage.

According to IEE regulation, this device is used when the total earth loop impedance of the earth acting multiplied by the current less than 40A.

For this reason, it is declared that disactivate current or unbalanced current must not exceed 2%normall current or the rating current (normal current or rating current).

Thus, for a 60A circuit, the maximum allowable leakage current is 1.2A. High sensitivity of ELCB may act at the current rate of 6 mA is commonly.



MCB( MANIATURE CIRCUIT BREAKER )

Single Pole MCB Double Pole MCB



Symbol



Maniature Circuit Breaker

• Because of this type is small, then it is referred to as miniature circuit breakers. • The excess current protection devices that have high rates of capacity determination.

• Shape is similar to the normal Tumbler switches, the difference is only in terms of size and shape only (4 in length). Durable and it is not influenced by environmental temperature for operating and protecting rates are just fine/small class.

• This Circuit breaker is divided into two, namely:

i- fixed rating- where used to replace the fuse.( 6A, 10A,20A & 32A )

ii- adjustable current rating were used to cover the burden of changing or uncertain rating values such as motor and so on.

• In addition to the excess current protection,It’s functions also as the protector of the excess heat to the motor windings to control the temperature specific heat of the motor and an isolating of the leakage current to ground on at every installation.



• It can be operated automatically or manually.

• It must be made and designed in accordance with BS 3871.

• Types of circuit breaker operation

Magnetic Thermal hydraulic



Advantages and disadvantages of circuit breakers Advantages Disadvantages

It’s small

Price is expensiveOperate more efficiently and quickly.

easy to connect to other mechanical parts for the delay reaction.

Easy to check fault circuit

Cannot Be repair/ difficult to repairLasts longer not easily damaged Operating current and the following

can be set.

control devices.ppt

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