For example, in the case of automatic disconnection of supply, basic protection is provided by insulation and barriers and enclosures while fault protection is provided by protective earthing, protective bonding and automatic disconnection of supply. Basic and fault protection are independent.
What is meant by fault protection?
Fault protection requires the protective devices to operate within a specified time under fault conditions. Carrying out an earth fault loop impedance test is the most common method used for verifying circuit disconnection, although this may increase the risk of unnecessarily coming into contact with live parts.
What does basic protection mean electrical?
Protection against direct contacts is called Basic Protection. Indirect Contacts: electric contact of persons or animals with exposedconductive-parts which have become live under fault conditions. I am subject to an indirect contact when I touch a metallic part that can become live due to a single fault.
What is used for fault protection?
The RCD has become an indispensable protective device, selected to provide fault protection, additional protection and, in certain circumstances, protection against ﬁre. RCDs are widely used and, therefore, it is necessary for electricians to have a sound understanding of this type of protective device.
What’s the difference between fault protection and additional protection?
The fault protection refers to cases like TT were the max Zs cannot be met so in a TNCS situation the RCD would not generally be required for fault protection because the Zs readings would be within limits. Additional protection is that extra bit of safety for sockets outside for eg.
What are the 3 types of protective devices?
Natures of Protection Devices
- Circuit Breaker.
- Metal Oxide Varistor.
- Inrush Current Limiter.
- Gas Discharge Tube.
- Lighting Arrester.
Is insulation basic protection?
All of the above have a requirement for basic protection, which is the primary line of defence against electric shock and is typically achieved by insulation over the live parts, such as the insulation around a conductor, or a barrier inside an enclosure.
How do you protect against fault current?
Overcurrent protection devices include circuit breakers and fuses. Overcurrent protection devices are meant to protect against the potentially dangerous effects of overcurrents, such as an overload current or a short-circuit current, which creates a fault current.
What are the four common forms of basic protection against electric shock?
Methods of Fault Protection
- Earthing of circuits and equipment.
- Protective equipotential bonding.
- Automatic disconnection.
What is Band 2 voltage?
Voltage Band II covers all voltages used in electrical installations not included in Band I. This means that all 230/400 V (240/415 V) supplies are included in Band II.
What is the first fault?
First fault situation. In IT system, the first fault to earth should not cause any disconnection. The earth-fault current which flows under a first-fault condition is measured in mA.
How many computers can I put on a 30mA RCD?
(1) PC computers typically leak 3-5mA to earth during normal operation. Adding these together, it seems that putting more than 3 computers on a 30mA RCD system is against regs. If all the sockets share a single RCD at the CU, then this puts a limit on the number of PCs you can run in a house.
Can you have 2 RCDs in a circuit?
Hi, I have two 30mA RCDs in series, first one as the main switch in the house consumer unit covering all 11 circuits, second one as the main switch on a garage consumer unit, covering three circuits.
|Technical discussion forums|
|·||Other and general engineering discussions|
What is MCB full form?
The full form of MCB is Miniature Circuit Breaker . It is a kind of electronic switch that functions automatically.
What are the two basic types of circuit protection devices?
There are two general categories of circuit protection: 1) Fuses 2) Electro-mechanical circuit breakers.
What is the difference between basic and reinforced insulation?
Basic, Double, and Reinforced are safety insulation levels. Basic is a single layer and Double is two layers. Reinforced is a single insulation system which is equivalent to Double. Products and components must remain safe even when there is a single fault or failure in the insulation.
Is XLPE double insulated?
CBL240XLPE XLPE Cable, Single Core, Double Insulated, SDI, 240mm2, 61/2.25, XLPE/PVC, X-90/V-90, 0.6/1KV, Plain Annealed Copper, Black, 100 mtr Drum.
What is no load protection?
The no-load protection feature is a new concept that is normally not available in commercially marketed motor protection devices. The microcontroller is used for fast computing and to take appropriate control action quickly.
What is the difference between Band 1 and 2?
Band I cables can include telecommunication, signalling, bell, control, and alarm circuits, whereas Band II covers electrical installations of all voltages, meaning 230V/400V supplies.
Is 3.3 kV low voltage?
Whilst low voltage generally refers to cables under 1kV voltage, the 1.9/3.3kV cables are often classified within this banding too.
How is fault formed?
A fault is formed in the Earth’s crust as a brittle response to stress. Generally, the movement of the tectonic plates provides the stress, and rocks at the surface break in response to this. Faults have no particular length scale.
What is a normal fault?
Normal Faults: This is the most common type of fault. It forms when rock above an inclined fracture plane moves downward, sliding along the rock on the other side of the fracture. Normal faults are often found along divergent plate boundaries, such as under the ocean where new crust is forming.
Do all electrical circuits need RCD protection?
Separate RCD protection is not necessarily required for each circuit of an installation but, in order to minimize the likelihood and consequences of tripping, a single (‘front end’) RCD should not be used to protect all the circuits.
What is the tripping time for a 30mA RCD?
However, it has become apparent that some Type A RCDs of rating of 30 mA or less are manufactured such that the maximum break (tripping) time (40 ms) is achieved at a current of 0.25 A (250 mA) rather than at 5IΔn (150 mA for a 30 mA RCD).
Can I use an RCD as a main switch?
1 – can you use the RCD as a main switch for the installation – yes, all RCCB’s that meet BS EN 61008 are rated for isolation.
What time should an RCD trip in?
The RCD should not trip. A current equal to the rated tripping current of the RCD should be passed between active and earth. It should trip within its specified time; 40 milliseconds for Type 1 RCDs, and 300 milliseconds for Type 2 RCDs.
How many MCB are in a RCD?
It is required by law to have 2 RCDs installed in your home such that they protect the power and light circuits. For circuit breakers, you need to have one MCB per circuit. The RCDs are usually installed near the main switchboard. The new MCBs are usually installed above or below the existing circuit breakers.
Do bathroom lights need to be RCD protected?
Electric showers require their own electrical circuit, which in general will have the highest electrical demand out of your household appliances. All circuits in a bathroom must be protected by a RCD (Residual Current Device).
Why is fault protection essential?
Grounding, bonding and ground fault protection are vital to decrease shock hazards to personnel during a ground fault such as when a current-carrying conductor’s insulation fails or inadvertently faults to ground.
What are the various types of protection?
Types of protection
- High-voltage transmission network.
- Generator sets.
- Overload and back-up for distance (overcurrent)
- Earth fault/ground fault.
- Distance (impedance relay)
- Low-voltage networks.
Is RCD and RCCB same?
RCCB is also known as RCB or RCD.
RCD stands for Residual Current Device, while RCB stands for Residual Current Breaker. RCCB is an electrical wiring device that disconnects the circuit as soon as it detects a current leak to the earth wire.
What is ELCB and RCCB?
ELCB is the old name and often refers to voltage operated devices that are no longer available and it is advised you replace them if you find one. RCCB or RCD is the new name that specifies current operated (hence the new name to distinguish from voltage operated).
What is circuit protection?
Circuit protection includes protection from equipment overload conditions, undervoltage and overvoltage conditions, ground faults, and short circuits. Although mandated by code for any electrical installation, the proper implementation of circuit protection products can be confusing at times.
What is the difference between MCB and fuse?
Fuse is an electrical device that self-destructs and stops the current flow in a circuit whenever the current exceeds the predefined value. MCBs are resettable circuit protection device that, on the occurrence of faults, stops the current flow in a circuit.
What is the difference between functional and basic insulation?
Functional insulation – basic level that is required for the supply to function. This does not prevent electric shock if touched. Basic insulation – provides the user a single and simple protection from electric shock.
How do you calculate bil?
An example is shown in Figure 1a below. The minimum level is known as the Basic Insulation Level (BIL) that must be that of all of the components of a system.
Basic insulation level, kV. (standard 1.5- × 40-μs wave)
|Basic insulation level, kV (standard 1.5- × 40-μs wave)|
What is meant by reinforced insulation?
Reinforced insulation means insulation of live parts for protection against electric shock equivalent to double insulation. Insulation may compromise several layers which cannot be tested individually as supplementary or basic insulation.
What is clearance distance?
Clearance distance – shortest separation in the air between two conducting parts. Determination in accordance with IEC:Identification of the overvoltage category. Definition of the pollution severity.
Which is better XLPE or PVC?
Water Proof Performance in Application Environment: PVC insulated cable is better than the XLPE insulated cable. Environment Protection aspect: For XLPE is not containing chlorine which will release toxic gases once burn, so XLPE insulated Cable is environment friendly compared with PVC insulated Cable.
Is XLPE waterproof?
In order to prevent the penetration of moisture and also to extend the duration of life, the XLPE insulated medium voltage cables are designed with longitudinally waterproof shielding including an additional swell tape and PE outer jacket.
How do you calculate fault line?
Causes of faults include things such as lightning strikes, animals, dirt and debris, dropped tools, corrosion, and human error. Fault current calculations are based on Ohm’s Law in which the current (I) equals the voltage (V) divided by the resistance (R). The formula is I = V/R.
How do you calculate kw to cable size?
Ok, let’s dive into calculations…
- Consumed Load = Total Load · Demand Factor: Consumed Load in KW = 80 · 1 = 80 KW.
- Consumed Load in KVA = KW/P.F.: Consumed Load in KVA = 80/0.8 = 100 KVA.
- Full Load Current = (KVA · 1000) / (1.732 · Voltage): Full Load Current = (100 · 1000) / (1.732 · 415) = 139 Amp.
What is full load current?
A full load current is the largest current that a motor or other device is designed to carry under particular conditions. The starters shall be suitably rated to continuously carry the full load current of the motor and also accept the starting current surges without tripping.
What is the no load voltage?
The no load voltage is the terminal voltage when zero current is drawn from the supply, that is, the open circuit terminal voltage. Some portion of voltage drops down due to internal resistance of voltage source.
What are the two different types of electricity?
There are two kinds of current electricity: direct current (DC) and alternating current (AC). With direct current, electrons move in one direction. Batteries produce direct current. In alternating current, electrons flow in both directions.
What is the most important rule of electrical safety?
For added safety, use a lock to prevent anyone from turning the power back on. Conclusion: Thus, the most important rule of electrical safety is to de-energize the electrical circuit before working on it.
What is meant by basic protection?
Basic protection includes one or more provisions that, under normal conditions, prevent contact with live parts.
What are types of voltage?
There are two types of voltage, DC voltage and AC voltage. The DC voltage (direct current voltage) always has the same polarity (positive or negative), such as in a battery. The AC voltage (alternating current voltage) alternates between positive and negative.