“Basic” earth leakage protection training course
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Transcript of “Basic” earth leakage protection training course
Final Distribution TrainingFinal Distribution Training
Schneider Electric - Residual Circuit Devices - 06/2012
“Basic” earth leakage protectiontraining course
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Instructions to read carefully before starting
You are going to have a 25 minutes e-learning
Please follow the below instructions :
● Open the module in a slide show format
● Read the question and click a mark on your answer You can put several marks ▲ But you cannot remove a mark you already put in a box (it opens the next slide)
● Click on the button to display the answer
● Then click anywhere on the answer’s page to move on to the next slide
And….enjoy your training !
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Training Objectives
●By the end of the course:
Be aware and understand current risks
Know how to protect against electrocution
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Introduction
●In the UK ● What is the average of people who die each year nationally
due to unintentional electrocution?
●In France ● How many severe electric shocks still occur?
● How many deaths per year due to electrocution?
●In the US ● What is Electrocutions rank in causes of industrial fatalities?
20
4000
100(40% of such deceases involve children aged between 0 and 9)
4th 600 people die(roughly 3,600 disabling injuries occur every year)
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Contents
Understand the current risks
Position earth leakage protection devices in an electrical installation
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A child sticks his fingers in the holes ofa socket outlet
there's a risk of electrocution....
● 1. By short-circuit.
● 2. By direct contact
● 3. No risk of electrocution
Right Wrong
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A child sticks his fingers in the holes of a socket outlet.
Can an earth leakage device protect the child from electrocution?
● Yes
● No
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A child sticks his fingers in the holes of a socket outlet.
Could a circuit breaker protectthe child against electrocutionby direct contact?
● Yes
● No
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Case 1: In the circuit below, the switch is open: the light is off.
Is there current in the installation?
● A. Is there current in the red conductor?
● B. Is there current in the blue conductor?
Right Wrong
The two conductors forming the cable.
Earth leakage protection device
Light (off)
Socket outlet
Light switch (open)
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Case 1: The switch is open, the light is off. The red conductor is damaged upstream of the switch. A person touches the cable in that location.What happens to the person?
● 1. Nothing happens.
● 2. He feels a shock.Current goes through his body.
● 3. He feels a shock but there is no current
● 4. The light goes on.
Right Wrong
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Case 1: The switch is open, the light is off. The red conductor is damaged upstream of the switch. A person touches the cable in that location.Where is there current in the installation?
● A. In the red conductor?
● B. In the blue conductor?
● C. In the light?
YES NO
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Case 1: The switch is open, the light is off.A person touches the damaged red conductor. Current flows in the red conductor and in the person's body.Where does the current go next?
● 1. It returns to the source via the blue conductor.
● 2. It returns to the source via the red conductor.
● 3. It returns to the source via the earth.
● 4. It does not return to the source.
Right Wrong
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● 1. Equal to 100 mA.
● 2. Less than or equal to 100 mA.
● 3. Greater than or equal to 100 mA.
● 4. Zero.
Right Wrong
Case 1: The switch is open, the light is off.A person touches the damaged red conductor.
If the current measured in the person’s body is 100mA, what is the current in the red conductor ?
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Case 1: The switch is open, the lamp is off.A person touches the damaged red conductor.
If the current measured in the person’s body and in the red conductor is 100mA, what is the current in the earth?
● 1. Equal to 100 mA.
● 2. Less than or equal to 100 mA.
● 3. Greater than or equal to 100 mA.
● 4. Zero.
Right Wrong
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Case 2: In the same circuit as previously, the switch is kept closed, the light is on.
Where is there current?
Right Wrong
● 1. In the red conductor?
● 2. In the blue conductor?
● 3. In the earth conductor?
● 4. In the earth?
4
3
1
2
?
?
?
?
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Case 2: The light is on. It consumes 1.5 A. The red conductor is damaged. A person touches the cable in that location. He feels a shock.Where is there current?(click on each item in the diagram through which current flows)
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Case 2: The light is on. It consumes 1.5 A.A person touches the damaged red conductor.A 150 mA current goes through a part of his body.
What is the current in the light, remembering that it was 1.5 A before the incident?
● 1. It doesn't change
● 2. It gets lower
● 3. It gets higher
Right Wrong
?
150 mA
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Case 2: The light is on. It consumes 1.5 A.A person touches the damaged red conductor.A 150 mA current goes through a part of his body.
What is the level of current in the blue conductor?
● 1. It doesn't change
● 2. It gets lower
● 3. It gets higher
Right Wrong
1.5 A
150 mA
?
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Case 2: The light is on. A person touches the damaged red conductor. A current goes through a part of his body. What is the current in the red conductor?
● 1.5 A
● 1.65 A
● 1.80 A
● 3 A
● 3.15 A
Right Wrong
1.5 A
150 mA
1.5 A
?
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Let's summarise: Current characteristics in the case of electric shock by direct contactthe difference between currents in the blue conductor and the red conductor is always:
● 1. greater than or equal to the current in the human body
● 2. equal to the current in the human body
● 3. less than or equal to the current in the human body
Right Wrong
1.5 A
150 mA
1.5 A
1.65 A
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As of what level can current flowing in the human body cause injuries?
discomfortno actual danger
1A
500 mA
80 mA
40 mA
10 mA
0.5 mA
heart stop
heart fibrillation
tissue burningsbreath paralysis
muscle and lung contractionno physiological damage
Personal injuries, according to level of current.
Right Wrong
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Given that a current of about 40 mA can injure tissues and organs, a device intended to protect against electrocution must trip whenever
● 1. The current in the cable increases by 40 mA.
● 2. There is a 40 mA difference between the currents in the red and blue conductors.
● 3. There is an 80 mA difference between the currents in the red and blue conductors.
Right Wrong
1.5 A
1.54 A
1.5 A
40 mA
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By definition, an earth leakage protection device trips if the difference in current in the two conductors is greater than its sensitivity (or pick-up level)
What is the sensitivity of an earth leakage device required to protect against electrocution by direct contact?
● 1. 30 mA
● 2. 40 mA
● 3. 1.5 A
● 4. 1.54 A
Right Wrong
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With an energised part, when does the earth leakage protection device trip?
Right Wrong
● 1. Before the person touches the damaged conductor.
● 2. Shortly after the person touches the damaged conductor.
● 3. As soon as the person touches the damaged conductor.
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Now, if the person is subjected to 20 mA, will the earth leakage protection device trip?
● Yes
● No
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If the light is off, will the earth leakage protection device trip to ensure the person's safety?
● Yes
● No
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● 1. In the human body.
● 2. In the socket.
● 3. In the power supply cables.
Right Wrong
Let's summarise: Earth leakage protection operation
The protection device prevents the current from rising above 30 mA?
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Protection against electrocution by direct contact
A person touches...
Because of...
Protection is ensured by...
The current detected by the earth leakage protection device is...
The sensitivity of the protection device is...
The protection device trips…
1. An electrical part
2. A non-electrical metal part
1. A short-circuit
2. A failure of accessible insulant
1. Always an earth leakage protection device
2. An earth leakage protection device or a circuit breaker
1. Different from the current felt by the person
2. Equal to the current felt by the person
1. Always 30 mA
2. Variable according to the installation
1. Following direct contact
2. Before direct contact
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Contents
Understand the current risks
Position earth leakage protection devices in an electrical installation
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Socket-outlets
Child's room in a new home
Do the socket-outlets comprise a risk...
● 1. High
● 2. Medium
● 3. Low
Right Wrong
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Lighting
Plastic ceiling fixture in the dining room of a new home
Does this ceiling fixture comprise a risk...
● 1. High
● 2. Medium
● 3. Low
Right Wrong
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Lighting
Plastic ceiling fixture in the bathroom of a new homeDoes this ceiling fixture comprise a risk...
● 1. High
● 2. Medium
● 3. Low
Right Wrong
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Lighting
Plastic fixtures in the bathroom of a new homeHow can protection be provided...
● 1. A 30 mA RCD
● 2. A 100 mA or higher RCD
● 3. Earthing + a device that trips in the event of an insulation fault
Right Wrong
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Circuits to be protected against electrocution by direct contact
Dry environment
Protection against direct contact
mandatory
Protection against direct contact recommended
Wall sockets
Fixed lighting / insulating casing
Wet environment
Lighting
Wall sockets
Fixed devices / metal casing
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This device is an RCCB.Will it trip in case of .....
Right Wrong
● 1. …overloads
● 2. …short-circuits
● 3. …earth leakage faults
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In this switchboard, which circuit should be equipped with earth leakage protection against direct contact?
Right
Wrong
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Where would you position this RCCB?
● 1. In place of the circuit breaker
● 2. In addition to the circuit breaker
● 3. At the incoming point of the switchboard
Right Wrong
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Where would you position the RCCB?
● 1. At the incoming point of the switchboard
● 2. On the socket-outlet circuits
Right Wrong
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