SELDIF is a model intended to make students aware of the hazards of electrocution in the event of indirect contact, and those related to the quality of the earth. This model also explains the role of the residual current circuit-breaker 30mA in a domestic installation.
The front synoptic shows:
- The public network, with its medium voltage/low voltage transformer substation, and the neutral to earth connection, in this substation.
- The transmission line from the transformer substation to the dwelling.
- The domestic installation, with the residual current circuit-breaker 30mA, the local earth, and a washing machine. The TT neutral system is the same as that of a domestic installation.
- A person in the right-hand part has an LED for a heart. If a dangerous leakage current flows here, the LED lights up.
- A two-pole industrial residual current circuit-breaker 30mA is located in the centre of the synoptic.
- Two jumpers enable the washing machine to be fully isolated, and current measurements to be taken.
- An ON pushbutton starts the washing machine, and a green LED lights up, symbolizing rotation of the machine.
Safety terminals 4mm, located on the front, let the student measure the fault currents, and insert different resistive modules. These modules simulate two earth resistance values, and two leakage current values.
One module with variable resistance enables the differential's tripping current to be measured.
To prevent any risk of electrocution to the student, the model operates at extra low voltage using an isolating transformer to standard NFEN60-742.
THEORETICAL SUMMARIES: DOCUMENTATION SUPPLIED
- Operation of a magneto-thermal circuit-breaker: rating, breaking capacity, tripping curve, symbols.
- Operation of a residual current circuit-breaker: rating, tripping time, symbols.
- Physiological effects of the current: hazard zones, current function times, dangerous voltages.
- Maximum resistance of the earth.
LIST OF PRACTICAL ASSIGNMENTS:
Earth < 100 Ohm and fault resistance with poor isolation:
- with person in contact with the metal enclosure of the machine.
- without contact.
Appearance of a fault current greater than 30mA, tripping of the differential.
Demonstration of the short circuit.
Earth < 100 Ohm and fault resistance with good isolation:
- Appearance of a fault current less than 30mA, no tripping of the differential.
- Measurement of the fault current in the person in contact with the machine.
Earth > 100 Ohm and fault resistance with good isolation:
- Appearance of a fault current less than 30mA, no tripping of the differential.
- Measurement of the fault current in the person in contact with the machine.
Earth > 100 Ohm and fault resistance with poor isolation:
- with person not in contact with the metal enclosure of the machine measurement of the fault current
- with person in contact with the enclosure: measurement of the fault current greater than 30mA, no tripping of the differential. LED symbolizing the heart, lighting up.
OTHER TECHNICAL CHARACTERISTICS:
Power supply: 230VAC 50Hz - Dimensions/Weight: 390x270x100mm / 2.8kg
Supplied with 5 resistive modules, coupling jumpers and leads.
The front synoptic shows:
- The public network, with its medium voltage/low voltage transformer substation, and the neutral to earth connection, in this substation.
- The transmission line from the transformer substation to the dwelling.
- The domestic installation, with the residual current circuit-breaker 30mA, the local earth, and a washing machine. The TT neutral system is the same as that of a domestic installation.
- A person in the right-hand part has an LED for a heart. If a dangerous leakage current flows here, the LED lights up.
- A two-pole industrial residual current circuit-breaker 30mA is located in the centre of the synoptic.
- Two jumpers enable the washing machine to be fully isolated, and current measurements to be taken.
- An ON pushbutton starts the washing machine, and a green LED lights up, symbolizing rotation of the machine.
Safety terminals 4mm, located on the front, let the student measure the fault currents, and insert different resistive modules. These modules simulate two earth resistance values, and two leakage current values.
One module with variable resistance enables the differential's tripping current to be measured.
To prevent any risk of electrocution to the student, the model operates at extra low voltage using an isolating transformer to standard NFEN60-742.
THEORETICAL SUMMARIES: DOCUMENTATION SUPPLIED
- Operation of a magneto-thermal circuit-breaker: rating, breaking capacity, tripping curve, symbols.
- Operation of a residual current circuit-breaker: rating, tripping time, symbols.
- Physiological effects of the current: hazard zones, current function times, dangerous voltages.
- Maximum resistance of the earth.
LIST OF PRACTICAL ASSIGNMENTS:
Earth < 100 Ohm and fault resistance with poor isolation:
- with person in contact with the metal enclosure of the machine.
- without contact.
Appearance of a fault current greater than 30mA, tripping of the differential.
Demonstration of the short circuit.
Earth < 100 Ohm and fault resistance with good isolation:
- Appearance of a fault current less than 30mA, no tripping of the differential.
- Measurement of the fault current in the person in contact with the machine.
Earth > 100 Ohm and fault resistance with good isolation:
- Appearance of a fault current less than 30mA, no tripping of the differential.
- Measurement of the fault current in the person in contact with the machine.
Earth > 100 Ohm and fault resistance with poor isolation:
- with person not in contact with the metal enclosure of the machine measurement of the fault current
- with person in contact with the enclosure: measurement of the fault current greater than 30mA, no tripping of the differential. LED symbolizing the heart, lighting up.
OTHER TECHNICAL CHARACTERISTICS:
Power supply: 230VAC 50Hz - Dimensions/Weight: 390x270x100mm / 2.8kg
Supplied with 5 resistive modules, coupling jumpers and leads.
Properties
- SELDIF/ELE