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close this bookIntroduction to Electrical Engineering - Basic vocational knowledge (Institut für Berufliche Entwicklung, 213 p.)
View the document(introduction...)
View the documentPreface
View the document1. Importance of Electrical Engineering
close this folder2. Fundamental Quantities of Electrical Engineering
View the document2.1. Current
View the document2.2. Voltage
View the document2.3. Resistance and Conductance
close this folder3. Electric Circuits
View the document3.1. Basic Circuit
View the document3.2. Ohm’s Law
close this folder3.3. Branched and Unbranched Circuits
View the document3.3.1. Branched Circuits
View the document3.3.2. Unbranched Circuits
View the document3.3.3. Meshed Circuits
close this folder4. Electrical Energy
View the document4.1. Energy and Power
View the document4.2. Efficiency
View the document4.3. Conversion of Electrical Energy into Heat
View the document4.4. Conversion of Electrical Energy into Mechanical Energy
close this folder4.5. Conversion of Electrical Energy into Light
View the document4.5.1. Fundamentals of Illumination Engineering
View the document4.5.2. Light Sources
View the document4.5.3. Illuminating Engineering
View the document4.6. Conversion of Electrical Energy into Chemical Energy and Chemical Energy into Electrical Energy
close this folder5. Magnetic Field
View the document5.1. Magnetic Phenomena
View the document5.2. Force Actions in a Magnetic Field
close this folder5.3. Electromagnetic Induction
View the document5.3.1. The General Law of Induction
View the document5.3.2. Utilisation of the Phenomena of Induction
View the document5.3.3. Inductance
close this folder6. Electrical Field
View the document6.1. Electrical Phenomena in Non-conductors
close this folder6.2. Capacity
View the document6.2.1. Capacity and Capacitor
View the document6.2.2. Behaviour of a Capacitor in a Direct Current Circuit
View the document6.2.3. Types of Capacitors
close this folder7. Alternating Current
View the document7.1. Importance and Advantages of Alternating Current
View the document7.2. Characteristics of Alternating Current
View the document7.3. Resistances in an Alternating Current Circuit
View the document7.4. Power of Alternating Current
close this folder8. Three-phase Current
View the document8.1. Generation of Three-phase Current
View the document8.2. The Rotating Field
View the document8.3. Interlinking of the Three-phase Current
View the document8.4. Power of Three-phase Current
close this folder9. Protective Measures in Electrical Installations
View the document9.1. Danger to Man by Electric Shock
close this folder9.2. Measures for the Protection of Man from Electric Shock
View the document9.2.1. Protective Insulation
View the document9.2.2. Extra-low Protective Voltage
View the document9.2.3. Protective Isolation
View the document9.2.4. Protective Wire System
View the document9.2.5. Protective Earthing
View the document9.2.6. Connection to the Neutral
View the document9.2.7. Fault-current Protection
View the document9.3. Checking the Protective Measures

9.2.6. Connection to the Neutral

A protective measure which can be realised, easily and at low expediture is the connection to the neutral; it provides a good protective effect. All conductive parts and units not belonging to the service circuit are connected with the protective conductor (PE) which is connected with the earthed neutral conductor (N). Protective conductor and neutral conductor may in this case be formed by a common conductor (PEN) (protective conductor carrying current in operation) or they may be installed separately (protective conductor not carrying current in operation).

In the case of a breakage of the PEN conductor at the supply side, a high contact voltage may occur at the protective conductor under unfavourable conditions (danger of Life!). Therefore, additional comprehensive regulations must be observed for the installation of the protective conductor carrying current in operations, especially in overhead local transmission lines. Further, a connection of the PEN conductor to the earth bus at the feeding point and sometimes also in the network spurs is required. An effective potential equalisation must be provided, in the customer installation.

If, for the connection of safety plugs, a two-core lead is used (protective conductor carrying current in operation), the lead (also known as supply line) must be connected to the protective contact first and then it must be brached off to the current carrying connection (see Fig. 9.6.). The fault-current circuit for body contact of L1 with the motor casing shows that the fault current flows through the fuse. For the breaking current the equation 9.2. also is applicable in this case.

Under certain conditions, monitoring of the voltage at PEN to reference earth may be required; in this case an all-pole cut-out is effected when a maximum permissible voltage is exceeded.

Fig. 9.6. Connection to the neutral (also known as multiple protective earthing)

1 - Protective contact socket
2 - Pipes and other conductive parts in buildings
IF = fault current
RB = operational earthing resistance