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Electrical Hazards

Electrician during test work on a control cabinet © Uwe Völkner, FOX photo agency

In the observation period from 2000 to 2015, between 36 and 100 people died annually as a result of electrical accidents. Approx. 90 % of these cases were caused by low voltage and approx. 10 % by high voltage. Low voltage includes alternating voltages of 50 to 1 000 volts and direct voltages of 75 to 1 500 volts. The high-voltage range borders on the low-voltage range, i.e. it addresses AC voltages from 1 000 volts (1 kV) and DC voltages from 1 500 volts (1.5 kV).

Existing electrical hazards can cause electrical accidents. These often damage the health of people and animals. Electricity can also cause fires and explosions. This chapter, considers those electrical hazards that lead to the endangerment of people only.

Electrical hazards due to electric shock or arcing can arise when using electricity at work (e.g. using electrical equipment) or when carrying out non-electrical work in the vicinity of live equipment. If an arc occurs unintentionally as a result of a defect or a switching operation, this is referred to as an arc fault.

Depending on the voltage level, both hazards can occur either simultaneously or individually. The hazard of electric shock is dominant in the range of voltages up to 1 000 V AC and the hazard of arc flash is dominant for voltages above 1 000 V AC. Due to the strong coupling of the two individual hazards "electric shock" and "arc fault", it is difficult to separate the assessment criteria and the occupational safety measures to be applied. For this reason, they are dealt with together in section 2.1.

Furthermore, an electrical hazard due to static electricity can occur even without the presence of a power source. This is caused, for example, by mechanical separation and thus isolation of similar or different substances (so-called charge separation). In addition to the possibility of igniting an explosive atmosphere by electrostatic discharge, static electricity can also have a direct hazardous effect on people by electric shock or cause secondary accidents by startle reactions. The latter relationships are described in section 2.2.
Although these electrical hazards are rather common, due to changes in technology, there are industries in which the safe operational handling of electrical hazards must first be "learned" through additional qualification of the employees, if necessary.


New requirements for the repair of electrically powered vehicles

Employees in the field of vehicle repair and maintenance are particularly affected by the changeover from classic combustion technology to electrically powered vehicles. In the electric drive trains present, there are components for energy storage (e.g. lithium-ion accumulators, fuel cells, buffer capacitors), energy transmission (e.g. DC link busbars, power lines), energy conversion (e.g. frequency converters and inverters), and actuators (e.g. wheel hub motors). Voltages significantly above conventional vehicle electrical systems (up to 30 V AC/60 V DC) can occur at all of the drive system components listed here as examples. In order to delimit this hazard area, the so-called high-voltage area was introduced in the electro mobility sector, which includes voltages < 30 V AC to ≤ 1 000 V AC and > 60 V DC to ≤ 1 500 V DC (cf. DGUV Information 200 005: Qualification for work on vehicles with high-voltage systems).

Repair, testing and maintenance work on such drive components may only be carried out by experts for work on high-voltage systems or by competently instructed persons under the supervision and direction of an expert for work on high-voltage systems (cf. DGUV Regulation 109-009: Vehicle Maintenance, Section 7.1).

In contrast, electrical equipment in motor vehicle attachments and mounted equipment (e.g. electric, speed-controlled winches) fall within the scope of the Machinery Directive. According to DGUV Regulation 3, electrical work on such components may only be carried out by individuals who, on the basis of their technical training, knowledge and professional experience as well as knowledge of the relevant regulations, can assess the work assigned to them and recognise possible hazards, such as a qualified electrician (cf. DGUV Regulation 109-009: Vehicle Maintenance, Section 7.1).

Author

  • Dipl.-Ing. Björn Kasper

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