Safety service is defined in IEC 60364-56 as an electrical system for electrical equipment provided to protect or warn persons in the event of a hazard, or essential to their evacuation from a location. Other standards such as IEEE refer to it as Emergency System.
Examples of safety services include:
- emergency (escape) lighting
- fire pumps
- fire rescue services lifts
- alarm systems (i.e. fire alarms, CO alarms and intruder alarms)
- evacuation systems
- smoke extraction systems
- essential medical systems.
The electrical supply system for safety services are classified as:
- non-automatic supply
- the starting of which is initiated by an operator, or
- automatic supply
- the starting of which is independent of an operator.
An automatic supply is further classified according to the maximum changeover time:
- no-break: an automatic supply which can ensure a continuous supply within specified conditions during the period of transition, for example as regards variations in voltage and frequency
- very short break: an automatic supply available within 0.15 s
- short break: an automatic supply available within 0.5 s
- average break: an automatic supply available within 5 s
- medium break: an automatic supply available within 15 s
- long break: an automatic supply available in more than 15 s.