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25
Technical terms
25.1
General
Protective measures
The test procedures are based on the existing protective measure
of the test sample the efficacy of which must be proven on the
respective accessible conductive part. For the
BENNING ST 755/ ST 760
appliance tester, the following
classification has been made:
Devices with PE connection (Class I)
The active parts of the device are protected against direct contact.
By connecting the accessible conductive parts of the housing to
the protective conductor, these parts are included in the protective
measure of the device concerning direct contact (fault protection).
The fault current is detected by means of the protective conductor
current measurement. The device might also have accessible
conductive parts which are not connected to the protective
conductor. In addition, the fault current is detected by means of the
contact current measurement. The device is provided with a
protective conductor connection (shock-proof plug).
Devices without PE connection (Class II)
Active parts are isolated by means of reinforced or double
insulation (basic insulation and additional insulation). Thus,
protection against direct contact is ensured. The device is also
protected against indirect contact, because an insulation fault is all
but impossible. Nevertheless, such devices might be provided with
accessible metal housing parts. Devices of protection class II are
equipped with a mains plug without protective conductor.
Devices on safety extra-low voltage circuits (Class III)
Devices of protection class III are connected to safety extra-low
voltage circuits (SELV/ PELV) only. Protection against dangerous
shock currents is ensured by the low voltage and safe isolation
regarding other circuits.
25.2
Technical terms according to VDE 0701-0702
Repair
Measures taken to restore the nominal condition of the technical
means of a system.
Modification
A modification is an intervention in the device which is admissible
according to the manufacturer's specifications.
Qualified electrician
A qualified electrician is someone who is able to evaluate the tasks
assigned to him/her due to his/her professional education,
knowledge and experience as well as to the knowledge of the
relevant provisions and who is able to recognize possible dangers.
Electrotechnically trained person
An electrotechnically trained person is someone who has been
informed and instructed (if necessary) by the qualified electrician
regarding the tasks assigned to him/her and regarding possible
dangers in case of improper behavior. Moreover, the
electrotechnically trained person has been instructed with regard
to the required protection equipment and protective measures.
Competent person
In terms of the German Health and Safety at Work Regulation, a
competent person is someone who has the required expert
knowledge for the testing of electrical equipment due to his/her
vocational education, professional experience and recent
occupational activity.According to the German technical guideline
for operational safety "Competent persons
– specific requirements
– electrical hazards" (TRBS 1203), the competent person must
have finished an electrotechnical vocational education or must
have another similar electrotechnical qualification suitable for the
testing of portable electrical equipment to ensure protection
against electrical hazards. The term professional experience
means that the person has at least one year of experience
regarding the installation, assembly or maintenance of electrical
equipment.For the intended testing of portable electrical
equipment, the competent person must have the required detailed
knowledge of electrical engineering as well as of the relevant
electrotechnical regulations and must regularly update this
knowledge.These demands show that safety-related evaluation of
portable electrical equipment basically requires the attributes of a
qualified electrician.
Test
The test comprises measures for determining and evaluating the
actual condition regarding the safety of the device.
Periodic inspection
A periodic inspection is a test which is carried out in certain time
intervals and which is intended for proving the electrical safety.
Contact current
If someone touches parts of a body of an electrical equipment
(device) that are not connected to the protective conductor, the
contact current is the current flowing to earth via the person
touching the device.
Differential current
Vectorial sum of all currents flowing via the active conductors at
the input (connection) of the mains side.
Protective conductor current
Sum of the currents flowing through the protective conductor of
devices of protection class I if the bodies of those devices are
insulated to earth.
Leakage current
Current flowing to earth or to an external conductive part via the
faultless insulation of a device.
Fault current
Current flowing to earth or to an external conductive part via the
faulty insulation of a device.
Alternative leakage current
Current which would flow through the active conductors of a test
sample and the protective conductor or the accessible conductive
parts at nominal voltage or at nominal frequency of the test
sample. Note: Please observe the test circuits!
Insulating resistance
Ohmic resistance of the insulation (insulating materials) between
conductive parts. Note: Only the insulating resistance between the
active parts and the accessible conductive parts is measured.
Protective conductor resistance
Resistance between a conductive part connected to the protective
conductor for protective reasons and the protective contact of the
mains plug or device plug or the protective conductor connection
point of the device.
Electrical appliance
Device (test sample) the condition of which shall be tested with
regard to electrical safety.
25.3
Technical terms according to VDE 0751-1
Accessible conductive part
Any part of a medical electrical device (except for the applied part)
which can be touched by the patient or by the operator touching
the patient or which might come into contact with the patient.
Device leakage current
Current flowing from mains supply units to earth via the protective
conductor as well as via accessible conductive parts of the
housing and via applied parts.
Functional connection
Any type of connection (electrical or other) including those used for
transmission of signals and/or electric power and/or substances.
Inspection
All measures taken to determine and evaluate the actual condition
of the device.
Medical electrical system (ME system)
Combination of individual devices as defined by the manufacturer
among which at least one must be a medical electrical device and
which are connected by means of a functional connection or by
using a multiple socket.
