Residual current protection devices specified in the C 60755 standard are primarily designed to provide protection against the danger of dangerous and potentially lethal electric shocks.
IEC 60755 specifies the operating characteristics for these devices, details of how they are to be installed to provide the desired level of protection are given in various sections of IEC 364(1).
There are two basic conditions for protection against the danger of electric shock: Protection against indirect contact and protection against direct contact.
Protection against indirect contact covers devices used to prevent dangerous voltages remaining on accessible metal parts, which must in all cases be earthed. Thus, these metal parts become live only under ground fault conditions.
In such circumstances, the danger does not arise from the user's direct contact with a live conductive part, but from touching grounded metal parts that are in contact with a live conductive part.
Rules; It recognizes that a residual current device of sufficient sensitivity (IEC 60755 Clause 5.14 Table IV) provides a high degree of protection also in direct contact with a live conductive part.
However, it is clearly stated that the use of the residual current device for this purpose is not seen as a different method of protection but as a complement to direct grounding.
In other words, the primary function of residual current devices is to provide protection against 'indirect contact', but with devices of sufficient sensitivity (e.g. units with operating residual currents not exceeding 30 mA), they provide an additional benefit of high-degree protection in the event of direct contact of the user with a live conductive part when other protection methods fail.
However, it is clearly stated that the use of the residual current device for this purpose is not seen as a different method of protection but as a complement to direct grounding.
In other words, the primary function of residual current devices is to provide protection against 'indirect contact', but with devices of sufficient sensitivity (e.g. units with operating residual currents not exceeding 30 mA), they provide an additional benefit of high-degree protection in the event of direct contact of the user with a live conductive part when other protection methods fail.
The operating characteristics given in IEC 60755 are based on the rules prepared according to the information contained in IEC 479.
These devices also provide very good protection against the possibility of fire as a result of earth leakage currents, which can continue for a long time without the overcurrent protection devices working.
IEC 60755 covers residual current-operated protective devices (hereinafter referred to as residual current devices) designed primarily to protect against the risk of electric shock, with a rated voltage not exceeding 440 Volts and a rated current not exceeding 200 Amperes in alternating current.
- IEC 60755 can also be used as a guide for residual current schemes with rated currents above 200 Amperes and voltages up to 1000 Volts in alternating current.
IEC 60755;
- Devices that simultaneously examine the residual current (IEC 60755 Clause 2.3.4) in comparison with the reference value (IEC 60755 Clause 2.3.5) and open the protected circuit when the residual current exceeds the reference value (IEC 60755 Clause 2.3.6),
- It is applied to a group of systems, each of which performs one or two of the above functions, but acts in a way that creates all three functions together.
Supplementary or special rules are required for residual current arrangements intended to fulfill only one or two of the above three functions, whether or not they include overcurrent protection as an integral whole.
For devices that perform other functions in addition to those mentioned above, IEC 60755 applies together with the standards for additional functions.
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