IEC TR 63167 pdf free download
IEC TR 63167 pdf free download.Assessment of contact current related to human exposure to electric, magnetic and electromagnetic fields.
It is noteworthy that different methods for evaluation of conformity to the guidelines are provided for multiple-frequency exposure for low-frequency (below 100 kHz) and high-frequency (above 10 kHz) ranges. In the frequencies between 10 kHz and 100 kHz, both evaluation methods are applied (see Annex A).
6 Consideration in evaluating contact currents
6.1 General
Clause 6 describes items to be considered in evaluating contact currents:
a) assumed situations of human exposure to a contact current (6.2);
b) methods for evaluating a touch current used in electrical safety standards for references (6.3);
c) some proposed methods for evaluating contact currents (6.4).
6.2 Assumed situations of human exposure to contact current
6.2.1 General
There are several situations to be considered for human exposure to a contact current.
Different cases have to be considered depending on the type of coupling between fields
(electric or magnetic) and human bodies/objects.
6.2.2 Capacitive coupling (power line)
An electric field induces, by capacitive coupling (electrostatic induction), a voltage in a person or a conductive object that is isolated from the ground. When a person touches an object having a different potential, a contact current flows so as to cancel the potential difference. This can be categorized into two cases: (a) an isolated person touches a grounded object and (b) a grounded person touches an isolated object (especially a large object such as a bus or a truck) [6]. Comprehensive studies have been carried out for typical cases encountered under overhead transmission lines [7].
6.2.3 Inductive coupling (power line)
By inductive coupling (electromagnetic induction), a magnetic field induces a voltage, especially in long conductive objects such as telecommunication lines, fences and gas pipelines, having at least one reasonable grounding, when they are installed close to and parallel to magnetic field sources such as overhead power lines [8]. When a person touches the object, a contact current flows. In particular, in the case of fault condition in overhead power lines, the limit values for the open-circuit voltage in telecommunication lines are set by an international regulation-setting body [9]. In contrast to the capacitive coupling, grounding a conductive object at a large distance from the point of contact will actually increase the amplitude of the open-circuit voltage, thereby increasing the contact current.
6.2.4 Induction heating equipment
Induction heating (IH) equipment is heating equipment using the Joule effect produced by magnetically induced currents. For a domestic IH cooker, a metal pan or pot is heated by a magnetic field, and when a person touches a conductive part of the pan or pot, a contact current can occur typically in the frequency ranges of around 20 kHz to 100 kHz. The method used to evaluate human exposure to magnetic fields produced by lH cookers is standardized in IEC 62233 [10]; however, the contact current is not mentioned in IEC 62233. Note that it may be appropriate to categorize this exposure situation as an issue of electrical safety. For industrial IH equipment, a method of evaluating touch current in terms of electrical safety is being standardized in IEC TC 27 (industrial electroheating and electromagnetic processing) for the frequency ranges between 1 kHz and 6 MHz [11].IEC TR 63167 pdf download.
