Page 279 - Electrical Safety of Low Voltage Systems

262 Chapter Fifteen

designers cannot rely upon balanced bridges to achieve safety in med-
ical locations.

Endnotes

1. The international standard IEC 60364–7-709; 2007–05, 2d ed., “Electrical Instal-
lations of Buildings—Part 7: Requirements for Special Installations or Locations—
Section 709: Marinas and Pleasure Craft” defines pleasure craft as any boat used
exclusively for sport or leisure.
2. We can assume the seawater to have a resistivity of 10 · m.
3. IEC 60950–1 “Information Technology Equipment—Safety—Part 1: General Require-
ments,” Ec1:2006–08.
4. Electrical noise is caused by unintentional, and unpredictable, high-frequency
potential differences between electronic units. These voltage differences may
be caused by electromagnetic interferences radiated and received by electronic
equipment. The noise can cause the failure of components, as well as errors in
data/signal processing.
5. Broken lines or dewired pantographs must be considered energized, as they
may also be in contact with other neighboring live pantographs or contact lines.
6. “Railway Applications—Fixed Installations Part 1: Protective Provisions Relating to
Electrical Safety and Earthing,” EN 50122–1:1997–06.
7. In fish tanks, failures of electrical items (e.g., oxygenators, light fixtures, etc.)
are generally not dangerous to the fish, as their exposed surface to the leakage
current is very small.
8. IEC 60364–7-702:1997–11, “Electrical Installations of Buildings—Part 7: Require-
ments for Special Installations or Locations—Section 702: Swimming Pools and Other
Basins.”
9. IEC 60364–7-706:2005, “Electrical Installations of Buildings—Part 7: Requirements
for Special Installations or Locations—Section 706: Conducting Locations with Re-
stricted Movement.”
10. IEC 60364–7-714:1996, “Electrical Installations of Buildings—Part 7: Requirements
for Special Installations or Locations—Section 714: External Lighting.”
11. A catheter is a tube, flexible or rigid, which allows both drainage of physio-
logical fluids and injection of solutions for therapeutic purposes (e.g., saline
solution). Both liquids must be considered conductive.
12. In conditions of macroshock, upon touch of an energized part, less than 10%
of the body current circulates through the cardiac muscle (see Sec. 5.4.2).
13. IEC 60601–1-SER, 1st ed. , 2008–01-22 “Medical Electrical Equipment.”
14. In ordinary locations, the second fault is not dangerous, as the nongrounded
equipotential bonding conductors reduce the potential difference between en-
closures to harmless values for persons (Fig. 2.18).
15. See App. B for more details on balancing bridges of impedances.