scope:

This document establishes a methodology to determine fault managed power system response to various simulated human contact scenarios. A human body resistance model is defined and presented in Annex A to include total body resistance values representing the vast majority of the population under a wide range of surface area of contact and skin conditions. Detailed fault test plans are presented for use in conjunction with the human body resistance model to measure system response to simulated human hand to hand and hand to foot contact situations.

The intent of this Technical Report (TR) is to review only the fault managed portion(s) of fault managed power systems. The fault managed portion(s) of a fault managed power system (FMPS) are comprised of the output power terminals of the Power Sourcing Equipment (PSE), the input and output power terminals of Active Extension Nodes (AEN) (when employed), the input power terminals of the Powered Device (PD) and the conductors connecting them. See figures 4.2 and 4.4 for graphical representations of the fault managed portion(s) of fault managed power systems.

This TR does not review power input to the PSE or power output of the PD or power within the PSE, AEN or PD equipment. This TR is not intended to cover or review the PSE, PD and AEN equipment. The PSE, PD and AEN equipment would be covered under their applicable hazard-based safety reviews.

This Technical Report addresses the risk of ventricular fibrillation under various human contact fault scenarios and is not intended to review reaction or startle response.

The FMPS criteria and test protocols established by this Technical Report:

• Apply to the fault managed portion of FMPSs used exclusively to provide power to communications equipment located in the communications space as defined by the NESC.

• Have been developed on the premise that only qualified communication workers who are trained to work with powered communication circuits shall have access to live parts.

This TR provides testing protocols for fault managed power systems that may allow human contact with energized power terminals and conductors comprising the fault managed portions of such systems. Human contact fault analysis presented in this TR is expected to serve as a subset of functional safety testing for fault managed power systems. This TR is not intended to evaluate facility access systems in the form of physical barriers or safety interlocks that may be incorporated into the design of some fault managed power systems. The effectiveness of a facility access system, if present, may be evaluated as part of the NRTL Listing of the overall fault managed power system. See Annex F for additional information on systems that provide preclusion from hazardous voltage contact.

There may be systems or sections of systems that provide inherent safety through the use of contact preclusion via systems such as interlocks and physical barriers. Such systems or sections of systems can be inherently as safe as a FMPS that monitors and reacts via fault detection to human contact with live parts such as bare conductors. For systems or sections of systems that provide contact preclusion, sections of this TR are not applicable since the TR is intended to review contact to live bare conductors. A test lab evaluating a system that incorporates preclusions to prevent contact with live parts, would indicate in the test report that the preclusion portion of the system is not applicable to testing. The system manufacturer shall indicate which sections of the system provide FMPS protection via human contact detection. See section 5 for additional information.

For any system or sections of systems that employ physical barrier (touch-preclusion) fault management that precludes FMPS testing in a prescribed section of the system (by eliminating hazardous voltages prior to human contact), the barrier protection must be avoided or defeated to perform that segment of fault testing.

This TR is limited to human contact fault analysis and does not address any fire safety requirements or testing procedures.

Additional topics discussed in this TR as they relate to FMPSs include transient tolerance testing, thermal exposure / thermal management, and software analysis & functional safety standard compliance.