SAFETY MANUAL - Tuv-fs.com

SAFETY MANUAL
2. Alternatively, the earth braid can be connected between the chassis earth
terminal and the equipment mounting rails. This method is acceptable only if
all the TMR equipment is located in a single cabinet or in multiple cabinets
that are joined together.
3.13.3 Electrostatic Handling Precautions
The following handling precautions shall also be observed:
1. Personnel should earth themselves before handling modules.
2. Modules should not be handled by their connectors.
3. Do not remove modules from their packaging until required for use.
4. The EMI gasket material on the chassis and modules is fragile. Do not touch
the gasket as this can leave an oil residue that will impair the effectiveness of
the gasket. Touching the gasket may also damage the flanges of the gasket.
3.14 SYSTEM POWER REQUIREMENTS
The system’s power supplies and distribution, if incorrectly designed, present a
potential common cause failure. It is therefore necessary to:
• Establish the power philosophy, specific earthing philosophy 4 , required
voltage and power requirements, and the separation requirements where
items of equipment are separately supplied, e.g. system internal supplies
and field loop supplies.
• Define the architecture of the Power Supply Units (PSU), e.g. 100%
redundancy, dual N+1 redundancy, etc. and ensure that each power
source is of adequate capability.
• Ensure that the PSUs are compatible with the power feeds provided.
Alternatively, measures should be implemented to ensure that the PSU
power feeds remain within the PSU specifications.
• Define the power distribution requirements, together with the protective
philosophy for each distribution, e.g. current limited at source or protective
devices. Where protective devices are used, it is important to establish
that the sufficient current be available to ensure their protective action and
that the protective device can break the maximum prospective fault
current.
• Ensure that the power distribution media is sized to accommodate the
maximum prospective fault currents and tolerable voltage losses. This is
specifically important where floating supplies are employed and other
power sources may result in high prospective fault currents in the event of
multiple earth-fault conditions.
The system modules require two 24V dc power feeds, with a common return path,
i.e. the 24V return is common between the power feeds.
4 ICS Triplex Technology Ltd. recommends that the negative side of the field supply be connected to
earth (ground). This will avoid possible fail danger conditions that can be caused by some earth fault
monitors used with floating power supplies.
Doc No P8094 Page 70 of 67
Issue 14 September 2003