Ieee std 1159-1995, ieee recommended Practice for Monitoring Electric Power Quality

7.1.2 Plug- and receptacle-type connections
Some sense cords have insulated plugs capable of being stacked one on top of the other. Caution shall be
exercised so that when stacking, only common connections are made rather than creating an inadvertent
short circuit. Always double-check the jumpers to assure that short circuits have not been introduced. Also,
connect the sense leads to the monitored circuit only after the leads have been connected (stacked) to the rear
of the analyzer and checked for correctness.
7.1.3 Guarding of live parts
Often panel covers are removed for hook-up or during the monitoring period. If so, all live parts must be
adequately protected and the area should be kept inaccessible. If screw terminals are used in the monitoring
equipment, exposed wire should be kept to a minimum and appropriate covers used to insulate the termina-
tions. Connecting multiple common wires with single set screws should be avoided.
7.1.4 Monitor placement
The monitor should be placed securely so that there is no chance of the instrument moving or loosening
connections. If a paper printer is used for reporting disturbances, adequate precautions should be taken to
ensure that accumulating paper does not present a hazard. Monitors should not be left where excessive heat,
moisture, or dust may damage the equipment or jeopardize the data collection process.
A monitor should not be placed in a heavily traveled hallway. The monitor should be placed so that it does
not pose a safety hazard to those working in the area. A protective enclosure or barrier can sometimes be
used to alleviate this concern. Also, the location should not pose an undue safety hazard to the person install-
ing the monitor. There are many locations that are too cramped, or in other ways, physically constrained, to
allow safe connection of monitoring leads. In these situations, an alternative location should be selected.
Any number of external environmental factors may affect the performance of a power monitoring instrument.
These environmental factors may include temperature, humidity, RFI Þelds, static discharge, and mechanical
shock and vibration.
Temperature is a critical factor in any microprocessor-based power monitoring instrument. The internal
physical geometry of the various electronic components are so small that signal path lengths, impedances,
and clearances may be affected if the temperature of the environment exceeds the speciÞcations of the
instrument.
Humidity, like temperature, is critical for the sensitive electronics enclosed in the power monitoring instru-
ment. Excessive humidity may cause condensation inside the instrument, which can lead to electrical shorts,
arcing, corrosion, and ultimately, erroneous data. Air that is too dry invites static discharge that can damage
electronic components within the instrument. Other symptoms of static discharge are signal disruption or
difÞculties in programming the instrument.
Erroneous data may be generated when monitors are installed in areas that are exposed to various levels of
radio frequency interference. Interference may be induced into the instrument through the input leads. If the
data collected looks unrealistic, it may be the result of external radio-frequency interference.

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IEEE
MONITORING ELECTRIC POWER QUALITY
Std 1159-1995
37
Mechanical shock and vibration can create stresses inside the instrument that weaken mechanical connec-
tions and cause arcing and erroneous data generation. When the instrument is installed in an area that is
susceptible to mechanical stresses, the user should be careful to assure that the instrument can withstand and
function correctly in the environment. Due to vibration and mechanical stresses in transporting instruments
to the monitoring site, instrument operation prior to use should be veriÞed.