User's Manual Part 3

Maintenance and Servicing - 153 -
Affinity® LBD-200C-N1 Transmitter
Product Manual
x Electronic equipment with control ground and power ground makes the issue of the
system grounding more complex.
x In new installations, connections may be left off or may not be properly tightened.
x Loads cycling on-and-off produce heating and cooling that eventually result in poor
joints with high impedance
x Periodic additions or modifications to the distribution system can result in missing,
improper, and poor quality connections.
x Multiple control or power grounds belonging to different facilities and connected to
the same ground will cause loop currents.
x With the introduction of many converter and solid-state power supplies, the steady
state neutral current becomes significant, which is not desirable and has to be
monitored and corrected.
Acceptance Criteria
A grounding audit must be performed to ensure that acceptance criteria are maintained. Voltage
limits, and neutral and ground bonding must be evaluated. Voltage limits: Line-to-ground
voltage, and line-to-neutral voltages, must be within 5% of the nominal voltage as per ANSI
Standard 84.1. Any voltage deviation above or below the defined limit may affect equipment
performance. Voltage drop-in feeders that serve sensitive electronic equipment shall be no
more than 2% under the actual load conditions as per IEEE Standard 1100. This is not a
requirement, but this practice may help to achieve better equipment performance.
Neutral and ground bonding: A voltage measurement between the neutral and ground will
indicate voltage in the milli-volt range under normal operating conditions. A reading of zero volts
indicates the presence of a nearby neutral-ground bond. This condition is acceptable.
x Excessive current on equipment ground can indicate the presence of a load-side
ground connection. This condition requires careful visual inspection.
x Open or ungrounded equipment has to be identified by visual inspection. This
condition must be remedied.
Corrective Measures
The following are some of the typical items that require corrective measures followed by the
results of field measurements.
x Missing equipment ground connection. This ground connection must be installed.
x Missing interconnection from the industrial ground to the utility ground has to be
connected.
x Reversed connection between the neutral and the ground must be corrected.
x Multiple control grounds from the adjacent facilities connected to the same ground
to provide isolated grounding for the facility.
x Rectify loose ground connections. Loose connection in the ground connections
produces high impedance connection and has contact resistance.