POWER May 2016 - 18

Battery-Monitoring
System Improves Safety,
Reliability, and Efficiency
When management decided to purchase
and install a new, vented lead-acid battery
system at the Dogwood power plant,
decision-makers also investigated the
benefits of adding a continuous batterymonitoring
system. The reasoning behind
the research was simple: In spite of the
battery's static presence in the plant, and
(hopefully) infrequent use, power plant
battery systems require a great deal of labor
to monitor and test. But monitoring
and testing is necessary due to the critical
importance of battery systems when an
emergency situation arises.
The Dogwood facility (Figure 1) is a
655-MW natural gas-fired, combined cycle
plant located in Pleasant Hill, Mo., near
Kansas City. It is equipped with two Siemens-Westinghouse
501FD2 combustion
turbines and one Toshiba T6065 steam
turbine. Through its operator, NAES Corp.,
owner Kelson Holdings has undertaken
this and several other initiatives to enhance
reliability, such as installing generator
flux probes to improve predictive
maintenance capability and adding a secondary
plant historian to consolidate data
from four different control systems and
streamline sampling and analysis.
Precarious Battery Monitoring and
Testing Situation
Given the amount of monitoring and testing
that batteries require, it's no surprise
that the work gets heavily scrutinized
during North American Electric Reliability
Corp. (NERC) audits: It's an easy target for
violation. Few other pieces of equipment
demand so much monitoring and testing
1. Dogwood power facility. The 655MW
combined cycle plant is located in Pleasant
Hill, Mo., near Kansas City. Courtesy:
NAES Corp.
or involve such a wide array of requirements
and intervals.
Dogwood operators were required to
take voltage readings manually on the entire
battery bank at the positive and negative
terminals of the first and 60th cells.
In practice, the work involved a considerable
stretch to place probes at the two
locations (Figure 2). Using a permanently
installed monitor would allow operators
to collect this metric at one convenient
location with less risk and less potential
for error.
Like many power plants, Dogwood has
a stacked and offset battery arrangement,
with the upper row set above and stepped
back from the lower set. Frequently, a ladder
was needed to reach over and across
the lower row of cells, and this was required
for each of 30 individual cells per
row of staggered cells.
Any time a worker must deal with the
individual cells of the battery, there's a
possibility of creating a short circuit in a
cell or range of cells if contact is made
with the battery posts. A monitoring system
would eliminate this hazard by displaying
the voltage of each cell at one
location for each of the two banks.
A Conluence of Safety and
Convenience
While full-time monitoring would provide
the great convenience of collecting bank
voltage, cell voltage, float amps, and cell
temperature at one convenient location,
management needed more than simply
convenience to justify the installation of
a new monitoring system. What the group
found was the confluence of convenience
with a number of major safety improvements
that could be realized.
Performing maintenance on a vented
lead-acid battery requires taking frequent
specific gravity readings. This means dealing
with the electrolyte, which is an acid
that can cause serious harm. Although
Dogwood's staff routinely wore all of the
proper protective gear, the job was still a
high-risk activity.
While the monitoring system doesn't
take specific gravity samples, according
to IEEE standard 450-2010, IEEE Recommended
Practice for Maintenance, Testing,
and Replacement of Vented Lead-Acid
Batteries for Stationary Applications, it
doesn't have to. The standard says, " For
technologies other than lead antimony, if
18
www.powermag.com
POWER | May 2016
battery float charging current is NOT used
to monitor state of charge, specific gravity
must be checked (number of cells is
dependent upon the periodicity of the test
being performed). "
Dogwood's owners made a point of procuring
a monitoring system that would in
fact monitor the float current. Because the
plant's batteries are lead calcium, the system
would preclude the need to perform
regular testing of the electrolyte and thus
eliminate exposure to the chemical hazard.
As mentioned, it would also reduce the
possibility of creating an induced short in
the battery system by eliminating the need
to reach over cells during testing.
Another benefit, besides the sheer convenience,
would be the increased efficiency
of collecting data. Operators could simply
go to the monitor (Figure 3) and collect
bank voltage, each cell voltage, representative
cell temperatures, and float amperage
at one location and in just a couple
of minutes-roughly the same amount of
time it took to visit one individual cell,
collect a reading, and record that value.
This would free up a substantial amount
of time to conduct other plant activities.
The reduction in time needed to perform
specific gravity readings reduced the time
spent doing preventive maintenance on
batteries even more.
2. Tight squeeze. Maintenance Coordinator
Glenn Brons demonstrates how difficult
it was to test bank voltage before the
new battery-monitoring system was installed.
Courtesy: NAES Corp.
http://www.powermag.com
POWER May 2016

Table of Contents for the Digital Edition of POWER May 2016
