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SEL APPLICATION GUIDE CASE STUDY
Mining Controls IncorporatedBeckley, West Virginia
Relays Event Reports Prevent Unnecessary Losses in
Materials and Production
SEL-587 Current Differential Relay generates precise event reports that enable
managers of electric power systems to make informed decisions after an equipment
failure or system outage has occurred.

With the high cost of gas and oil fueling the
demand for coal, some coal mining opera-
tions are straining to achieve higher produc-
tion capacities. In addition to vigilance
about safety, this situation underscores the
importance of supplying and distributing
reliable electric power to operate mining
equipment and support the needs of person-
nel above and below ground.
The reliability of such electric power
systems depends on the devices that monitor
and protect them, including relays.
However, in the event of a fault, it is also
vital to mine safety and production that
power systems engineers know what
happened. This information is now available
in the form of event reports that are gen-
erated by some of todays microprocessor-
based protective relays.
In many cases, you have only 15 minutes
before you would have to evacuate a mine
section if an electric power system goes
down, says Jim Goble, Manager of Engi-
neering at Mining Controls Inc. (MCI), a
manufacturer of electrical equipment for the
mining and industrial markets. Located in
Beckley, West Virginia, the heart of coal
mining country, MCI is involved in the
custom design and manufacture of electrical
power distribution equipment and controls
for both surface and underground mining
installations in the coal, precious metals, and
other metal/nonmetal mining industries.
MCI also designs and manufactures spe-
cialty equipment for the tunneling industry.
Event reports can instantly provide a
snapshot of power system conditions when a
fault occurred, Goble continues, which
can be a crucial aid in post-fault analysis and
help determine quickly what should be done
about it. Additionally, event reports can
improve an engineers understanding of both
simple and complex protective scheme
operations and also aid in testing and
troubleshooting relay settings and protection
schemes.

Figure 1With the high cost of gas and oil fueling the
demand for coal, some coal mining operations are straining
to achieve higher production capacities while remaining
vigilant about safety. This underscores the importance of
supplying and distributing reliable electric power to operate
mining equipment and support the needs of personnel above
and below ground.
Goble recently experienced the value of
event reports when commissioning a trans-
former for one of MCIs many coal mine
customers. For monitoring and protection,
Case StudyMining Controls Incorporated
Page 1
MCI used the SEL-587 Current Differential
Relay, a sophisticated yet economical device
from Schweitzer Engineering Laboratories,
Inc. (SEL) based in Pullman, Washington.
Typically used for transformer and motor
protection applications, the SEL-587 Relay
provides oscillographic event reports (up to
ten 15-cycle reports) and metering functions
that reduce or eliminate external recorder
and metering requirements. Because SEL is
an innovator in microprocessor-based relays
with wide acceptance among electric power
utilities, products such as the SEL-587 are
becoming popular in industrial applications
where advanced metering, monitoring,
reporting, and protection features are be-
coming increasingly important.

Figure 2For monitoring and protection, MCI used the
SEL-587 Current Differential Relay, which provides oscillo-
graphic event reports and metering functions that reduce or
eliminate external recorder and metering requirements.
This transformer commissioning project
was the first time we ever used the SEL-587
Differential Relay, Goble explains. We
were simply doing a soak, energizing the
transformer without a load. So at first, we
were concerned that it might not have been a
fault with the new transformer but actually a
problem of the relay tripping, possibly due
to improper settings.
To confirm that the problem was indeed
with the transformer, MCI contacted Derek
Ashby, a sales engineer at Robinson Sales,
the SEL representative in nearby McHenry,
Maryland. Ashby assured Goble that the
SEL relays and reports were highly reliable
but suggested that he email the event report
data to SEL.
The event report clearly indicated that there
was a fault in the transformer, says Greg
Hataway, an SEL Field Application Engi-
neer. And later when they opened up the
transformer, they located the problem.
Hataway adds that event reports show what
went wrong on both sidesthe transformer
and the relay, for example. If you dont
have that information, you have to make
your best estimate. In this case, you would
have to decide whether you would try the
transformer again without knowing for sure
that it was even a transformer problem.

Figure 3Displaying the SEL-587 event report graphically
with the
AC
SEL
ERATOR
�
Analytic Assistant SEL-5601 Soft-
ware quickly indicated that there was a fault in the
transformer.
With an electromechanical relay, Hataway
explains, you would know that the relay
tripped, but it doesnt give you any indi-
cation of the level of currents or how they
distribute in the transformer windings. There
are tests that can be performed, such as
dissolved gas, to detect a transformer fault.
But at some point, you have to decide if
you are going to energize the transformer
again and risk catastrophic damage or an
emergency shutdown once the transformer is
in service, says Hataway. Conversely,
with the event report, you have good infor-
mation from which to make a good deci-
sion.
Lee Underwood, another SEL Field
Application Engineer, helped Mining
Controls set the SEL-587 installation on the
MCI transformer. Underwood says that this
fault was a classic that he uses as an
example of the value of event reports.
Page 2
Case StudyMining Controls Incorporated
What we notice immediately from the
Mining Controls event report is that the
transformer event has the classic signature
of a phase-to-phase fault, in that the A- and
B-phase currents are exactly the same
magnitude and exactly 180 degrees out of
phase, Underwood says. He adds that MCI
did all the right things when the event
occurred.

Figure 4The phasor view of the captured event was
another tool available in the investigation, which showed that
the Winding 1 A- and B-phase currents were exactly the same
magnitude and exactly 180 degrees out of phase.
They took the time to set the relay properly
for the application so that the relay was able
to do what it was designed to do, he says.
When the relay operated, they had enough
confidence in their settings and in the relay
to consider that something could actually be
wrong in the transformer. There is a ten-
dency within the industry to assume that
relay trips during commissioning are due to
improper relay settings or relay problems,
and all too often we hear of situations where
settings are changed more or less randomly
in an attempt to fix what is perceived to be
improper operation. This event serves as an
excellent reminder that we should always
take advantage of the event reporting capa-
bility within modern relays to analyze opera-
tions before deciding what action to take.
The event report will almost always reveal
either that an actual fault has occurred or
will tell us exactly which setting needs to be
changed. In this case, taking the time to use
the tools available to do a thorough analysis
likely saved the transformer from the even
more significant damage which would have
occurred if they had just closed the breaker
back in.
Derek Ashby of Robinson Sales adds that
while coal mining operations are a good
example of how industry can benefit from
industrial grade power system protection
such as that provided by the SEL-587, there
are many other industrial applications that
could benefit in similar ways.
Weve had problems in the past in different
industries that use rock crushers and similar
applications where motor protection is im-
portant, Ashby says. These are applica-
tions where they get premature tripping in
their motor protection relays because the
loads are very cyclical. SELs motor protec-
tion relay, because it has a true thermal
model and not an overcurrent-based thermal
model, solves that problem. The result is
prevention of premature tripping and,
consequently, avoids unplanned stoppage in
production. Thats the name of the game in
industrydont stop the process.
Ashby adds that he sees many instances
where critical motors are involved in
manufacturing processes. If these motors are
tripped