Download Power Quality

© 2001 POWERVAR, Inc.
POWERVAR Ground Guard
TM
A new solution for an old (and usually
expensive) installation problem
POWERVAR Ground Guard
 POWERVAR Ground Guard is a solution that
makes it possible to eliminate the need for
dedicated/isolated electrical circuits for
sensitive electronic systems.
 Ground Guard is based on patented
POWERVAR technology.
 Ground Guard power conditioning is paid
for by savings in wiring costs.
© 2001 POWERVAR, Inc.
Some History on Wiring
 Many installation specifications continue
to include dedicated/isolated electrical
circuits out of habit.
 Most of these specifications are based on
inaccurate beliefs about the capabilities of
dedicated/isolated electrical wiring.
 Such special wiring techniques offer
almost no protection for the system.
© 2001 POWERVAR, Inc.
The definition . . . . .
A dedicated/isolated electrical circuit is one in
which the circuit’s three conductors (hot, neutral, and
ground) run continuously (with no splices) from a
distribution panel with a neutral to ground bond
(NEC defined newly derived source) directly to the
protected load in a dedicated conduit and
terminating in an approved isolated grounding
(IG) receptacle.
© 2001 POWERVAR, Inc.
This is a standard circuit
© 2001 POWERVAR, Inc.
This circuit is dedicated/isolated
G
© 2001 POWERVAR, Inc.
Isolated Ground Receptacles
Dedicated/isolated
circuits must be
terminated in an
isolated ground (IG)
receptacle.
 IG receptacles
generally look like
this. They are not like
normal receptacles.

© 2001 POWERVAR, Inc.
The non-isolated receptacle
Non-isolated receptacles
are grounded via the
mounting strap of the
fixture.
 There may be a separate
ground wire or conduit
may be used as ground.
 The receptacle ground is
common with other
grounds.

© 2001 POWERVAR, Inc.
The isolated (IG) receptacle
The ground of an isolated
ground receptacle is only
grounded via the
dedicated/insulated
grounding conductor.
 Receptacle ground is not
common with the conduit
or other grounds.

© 2001 POWERVAR, Inc.
Dedicated/isolated circuits
 Must have their own hot, neutral, and
insulated ground conductors, and . . .
 Must be in their own conduit.
 Must be terminated in an IG receptacle.
 Must originate from a location with a
neutral to ground bond (NEC defined “newly
derived source” -- Paragraph 250-5D).
© 2001 POWERVAR, Inc.
What do people believe . . . . . . ?
 Dedicated/isolated circuits provide surge
protection.
 Dedicated/isolated circuits provide noise
protection.
 Dedicated/isolated circuits provide
voltage regulation.
 Dedicated circuits provide computer grade
power.
© 2001 POWERVAR, Inc.
Do you get surge protection ?
 Because no other load shares the circuit,
the computer is protected from transient
voltages generated on its own circuit.
 If transient voltages occur as a result of
other loads connected to the same
distribution panel, the dedicated/isolated
circuit cannot prevent them from reaching
the protected load.
© 2001 POWERVAR, Inc.
Do you get noise protection ?
 Because no other load shares the circuit,
the computer is protected from electrical
noise generated on its own circuit.
 If electrical noise occurs as a result of
other loads connected to the same
distribution panel, the dedicated/isolated
circuit cannot prevent these disturbances
from reaching the protected load.
© 2001 POWERVAR, Inc.
Do you get voltage regulation ?
 Dedicated circuits do not regulate voltage
(and the computer doesn’t need it).
 Because no loads share the circuit, there
are no other current demands that may
cause voltage on the circuit to vary.
However, if voltage levels vary at the
distribution panel, they will vary at the load,
too, even if the circuit is dedicated.
© 2001 POWERVAR, Inc.
Computer grade power ?
 Dedicated/isolated circuits have nothing
to do with “computer grade power.”
 Perhaps the reason dedicated/isolated
circuits are popular is because we’ve used
them since the days of the first computer.
 Unfortunately, they are no longer adequate
to protect today’s system topologies.
 Do these circuits provide any benefit?
© 2001 POWERVAR, Inc.
Yes -- but a questionable one
 When a system is on a dedicated circuit, it
is thought to be unlikely that someone will
accidentally turn that circuit off .
 This assumes that individual breakers in a
panel are properly identified (something
that should happen anyway). Dedicated
circuits are expensive insurance against
poor workmanship and panel maintenance.
© 2001 POWERVAR, Inc.
Problems . . . .
 Dedicated/islolated circuits are clean only
to the extent that the distribution panel is
clean.
 Voltage regulation on a dedicated/isolated
circuit is only as good as regulation at the
distribution panel.
 Dedicated/isolated circuits do not prevent
or eliminate induced or radiated power
disturbances.
© 2001 POWERVAR, Inc.
Problems . . . .
 Dedicated/isolated circuits do not protect
systems from problems entering facilities
from outside such as lightning.
 Dedicated/isolated circuits are expensive,
difficult to manage, impossible to maintain.
 Electricians and inspectors often disagree
on how to interpret wiring specifications.
 And most importantly . . . .
© 2001 POWERVAR, Inc.
The biggest problem . . . . .
 Dedicated/isolated electrical circuits do
not have the ability to prevent “ground
loops” in today’s networked system
environment.
 Ground loops are the source of what one
manufacturer calls “inter-system noise”.
 Inter-system noise can destroy system
hardware and disrupt system reliability.
© 2001 POWERVAR, Inc.
What are “ground loops”?
Courtesy of PowerCET
Fig. 2 illustrates two circuits of different length. The safety ground at each receptacle will have a small
voltage potential with reference to safety ground at the panel. These voltage potentials will be different
because of the differences in circuit length and impedance (illustrated by the oscilloscope in the drawing).
Connecting a data cable (white line) between the two computers powered by these circuits will create a
“ground loop” in which noise currents will flow as a result of the voltage potential difference between the
safety grounds of the two circuits. The “loop current” can induce disruptive disturbances into data lines.
© 2001 POWERVAR, Inc.
Why worry about ground loops?
Inside the data cable, the signal ground and/or frame ground conductor
lies next to the signal conductors themselves for the entire length of the
cable. The conductors can act like a transformer for an unwanted signal
allowing a power disturbance in the ground to couple into the data
circuit itself. Disruption of or damage to the system may occur. This
may manifest itself as communication errors, I/O driver failures, or
numerous unexplained network collisions and wasted system resources.
Typical RS232 Data Cable(example only)
Data terminal ready
Modem ready
Receive data
Send data
Signal Ground
© 2001 POWERVAR, Inc.
Even ungrounded data cables
 Networks using “differential” data
pathways with unshielded data cable such
as 10baseT ethernet will still experience
problems.
 In such installations the ground referenced
offset voltages will be felt directly across
the I/O port. If they exceed the port’s
design limits, failure will occur.
© 2001 POWERVAR, Inc.
Don’t power conditioners stop this?
A power conditioner addresses normal mode
noise and common mode noise. Ground
loops are not the same thing. Traditional
power conditioners should not be thought of
as portable dedicated/isolated circuits.
Safety ground is
continuous. If
data line grounds
exist to other
computers, a
ground loop may
still occur.
© 2001 POWERVAR, Inc.
What about Ground Guard
TM
Control
Impedance
Ground Guard contains a specially engineered “ground
conditioning filter” that prevents power disturbances from
entering data cable grounding conductors or reaching I/O
ports. The impedance is patented and safety agency
approved. (UL, cUL, and VDE) Ground Guard completes
the power conditioning picture by conditioning ground, too.
Ground Guard does replace a dedicated/isolated circuit.
Data Cable Ground
© 2001 POWERVAR, Inc.
What are the benefits?
 Elimination of dedicated/isolated wiring
 No compliance problems with wiring codes
 Elimination of the scheduling, time, hassles
expense, and delays involved with using
electrical contractors
 Uniform installation environment
 Portability - easy to remodel and rearrange
© 2001 POWERVAR, Inc.
Other benefits . . . .
 Grows with the system -- unlike wiring
 Ground Guard is a hardware solution that can
be leased. Electrical wiring cannot be
leased. It’s cash out of pocket.
 Ground Guard provides complete power
conditioning, and since Ground Guard is paid
for with resources that are normally spent on
wiring, power protection is virtually free.
© 2001 POWERVAR, Inc.
What do customers say?

“Our contractor estimated it would cost about
$30,000 to rewire the place. The Ground Guard
alternative was about $4500.
» Grant DePorter, Managing Director, Harry Carey’s Restaurant

Thanks to POWERVAR’s Ground Guard power
conditioners, we no longer worry about variations
in local utility companies or electrical contractors.
Ground Guard has made our power problems go
away. It’s just that simple.
» Craig K. Herzer, Manager of Info Systems, IHOP Corporation
© 2001 POWERVAR, Inc.
What do customers say?

We’re very pleased to be associated with
POWERVAR. The Ground Guard series of power
conditioning products are a huge benefit to our
customers because they provide a cost-effective
method of helping to ensure reliable computer
operation. As well, in cases where we retrofit an
older POS system, the need to completely replace
the existing wiring is eliminated. This is a
considerable saving in both time and money.
» Linda Gillis, Product Marketing Mgr., Squirrel Companies
© 2001 POWERVAR, Inc.
Finally . . . .
 Ground Guard is covered by POWERVAR’s
five year warranty against defects in
materials and workmanship.
 Ground Guard is safety agency listed for
use throughout the world.
© 2001 POWERVAR, Inc.
 To learn more about Ground Guard, contact
your POWERVAR representative or call
POWERVAR at (800) 369-7179
 You may also learn more about Ground
Guard by visiting us on the World Wide Web
at http://www/powervar.com
© 2001 POWERVAR, Inc.
© 2001 POWERVAR, Inc.