Surge Protection 2014
Presented by:
Ken Pitt
TPS3 Product Manager
Schutzvermerk / Copyright-Vermerk
Agenda
• Why SPDs are necessary?
• What are Surges? (causes & effects)
• How does a SPD protect?
• UL, NEC, IEEE standards
• Applying SPDs
• Installation Tips
Everything is Electronic
Insurance Claims
185, 789 Claims
2009 - Nearly $800 Million
2008 – Over $1 Billion in
claims!!
What Is a Surge/Transient?
Super Bowl XLVII, February 3, 2013
“…power
surge caused
the outage.”
- James Brown, CBS
halftime crew host
What Is a Surge/Transient?
• High amplitude, short duration overvoltage
• Can be positive or negative polarity
• Can be from energized or grounded conductor
Transient Overvoltage –
Can be thousands of volts
Millionths of second
Surge Suppressors
•
A SPD, TVSS or Surge
Suppressor will Not
effectively control:
• Utility “swells” lasting
several cycles
• Utility “sags”
• Harmonics
• Certain noise problems
• Not a substitute for
Lightning Protection
System
• Will not save energy or
lower utility billing
What Causes Surges/Transients?
•
•
•
•
Lightning
Switching:
• Load Switching – utility & customer
Motors, Large Loads, Faults, Fuse Operation
• Source Switching
• Smart Grid, Gensets, PV, Wind Turbine
Internally generated surges: ≈70%
Externally generated surges: ≈30%
In outdoor environment, this
ratio probably reverses
Remember Differential Equations?
Solved for steady-state solution and
transient solution
Math: v(t) = 3te-2t + 2t – 1
transient
Effects of Transient Voltages?
•
•
•
•
Microelectronics Intolerant to Surges
Disruption
• Lockups, Downtime & Interruption costs
• Computing glitches and errors
Degradation
• Microelectronics
• Slow & continuous damage to motor
insulation
Destruction
• Failed microelectronics, ballasts,
motors, controllers, etc.
Maybe analogous to:
- ‘Water hammer’ in a plumbing system
- ‘Rust’ to microelectronics
Power Quality Tolerance Curve
Equipment will tolerate 500%
overvoltage for 100 s
5 x 120V = 600Vrms
600Vrms x 1.414 = 850Vpeak
Goal is to reduce transient overvoltages
to tolerable level – in this case
850Vpeak
MOV - Metal Oxide Varistor
•
•
•
•
•
Varistor - variable resistor
Semiconductor; generally zinc oxide
Connects parallel to load (not series)
Thickness determines clamping voltage
Diameter determines current capacity
MOV symbol
MOV - Metal Oxide Varistor
MOV seeks to equalize overvoltage
diverted through MOV as current
Voltage sensitive conductor: V = IR & I
= V/R
At ‘low’ voltages: very high impedance,
109 : I 0A
Above ‘threshold’ voltage: resistance
approaches 0 : I = high A
Current diverts through MOV as I =
V/R (high V, low R)
MOV does not ‘absorb’ surge, however,
I2R heat is retained
Bidirectional – Operates same for
positive or negative surges
Creates a momentary short-circuit to
pass transient energy to earth;
analogous to water heater pressure
relief valve
Normal voltage
V 120V
I=
= 0.12A
R 109
Trivial leakage current
Overvoltage
V 6000V
I=
= 6000A
R 1
Surge Current
+
+
-
SPD Operation
Zsource
Zsurge
B
D
A
SPD Operation
Load 5
Load 1
Load 2
MOV/SPD Acts as a momentary ‘short circuit’
‘short circuit’ ≈ no overvoltage ≈ protected load
Load 3
Load 4
How Surges Propagate
Internal or
External?
External
SPD
Internal
SPD
SPD/TVSS Terminology
Modes of Protection
•
•
•
•
•
‘Mode of Protection’ is a surge path
MOVs equalize potential
across either side of MOV
Various ways to connect MOVs,
i.e., various Modes of Protection
• L-N
• L-G
• N-G
• L-L
IEEE recommends defining modes:
L-N, L-G, N-G, etc. (because ‘Common
Mode’ and ‘Normal Mode’ mean different
things to different folks)
A
B
C
True 10-Mode Protection provides directly
connected L-L MOVs
= Parallel MOVs
N
G
SPD/TVSS Terminology
•
Let-through voltage, clamping voltage, suppressed voltage, measured limiting
voltage (measured in Vpeak)
•
Surge current, peak-amp current, maximum current, (measured in Apeak)
•
MCOV - Maximum Continuous Operating Voltage of the electrical system
(measured in Vrms)
Clamping or
Let-Through
Voltage
MOV/SPD
MCOV Surge Current
(thru SPD)
Load
Surge Current vs. Fault Current
Surge Current – Normal Operation - Momentary
MOV/SPD
Load
Fault Current – Drawn by Failed SPD - Continuous
MOV/SPD
Load
SPD fails short-circuited and draws Fault Current
to be continued…
SPD/MOV Failures
Industry Issues – Lot of UL & NEC action
MOV is a sacrificial element - will protect load or die trying
Failure caused by:
Sustained Overvoltage - TOV
(Can be as few as 2-3 cycles)
Sequence: MOV protects, fails, fails short,
follow-on fault current causes MOV to
catastrophically overheat
Typical causes:
– Loss of neutral
– Missing or Loose N-G bond
– Loss of phase (ungr. wye-delta)
– Incorrect installation
– 120V SPD on 277V system
– Cross Phase with N or G
– Improper application
– Ungrounded or impedance ground
– Genset related
19
SPD Damage from Missing N-G Bond (Three Phase)
(Enter for Animation)
A-N
A-G
B-N
B-G
C-N
C-G
The Pin represents the system’s Neutral
Bonding
to Ground. If N-G
SPD chases
L-G overvoltage
If N-G Bond is NOT made, the
Bond is made, the electrical system has a fixed reference to ground.
system becomes Ungrounded.
A-G B-G
The system will not ‘move’, from instability, resonance, arcing, etc.
SPD
Only L-G affected,
Not L-N
Ground
Ungrounded systems are inherently unstable. Nothing ‘holds’ or
System voltages remain stable. A ground fault
‘stabilizes’ the system. If/when something happens, the system
tryingand
to short
a Phase
tofluctuate.
Ground will
‘moves’
L-G voltages
will
The Not
SPDskew
will attempt to
the system.
I.e.,
L-G
voltages
do notfail.
change.
control
these until
the
SPD’s
L-G mode(s)
(Enter for More Animation)
20
MOV Failure Intensity Increases With The
Amount of Fault Current Drawn by the MOV
MOV/SPD
‘Lower’ Fault
Currents (0-20A)
Time
Load
‘Intermediate’ Fault
Currents (20-1000A)
‘Higher’ Fault
Currents (>1000A)
Current
21
SPD Overcurrent Protection Flaws
Cannot assume MOV to fault at
low impedance, and draw enough
fault current to open fuse:
1.) OCP needs low enough
rating to open, and
2.) OCP needs to open
before MOV ruptures

MOV(s) can fail
short here

500A test

time
Then, MOV(s) can
Suppose Fuse clears here
overheat & rupture
(after a few cycles)
before OCP clears
UL 1449 THIRD Edition
Combine TVSS and Surge Arresters
into one UL Standard, UL 1449 3rd
Edition renamed:
Surge Protective Devices (SPDs)
Effective: Sept 29, 2009
SPD
Surge
Arresters
• New SPD Types: Types 1, 2, 3, 4 (& 5)
• New Voltage Protection Ratings (VPRs) replace
old-style Suppressed Voltage Ratings (SVRs)
• New I nominal ratings
• Bid Specifications become Obsolete as product
evaluation & ratings change
(Expensive big deal to manufacturers)
TVSS
UL 1449-3 & NEC Art. 285
• Changed term TVSS to SPD
TVSS
XX
SPD
Aligns with IEC, EN and international usage of term
‘Surge Protective Device’
• Old-style Surge Arrestors are now gone
replaced SPD ‘Type’ classification
Type 1 – 20kA or 10kA
Type 2 – 20kA, 10kA, 5kA or 3kA
Type 3 – 3kA
Type 4 – Based on intended usage as Types 1, 2 or 3
Type 5 – Suppressor components
24
UL 1449-3 & 2011 NEC Art 285
SPD Types: Types 1, 2, 3 & 4 Based on Location within electrical distribution system
Meter
Svc.
Disc.
Panel
10m (30feet)
Trans
Type 1
OCP built in to
SPD, more
rigorous testing
Type 2
Type 3
Type 4 (Component) tested to Type 1or Type 2
SPD Types
UL 1449-3
I nominal Testing – In - (Nominal Discharge Current)
- New Concept to USA – Originated from IEC 61643
- Duty Cycle Testing
- 15 8x20 s surges through every mode of three
samples used for VPR testing
Type 1 – 20kA or 10kA
Type 2 – 20kA, 10kA, 5kA or 3kA
Type 3 – 3kA or None
Type 4 – Based on intended usage as Types 1, 2 or 3
27
UL 96A Master Labeling
•
•
Service entrance SPDs are no longer required in order to obtain Master Label
certificate.
Lightning Protection systems without service entrance SPDs installed will
have the cautionary disclaimer added to their Master Label certificate.
“At the request of the installer, surge protection may be excluded from the scope of the
inspection. The Certificate specifically states this exclusion with one of the following
statements, as applicable:
"Surge protection was not inspected.“
"The electrical service entrance surge protection system was not inspected.“
"The communication surge protection system was not inspected."
The above wording is followed by the cautionary statement:
”Surge protection devices are an integral component of a complete lightning protection
system and should be provided on all incoming and exiting electric power, data, and
communication services."
UL 1449-3
More For Reference now that Standard is 3+ years in use
Performance Test Format Changed
New Testing uses Six (6) Times More Energy
• As surge amplitude goes up,
clamping voltage goes up too
• Specs become obsolete
• Need new VPRs in specs
3000A
500A
Old – 6kV / 500A
Suppressed Voltage Ratings
(SVR)
New – 6kV / 3,000A
Voltage Protection Ratings
(VPR)
How Large are Surges?
IEEE Research
It takes 10kV to push a 10kA surge, 10 meters
It takes 27kV to push a 10kA surge, 30 meters
It takes 45kV to push a 10kA surge, 50 meters
10,000V
(0.1 /m)
(0.09 /m)
(0.09 /m)
L - slight inductance of wire
‘Inductance Police’
10m
27,000V
30m
45,000V
50m
A B C
Panel
Voltage becomes so
high that it flashes over
upstream, so surge
current is not pushed
Similar to shooting fire hose
as hard
through soda straw – won’t all go!
30
IEEE C62.41.2 - 2002
“Expected voltages and current surges”
Table 4 – Scenario I tests for SPDs intended for Location Category C3
Standard tests
Optional test
1.2/50µs Voltage generator
8/20µs Current generator
Minimum open-circuit voltage to be
applied to SPD
Current to be driven through the
SPDb
100kHz Ring Wave for
front-of-wave response
evaluation
Low
6kV
3kAc
6kV
High
10kV
10kA
6kV
Exposure
Table 3 – Standard 1.2/50 s – 8/20 s Combination Wave
Expected voltages and current surges in Location Categoriesa A and Bb
Single-phase modesc : L-N, L-G and [L&N]-G
Polyphase modes: L-L, L-N, L-G and [L’s]-G
(See Table 5 for N-G modes)
Peak Valuesd
Location Categorya
Voltage
(kV)
Current
(kA)
Effective Impedance ( )
A
6
0.5
12f
B
6
3
2
Surge Protection
NEC 2011, Article 285
Page 32
NEC 2011, 285
NEC Article 285 Pertains to Low Voltage
Surge Protective Devices (SPDs)
Things We See That Are Worth Sharing:
NEC 2011, Article 285
Nomenclature:
Appropriate term is Surge Protective Device (SPD)
Term TVSS is now gone.
Aligns with worldwide usage of term ‘Surge’ and ‘SPD’
Unfortunately, America has a colloquial meaning for ‘Surge’, which
is not consistent with the intended meaning of ‘transient
overvoltage’
For example, last year’s Super Bowl was delayed by a partial power
outage, not a surge.
NEC 2011, Article 285
285.3: Uses Not Permitted
1.) Circuits exceeding 1kV
Why: UL 1449 safety standard only applies to 1kV. Interestingly, there is no
safety standard for SPDs/arrestors over 1kV and the Listing requirement in
NEC 280 was removed in the 2008 NEC.
2.) On ungrounded systems, impedance grounded systems, or
corner grounded delta systems unless specifically listed for use on
these systems.
Why: SPDs activate upon sensing higher voltages, and these power
systems have no reference to ground, or different references to ground.
This can (will) fail the SPD if it is not configured correctly.
NEC 2011, Article 285
285.3: Uses Not Permitted
3.) Where the rating of the SPD is less than the maximum
continuous phase to ground power frequency voltage available at
the point of application
Why: SPDs activate upon sensing higher voltages. If a 120V SPD is
installed on a 277V system, the SPD will attempt to chase the overvoltage
until it internally overheats and fails (within seconds). The SPD needs to be
rated at sufficient voltage to prevent instantaneous failure.
NEC 2011, Article 285
285.5: SPDs Need to be Listed Devices
Listed to UL 1449 per NEC Informative Annex A
UL 1449 Third Edition (eff. Sept 09) includes rigorous safety testing:
Most ‘old-school’ arrestors are gone due to safety issues
Some SPDs are not listed, or listed to inappropriate standard (IEEE
standard for secondary arrestors, IEC 61643, etc.)
Recognized SPDs have requirements that need fulfilled: Did not
complete all the failure testing, needs fuses or specific enclosures, etc.
Some are very good. Some have deficiencies so severe that they are
almost impossible to overcome; intentionally sold (cheap) on the
premise that no one will take the time to check.
Plenty of DIN-rail mount SPDs come from overseas, with less safetyconscious IEC markings, not UL 1449 Listed. Some do not identify their
specific overcurrent protection requirements.
NEC 2011, Article 285
285.6: Short Circuit Current Rating (SCCR):
Must be greater than or equal to available
fault current
Most SPDs have 100-200kA SCCRs, which is good
Be Aware:
Some have very low SCCRs
Some require specific fuses or overcurrent protection
As a generalization, UL distinguishes between fuses and breakers
because fuses have a tendency to clear faster than breakers. If the SPD
requires external overcurrent protection, it may have been evaluated &
Listed with fuses instead of breakers. But breakers tend to end up on the
job, which may not clear fast enough.
NEC 2011, Article 285
285.12: Routing of Conductors
Must be short and straight as possible
Why: Large voltage drops at high surge currents &
frequencies. Surges are Not 60Hz & 75A, but are
30,000Hz and possibly 10,000A (!!!)
Because of conductor inductance (not resistance), voltage drops can be ≈50
- ≈200 volts per foot. Different physics applies. (V = - L di/dt) This hurts the
performance of the SPD. Shorter wires are better. Inches matter.
Need gentle bends. No sharp bends or kinks in conductors, avoid wire nuts
Gently twisting conductors together like twisted pair reduces inductance
SPD Types: Types 1, 2, 3 (4 & 5)
Based on SPD Location within electrical distribution system
(also coincides with ANSI/IEEE C62.41.2-2002 Categories C, B & A
Meter
Svc.
Disc.
Panel
10m (30feet)
Trans
Type 1
replaces
old-school
arrestors
Type 1
OCP built in to
SPD, more
rigorous testing
Type 1 may be used on load side too
Type 2
Type 3 (Plug-In)
Type 4 is Recognized or Component Assembly tested
to Type 1 or Type 2
Type 5 is a
bare
component,
such as
MOV
40
NEC 2011, Article 285
Interesting Tidbits:
SPD disconnect should not be counted as one the six disconnects (NEC
230.71(A) beginning 2005)
Common to see 10-foot tap rule on SPD retrofits - NEC 240.21(B)(1). Note
the inherent advantages of Type 1 SPDs in such applications because
OCP is built-in.
The surge industry sees a disproportionate number of SPDs fail from
improper reference to ground of the power system. Specifically, if the
Neutral (X0) is not bonded to Ground at the upstream transformer. See
animation next slide.
Surge Protection
NEC 2011, Article 708
Page 45
2011 NEC Article 708
708.2 Definitions:
Critical Operations Power Systems (COPS). Power systems for facilities or parts of facilities that require
continuous operation for the reasons of public safety, emergency management, national security or business
continuity.
708.20(D) Surge Protective Devices. Surge protective devices shall be provided at all facility distribution voltage
levels.
Page 46
46
Surge Protection
NEC 2014, Article 700.8
Page 47
2014 NEC Article 700.8
700.8 Definitions:
•
Voltage surge protective devices (SPD’s) are required to be installed for all switchboards and
panelboards of emergency systems.
•
These surge protection devices and products must be listed. Doesn’t specify ‘Type’
Reasoning
Implementation of this rule could prevent damage to emergency power controls and critical electronic
loads, thereby enhancing the reliability of emergency systems.
48
Manufacturing Plant
Service Entrance – Applying surge protection at the
incoming electrical service “Stops Surges Before They
Get In.” These types of surges contain the largest surge
energy warranting 300kA or more of surge current
redundancy.
Outside Loads – SPDs should be installed at distribution
panels feeding remote warehousing, parking lot lights, etc.
to prevent back feeding surges entering the main building.
Lower Voltage Panels – If the facility is supplied with a
higher system voltage (i.e. a 480Y/277V service), 120V
panels need SPDs to condition residual surges leaving the
service entrance SPD as well as any internally generated
surges. Examples could be panels powering in house data
center, administrative offices, or any other panels
powering sensitive, electronic-rich class locations.
Individual Critical Loads – Even if surge protection is
applied at the previous locations, redundant protection
maybe warranted for sensitive, costly equipment. This
may include PLCs, CNCs, drives, control rooms, etc.
Data – Security, fire alarm, and telephone systems using
copper communications lines need protection especially
for computers and automation control circuits.
Page
Selecting kA Ratings
•
Realistic kA Per Phase ratings:
Service Entrance: 200kA-300kA per phase
Distribution: 100kA-200kA per phase
Point of Use: 50kA-100kA per phase
kA buys redundancy - up to a point
A
B
MOVs
C
MOVs
Not carved in stone:
Consider upsizing at critical loads, larger
panels, outdoor loads, isokeraunic
activity, etc.
N
MOVs
G
MOVs
MOVs
MOVs
MOVs
MOVs
MOVs
MOVs
Consider downsizing based on value,
budget, etc.
•
Specific Modes? L-N, L-G, N-G, L-L
MOVs
= Parallel MOVs
Tire Tread Analogy:
• Thicker the tread, the longer it
lasts & harder to get a nail through
• Bigger SPDs are more robust and
withstand more abuse
SPDs for Food and Beverage
Parallel connected SPD
• Service Entrance Panels
• Ahead of critical loads (UPS, ATS)
• Protects from large surges
Series Filter
• Process control panels
• Broadcast transmitters
• Cleans high frequency noise on the power line
Data Signal
• Cameras
• Control wires
Surge Protection
Installations
Supply Side
• Only Type 1 Rated SPDs
• SPDs are granted exceptions
• Conductor sizing undefined in
NEC
• UL 96A recommends SPD to have
I-n = 20kA
• Recommend following tap rule
• Not required, but good practice is
to connect to a disconnect
56
Secondary Side
• Type 1 or Type 2 Rated SPDs
• SPDs are granted exceptions
• Conductor sizing undefined in
NEC
• Recommend following tap rule
• Not required, but good practice
is to connect to a disconnect
57
How to land conductors
Permissible tap connections
• Accessories used to land
control wire taps can be used
for SPDs
• Lug change out kits
• Multi-Barrel lugs
58
Monitoring Features
•
•
•
•
•
•
•
Dry Contacts
Surge Counter
Remote Monitor
NEMA Enclosure Ratings
Flush mounting
Interfaces
N-G Voltage Detection
61
SIEMENS Here to Help
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Sounding Board for issues
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General Help
On-Line Live Support
Forensic Testing & Analysis of failed
SPDs
Etc.
888.333.3545
kpitt@aptsurge.com